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Chapter 4 Continued
 
J. RANGE AND COURSE-ANGLE FINDER
 
4J1. General description. The periscope has an internal range finding device of the stadimeter type capable of giving both ranges and course angles. The change from direct observation to range reading or course measuring is quickly and positively effective.   The range and course-angle finding device is of the duplicate image type; the distance between the images may be varied at will, so that, for example, the water line of one image may be brought into contact with the masthead or funnel top of the other image. If the length
 
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of the vessel is known or estimated and set on the length of the target scale dial, the angle subtended is indicated in yards on the range scale dial, against the known height of the vessel on the height scale dial.

The device may be rotated 90 degrees in a plane normal to the optical axis of the periscope. This is done by continuing the clockwise motion of the operating gear beyond the limit of the vertical position of the separating mechanism; thus the whole divided lens unit rotates 90 degrees. In this position, the two images of the target are at opposite edges of the field and the mechanism is in contact with its stops. Turning the handwheel counterclockwise makes the two images approach each other. Since the known length of the target has been set on the length of target scale dial opposite the stationary index mark on the bottom of the stadimeter housing, when the bow of one image touches the stern of the other, the course angle is indicated on the length of target scale dial against the previously found range on the range scale dial.

The duplicate images are obtained in the following manner: The lower objective lens is divided into two substantially equal parts and mounted in such a manner that the parts may be moved against each other in a plane normal to the vertical optical axis of the periscope and also may be rotated in the same plane through 90 degrees.

The mechanism for these movements is operated by a handwheel on the right-hand side of the lower end of the periscope at a height convenient for the operator.

Ordinary observation is obtained when each half of the divided lens supplements the other and thus forms a complete circle; then a single image is visible in the eyepiece, and the joint between the two halves of the lens lies in the vertical centerline. The stops of the mechanism are in contact in this position.

When the lens halves are in the position for ordinary observation, clockwise rotation of the handwheel causes the halves to slide against each other in opposite directions; this causes duplicate images to appear in the eyepiece. The separation of the images increases until a maximum is reached, when further clockwise rotation causes the divided lens unit to rotate through 90 degrees.

  Counterclockwise rotation of the handwheel then causes the two images to approach each other until the two halves of the objective supplement each other and produce a single image. Further counterclockwise rotation of the handwheel causes the divided lens unit to rotate and return to the ordinary observing position, ready for the next range and course angle finding operation.

The device gives readings independent of the focus setting of the individual observer. It is capable of bringing into coincidence two points of the image that subtend an angle of from 0 degrees to not more than 2 degrees of the field at high power. It is provided with duplicate scale dials of Bakelite attached to the outside of the periscope so that range and course angle data may be read by an assistant, if desired. One set of scale dials is located under the eyepiece at the lower end of the eyepiece box, and the other set diametrically opposite on the back of the periscope. Such scale dials are not less than 2-inch outer diameter in the case of the smallest scale dial, and so located as to be easily readable. The graduations and numbering on each scale dial are clear and legible and each scale dial occupies as great an angular portion on the dial on which it is engraved as is practicable. The angular movement of the scale dial or scale dials connected to the handwheel is directly proportional to the angular movement of the handwheel.

Each device is adjusted to suit the exact magnification of the periscope in which it is incorporated.

The indicating scale dials are circular, arranged concentrically, and engraved in Arabic numerals as follows:

1. Outer ring. Outside graduated 100 to 1,000 feet and inscribed Length of Target in Feet; inside graduated 30 minutes to 85 degrees and inscribed Course angle.

2. Intermediate ring. Outside and inside graduated 2.2 to 110 and inscribed Range in 100 Yards.

3. Inner ring. Outside graduated 15 to 130, feet and inscribed Height in Feet.

The range and course-angle finder consists chiefly of three main assemblies:

 
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1. Lower (split) objective lens and mount assembly (Figure 4-22).

2. Objective operating mechanism assembly (Figure 4-23).

3. Stadimeter housing assembly (Figure 4-24). These three assemblies are not in contact with each other for actuation in direct series. The objective operating mechanism assembly and the lower (split) objective lens and mount assembly connect directly with each other. However, the three assemblies are so connected by shafts and couplings that they act as a unit. Three other assemblies are placed between the objective operating mechanism assembly and the stadimeter housing assembly for mechanical and optical reasons. These three assemblies are:

1. First inner tube section assembly (Figure 4-27).

2. Eyepiece skeleton assembly (Figure 4-28).

3. Eyepiece box and miscellaneous assemblies (Figure 4-29).

The stadimeter housing assembly contains gearing which is connected to the internal mechanism of the eyepiece box (11, Figure 4-29) and eyepiece skeleton assembly by a female tang coupling (68, Figure 4-24) that projects upward from the stadimeter housing assembly and engages on a milled tang at the lower end of the stadimeter transmission shaft (22, Figure 4-27) in the eyepiece box 11, Figure 4-29).

The stadimeter housing assembly, by means of the stadimeter transmission shaft (22, Figure 4-27) and the stadimeter transmission shaft coupling (14, Figure 4-23), is coupled with the operating gear pinion shaft (13) of the objective operating mechanism assembly. The stadimeter transmission shaft (22, Figure 4-27) extends through a bearing hole in the spider (2) where its thrust is restrained by two thrust collars (4) secured with taper pins (10). These two thrust collars (4) restrain the axial thrust of the shaft on either side of the spider (2), thereby restricting axial movement of the shaft. The eyepiece skeleton (42, Figure 4-28) has a clearance hole in its large shoulder flange to accommodate the stadimeter transmission shaft (22, Figure 4-27).

The lower (split) objective lens and mount assembly is secured to the objective operating

  mechanism assembly by means of four stadimeter collimating screws (13, Figure 4-22). The stadimeter housing assembly (Figure 4-24) is secured to the eyepiece box (11, Figure 4-29) by means of four stadimeter housing bolts (30, Figure 4-24).

4J2. Description of the lower (split) objective lens and mount assembly. Figure 4-22 shows the

Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
1 P-1158-1 1 Right mount half
2 P-1158-2 1 Left mount half
3 P-1158-9 4 Tension plugs
4 P-1158-10 4 Tension plug springs
5 P-1158-13 2 Half ring clamps
6 P-1158-13A 12 Variable thickness washers
7 P-1159-7 2 Large side clamps
8 P-1159-8 2 Small side clamps
9 P-1159-9 4 Mount keys
10 P-1179-25 12 Half ring clamp lockscrews,
11 P-1179-26 12 Large and small clamp lockscrews
12 P-1179-31 8 Tension plug spring lockscrews
13 P-1179-34 4 Stadimeter collimating screws
14 P-1179-34A 4 Washers for stadimeter collimating screws
15 P-1179-189 4 Mount dowel pins
16 P-1418-12A 2 Crown halves
17 P-1418-12B 2 Flint halves
18 P-1418-12C 6 0.001 inch tin foil, to separate the lower objective split lens halves

lower (split) objective lens and mount assembly. All bubble numbers in Sections 4J2, 3, and 4 refer to Figure 4-22 unless otherwise specified.

a. Lower (split) objective lens. The lower (split) objective lens is made of two optical elements; one is a double convex crown element (16) while the other is a concave plano flint element (17) separated with 0.001-inch tin foil (18) forming an air-space doublet.

Both elements are split individually and when assembled in the mount halves have an approximate gap of 0.055 inch between the split. The lens halves are carried by the objective operating mechanism to a maximum displacement of both halves of 9/16 to 5/8 inch.

Each half is separated with three strips of 0.001-inch tin foil (18) equally spaced and placed

 
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Figure 4-22. Lower (split) objective lens and mount assembly.
Figure 4-22. Lower (split) objective lens and mount assembly.
near the periphery. This provides spacing sufficiently uniform to keep color constant over the outer surface where the lens halves are separated, thereby preventing newton rings. Lenses of large diameter cannot be cemented because of the difference in the thermal expansion coefficients of crown and flint glasses.

The plano surface of the flint element rests against the lower shoulder seat of each mount, while the inner circumference is scraped to a true bearing seat with the periphery of the lens doublet. The opposite corners of the split section of the doublet halves are beveled at a 45 degrees angle. These beveled faces are clamped sufficiently radially

  by the scraped 45 degrees angle contact seats of the large and small side clamps (7 and 8).

The split lens doublet of each assembled mount is clamped snugly, without restricting the movement of the lens under constant spring pressure applied to the tension plugs. Changes in the relative position of the split halves of the doublet caused by expansion and contraction of the lens mount are sufficient to destroy its collimation. Therefore, the angle of the beveled contact surfaces of the lens and their angular relation to the movement of the tension plugs, centralizes the split halves of the doublet against the 45 degrees angle contact seats of the side clamps, thus maintaining

 
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the proper, relation of the split lens doublet halves.

b. Right and left mount halves. The right and left mount halves (1 and 2) are made of cast aluminum. Each is provided with eccentric flanges with an offset of 0.197 inch from the original axis. The mounts are not a complete half circle, as a part is cut away to provide clearance for the attachment of large and small side clamps (7 and 8) secured with lockscrews (11) to the split faces of the mounts. The lens walls project upward from the eccentric flange with a nominal wall thickness. A narrow shoulder is provided next to the bottom of the inner circumference of the lens wall, to which the plano surface of each split flint element is retained.

Each lens wall has two radial slotted openings of appropriate length, separated at a 90 degrees angle for the insertion of two tension plugs (3). These are retained by tension plug springs (4) which are secured with two lockscrews each (12).

Each eccentric flange has two elongated holes to provide the necessary adjustment over the inserted stadimeter collimating screws (13). The outer face of each elongation is countersunk for the stadimeter collimating screw washers (14). The lower face of each eccentric has two key recesses for the mount keys (9). The elongations and keys are parallel in each mount half. In the right mount half (1) the elongations and keys are located perpendicular to the split of the lens halves. The inserted mount keys are a sliding fit in keyways of the same perpendicular location in the right mounting plate (5, Figure 4-23) of the objective operating mechanism assembly. This mount half can be adjusted at perpendicular plane to the split of the lens halves, moving it away from the axis and increasing the gap between the split lens halves, or moving it toward the axis and decreasing the gap.

The left mount half (2) has the elongations and keys located parallel to the split of the lens halves. The inserted mount keys are a sliding fit in keyways of the same parallel location in the left mounting plate (5, Figure 4-23) of the objective operating mechanism assembly. This mount half can be adjusted parallel to the split lens halves, moving it to either side of the axis as is necessary.

  The split lens doublet halves are retained radially in the mount halves by the large and small side clamps (7 and 8). The clamps are secured to each side of the split faces of the mount with lockscrews (11). The split lens doublet halves are retained axially in the mount halves by the half ring clamps (5). The clamps fit over the six variable thickness washers and are secured to the face of each lens wall with six lockscrews (10).

Each mount is secured to each mounting plate half (5, Figure 4-23) with two stadimeter collimating screws (13) and two dowel pins (15) after collimation of the stadimeter.

e. Half ring clamps. The half ring clamps (5) are made of brass tubing of one solid ring having an outside diameter of 4.900 inches which conforms to the contour of the lens wall of the mount halves (1 and 2). The inner circumference is bored with a counterbore of shallow depth, its counterbored diameter conforming to the inner circumference of the lens wall of the mount halves. The ring is chamfered at a 30 degrees angle from the bore. The ring is split after machining with a 3/16-inch cutter, thus forming a half ring clamp for each split lens doublet half. Each half ring clamp has six equally spaced clearance holes for lockscrews (10). These lockscrews screw into tapped holes of each lens wall of the mount halves. The half ring clamps are assembled to the face of each lens wall of the mount halves (1 and 2) over six variable thickness washers (6).

The shoulder face of the counterbore fits snugly against the shortest radius surface of the split crown element of the doublet half. The adjustment of these half ring clamps is of sufficient tension only to allow the tension plugs under spring pressure to centralize the split lens doublet halves against each beveled contact surface of the large and small side clamps (7 and 8).

d. Large and small side clamps. The large and small side clamps (7 and 8) are made of phosphor bronze 0.125 inch thick. These clamps are shaped to conform to each part of the split contact faces of each mount half and are secured with three lockscrews each (11). The lockscrews are inserted into countersunk clearance holes in the clamps and screwed into tapped holes in their large and small split contact faces respectively. Each side clamp projects 1/8 inch inward of the inner circumference of the lens wall. The lower

 
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face of this projecting section is beveled at a 45 degrees angle and serves as a contact seat for the 45 degrees angle beveled split face of the right and left side of the split lens doublet halves. A 1/32-inch slot of nominal depth in the beveled 45 degrees angle seat is provided at the intersection of the crown and flint elements, to allow clearance for the variance of thermo coefficients of expansion of the crown and flint elements. The large and small clamps on each side of the split lens doublet halves retain the lens from radial displacement in the mount halves (1 and 2).

e. Tension plugs. The four tension plugs (3) are made of brass and are 0.625 inch in length and 5/16 inch in width. Both ends of each tension plug have the corners rounded off. Two tension plugs are inserted in the radial slotted openings of the lens wall of each mount half (1 and 2) and fit loosely. The inner face of each tension plug conforms to the contour of the periphery of the split lens doublet halves. They are held against the periphery of the lens doublet halves by the spring pressure of tension plug springs (4) mounted to the periphery of the lens walls of the mount halves (1 and 2) and are secured with lockscrews (12).

f. Tension plug springs. The tension plug springs (4) are made of spring steel of 22 gage, and blued. The contact surface of each spring is bent with a 38-inch radius inward to contact the tension plug (3) from the remaining contour of the spring a distance of 0.093 inch. Each has two clearance holes to accommodate lockscrews (12) securing the two tension plug springs to the lens wall of each mount half (1 and 2). These to screws are inserted into clearance holes in each spring and screwed into the tapped holes in the lens wall. The springs have sufficient applied tension on the tension plugs to centralize the split lens doublet halves, with their contacting 45 degrees beveled seats against the 45 degrees beveled seat faces of the large and small side clamps (7 and 8).

4J3. Disassembly of the lower (split) objective lens and mount assembly. The lower (split) objective lens and mount assembly is disassembled in the following manner:

1. Remove the four stadimeter collimating screws (13), holding each lower, (split) objective lens and mount assembled half while unscrewing the two collimating screws (13). Remove each

  assembled lower (split) objective lens and mount carefully, as the two dowel pins (15) are a push fit in the mounting plates (5, Figure 4-23) of the objective operating mechanism assembly.

2. Remove the two lockscrews (12) from the two tension plug springs (4). These lockscrews are unscrewed from tapped holes in the lens wall of each mount half (1 and 2). Remove the four tension plug springs (4) and the four tension plugs (3).

3. Before removing the six lockscrews (10) of each mount half, construct a wooden fixture with six wire nails with reference marks. This is necessary for each mount half (1 and 2) because of the variable thickness washers, and it enables the repairman to assemble them correctly.

4. Remove the six lockscrews (10) from each of the half ring clamps (5). These lockscrews are unscrewed from tapped holes in each lens wall of the mount halves (1 and 2). Lift away the half ring clamps and place the variable thickness washers on the wire nails of each wooden fixture in their respective order.

5. Remove the three lockscrews (11) from the small side clamp (8). These lockscrews are unscrewed from tapped holes in the split center con tact face of the small section of the mount half. Remove the small side clamp.

6. Carefully remove the split lens doublet half by pressing downward radially on the lens next to the large side clamp (7) on the split center section rotating the lens out of the mount half. This permits the lens halves to be freed. Handle the split lens doublet half with lens tissue.

7. Place pencil marks on the periphery of the split lens doublet halves and on the inner circumference of the mount half to provide a proper reference for reassembly. Place the three strips of 0.001-inch tin foil (18) in a small box to prevent damage or loss. Place the crown and flint elements of this half to one side to prevent scratches or breakage.

8. Follow the procedure stated in Steps 5, 6, and 7 for the other mount half.

9. Remove the three lockscrews (11) from each large side clamp (7) of both mount halves

 
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(1 and 2). These lockscrews are unscrewed from tapped holes in the split center contact face of the large section of each mount half, removing the large side clamps.

10. Check the lacquered split center flat sections of each split lens doublet half, and re-lacquer them if necessary. Slack lacquer is used to prevent light from entering or escaping from the split flat center section of the split lens doublet halves (16 and 17).

4J4. Reassembly of the lower (split) objective lens and mount assembly. The lower (split) objective lens and mount assembly is reassembled in the following manner:

1. Assemble the large side clamps (7) to their respective mount halves. Insert and secure the lockscrews (11), screwing them into the tapped holes of the large section of the split contact surfaces of each mount half.

2. Clean the crown and flint elements (16 and 17) of the split lens doublet halves with clean lens tissue. All surface dirt, grease, or foreign matter must be removed with alcohol. Wipe each surface dry with a clean untouched lens cloth or lens tissue. Specks of dirt which have a tendency to adhere may be removed with a sable brush which has been cleaned with ether. A vacuum brush with ether is also effective. All lens elements must be cleaned in the same careful manner. A rubber air bulb removes most of the surface dust.

3. Place the three strips of 0.001-inch tin foil (18) at three equally spaced places near the periphery, to separate the crown and flint elements. The strips of tin foil are placed on the concave surface of the flint element, and the crown element having the longest radius is place on the three strips of tin foil.

4. Holding the split lens do let halves (crown and flint) together with lens tissue, place them in the mount half (1), with the large side clamp (7) in place. Press downward from the split flat center section on the opposite side until the lens is rotated up tight against the 45 degrees angle contact seat face of the large side clamp.

5. Proceed to fit the small side clamp (8) until the lockscrews (11) inserted in the tapped holes in the small section of the split contact face of the mount half are within 1/8-turn of being

  tight. The lapped 45 degrees angle contact surface of the small side clamp (8) to the 45 degrees angle contact beveled face of the split lens doublet halves should be fitted to allow only 1/8-turn of the lockscrews (11), to prevent angular movement, and to allow sufficient clamping without placing any strain in the crown and flint elements.

6. Follow the procedure stated in Steps 4 and 5 for the mount half (2).

7. Place the six variable thickness washers (6) from the reference fixture at their respective places on the face of the lens wall of the mount half (1). Place the half ring clamp (5) over the variable thickness washers (6) and line up the holes of the half ring clamp and the washers. Insert the six lockscrews (10) through the clearance holes in the half ring clamp and the washers, and screw them into tapped holes in the lens wall of the mount half. Using a 0.001-inch piece of shim stock, tighten the lockscrews maintaining 0.001-inch clearance between the half ring clamp and the face of the crown element. The half ring clamp prevents axial displacement of the split lens doublet halves, and is tightened sufficiently that it does not restrict the free movement of the tension plugs (3). A strain testing device using polarized light should be used to ensure that there is no strain in the assembled lens element.

8. Follow the procedure stated in Step 6, for the opposite mount half (2).

9. Insert the four tension plugs (3) in the two radial slotted openings of each mount half, placing the concave surface of the tension plug to ward the periphery of the split lens doublet halves. Assemble the tension plug springs (4) securing each with two lockscrews (12) placing the tension plugs (3) under spring pressure. The lockscrews are inserted into clearance holes in the tension plug spring and screwed into tapped holes in the lens wall of each mount half.

10. Assemble both mount halves (1 and 2) to the mounting plates (5, Figure 4-23) after the 90 degrees rotation is adjusted and checked.

4J5. Description of the objective operating mechanism assembly. This mechanism consists of the necessary parts which transmit the displacement of the lower (split) objective lens and

 
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Figure 4-23. Objective operating mechanism
assembly.
Figure 4-23. Objective operating mechanism assembly.

mount assembly, and is described in the following manner: Figure 4-23 shows the objective operating mechanism assembly. All bubble numbers in Section 4J5, 6, and 7 refer to Figure 4-23 unless otherwise specified.

 
Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
1 P-1156-1 1 Operating gear
2 P-1156-2 1 Track sleeve
3 P-1156-3 1 Sliding track
4 P-1156-4 2 Cam shoes
5 P-1158-3 2 Mounting plates
6 P-1158-5 1 Detent pawl spring
7 P-1158-6 2 Detent pawls
8 P-1158-7 1 Detent pawl rest
9 P-1158-8(a) 2 Long detent pawl rest lockscrews
10 P-1158-8(b) 2 Short detent pawl rest lockscrews
11 P-1158-12 2 Sliding track lock rings
12 P-1159-1 1 Operating gear pinion
13 P-1159-2 1 Operating gear pinion shaft
14 P-1159-3 1 Stadimeter transmission shaft coupling
15 P-1159-4 2 Mounting plate guide key with integral shafts
16 P-1159-5 2 Detent pawl shafts
17 P-1159-6 2 Mounting plate guide keys
18 P-1159-10 2 Mounting plate guides
19 P-1163-4 1 Operating gear stop
20 P-1163-5 2 Maximum displacement stop and observation position stop
21 P-1172-15 1 Operating gear pinion key
22 P-1179-23 4 Coupling sleeve lockscrews (upper end)
23 P-1179-24 4 First inner tube section upper end coupling lockscrews
24 P-1179-27 2 Operating gear pinion lock screws
25 P-1179-28 4 Operating gear retaining ring lockscrews
26 P-1179-29 6 Detent pawl spring lockscrews
27 P-1179-30 15 Coupling sleeve lockscrews (lower end)
28 P-1179-32 2 Mounting plate guide key lockscrews
29 P-1179-33 6 Mounting plate guide lockscrews
30 P-1179-73 6 Operating gear stop, observation position stop and maximum displacement stop lockscrews
31 P-1179-177 2 Mounting plate guide key shaft taper pins
32 P-1179-178 2 Detent pawl shaft taper pins
33 P-1179-179 2 Stadimeter transmission shaft coupling taper pins
34 P-1205-5 1 Coupling sleeve
35 P-1205-8 1 Operating gear retaining ring
36 P-1310-15 1 Sliding track lock ring lockscrew
 
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a. Sliding track. The sliding track (3) is made of cast phosphor bronze and is 12.574 inches in length. It is machined cylindrical, with a large shoulder flange of nominal thickness at the upper part. Its internal diameter is machined for light transmission and has anti-reflection threads throughout.

A brass plate spacer 1/16 inch thick and 1/4 inch wide is inserted and soldered in the slots cut directly in the centerline in each side of the bore of the large shoulder flange. The spacer when assembled is flush with the face of the large shoulder flange. It prevents stray light from entering the gap between the two split lens doublet halves of the lower (split) objective lens (16 and 17, Figure 4-22).

Two longitudinal T-slots are milled parallel to the horizontal centerline, at an appropriate center distance from the vertical centerline on each side; there are two more 180 degrees apart on the opposite side in the large shoulder flange. These longitudinal T-slots project inward horizontally on each side an appropriate distance, to correspond to an appropriate center distance from the vertical centerline, to receive two mounting plate guide keys with integral shafts (15) and mounting plate guide keys (17). The large shoulder flange face has two shallow recesses 1 5/16 inches wide located an appropriate distance from the horizontal centerline, and parallel with it. The remaining part of the face serves as a bearing for the lower surfaces of two mounting plates (5) retained with two mounting plate guides (18). The mounting plate guides are mounted parallel to the horizontal centerline, on opposite sides, and are secured with three lockscrews (29) each. The mounting plates (5) are moved against each other over the bearing faces of the large shoulder flange of this sliding track with their sides under the mounting plate guides (18).

The sliding track has a cylindrical tube section of about 1 foot below the large shoulder flange. Next to the large shoulder flange is a small shoulder to receive the small counterbored section in the operating gear (1). Sections of the external diameter are undercut to provide only the necessary bearing surface for the operating gear (1) and the track sleeve (2) over this tube section. The lower part is threaded a short distance to receive two lock rings (11).

  b. Operating gear. The operating gear (1) is made of cast phosphor bronze and is 2.687 inches in length. It is machined cylindrical with a large shoulder flange in the upper part. It is counterbored in the center part of the bore to provide only sufficient bearing surface over the bearing section shoulders of the sliding track (3). The large shoulder flange is counterbored a shallow depth, and is a sliding fit over the small shoulder next to the shoulder flange of the sliding track (3).

The large shoulder flange has two cam grooves of appropriate depth and width in its face, which extend 1 degree beyond the vertical centerline. This 1 degree extension provides sufficient clearance for the cam shoes (4) which have centers in the vertical centerline of the operating gear (1) at zero displacement of the lower (split) objective lens (16 and 17, Figure 4-22). Using the vertical centerline as a reference, these two cam grooves are machined 153 degrees circumferentially on opposite sides starting 180 degrees apart.

The operating gear fits over the bearings of the sliding track (3) with its large shoulder flange making a metal-to-metal bearing contact with the lower face of the sliding track large shoulder flange. It is retained from axial displacement on the sliding track by an operating gear retaining ring (35) which is secured with four lockscrews (25).

The periphery section below the large shoulder flange has two shoulders, one near the center inch wide and the other at the lower part. The center shoulder has 160 teeth of 32 pitch cut around its periphery, which engage with an assembled operating gear pinion (12) that projects upward from the bearing projection of the track sleeve (2) on the operating gear pinion shaft (13).

The operating gear stop (19) is assembled to the lower shoulder of the operating gear (1) so that its centerline is 22 degrees from the reference line, and is secured with two lockscrews (30) in tapped holes in the lower shoulder of the operating gear (1). When the cam shoes (4) are at the limit of their travel, the operating gear is reversed 0.125 inch. At this position of the operating gear (1), a line is scribed on the operating gear retaining ring (35). At this line, the maximum displacement stop (20) is secured to the retaining ring with two lockscrews (30). The scribed line is the

 
106

point of contact of the operating gear stop (19) and the maximum displacement stop (20).

The observation position stop (20) is secured during the process of collimation. (Refer to Section 4V11 Step, 25.)

c. Track sleeve. The track sleeve (2) is made of cast phosphor bronze and is 11.827 inches in length. The upper part has a cast rectangular bearing projection that extends upward from the shoulder flange, and is provided with a reamed hole in its center axis which serves as a bearing for the operating gear pinion shaft (13).

The main body is machined cylindrical with two cast hinge projections located 180 degrees apart, a short distance from the upper shoulder flange. One raised section of appropriate size, at a perpendicular plane to the two hinge projections, serves as a mount for the detent pawl spring (6). A circumferential slot 128 degrees long and 3/8 inch wide is located in the center of this raised section, with the slot running 64 degrees on each side of the vertical centerline. This circumferential slot receives the detent pawl rest (8) attached to the sliding track (3) with two long and short lockscrews (9 and 10), secured in tapped holes in the sliding track.

The hinge projections have a 1/4-inch slot through their center located in the same plane as the 128 degrees circumferential slot, and reamed holes perpendicular to this slot through the center of the hinge projections on both sides of the 1/4-inch slot. The hinge projections receive the hinge section of two detent pawls (7), with two detent pawl shafts (16) forming the hinge pins, secured with a taper pin (32) each.

The track sleeve is bored and ground with bearings in the upper and lower internal part, a sliding fit over the bearings on the periphery of the sliding track tube section (3). One inch from the upper face it has a counterbore of shallow depth a distance of 6 3/8 inches, allowing a 1-inch bearing in the lower part near the lower end and also in the upper part. The track sleeve is counterbored below the lower bearing a distance of 2.187 inches, to accommodate two sliding track lock rings (11) that secure the sliding track axially. It serves as an alignment support section also with the lower end threaded a 3/4-inch distance, to receive the alignment support section

  and the threaded periphery of the first inner tube section upper end coupling (11, Figure 2-27) and is secured with four lockscrews (23). These lockscrews are inserted into countersunk clearance holes in the lower part of the track sleeve (2) and screwed into tapped holes in the upper alignment support section of the first inner tube section upper end coupling (11).

The lower external part of the track sleeve (2) has a cylindrical shoulder flange, which projects upward with a cored inner wall 1 1/2 inches in length. This wall section is turned to serve as an alignment support section or the lower part of the lower (split) objective lens coupling sleeve (34) fitting up to a shoulder in the lower part. The coupling sleeve is secured to this alignment support section with 15 lockscrews (27). These lockscrews are inserted into countersunk clearance holes in the coupling sleeve and screwed into tapped holes in the alignment support section. A section of the cored section is solid with a reamed hole, having its centerline in the same axis as the extended projection of the upper cast bearing flange, located 180 degrees opposite to the centerline of the raised mount and the radial slot for the detent pawl spring; this reamed hole serves as a bearing for the operating gear pinion shaft (13).

Four tape slots are provided in the bearing flange of the track sleeve (2), two opposite the others, for the prism tilt and change of power shifting wire tapes (38, Figure 4-28). An air line slot is provided at assembly at a perpendicular plane to the tape slots, for the air line section (29, Figure 4-21) extending downward from the second inner tube section (22).

d. Mounting plates. The two mounting plate halves left and right (5) are made of cast phosphor bronze and are 1/2 inch wide. Each is of eccentric design with the inner circumference 0.197 inch offset from the outer diameter, and is bored for light transmission. The design of each complies to the eccentric flange and lower face of the right and left mount halves (1 and 2, Figure 4-22). Each half has a 50 degrees minor chord section removed from the outer circumference and is provided with a narrow shoulder to slide on the bearing face of the sliding track large shoulder flange under the parallel shoulder of the mount guide (18) which is secured with three

 
107

lockscrews (29) in the large shoulder flange of the sliding track (3).

The mounting plates are assembled to the bearing faces of the large shoulder flange of the sliding track (3) for operation with the operating gear (1) in the following manner: The large part of the right mounting plate has a reamed hole to receive the integral long shaft section of the mounting plate guide key (15) inserted from the lower face, and is secured with a taper pin (31) from the periphery of this part. The T design of the mounting plate guide fits in the elongated T-slot in the sliding track large shoulder flange. The integral stub shaft located in the lower part of the mounting plate guide key (15)fits into the reamed hole in the cam shoe (4) located in the cam groove of the operating gear (1) to provide for operation of this half.

The narrow eccentric part of this mounting plate half located on the opposite side, has a tapped hole to receive the lockscrew (28). This lockscrew is inserted into the countersunk clearance hole in the mounting plate guide key (17) and screwed into the tapped hole in this narrow eccentric part. The mount guide keys (15 and 17) located in the sliding track large shoulder flange elongated T-slots provide parallel guidance for this mounting plate half.

The upper face of this mounting plate has two horizontal keyways at a perpendicular plane to vertical movement of this mounting plate to receive the two inserted mount keys (9) of the right mount half (1, Figure 4-22) a sliding fit in the keyways. These keyways provide a positive movement in two directions of the axis, INWARD and OUTWARD, for collimation of the right half of the lower (split) objective lens and mount assembly. This mounting plate half has two tapped holes to receive the stadimeter collimating screws (13) securing the above assembled lens half also with two drilled holes for two dowel pins (15, Figure 4-22) after collimation. The dowel pins provide the factory collimation setting of this collimated lens half.

The upper face of the left mounting plate has one vertical keyway located in the same plane as its movement, to receive the two inserted mount keys (9, Figure 4-22) of this mounting plate half (2) a sliding fit in the keyway. This keyway provides a positive movement in two directions parallel

  to the vertical centerline, INWARD and OUTWARD of the horizontal centerline, for collimation of this mounting plate half.

The left mounting plate half is assembled and secured to the sliding track (3) and operates in similar manner in the opposite direction with the use of the second cam groove of the operating gear (1).

e. Mounting plate guide keys and integral shafts. The two mounting plate guide keys and integral shafts (15) are made of monel metal and are 1.031 inches in length. The long shaft section is integral with the milled T-shaped section. This shaft section fits into each reamed hole in the large part of each eccentric mounting plate and is secured with a taper pin (31). The T-shaped section is 3/8 inch in length and is a sliding fit in the elongated T-slots on opposite sides in the sliding track large shoulder flange.

The stub shaft section is an integral part of the lower part of the T-shaped section and fits into the reamed hole in the cam shoe (4) assembled in the cam groove of the operating gear. The cam shoes on the mounting plate guide keys and integral shafts operating in the cam grooves in the operating gear (1) displace the mounting plate halves laterally.

f. Mounting plate guide keys. The two mounting plate guide keys (17) are made of monel metal and are 3/8 inch in length. They are milled of a T-shape with a countersunk clearance hole in their axis for a lockscrew (28). The lockscrew secures them to the narrow eccentric part of the eccentric mounting plate, extending into the tapped hole in this narrow eccentric part. These guide keys are a sliding fit in the elongated T-slots in the sliding track large shoulder flange and by means of the operating guide keys (15) provide a parallel guidance to the mounting plate halves (5) which carry the lower (split) objective lens and mount assembly halves (Figure 4-22) in the same vertical plane for displacement from minimum to maximum displacement and vice versa.

g. Mounting plate guides. The mounting plate guides (18) are made of monel metal and are 1.750 inches in length. It is a step design with the narrow shoulder having a nominal fit on the shoulder section of each mounting plate

 
108

half (5). They are held to the large shoulder flange face of the sliding track (3) with three lockscrews (29) each. These lockscrews are inserted into countersunk clearance holes in the mounting plate guides (18) and screwed into three tapped holes in opposite sides of the sliding track large shoulder flange (3). These guides allow free movement to each mounting plate half and retain them axially.

h. Cam shoes. The two cam shoes (4) are made of hardened drill rod steel and are 5/16 inch in length. The ends are rounded off to conform to the width of 0.218 inch. A reamed hole in their axis accommodates the integral stub shaft section of the mounting plate guide keys and integral shafts (15). The cam shoes are a sliding fit in each cam groove in the operating gear large shoulder flange (1). The cam shoes operate the mounting plate guide keys (15)-for displacement of the assembled lower (split) objective lens and mount assembly halves (Figure 4-22).

i. Operating gear retaining ring. The operating gear retaining ring (35) is made of old rolled steel and is 1/2 inch in width. It is cylindrical with a nominal wall thickness, and fits over the sliding track tube section (3) up to the lower face of the operating gear (1) and is secured with four lockscrews (25). These lockscrews are inserted into countersunk clearance holes in the retaining ring and screwed into tapped holes in the sliding track (3). It serves to retain the operating gear (1) axially and also serves as a stationary support for the maximum displacement and observation position stops (20) secured with two lockscrews (30).

j. Maximum displacement stop. The maximum displacement stop (20) is made of cold rolled steel 3/4 inch wide and 7/8 inch long. It is a step radius design, with the seat of the stop conforming to the contour of the operating gear retaining ring (35) and secured to it with two lockscrews (30). These lockscrews are inserted in countersunk clearance holes in the thick section of the stop and screwed into tapped holes in the retaining ring (35) and the sliding track. The radius step projects over the lower shoulder of the operating gear with sufficient clearance.

The maximum displacement stop serves to relieve the torque from the two cam shoes (4) in the ends of the cam grooves in the operating

  gear (1) for the necessary additional torque required to rotate the sliding track (3) simultaneously with the operating gear (1) for the 90 degrees rotation from the range position to the course angle position. It also serves to overcome the locking device of the sliding track (3), namely, the detent pawl (7) engaged in the 90 degrees V-groove in the detent pawl rest (8).

k. Observation position stop. The observation position stop (20) is identical to the maximum displacement stop, and is located on the retaining ring (35) during collimation. It serves to relieve the torque from the two cam shoes (4) in the ends of the cam grooves in the operating gear (1) for the necessary additional torque required to rotate the sliding track (3) simultaneously with the operating gear (1) for the 90 degrees rotation from the course angle position back to the range position. It is fitted during collimation (refer to Section 4V11 Step 25) to restrict the movement of the lens halves to zero displacement, that is, to form a single image.

l. Operating gear stop. The operating gear stop (19) is of similar design and material to the maximum displacement and observation position stops (20). The seat of the stop conforms to the contour of the lower shoulder of the operating gear (1) and is secured with two lockscrews (30). These lockscrews are inserted into countersunk clearance holes in the thick section of the stop and screwed into tapped holes in the lower shoulder of the operating gear. The radius step projects over the operating gear retaining ring (35) with sufficient clearance. This stop is secured to the operating gear with its centerline located 22 degrees from the reference line of the cam groove. This allows sufficient movement of the operating gear for minimum and maximum displacement of the lower (split) objective lens. This stop overlaps the maximum displacement stop (20) for clockwise rotation to carry the sliding track (3) simultaneously with the operating gear (1) through the 90 degrees rotation from the range position to the course angle position. It overlaps the observation position stop (20) for the counterclockwise rotation to carry the sliding track (3) simultaneously with the operating gear (1) through the 90 degrees rotation from the course angle position back to the range position.

m. Operating, gear pinion. The operating gear pinion (12) is made of phosphor bronze and

 
109

is 1.531 inches in length. It is cylindrical in design with a large hub section in the upper part which is filleted at a radius of 1.750 inches in a distance of 5/16 inch to conform to the circumference of the gear cutter used in cutting the teeth in the lower large diameter. The large diameter of the pinion section has 20 teeth of 32 diametral pitch, cut in a pinion section 0.718 inch long. The lower part of this pinion section is undercut to the root of the gear teeth and chamfered.

The axis is provided with a reamed hole, a push fit over the upper part of the operating gear pinion shaft (13). The reamed hole has an undercut groove 1/16 inch wide located above the upper end of the pinion section, to serve as a relief for the insertion of a keyseat 0.063 inch wide and 0.036 inch deep. This keyseat allows the pinion to slide over the inserted woodruff key (21) in the upper part of the operating gear pinion shaft (13). The hub section is provided with two tapped holes directly on opposite sides for two lockscrews (24). These lockscrews are inserted in tapped holes in the pinion and extend into spotted recesses in the operating gear pinion shaft (13) at assembly to secure the pinion.

The operating gear pinion teeth mesh with the teeth in the operating gear (1) for its operation.

n. Operating gear pinion shaft. The operating gear pinion shaft (13) is made of cold rolled steel rod and is 14.625 inches in length and 5/16 inch in diameter. It is provided with a woodruff keyseat located near the upper end, for a number 10 woodruff key (21). The operating gear pinion (12) with a keyseat is a push fit on the upper part of this shaft and is secured with two lockscrews (24). This shaft fits through the reamed hole in the cast projection located in the upper part of the track sleeve (2) and the reamed hole in the solid section in the cored alignment support section of the lower part.

The lower part of the shaft receives the upper part of the stadimeter transmission shaft coupling (14) secured with a taper pin (33) during collimation.

o. Stadimeter transmission shaft coupling. The stadimeter transmission shaft coupling (14) is made of phosphor bronze and is 1.812 inches in length. It is 5/8 inch in diameter, with the axis provided with two reamed holes. The

  upper part is reamed to fit on the lower part of the operating gear pinion shaft (13) and is secured with a taper pin (33). The lower part is reamed to receive the upper part of the stadimeter transmission shaft (22, Figure 4-27) and is secured with a taper pin (33) during collimation. The lower part is provided with three irregular tapped holes at assembly for the insertion of 8-36 setscrews used primarily to secure the coupling to the stadimeter transmission shaft (22, Figure 4-27) during collimation, and the taper pin provision is made upon completion of collimation.

p. Detent pawl rest. The detent pawl rest (8) is made of tool steel and is 1 5/8 inches in length. Its bottom face conforms to the contour of the sliding track periphery (3), while the upper faces on each side of the horizontal centerline are beveled to 27 1/2 degrees. It is a sliding fit in the milled 128 degrees circumferential slot in the track. sleeve (2). A 90 degrees V-groove is provided in the horizontal centerline to a depth of 0.407 inch, for the engagement of the detent pawls (7) for the range and course angle positions. The opposite ends of the detent pawl rest are finished to approximately 38 degrees or 19 degrees on each side of the horizontal centerline to contact each end in the 128 degrees circumferential slot, when the operating gear (1) and the sliding track (3) have rotated 90 degrees. The opposite ends of the detent pawl rest are finished off at assembly and the collimation procedure of the 90 degrees rotation. A dowel pin of a body fit is inserted in the hole in the center of the 90 degrees V-groove and fitting into the snug hole in the sliding track, is inserted for proper location of the four tapped holes. The detent pawl rest is secured to the periphery of the sliding track (3) through the circumferential slot with two long and short lockscrews (9 and 10). These lockscrews are inserted into countersunk clearance holes in the detent pawl rest (8) and screwed into tapped holes of the sliding track (3).

q. Detent pawls. The detent pawls (7) are made of tool steel and are 2 1/2 inches in length. The arms of each detent pawl are 1/4 inch wide and 5/32 inch thick. The detent section is enlarged to 3/8 inch in width and inclined at an angle of 22 degrees of the arm section. Its engaging detent section of 90 degrees engages in the 90 degrees V-groove in the detent pawl rest (8), to maintain it at the 90 degrees rotation position under spring tension.

 
110

The lower part of the detent pawl arm section is enlarged inward, thus forming a partial circle of 7/16-inch diameter, with a reamed hole to receive the detent pawl shaft (16). The circle section fits in the milled slot between both hinge projections, with the shaft inserted in the reamed holes in the hinge projections and the circular section. Each of the two shafts is secured with a taper pin (32) in the lower hinge projections.

The detent pawls for the range and course angle positions are retained in the 90 degrees V-groove under spring pressure by the detent pawl spring secured to the raised mount section on each side of the 128 degrees circumferential slot with six lockscrews (26).

r. Detent pawl shafts. The detent pawl shafts (16) are made of cold rolled steel and are 0.812 inch in length. These shafts fit into reamed holes in the two sets of hinge projections of the track sleeve (3) and are secured with a taper pin (32) after assembly. These shafts serve as a pivot pin on which the circular section of the detent pawls pivot for engagement and disengagement in the detent pawl rest (8).

s. Detent pawl spring. The detent pawl spring (6) is made of 17-gage blued spring steel. The center part is 1 inch in width, to extend over the width of the raised mount section on each side of the circumferential slot. Each side of the spring starting from 3/4 inch of the center is filleted to 14 inch width, a proportional amount on each side. The spring is bent from the filleted point inward to a radius of 1.500 inch, on each side with an outward radius bend of 3/16 inch. It is oil hardened in this form, and when assembled it overlaps to contact the 22 degrees angle outer section of both detents. It is secured on this section of the detent pawls (7) to the raised mounts on each side of the circumferential slot with three lockscrews (26). These lockscrews are inserted in clearance holes in this spring and screwed into tapped holes in the raised mount on opposite sides of the 128 degrees circumferential slot.

t. Sliding track lock rings. The two sliding track lock rings (11) are made of cast phosphor bronze 5/16 inch wide. The rings are cylindrical, and are a sliding fit in the counterbore of the track sleeve. The inner surface is threaded to screw can the threaded periphery of the sliding track (3). These rings preserve the axial thrust

  clearance of the sliding track (3) in the track sleeve (2). Each is provided with opposite slots in the lower side face for insertion of a special wrench. The lower of the two lock rings (11) is secured against the upper by a lockscrew (36). This lockscrew screws into the tapped hole in the threaded intersection of the lower face of the lock ring and the sliding track, and thus prevents axial displacement of the sliding track (3) in the track sleeve (2).

u. Coupling sleeve. The coupling sleeve (34) is made of brass tubing material 14.875 inches in length. The inner and outer diameters of this coupling sleeve are uniform throughout its length. This sleeve section forms the outer wall to enclose the lower (split) objective lens and mount assembly (Figure 4-22) and the objective operating mechanism assembly. It also connects the upper telescope system assembly Part II (Figure 4-21) with the lower main telescope system. Connection is made after primary and final collimation of the periscope.

The upper part has an internal threaded section 1 1/4 inches in length to screw on the threaded periphery and lower alignment support section of the second inner tube section lower end coupling (26, Figure 4-21) and is secured with four lockscrews (22). These lockscrews are inserted in, countersunk clearance holes in the upper part of the coupling sleeve (34) and screwed into tapped holes in the lower alignment support section of the second inner tube section lower end coupling (26, Figure 4-21).

The inner wall is provided with an 11-inch axial recess groove with a 3/4-inch radius. This axial recess groove starts at the lower end of the coupling sleeve. The center of the radius is located 19 degrees 30' from the horizontal centerline of the prism tilt shifting wire tape slots. The radius is cut to a depth of 0.050 inch in the inner wall. This axial recess groove provides clearance for the operating gear pinion (12) which is necessary to permit the lower telescope system to be pulled axially clear of the coupling sleeve for disassembly or vice versa.

Four vertical tape slots are provided in the outer circumference, two opposite the others for the entire length, for the prism tilt and change of power shifting wire tapes (38, Figure 4-28). An air line slot is provided its entire length at a

 
111

perpendicular plane to the tape slots for the air line section (29, Figure 4-21) extending downward from the second inner tube section (22).

The lower part is a push fit over the alignment support section of the lower shoulder flange of the track sleeve (2) and is secured with 15 lockscrews (27). These lockscrews are inserted into countersunk clearance holes in the lower part of the coupling sleeve and screwed into tapped holes in the alignment support section of the lower shoulder flange of the track sleeve (2).

4-16. Disassembly of the objective operating mechanism assembly. The objective operating mechanism is disassembled in the following manner:

1. Remove the six lockscrews (26) from the detent pawl spring (6). These lockscrews are unscrewed from tapped holes in the raised mount of the track sleeve (2). Remove the detent pawl spring.

2. Remove the taper pins (32) from the lower two hinge projection sets of the track sleeve (2) to free the detent pawl shafts (16). Drive these shafts upward through the clearance hole in the upper shoulder flange of the track sleeve, removing the detent pawl shafts (16) and the detent pawls (7).

3. Remove the two long and two short lockscrews (9 and 10) from the detent pawl rest (8) and remove the detent pawl rest from its insertion in the circumferential slot of the track sleeve (2). The lockscrews are unscrewed from tapped holes in the periphery wall of the sliding track (3).

4. Remove the lockscrew (36) from the tapped hole in the threaded intersection of the lower face of the lower sliding track lock ring (11) and the sliding track (3). Unscrew the lower lock ring (11) which is a tap fit, using a special wrench. Then unscrew the upper of the two lock rings (11) in the same manner.

5. Remove the sliding track (3) from the track sleeve (2). At the same time, remove the assembled operating gear pinion (12) and shaft (13). The operating gear pinion and shaft must be removed with the sliding track to prevent damage to these parts.

  6. Remove the two lockscrews (24) from opposite sides of the operating gear pinion (12). Pull the operating gear pinion off the operating gear pinion shaft (13). The woodruff key (21) remains in the shaft.

7. Remove the two lockscrews (30) from the maximum displacement stop (20). These lockscrews are unscrewed from tapped holes in the operating gear retaining ring (35) and the sliding track (3).

8. Remove the two lockscrews (30) of shorter length from the observation position stop (20). These lockscrews are unscrewed from tapped holes in the operating gear retaining ring (35).

9. Remove the four lockscrews (25) from the operating gear retaining ring (35). These lockscrews are unscrewed from tapped holes in the sliding track (3). Remove the retaining ring.

10. Remove the operating gear (1) from the tube section of the sliding track (3).

11. Remove the two lockscrews (30) from the operating gear stop (19). These lockscrews are unscrewed from tapped holes in the lower shoulder of the operating gear (1).

12. Remove the two cam shoes (4) from the stub shaft of the two mounting plate guide keys and integral shafts (15), or lift them from the cam grooves in the operating gear (1).

13. Remove the two lockscrews (29) from each, of the two mounting plate guides (18). These lockscrews are unscrewed from tapped holes in the large shoulder flange on opposite sides of the sliding track (3). Remove the two mounting plate guides.

14. Remove the two lockscrews (28) from the two mounting plate guide keys (17). These lockscrews are unscrewed from tapped holes in the narrow eccentric section of the two mounting plate halves (5). Remove the mounting plate guide keys from the T-slots on opposite sides of the sliding track (3).

15. Carefully slide out each mounting plate half (5) with the mounting plate guide keys and integral shafts (15), moving them outward in opposite directions from the T-slots on opposite sides of the sliding track (3).

 
112

16. Remove the two taper pins (31) from the large eccentric section of the two mounting plate halves (5). Drive out the two mounting plate guide keys and integral shafts (15) from both mounting plate halves.

4J7. Reassembly of the objective operating mechanism assembly. The objective operating mechanism is reassembled in the following manner:

1. Apply Lubricate No. 110 lightly to all rotating parts as the reassembly procedure is followed.

2. Assemble the mounting plate guide keys and integral shafts (15) in the reamed holes in the large eccentric art of the two mounting plate halves (5) checking their corresponding reference marks for proper assembly. The long section of the integral shaft sections is inserted from the lower face. Each is secured with a taper pin (31).

3. Stand the sliding track (3) in a vertical position resting it on its lower face. Place one and then the other of the two mounting plate halves on the large shoulder flange face of the sliding track (3). Carefully slide the mounting guide keys of the assembled integral shafts into the elongated T-slots in opposite directions, noting the reference marks for correct reassembly.

4. Assemble one and then the other of the mounting plate guide keys (17) in the elongated T-slots on opposite sides of the sliding track large shoulder flange face (3). Secure each with a lockscrew (28) screwing them into the tapped holes in the narrow eccentric part of the two mounting plate halves (5).

5. Place one and then the other of the two mounting plate guides (18) over the side shoulder of each mounting plate half (5), noting their reference marks on the sliding track large shoulder flange face (3). Secure each with three lockscrews (29) screwing them into tapped holes in the large shoulder flange on opposite sides. The mounting plate guides are placed 180 degrees apart.

6. Place the two cam shoes (4) on the two mounting plate guide keys and integral stub shafts (15), placing the thinner wall of the cam shoe outward on each side.

  7. Place the operating gear (1) over the tube section of the sliding track (3). The upper face of the operating gear large shoulder flange contacts the lower face of the sliding track large shoulder flange, and the two cam shoes (4) are fitted into the cam grooves in the operating gear (1). The proper position of the operating gear (1) for its contact with the sliding track shoulder large flange (3) is obtained from corresponding reference marks on the sliding track.

8. Place the operating gear retaining ring (35) on the tube section of the sliding track (3). Check to ascertain that the 10 degrees rotation scribe lines coincide with similar scribe lines on the operating gear shoulder, and that lockscrew holes coincide. Secure the retaining ring with four lockscrews (25) which screw into tapped, holes in the sliding track (3).

9. Assemble the operating gear stop (19) to the operating gear lower shoulder section and secure it with two lockscrews (30). These lockscrews are screwed into tapped holes in this lower shoulder section.

10. To assemble the maximum displacement stop (20) to the retaining ring (35), first rotate the operating gear (1) until the cam shoes (4) are at the limit of their travel; scribe a line on the operating gear lower shoulder section and the retaining ring (35). Reverse the operating gear 0.125 inch and note the tapped holes in the retaining ring (35). Secure this stop with two lockscrews (30) screwing them into the tapped holes in the retaining ring (35) and the sliding track (3).

11. The observation position stop (20) is located and secured to the retaining ring (35) during the procedure of collimation. (Refer to Section 4Vll, Step 25.)

12. Place the operating gear pinion (12) on the operating gear pinion shaft (13) sliding it over the inserted woodruff key (21) located in the upper part of this shaft. Secure the pinion with two lockscrews (24), screwing them into tapped holes in opposite sides of the pinion and into spotted recesses in the shaft.

13. Check the reference marks of the operating gear pinion teeth (12) for corresponding reference marks on the operating gear teeth (1) and engage the pinion in mesh with the teeth of the

 
113

Figure 4-24. Stadimeter housing assembly.
Figure 4-24. Stadimeter housing assembly.
 
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operating gear. Holding, the pinion in mesh, place the operating gear (1) and the operating gear pinion (12) together in the track sleeve (2). The operating gear pinion shaft enters the reamed hole of the bearing projection before the tube section of the sliding track enters the track sleeve. This method permits correct alignment for the assembly of the stadimeter transmission shaft coupling (14) so that the taper pins (33) can be inserted correctly in relation to the position of the upper part of the stadimeter transmission shaft (22, Figure 4-27).

14. Place the sliding track lock rings (11) in the counterbore of the track sleeve. The upper ring has a slight counterbore. Screw this lock ring on the threaded periphery of the sliding track (3) and between the overlapping section of the track sleeve (2) using a special wrench until it comes up tight. Tap it lightly. Place the lower lock ring (11) on in the same manner. When this lock ring is tightened sufficiently against the upper lock ring, the tapped recesses of the lock ring and sliding track intersection (3) should coincide, forming a tapped hole. Insert the lockscrew (36) in this tapped hole in the threaded intersection. If the tapped recesses do not coincide, the upper ring requires further tightening.

15. Place the detent pawl rest (8) in the 128 degrees circumferential slot. A dowel pin fits into its aligning hole in the sliding track (3) and will fit only one way. Secure the detent pawl rest to the periphery of the sliding track (3) with two long and two short lockscrews (9 and, 10). These lockscrews are inserted into countersunk clearance holes in the detent pawl rest and screwed into tapped holes in the sliding track. The true 90 degrees rotation of this objective operating mechanism assembly must be checked on the V-blocks of an optical I-beam bench before collimation.

16. Place the detent pawls (7) which have reference marks to correspond to hinge projections of the track sleeve (2) at their respective places. Insert the detent pawl shafts with similar reference marks, through the reamed holes in the track sleeve shoulder flange, and carry them into the reamed holes in the hinge projections and the detent pawls. Secure each shaft

  with a taper pin (32) inserted in the lower part of each set of hinge projections.

17. Place the detent pawl spring (6) over both detent pawls (7). Secure it with six lockscrews (26), screwing three of these lockscrews into tapped holes in each raised mount on opposite sides of the circumferential slot.

18. Check the 90 degrees rotation before reassembly of the lower (split) objective lens and mount assembly halves (Figure 4-22) to the objective operating mechanism assembly.

4J8. Description of the stadimeter housing assembly. The stadimeter housing assembly is constructed as follows. (Figure 4-24 shows the stadimeter housing assembly.) All bubble numbers in Sections 4J8, 9, and 10 refer to Figure 4-24 unless otherwise specified.

Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
1 P-1159-11 1 Handwheel key
2 P-1159-12 1 Transmission gear pinion
3 P-1159-13 1 Handwheel shaft bevel gear
4 P-1159-14 1 Long transmission shaft
5 P-1159-17 1 Transmission shaft bevel gear
6 P-1159-18 1 Handwheel bracket
7 P-1163-10 8 Length of target scale mount retaining screws
8 P-1169-2 2 Scale ball bearing housings
9 P-1169-3 2 Scale housings
10 P-1169-4 2 Range scale actuating bevel gear pinions (front and rear)
11 P-1169-8 2 Range scale actuating bevel gears (front and rear)
12 P-1170-2 1 Handwheel
13 P-1170-13 2 Spring handle hinge screws
14 P-1171-1 4 Scale and transmission ball bearings
15 P-1171-16 2 Index line plates
16 P-1171-17 2 Length of target scale clamp screws
17 P-1171-18 4 Length of target scale knobs
18 P-1172-1 2 Length of target scale clamp screw retaining collars
19 P-1172-2 2 Length of target scale clamp screw retaining collar rivets
20 P-1172-3 5 Transmission ball bearings
21 P-1172-4 2 Transmission ball bearing housings
22 P-1172-5 2 stadimeter housing dowel pins
23 P-1172-6 1 Handwheel shaft
 
115

Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
24 P-1172-7 1 Spring handle stud
25 P-1172-8 1 Spring handle
26 P-1172-9 1 Spring handle plunger
27 P-1172-10 1 Spring handle plunger nut
28 P-1172-11 1 Spring retaining nut
29 P-1172-12 1 Plunger spring
30 P-1172-13 4 Stadimeter housing bolts
31 P-1172-15 1 Transmission shaft pinion bevel gear key
32 P-1172-17 2 Front and rear range scale actuating bevel gear ball bearings
33 P-1179-37 4 Star wheel lock plunger housing lockscrews
34 P-1179-46 6 Stadimeter housing cover plate lockscrews
35 P-1179-50 1 Handwheel lockscrew
36 P-1179-60 1 Transmission shaft pinion bevel gear lockscrew
37 P-1179-68 4 Handwheel bracket lockscrews
38 P-1179-69 4 Index line plate lockscrews
39 P-1179-70 8 Height scale mount lockscrews
40 P-1179-71 8 Range scale mount lockscrews
41 P-1179-72 8 Ball bearing housing lockscrews
42 P-1179-73 16 Scale housing lockscrews
43 P-1179-74 32 Various dial lockscrews
44 P-1179-197 4 Transmission gear pinion, handwheel shaft bevel gear, star wheel, and star wheel key taper pins
45 P-1179-198 2 Front and rear range scale actuating gear pinion taper pins
46 P-1179-200 8 Scale dowel pins
47 P-1184-1 2 Length of target scale mounts
48 P-1184-2 2 Length of target scale dials
49 P-1184-3 2 Range scale mounts
50 P-1184-4 2 Range scale dials
51 P-1184-5 2 Height scale mounts
52 P-1184-6 2 Height scale dials
53 P-1264-2 1 Short transmission shaft
54 P-1264-3 1 Transmission gear pinion
55 P-1264-4 1 Transmission gear pinion lockscrew
56 P-1264-5 1 Transmission gear pinion
57 P-1310-37 4 Pinion ball bearing retainer lockscrews
58 P-1310-202 2 Transmission shaft pinion thrust collar and female tang coupling taper pins
59 P-1316-1 1 Star wheel
 
Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
60 P-1316-2 1 Star wheel key
61 P-1316-3 1 Star wheel key holder
62 P-1316-4 1 Star wheel lock plunger
63 P-1316-5 1 Star wheel lock plunger spring
64 P-1316-6 1 Star wheel lock plunger housing
65 P-1316-7 1 Transmission shaft pinion
66 P-1316-10 1 Transmission shaft pinion thrust collar
67 P-1404-1 1 Stadimeter housing
68 P-1409-6 1 Female tang coupling
69 P-1409-9 1 Housing cover plate
70 P-1409-10 1 Ball bearing retainer
71 P-1422-3 2 Lower pointer knob lockscrews
72 P-1422-10 6 Upper pointer lockscrews
73 P-1429-1 2 Upper pointers
74 P-1429-2 2 Upper pointer knobs
75 P-1429-3 2 Pointer shoulder screws
76 P-1429-4 2 Lower pointer collars
77 P-1429-5 2 Spring washers
78 P-1429-6 2 Lower pointers
79 P-1429-7 2 Lower pointer knobs
80 P-1429-8 2 Brass friction washers
81 P-1429-9 2 Felt friction washers
82 P-1448-7 2 Alemite fittings

a. Stadimeter housing. The stadimeter housing (67) is made of cast phosphor bronze. It consists of a cored rectangular box section called the center section, with front and rear projections forming a part of the casting. These are called the front and rear scale housings. The center section carries the transmission mechanism to operate the scale dial mechanisms of the front and rear housings simultaneously with the various interconnecting shafts and couplings to operate the objective operating mechanism assembly (Figure 4-23) and the lower (split) objective lens and mount assembly (Figure 4-22) as a single unit called the stadimeter.

The walls of the center section are of rectangular design and have their outer four corners beveled. The inner four corners of this section are filleted inward sufficiently to accommodate clearance holes for the four stadimeter housing bolts (30). These bolts, inserted from the four spot faced corners of the base, secure the stadimeter housing to the eyepiece box (11, Figure 4-29). There are two dowel pins (22) inserted in the upper wall face which are located

 
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diagonally to insure a rapid reference for reassembly of this housing. These dowel pins are a force fit into the reamed holes in the eyepiece box base (11, Figure 4-29).

An inward projecting semi-circular lug of sufficient thickness provides the necessary support for the transmission shaft pinion (65) and its perpendicular, supporting parts, for interconnection with the stadimeter transmission shaft (22, Figure 4-27), of the first inner tube section assembly. Directly below this semicircular lug, in the base of the center section, a semi-circular raised section accommodates the lower supporting parts of the transmission shaft pinion (65).

A raised section shaped like the letter G, 0.937 inch in height, is supported by a narrow rib from the front filleted corner, extending forward from the inner rear wall of the center section. This part, having ample wall thickness, accommodates the three way interconnection of the transmission, by means of four mounted ball bearings (14 and 20).

The lower part of the stadimeter housing is cored inward to the center part, with supporting ribs to the front and rear scale housing section walls. The center section and lower face are bored, faced, and threaded. The lower fate of this section contacts the bumper located in the well of the submarine. At various times it is necessary, because of the construction of a submarine, to insert a filler piece in the threaded section in the lower center part of the stadimeter housing base.

The front, rear, and right side walls of the center section have openings to accommodate ball bearings for the operation of the transmission and the front and rear scale housing mechanisms. The lower wall of each scale housing section has a tapped hole to receive alemite fittings (82) for the introduction of grease.

b. Handwheel. The handwheel (12) is made of cast phosphor bronze. It is of sufficient. diameter to permit easy operation of the stadimeter, with the periphery scalloped. The inner scalloped circumference is cored and allows only sufficient wall thickness for six of the scallops. Three of the scallops of one section are solid for the assembly of a spring handle.

  This assembly is swung vertically or horizontally at will by the observer, and is locked in either position by means of a plunger under spring pressure, extending into clearance holes in the inner wall of the remaining wall of the machined scallop. This spring handle when swung horizontally, provides the observer with a means for rapid turning of the handwheel if desired. One scallop opposite the spring handle assembly is solid to balance the handwheel for the increased weight.

The inner wall of the handwheel is scored with four flat spokes which project inward to the hub section and have a square appearance. The hub section is filleted toward its diameter, and has a reamed hole and a keyseat to receive the outer part of the handwheel shaft (23) with an inserted key (1). The handwheel is secured to the handwheel shaft with a lockscrew (35). This lockscrew is inserted into a tapped hole in the handwheel hub section and extends into a spotted recess, thus preventing the handwheel from coming off the shaft.

The center of the three solid scallops is machined out to receive the hinge section of the spring handle stud (24) and its cylindrical shoulder. This milled out section is provided with sufficient clearance to allow the spring handle stud (24) to rotate 90 degrees. It is secured in the handwheel by two spring handle hinge screws (13). These screws fit into countersunk tapped holes located on opposite sides of the machined scallop in the periphery, with their centerline offset from the scalloped periphery wall 1/16 inch. Two clearance holes are provided in this machined scallop, located 90 degrees apart, for the spring handle plunger (26). This allows the spring handle assembly to be locked in either the extended or folded position.

c. Spring handle stud, plunger, plunger spring, spring retaining nut, and spring handle. 1. Spring handle stud. The spring handle stud (24) is made of rolled bronze and is nickel plated. The hinge section is square with the corners rounded off to provide 90 degrees rotation in the milled section of the handwheel (12). Two opposite reamed holes in this section serve as pivot bearings for the spring handle hinge screws (13) which extend from countersunk tapped holes in the scalloped periphery

 
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into reamed holes in each wall of the hinge section. The undercut section of the screws fits into the reamed holes. The outer surface of the main body carries the spring handle (25) up to "the narrow shoulder. The diameter of the shoulder conforms to the diameter of the contacting part of the spring handle.

The inner surfaces are provided with two reamed holes, the smaller of which receives the shorter stem of the spring handle plunger (26), and the larger receives the narrow shoulder section of the spring handle plunger and the plunger spring (29). The outer part of the large reamed hole is threaded 1/8 inch deep to receive the spring retaining nut (28) to compress the plunger spring.

2. Spring handle plunger. The spring handle plunger (26) is made of monel metal and is 2 5/8 inches long. The shorter stem which is 1 5/16 inch long is rounded off at the end; this section extends from the reamed hole in the spring handle stud (24) under tension of the plunger spring (29) to snap into either of the 90 degrees clearance holes in the handwheel (12) to retain the assembled spring handle in the extended or folded position.

The narrow shoulder section of the handle is a sliding fit in the large reamed hole in the spring handle stud (24) with the plunger spring (29) fitting over the long stem section against the narrow shoulder section. The plunger spring under tension carries this shoulder to the bottom of the large reamed hole. The outer part of the long stem section is undercut and threaded, and carries the small reamed and countersunk outer part of the spring handle, securing it with a plunger nut (27).

3. Plunger spring. The plunger spring (29) is made of No. 16 gage music wire and is 3/4-inch free length. The spring fits over the long section of the spring handle plunger (26) and is placed under a nominal tension by the spring retaining nut (28) to retain the narrow shoulder section of the plunger against the bottom shoulder of the large reamed hole. Sufficient compression of the spring allows the short section of the plunger to be released from the locking clearance holes in the handwheel (12).

4. Spring retaining nut. The spring retaining nut (28) is made of rolled bronze and is

  1/8-inch thick. It is cylindrical and has a threaded periphery to screw into the threaded outer part of the spring handle stud (24). It has a reamed hole in its axis to allow the long section of the plunger a sliding fit. Two shallow drilled holes are provided in the side face for a special wrench. The retaining nut compresses the plunger spring (29) normally and is secured tightly in the bottom of the threaded outer part of the spring handle stud.

5. Spring handle. The spring handle (25) is made of rolled bronze and is nickel plated. It is of sufficient length with the outer corners rounded off. The outer surface has a 1/2-inch knurled band to offer a firm grip to the observer.

The inner surface has a reamed hole which is countersunk in the outer part. The reamed hole is a sliding fit over the long section of the spring handle plunger (26). It is counterbored a sliding fit over the main body of the spring handle stud (24), and is secured with nominal clearance by a plunger nut (27). The plunger nut is a sliding fit in the outer countersunk reamed hole in the outer part, and is slotted in its side face for a special wrench. The upward movement of the spring handle against spring tension causes its countersunk face to contact the plunger nut (27) which is attached to the spring handle plunger (26) thus carrying the plunger outward, compressing the plunger spring (29), and removing the short stem section of the plunger from its locked position in the handwheel (12). Once the plunger is released from its locked position, it automatically snaps into the opposite locked position upon rotation and when lined up for proper engagement.

d. Handwheel bracket and shaft. 1. Handwheel bracket. The handwheel bracket (6) is made of phosphor bronze and is 5/8 inch in length. The large diameter of the shoulder flange is of nominal thickness and is filleted to the hub section. It is secured to the right side wall of the stadimeter housing center section with four lockscrews (37). These lockscrews are inserted in countersunk clearance holes and screwed into tapped holes in the center section wall. The inner surface has a reamed hole for the handwheel shaft (23) and a shallow counterface to allow clearance over the ball bearing (20) extending from the alignment counterface

 
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of the center section wall. The small raised alignment shoulder of the bracket is a push fit into the alignment counterface. The bracket serves as a support for the weight of the handwheel (12) and the protruding part of the handwheel shaft (23). It also prevents foreign matter from entering the ball bearing (20).

2. Handwheel shaft. The handwheel shaft (23) is made of corrosion-resisting steel rod and is 7 1/8 inches in length. The outer part of the shaft is provided with a keyway for the insertion of a handwheel key (1), and receives the handwheel (12) which is secured with a lockscrew (35) that protrudes from the tapped hole in the handwheel hub and extends into a spotted recess in the shaft. This shaft is mounted in three ball bearings (20), with the first ball bearing in the right side wall of the center section. The shaft protrudes into the center section from the right side wall of the stadimeter housing. In the center section, a nominal distance from the inner right wall, a star wheel (59) is secured to the handwheel shaft (23) with a taper pin (44) inserted through the hub section. This section faces the inner wall. A star wheel lock plunger housing (64) is provided between the star wheel (59) and the next ball bearing (20).

The second ball bearing (20) is a push fit over the handwheel shaft (23) and is mounted in a transmission ball bearing housing (21). The housing is secured to the lower part of the raised G-wall in the center section with two lockscrews (41). These lockscrews are inserted into countersunk clearance holes in the housing and screwed into tapped holes in the raised G-wall section.

Directly inward of this mounted ball bearing (20), a handwheel shaft bevel gear (3) is attached to the handwheel shaft with a taper pin (44) inserted through the hub section. This section faces the second ball bearing (20).

The shaft is mounted a push fit in the third ball bearing (20) mounted in a housing (21) which is secured to the upper part of the raised G-wall section in the center section. The housing is secured to this wall face with two lockscrews (41). These lockscrews are inserted into countersunk clearance holes in the housing and screwed into tapped holes in this raised G-wall section face.

  Directly outward of this ball bearing on the opposite end of the handwheel shaft, a woodruff keyway is cut in this stub section, to accommodate a No. 10 woodruff key (31). This woodruff key is inserted in the stub section to receive the transmission shaft bevel gear (5). This bevel gear is secured to the handwheel shaft (23) by means of a lockscrew (36). The lockscrew is inserted into a tapped hole in the bevel gear hub section and extends into a spotted recess in the shaft.

The handwheel shaft mounted in three ball bearings, operates the front and rear scale housing mechanisms by means of the handwheel shaft bevel gear (3) which engages with the front and rear transmission gear pinions (2 and 54). It also operates the objective operating mechanism assembly by means of the transmission shaft bevel gear (5) which engages with the transmission gear pinion (65). Both of the scale housing mechanisms and the transmission shaft pinion are rotated simultaneously as the handwheel (12) operates the handwheel shaft (23) for clockwise or counterclockwise rotation.

e. Transmission shaft pinion. The transmission shaft pinion (65) is made of corrosion resisting steel and is 2.933 inches in length. The pinion is cut as an integral part of the shaft. It has 26 bevel teeth of 32 diametral pitch which mesh at right angles with 54 bevel teeth of the transmission shaft bevel gear (5). This transmission shaft pinion is mounted vertically in the center section at right angles to the handwheel shaft (23) and parallel to its centerline.

A part of the long section of the pinion shaft is undercut below the pinion to allow clearance for cutting of the bevel teeth. The lower part of the pinion shaft is a push fit in a ball bearing (20) which in turn is a push fit in the raised semicircular section in the lower wall of the center section. The upper part of the stub shaft section above the pinion is mounted a push fit in a ball bearing (20), which in turn is mounted a push fit into the semicircular lug section of the center section projecting inward. The face of this semicircular lug section is provided with a ball bearing retainer (70) secured with four lockscrews (57).

The upper part of the stub shaft section is cut away a depth of 3/8 inch forming a male tang

 
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section far the assembly of a female tang coupling (68) secured snugly against the race of the ball bearing with a taper pin (58). This stub shaft section projects upward with the assembled female tang coupling from the upper face of the stadimeter housing center section.

The lower part of the long shaft section of the pinion shaft is provided with a thrust collar (66). This thrust collar is secured to this part of the shaft in contact with the lower ball bearing race with a taper pin (58). The thrust collar is adjusted before securing, so that the pinion teeth are engaged with the transmission shaft pinion bevel gear (5) at operating depth, with no lost motion in the pinion or its mating bevel gear.

f. Star wheel. The star wheel (59) is made of corrosion-resisting steel 1/2 inch wide. It is provided with a large shoulder section in which 22 teeth of non-standard design are cut for the engagement of a star wheel key (60). The inner surface has a reamed hole which is a sliding fit on the handwheel shaft (23). It is secured to this shaft with a taper pin (44) inserted through the hub section of the star wheel, with the hub section facing the inner right side wall of the stadimeter housing center section. The face of the star wheel is fitted close to the star wheel lock plunger housing (64), and receives the star wheel key (60) which is secured in a star wheel key holder (61) with a taper pin (44) under tension of a star wheel lock plunger spring (63).

g. Handwheel and transmission shaft bevel gears. 1. Handwheel shaft bevel gear. The handwheel shaft bevel gear (3) is made of phosphor bronze with a reamed hole in its center axis, a sliding fit on the handwheel shaft (23). The large diameter is provided with 40 bevel teeth of 32 diametral pitch, which mesh at right angles with a transmission gear pinion (2) of 20 beveled teeth on the front side of the handwheel shaft (23). It also meshes with a transmission gear pinion (54) on the opposite (or rear) side for actuation of the front and rear scale housing mechanisms. This bevel gear is provided with a hub section into which the taper pin (44) is secured, with this section facing away from its mating pinions.

2. Transmission shaft bevel gear. The transmission shaft bevel gear (5) is made

  of phosphor bronze with a reamed hole in its center axis, and is provided with a keyseat. It is a push fit over the inserted woodruff key (31) on the stub section of the handwheel shaft (23). The large diameter is provided with 54 bevel teeth of 32 diametral pitch, which mesh with the 20 bevel teeth of the transmission shaft pinion (65) located vertically at right angles. It is provided with a hub section which faces the shoulder of the handwheel shaft (23) and is secured with a lockscrew (36). This lockscrew is inserted in a tapped hole in the hub section of this bevel gear and extends into a spotted recess in the handwheel shaft (23).

h. Transmission ball bearing housings, ball bearing retainer, and ball bearings. 1. Transmission ball bearing housings. The transmission ball bearing housings (21) are made of cast phosphor bronze and are 1 5/8 inches long. They are of proportional thickness to provide a rigid foundation for the ball bearings (20) and actuation of the transmission. Each is bored to accommodate the handwheel shaft (23) and to permit the rapid removal of each ball bearing. A counterbore 1/4 inch deep is provided in each housing for the assembly of two ball bearings (20), a press fit in each of the counterbores. The height of the housings is proportional to the establishment of a parallel transmission centerline, with each upper part having a radius to accommodate sufficient wall thickness. Each housing is provided with two dowel pins, for rapid alignment upon reassembly. These dowel pins fit into shallow holes in the face of the raised G-wall section face. Each housing is secured to this raised G-wall section face with two lockscrews (41) located in tapped holes in the wall. These lockscrews are inserted in countersunk clearance holes of appropriate center distance in the housing and screwed into tapped holes in the raised G-wall section. The bored holes in the assembled housings face each other at assembly.

2. Ball bearing retainer. The ball bearing retainer (70) is made of 1/16-inch thick brass. It is cylindrical with a clearance hole in the center axis. It is secured in contact with the ball bearing (20) to the face of the semi-circular lug section with four lockscrews (57). These lockscrews are inserted in four equally spaced countersunk clearance holes in the retainer and

 
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screwed into tapped holes in the semi-circular lug section. This retainer prevents the transmission shaft pinion (65) from being displaced axially. A recess is provided in the periphery, where it overlaps the clearance holes for the stadimeter housing bolt (30).

3. Ball bearings. The ball bearings (20) for the transmission shaft pinion (65) are mounted a push fit in the bored holes of the semicircular lug section and the semicircular raised section, a part of the lower base wall of the center section. Each ball bearing is a push fit over the lower part of the long shaft section of the transmission shaft pinion (65) and also over the stub section of the upper part.

i. Female tang coupling. The female tang coupling (68) is made of phosphor bronze- and is 0.812 inch in length. The outer surface is cylindrical with a broached hole of a partially circular design in the center axis. This broached hole fits over the transmission shaft pinion (65) male tang to contact the ball bearing (20) and is secured with a taper pin (58). The remaining part of the coupling receives the stadimeter transmission shaft male tang section (22, Figure 4-27) for actuation, and is a sliding fit in this part. The coupling projects above the face of the stadimeter housing center section and is connected to the stadimeter transmission shaft tang section (22, Figure 4-27) upon assembly of the stadimeter housing assembly to the base of the eyepiece box (11, Figure 4-29).

j. Star wheel lock plunger housing, plunger, key holder, and key. 1. Star wheel lock plunger housing. The star wheel lock plunger housing (64) is made of cast phosphor bronze and is 2 3/4 inches in length. The outer surface is cylindrical, with a rectangular flange in the lower part. The inner surface has a reamed hole and two counterbored sections; the small counterbored section and reamed hole receive the lock plunger (62) which is a loose fit. The large counterbored section receives the keyholder (61) which is also a loose fit. Both sides of the housing perpendicular to the narrow rectangular part of the flange are slotted to allow the protruding parts of the star wheel key (60) vertical guidance and also to fit over the handwheel shaft (23). The

  rectangular base is secured to the machined center section boss over the handwheel shaft (23) with four lockscrews (33). These lockscrews are inserted into counterfaced clearance holes in the housing flanges and screwed into tapped holes in the center section boss. The periphery of the housing on the slotted sides is filed off for clearance between the ball bearing housing (21) and the star wheel (59).

2. Star wheel lock plunger. The star wheel lock plunger (62) is made of phosphor bronze and is 1 1/2 inches in length. It is cylindrical, with a small undercut section a loose fit in the reamed hole in the plunger housing (64), while the large periphery is a loose fit in the small counterbored section in the same housing. The larger diameter is slotted to a distance of 3/4 inch, to allow its free vertical movement over the handwheel shaft in the housing. The lower part rests in the counterfaced upper part of the keyholder (61). This plunger, in contact with the keyholder (61) under tension by the plunger spring, is carried to its upper extreme position, and the star wheel key (60) is engaged with the star wheel (59) locking the handwheel shaft (23) and the transmission.

3. Star wheel key holder. The star wheel key holder (61) is made of phosphor bronze and is 0.781 inch in length. Its outer surface is cylindrical, a loose fit in the large counterbore of the lock plunger housing (64). The upper part is counterfaced a shallow depth to provide a seat for the lower part of the lock plunger (62), while the lower part is counterbored 3/16 inch to provide clearance and guidance for the plunger spring (63). A reamed hole is provided perpendicular to its axis a short distance from the upper part to receive the star wheel key (60) which is secured with a taper pin (44) in its center axis. The rear side of the key extends beyond the periphery 1/32 inch to provide vertical guidance of the assembled key holder and key in the vertical slots of the plunger housing (64).

4. Star wheel key. The star wheel key (60) is made of corrosion-resisting steel material and is 1 1/8 inches in length. The key section is 0.281 inch in length and is a true profile of the star wheel non-standard teeth. The supporting body of the key is a push fit in the

 
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reamed hole in the key holder (61) and is secured with a taper pin (44).

k. Automatic stop. The automatic stop prevents rotation of the handwheel (12) when the stadimeter housing is not in place, and insures correct reassembly. The locking device consists of a star wheel (59) mounted on the handwheel shaft (23) which is secured with a taper pin (44), and with the following parts enclosed in a star wheel lock plunger housing (64): star wheel lock plunger (62), star wheel key (60), its holder (61), and a plunger spring (63).

The star wheel key (60) in the locked position is engaged in the teeth of the star wheel (59) by means of the tension placed against the key holder (61) by the plunger spring (63). In this position the lock plunger (62) is carried to its upward position by the key holder (61). When the stadimeter housing assembly is attached to the base of the eyepiece box (11, Figure 4-29) and secured with four stadimeter housing bolts (30), the screw head (6, Figure 4-29) projecting from the base of the eyepiece box (11, Figure 4-29) contacts the lock plunger (62) and pushes it downward, disengaging the star wheel key (60) from the star wheel (59) compressing the plunger spring (63). This automatic device locks the handwheel (12) and the transmission that the broached tang hole of the female tang coupling (68) couples with the stadimeter transmission shaft male tang section (22, Figure 4-27) for proper relation to the proper position of the lower (split) objective lens and the stadimeter dials.

l. Long transmission shaft and gear pinion. 1. Long transmission shaft. The long transmission shaft (4) is made of corrosion-resisting steel and is 3 3/8 inches in length. It is mounted in two ball bearings (14). One is located in the center section front wall, while the other is located in the scale ball bearing housing (8) located on the face of the raised G-wall sections and perpendicular to the ball bearing housings (21). On the inner end of this shaft a transmission gear pinion (2) is secured with a taper pin (44), while the opposite end extends into the front scale housing section to receive the range scale actuating bevel gear pinion (10) which is secured with a taper pin

  (45). This shaft operates the front scale housing mechanism by means of the attached pinions.

2. Transmission gear pinion. The transmission gear pinion (2) is made of phosphor bronze with a reamed hole in its center axis a push fit on the inner end of the long transmission shaft (4). The large diameter is provided with 20 bevel teeth of 32 diametral pitch, to mesh at right angles with the 54 bevel teeth of the handwheel shaft bevel gear (3). It is provided with a hub section which faces toward the mounted ball bearing (14) in the scale ball bearing housing (8) and is secured with a taper pin (44). This gear pinion transmits motion to the long transmission shaft (4) for actuation of the front scale housing mechanisms.

m. Short transmission shaft and gear pinion. 1. Short transmission shaft. The short transmission shaft (53) is made of corrosion-resisting steel and is 1 1/2 inches in length. It is mounted in two ball bearings (14). One is located in the center section rear wall, while the other is located in the scale ball bearing housing (8) located on the face of the raised G-wall section and perpendicular to the transmission ball bearing housings (21). The inner part of this shaft is provided with a keyway for the insertion of a key (56). It is provided with a tapped hole in the center axis of this end for a lockscrew (55).

On the inner end of this shaft a transmission gear pinion (54) is secured over the inserted key (56) by means of a lockscrew (55). The lockscrew screws into the tapped hole in the center axis of the shaft. The opposite end of this shaft extends into the rear scale housing section to receive the range scale actuating gear pinion (10) secured with a taper pin (45). This shaft operates the rear scale mechanism by means of attached pinions.

2. Transmission gear pinion. The transmission gear pinion (54) is made of phosphor bronze with a reamed hole in its center axis, and is provided with a keyseat. This pinion is a push fit over the inserted key (56) located in the inner end of the short transmission shaft (53) and is secured against the race of the ball bearing (14) snugly by means of the lockscrew (55). This lockscrew screws into the tapped hole in the inner end of the shaft. The large diameter

 
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of this pinion is provided with 20 bevel teeth of 32 diametral pitch which mesh at right angles with the 54 bevel teeth of the handwheel shaft bevel gear (3) for actuation of the rear scale housing mechanism.

n. Scale ball bearing housings and ball bearings. 1. Scale ball bearing housings. The scale ball bearing housings (8) are similar to the two transmission ball bearing housings (21) except for the diameter of the clearance holes, the counterbored sections, and the radius of the upper wall. They are used to mount each ball bearing (14) a press fit into each counterbored, section. Both of these housings are located on the raised G-wall section and perpendicular to the two transmission ball bearing housings. They are secured with two lockscrews (41) each, which are inserted into countersunk clearance holes in the housing and screwed into tapped holes in the raised G-wall section. Both housings provide a rigid support for the transmission gear pinions (2 and 54) for their actuation with the handwheel shaft bevel gear (3).

2. Ball bearings. The four ball bearings (14) provide smooth actuation to the long and short transmission shafts (4 and 53) in the center section mounted in scale ball bearing housings (8) for the inner parts of these shafts. Two ball bearings are mounted, a press fit into the counterbored sections in the front and rear walls of the scale housing sections. They are inserted from the scale housing side with a clearance hole of sufficient size for their removal. These two ball bearings support the outer part of the long and short transmission shafts (4 and 53) for the free actuation of each scale housing mechanism.

o. Range scale actuating bevel gear pinions. The two range scale actuating bevel gear pinions (10) are made of phosphor bronze with a reamed hole in each center axis. The large diameter of each is provided with 20 bevel teeth of 32 diametral pitch, with a pitch cone line angle of 17 degrees 4', which mesh with 80 bevel teeth of a range scale actuating bevel gear (11) having a pitch cone line angle of 72 degrees 56'. Each is provided with a hub section which faces toward the assembled ball bearing (14) located in the wall of each scale housing section. The gear pinions are a push fit on each long and short

  transmission shaft (4 and 53) and are secured with a taper pin (45). Both pinions operate the range scale actuating bevel gears (11) of the front and rear scale housing mechanisms.

p. Scale housings. The scale housings (9) are made of cast phosphor bronze and are 1 13/16 inches in length. Both housings are provided for the front and rear scale housing sections of the stadimeter housing (67). The outer and inner walls are beveled at 45 degrees forming a conical shape, and have equal wall thickness. This conical wall is undercut on the outer surface to form a shoulder flange, and is a sliding fit in the bored and counterbored section of the scale housing section. It is secured with eight lockscrews (42) which are inserted in countersunk clearance holes in the scale housing shoulder flange and screwed into tapped holes in the counterbored face of the scale housing section.

The lower part of the conical wall is flat with a diameter of 2 9/16 inches, with the conical wall and lower part conforming to the inner cored conical and flat walls of the scale housing section. A clearance hole of sufficient size is provided in the conical wall to accommodate the long transmission shaft (4) and the range scale actuating gear pinion (10) of the front scale housing section. The same provision allows clearance for the protrusion of the short transmission shaft (53) and the range scale actuating gear pinion (10) of the rear scale housing section.

The inner lower wall face is provided with two raised shoulders of varying diameter, wall thickness, and depth. The space between the two shoulders allows clearance for the small chamfered shoulder of the range scale actuating bevel gear (11) and serves as a grease cell. The large shoulder is a contact face with the inner side face of the range scale actuating bevel gear (11), thereby providing the height or thrust adjustment to this bevel gear. The counterbored section of the small shoulder receives the lower face of the height scale mount (51), and is secured with four equally spaced lockscrews (39). These screws are inserted in countersunk clearance holes in the height scale mount (51) and screwed into tapped holes in this counterbored face. A tapped hole in the center axis of this counterbored face is provided for the insertion of a jacking screw for the removal of the scale housing.

 
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The inner surface of the shoulder flange section has two counterbored sections to carry the length of target scale mount (47). The smaller of the two counterbored sections has four equally spaced tapped holes, countersunk in the periphery to receive four length of target scale mount retaining screws (7), thus retaining, the length of target scale mount (47). These screws project into an undercut groove in the mount periphery, to retain it in the scale housing and also to allow its free actuation.

The shoulder flange of this scale housing is provided with a clamp screw (16) which screws into the countersunk tapped hole in the shoulder flange. It is secured from backing out of the tapped hole with a retaining collar (18) which in turn is secured with a rivet (19). The clamp screw shoulder (16), when in contact with the assembled length of target scale dial (48), clamps it with the mount at any desired length of target suitable for obtaining the course angle of an enemy ship by the observer. The counterbored shoulder of each scale housing section is slotted to provide clearance for the clamp screw assembly located in the right side of the scale housing outer face, at right angles to the conical wall clearance hole.

An index line plate (15) is attached to the scale housing face located opposite the conical wall clearance hole and is secured with two lockscrews (38).

q. Length of target scale mounts. The two length of target scale mounts (47) are made of cast phosphor bronze, and are provided for the stadimeter housing front and rear scale housing sections. The mounts are cylindrical, of single step design, with small and large diameter shoulders which are a sliding fit in the small and large counterbores in the scale housings (9). The small periphery shoulder is provided with an undercut groove to accommodate the protrusion of four retaining screws (7). These screws extend inward from four equally spaced countersunk tapped holes in the scale housings (9) for their protrusion in this groove, to retain the mount in its seat, and to offer free actuation to the mount.

The inner surface is bored for operational clearance over the range scale mount (49), and is provided with a chamfer to break off

  the inside shoulder. The mount face carries a length of target scale dial (48) secured with six. lockscrews (43) and two lengths of target scale knobs (17). The lockscrews are equally spaced and are inserted in countersunk clearance holes in the scale dial and screwed into tapped holes in the mount. The knobs are located on opposite sides and are secured in tapped holes in the mount. They serve to allow the observer to rotate and set the assembled mount to the reference line of the index line plate (15) to any desired length of an enemy ship.

r. Range scale actuating bevel gears, ball bearings, and mounts. 1. Range scale actuating bevel gears. The two range scale actuating bevel gears (11) are made of phosphor bronze and are used for the front and rear scale housing mechanisms. The large diameter has 80 bevel teeth of 32 diametral pitch, with a pitch cone line angle of 72 degrees 56' which mesh with a range scale actuating gear pinion (10) of 20 bevel teeth having a pitch cone angle of 17 degrees 4'.

The lower face has a chamfered shoulder which forms a sufficient wall for the counterbored section to receive the ball bearing (32), a press fit in this part against the inner shoulder seat. The shoulder is bored for the protrusion of the lower part of the height scale mount (51). The large lower face revolves in contact with the large raised shoulder of the scale housing (9) to maintain its axial height adjustment.

The upper face has a shallow counterfaced recess serving as an alignment seat for the range scale mount (49) which is secured with four lockscrews (40). The lockscrews are inserted into clearance holes located in the small counterbored face of the range scale mount and screwed into tapped holes in this bevel gear. The bevel gear carries the range scale mount (49) and its attached range scale dial (50) for all ranges of its engraved graduations.

2. Range scale actuating bevel gear ball bearings. The two range scale actuating bevel gear ball bearings (32) are of a torque tube type. Both ball bearings are used for the front and rear scale housing mechanisms. They are mounted a press fit into the counterbored sections in each range scale actuating bevel gear (11) and the other races rest against the counterbored shoulder seat The height scale mount

 
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(51) lower part is a push fit in its center race. These ball bearings offer smooth actuation to the range scale actuating bevel gears.

3. Range scale mounts. The two range scale mounts (49) are made of cast phosphor bronze and are used for the front and rear scale housing mechanisms. The mounts are cylindrical with a large diameter shoulder flange section of nominal thickness. The outer surface of the shoulder flange is chamfered at 30 degrees, while the remaining outer wall is beveled conical. The lower part of the conical wall is provided with a small shoulder, which serves as an alignment support section and is a push fit into the alignment recess seat in the range scale actuating bevel gear (11).

The inner surface is a three step design; it has a bore of sufficient size for operational clearance of the ball bearing center race (32), and the protrusion of the height scale mount lower part (51). It has small and large counterbored sections. The smaller counterbored section lightens the mount with sufficient clearance to carry the four lockscrews (40). These lockscrews are inserted into four equally spaced clearance holes in the lower shoulder and screwed into tapped holes in the range scale actuating bevel gear (11).

The large counterbored section provides clearance for the large periphery of the height scale mount (51) and also lightens it. The outer face of the mount is provided with two dowel pins (46), a drive fit into opposite drilled holes, which are not both located in the centerline for reassembly alignment of the range scale dial (50). This outer face carries the range scale dial secured with six lockscrews (43). These lockscrews are inserted into equally spaced countersunk clearance holes in the range scale dial and screwed into tapped holes in the range scale mount flange.

s. Height scale mount. The two height scale mounts (51) are made of phosphor bronze and are used for the front and rear scale housing mechanisms. The periphery of the mount is a solid shoulder of nominal thickness and serves to carry the height scale dial (52). It is provided with two small shoulders, the smaller a push fit in the ball bearing (32) with the larger shoulder seat resting against the face of the ball bearing

  center race. The mount is secured to the ball bearing race with four lockscrews (39). The mount does not actually touch the small counterbored face of the scale housing (9), but is a sliding fit in the small counterbored section in the scale housing raised shoulder.

Four equally spaced countersunk clearance holes extend the entire length of this mount for the lockscrews (39). These lockscrews secure the mount to the ball bearing race by their protrusion into tapped holes in the scale housing lower wall. The outer face of the mount is provided with two dowel pins (46), a drive fit into opposite drilled holes, which are not both located in the centerline for reassembly alignment of the height scale dial (52). This outer face carries the height scale dial (52) secured with four lockscrews (43).

In the center axis of both mounts tapped holes are provided for pointer shoulder screws (75) to retain pointer assemblies. These mounts are stationary in the scale housings (9).

t. Length of target scale dials, index line plates, range and height scale dials. 1. Length of target scale dials. The two lengths of target scale dials (48) are made of 1/16-inch bakelite and are cylindrical. These dials are provided for the front and rear scale housing mechanisms. The inner and outer surfaces conform with their mounts, to which they are secured with six lockscrews (43) each. These lockscrews are inserted into equally spaced countersunk clearance holes and screwed into tapped holes in the length of target scale mounts (47).

Two clearance holes directly opposite are provided for each set of length of target scale knobs (17) which extend into tapped holes in the mount. It is graduated as before mentioned.

2. Index line plates. The two index line plates (15) are made of brass and are 5/8 inch in length. They are used for the front and rear scale housings (9). The width is proportional to the scale housing outer face, with the inner and outer radius conforming to the contour of its inner circumference and periphery. The inner radius is chamfered at 45 degrees and is provided with an index line 0.025 inch deep. The plates are secured with two lockscrews (38) to the

 
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scale housing outer faces with the index line located in the centerline opposite the conical wall clearance hole.

3. Range scale dials. The two range scale dials (50) are made of 1/16-inch bakelite and are cylindrical. These dials are provided for the front and rear scale housing mechanism. The inner and outer surfaces conform to their mounts, to which they are secured with six lockscrews (43) each. These lockscrews are inserted into equally spaced countersunk clearance holes in the scale dials and screwed into tapped holes in each range scale mount (49).

Two opposite clearance holes in each dial not directly in the centerline fit over inserted dowel pins (46) in each mount for proper reassembly. Both dials are graduated as before mentioned.

4. Height scale dials. The two height scale dials (52) are made of 1/16-inch bakelite and are cylindrical. These dials are provided for the front and rear scale housing mechanisms. The periphery of the dials conforms to the periphery of their mounts. The dials have opposite clearance holes not directly in the centerline to fit over the inserted dowel pins (46) of their mounts. Each is secured to its respective height scale mount face (51) with four lockscrews (43). These lockscrews are inserted into countersunk clearance holes in each dial and screwed into tapped-holes in each mount.

The clearance hole in each dial center axis receives the lower pointer collar (76) of the pointer assemblies. The dials are graduated as before mentioned.

u. Factors governing the graduations. The factors governing the graduation of the height, range, and length of target scale dials are: 1) focal length of the whole optical system (that is, the magnification or power), 2) angular displacement of the lower (split) objective lens, and 3) equivalent focal length of the upper eyepiece lens.

v. Pointer assemblies. The two pointer assemblies are provided for the front and rear scales. They consist of two pointers each located on the center of the height scale dials. The lower pointer is used for the height scale

  dials (52), while the upper is used for the course angle graduation of the length of target scale dials (48).

1. Lower pointers. The two lower pointers (78) are made of 1/16-inch clear lucite and are 2 3/32 inches in length. They are provided with clearance holes in their axis point to rotate over the lower pointer collars (76). The long and short sections on each side of their axis taper to 1/4-inch width, with rounded corners.

The long section lower face of each is provided with an engraved groove of shallow depth in the centerline which projects inward 1/2 inch and is filled with red lacquer. The short section of each is provided with a clearance hole near the end, countersunk from the lower face to accommodate a lockscrew (71). These lockscrews are inserted in countersunk clearance holes in each to attach to a lower pointer knob (79) to their upper face. The lower pointers are assembled to the height scale dials over the lower pointer collars (76), each on a felt friction washer (81).

2. Upper pointers. The two upper pointers (73) are made of 1/16-inch clear lucite and are 1.530 inches in length. The wider parts are 1 5/32 inch, with a clearance hole located in the center of a 5/16-inch radius. They are provided with three equally spaced countersunk clearance holes in each lower face for lockscrews (72). These lockscrews are inserted into tapped holes in the upper pointer knobs (74) and secured to each upper face of the pointers.

The upper pointers taper from their wider part to a 1/4-inch width, with rounded corners. These wider parts have an engraved groove of shallow depth in their centerline located in the lower faces, which projects inward 1/2 inch and is filled with red lacquer.

The periphery of the upper pointer knob is knurled to offer a firm grip. It has countersunk clearance holes in the axis to receive spring washers (77) and the pointer shoulder screws (75).

3. Pointer shoulder screws. The two pointer shoulder screws (75) are made of brass and are 0.700 inch in length. The large diameter forms the heads, with screw driver slots of appropriate depth. The medium shoulders fit into the clearance

 
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holes in the upper pointer knobs (74) with assembled spring washers (77) below the heads. The medium shoulders are provided with 0.030-inch depth tangs to fit into the broached tang clearance holes of the 1/32-inch brass friction washers (80). The brass friction washers (80) remain stationary between the upper pointers (73) and the lower pointers (78), thus separating the pointers, and providing sufficient friction to maintain the setting of the pointers. These shoulder screws extend into the tapped holes in the height scale dials' center axis to retain the complete pointer assemblies.

w. Housing cover plate. The housing cover plate (69) is made of 1/16-inch brass plate. Its outer surface conforms to cover the stadimeter housing center section. Each of the four corners has a clearance hole that coincides with the clearance holes for the stadimeter housing bolts (30). Two clearance holes diagonally opposite are provided for the inserted dowel pins (22) projecting upward from the front and rear side walls.

A clearance hole of appropriate size is provided at a proper location for the star wheel lock plunger (62) projecting above the face of the center section. A large clearance hole of 1 11/32 inches in diameter is provided to fit over the periphery of the ball bearing retainer (70).

The cover plate is secured to the center section face with six lockscrews (34). These lockscrews are inserted into countersunk clearance holes, properly located in all four sides and screwed into tapped holes in the four side walls of the center section. The cover plate covers the transmission center section of the stadimeter housing (67) after it is filled with mineral grease grade II medium.

4J9. Disassembly of the stadimeter housing assembly. The stadimeter housing assembly is disassembled in the following manner:

1. Remove the two alemite fittings (82) from the front ands rear scale housing section of the stadimeter housing (67).

2. Remove the six lockscrews (34), unscrewing them from the tapped holes in the four walls of the center section. Remove the housing cover plate (69). Check the stadimeter dials; they should be located at the observing position

  referred to by the stamped numerals on the stadimeter housing.

3. Clean out all grease and wash out the transmission center section with a grease solvent.

4. Remove the four lockscrews (33) and remove the star wheel lock plunger housing (64). This allows the star wheel lock plunger (62), star wheel key (60), its holder (61), and the plunger spring (63) to be removed.

5. Remove the four lockscrews (57) and the ball bearing retainer (70).

6. Remove the transmission shaft pinion (65), carrying with it vertically the transmission shaft pinion thrust collar (66), its taper pin (58), ball bearing (20), female tang coupling (68), and its taper pin (58). It may be necessary to tap the female tang coupling lightly with a rawhide mallet around the periphery to loosen this assembly.

7. Remove the taper pin (58) and the female tang coupling (68) from the integral stub shaft section of the transmission shaft pinion (65).

8. Remove the ball bearing (20) from the integral stub shaft section of the transmission shaft pinion (65).

9. Remove the taper pin (58) from the transmission shaft pinion thrust collar (66), removing the thrust collar from the long integral shaft section of the transmission shaft pinion (65). Pay particular attention to reference marks on all gears, as these gears are lapped to make synchronization of both dial units possible.

10. Remove the taper pin (44) from the star wheel hub section (59) and remove the lockscrew (36) from the hub section of the transmission shaft bevel tear (5). The woodruff key (31) remains in the stub section of the handwheel shaft (23).

11. Remove the taper pin (44) from the hub section of the handwheel shaft bevel gear. (3), freeing the handwheel shaft (23) for removal.

12. Remove the handwheel shaft (23) by grasping the handwheel (12) and pulling it outward slowly. This allows the transmission shaft bevel gear (5), handwheel shaft bevel gear (3), and star wheel (59) to be removed.

 
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13. Remove the lockscrew (35) from the hub section of the handwheel (12), removing the handwheel from the outer part of the handwheel shaft (23). The handwheel key (1) can remain in the shaft.

14. Remove the two spring handle hinge screws (13) from the countersunk tapped holes in the scalloped periphery of the handwheel (12). The spring handle assembly slides out easily.

15. To disassemble the spring handle assembly, remove the plunger nut (27). Unscrew this nut from the spring handle plunger (26) by compressing the plunger spring (29). The plunger nut can then be removed easily by hand.

16. Remove the spring handle (25) from the spring handle stud (24).

17. Using a special wrench, remove the spring retainer nut (28) from the internal threaded section in the spring handle stud (24).

18. Remove the plunger spring (29) and the spring handle plunger (26) from the internal body section of the spring handle stud (24).

19. Remove the four lockscrews (37) from the handwheel bracket (6), unscrewing them from tapped holes in the center section right side wall. Remove the handwheel bracket.

20. Remove the pointer assembly from the front scale housing mechanism as follows: Remove the pointer shoulder screw (75), unscrewing it from the tapped hole axis in the height scale mount (51). This removes the pointer assembly of the following: pointer shoulder screw (75), spring washer (77), upper pointer knob (74), its lockscrews (72), upper pointer (73), brass friction washer (80), lower pointer knob (79), its lockscrews (71), lower pointer (78), lower pointer collar (76), and the felt friction washer (81).

21. The removal of the pointer assembly of the rear scale housing mechanism is followed in similar manner to that described for the front scale housing mechanism. Refer to Step 20.

22. Remove the front scale housing mechanism as follows: Remove the two length of target scale knobs (17), unscrewing them from

  the tapped holes in the length of target scale mount (47).

23. Remove the four lockscrews (43) from the height scale dial (52), six from the range scale dial (50), and six from the length of target scale dial (48). A total of 16 lockscrews (43) is removed.

24. Remove the height scale dial (52), range scale dial (50), and length of target scale dial (48).

25. Remove the four lockscrews (39) from the height scale mount (51). These lockscrews are unscrewed from the tapped holes in the scale housing base (9). Precaution must be taken to observe reference marks on all these parts upon disassembly in order to reassemble them correctly later.

26. Insert the pointer shoulder screw (75) in the tapped hole axis of the height scale mount (51) tapping the outer wall of the scale housing section with a light rawhide mallet and using an outward thrust on the above screw head and body to remove the height scale mount.

27. Remove the range scale mount (49), carrying with it the range scale actuating bevel gear (11) and the mounted ball bearing (32). The mount is removed by pulling it out of the scale housing (9).

28. Remove the four lockscrews (40) from the small counterbored face of the range scale mount (49). These lockscrews are unscrewed from tapped holes in the range scale actuating bevel gear (11). The ball bearing (32) should not be removed from the counterbore of the above bevel gear (11) unless corroded, in which case it should be pressed out and renewed.

29. Remove the eight lockscrews (42) from the outer face of the scale housing (9). These lockscrews are unscrewed from the tapped holes in the large counterbored face of the scale housing section.

30. To remove the scale housing (9) it is necessary to place four fingers of each hand below the length of target scale mount (47) and tap the outer wall of the scale housing section lightly with a small rawhide mallet. An alternate method is to insert an 8-36 jacking

 
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screw in the tapped hole axis in the scale housing, and slowly jack the scale housing out; it may also be necessary to use a rawhide mallet to break the paint seal. The jacking screw rests against the lower inner wall of the scale housing section.

31. When the scale housing (9) is loosened from the large counterbore, tip it at an angle, and follow the first method for its removal.

32. Remove the four retaining screws (7) from the small periphery shoulder of the scale housing (9). These retaining screws are unscrewed from countersunk tapped holes in the scale housing and their protrusion in the undercut groove in the periphery of the length of target scale mount (47). Remove the length of target scale mount from the scale housing (9).

33. Remove the two lockscrews (38) from the index line plate (15). These lockscrews are unscrewed from the tapped holes in the scale housing outer face (9).

34. The removal of the rear scale housing mechanism is followed in similar manner to that described in Steps 22 to 34 inclusive for the front scale housing mechanism.

35. Remove the taper pin (44) from the transmission gear pinion (2) and the inner part of the long transmission shaft (4), and remove the transmission gear pinion (2).

36. Remove the long transmission shaft (4), carrying it out of the mounted ball bearing (14) located in the scale ball bearing housing (8), carrying with it the range scale actuating bevel gear pinion (10). It is further carried out of the ball bearing (14) mounted in the front scale housing section.

37. Remove the taper pin (45) from the front range scale actuating bevel gear pinion (10) and the outer part of the long transmission shaft (4), and remove the gear pinion (10) from the shaft.

38. Remove the lockscrew (55) by the insertion of a long screw driver blade protruding through the ball bearings (14) mentioned in Step 37. The lockscrew is unscrewed from the tapped axis hole in the inner part of the short transmission shaft (53). Remove the transmission gear pinion (54).

  39. Remove the key (56) from the inner part of the short transmission shaft (53).

40. Remove the short transmission shaft (53) carrying it out of the mounted ball bearing (14) in the scale ball bearing housing (8). It is further carried out of the ball bearing (14) mounted in the rear scale housing section, carrying with it the range scale actuating bevel gear pinion (10).

41. Remove the taper pin (45) from the rear range scale actuating bevel gear pinion (10) and the outer end of the short transmission shaft (53) and remove the gear pinion (10) from the shaft.

42. Remove the two lockscrews (41) from each of the two transmission ball bearing housings (21). Remove the assembled ball bearings (20) with their housings.

43. Remove the two lockscrews (41) from each of the two scale ball bearing housings (8). Remove the assembled ball bearings (14) with their housings.

44. Remove the two ball bearings (14) from the front and rear scale housing section walls, and remove the one ball bearing (20) from the right side wall of the center section. Remove the ball bearing (20) from the raised semi-circular section in the center section base. This ball bearing is removed by inserting a special pair of calipers in the center clearance hole of the center race, allowing the calipers to get below the center race, and tapping on the stadimeter housing with a small rawhide mallet while an upward thrust is maintained with the calipers.

45. The length of target scale clamp screws (16) are not removed from the retaining collars (18) mounted in the right side of each scale housing (9), as this removal would necessitate drilling out the retaining collar rivets (19).

46. Clean all parts thoroughly with a grease solvent.

4J10. Reassembly of the stadimeter housing assembly. The stadimeter housing assembly is reassembled as follows:

1. Apply Lubriplate No. 110 lightly to all rotating parts as the reassembly procedure is followed.

 
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2. Various parts have reference numerals with mating numerals stamped in or on the various parts to establish coincidence of these parts for correct reassembly.

3. Place the two ball bearings (14) in the front and rear scale housing section walls of the stadimeter housing (67).

4. Place one ball bearing (20) in the right side wall of the center section, and one in the raised semi-circular section in the center section base. Tap this bearing all the way in until it touches the bottom.

5. Place the two transmission ball bearing housings (21) with the mounted ball bearings (20) at their respective places on the upper face of the raised G-wall section in the center section. The dowel pins of each housing base fit into aligning holes. Secure these two housings with two lockscrews (41) each. These lockscrews are inserted into two countersunk clearance holes in each housing and screwed into tapped holes in the raised G-wall section.

6. Place the two scale ball bearing housings (8) with the mounted ball bearings (14) in their respective places on the upper face of the raised G-wall section in the center section. These two housings are located perpendicular to the two assembled transmission ball bearing housings (21). The dowel pins of each housing base fit into aligning holes. Secure these two housings with two lockscrews (41) each. These lockscrews are inserted into two countersunk clearance holes in each housing and screwed into tapped holes in the raised G-wall section.

7. Place the rearrange scale actuating bevel gear pinion (10) on the outer end of the short transmission shaft (53) and secure it by the insertion of a taper pin (45). The insertion of the taper pin should be done with the gear pinion hub held on a soft metal V-block.

8. Insert the short transmission shaft (53) from the rear scale housing section side into the first mounted ball bearing (14), carrying it farther through the second mounted ball bearing (14) in the scale ball bearing housing (8). The shaft is a push fit into both ball bearings.

9. Insert the key (56) in the keyway in the short transmission shaft inner part (53).

  10. Place the transmission gear pinion (54) on the short transmission shaft (53) over the inserted key (56). Secure it with a lockscrew (55), screwing it tight by the use of a long screw driver blade inserted from the front scale housing section, and protruding through the two mounted ball bearings (14).

11. Place the front range scale actuating bevel gear pinion (10) on the outer end of the long transmission shaft (4) and secure it by the insertion of a taper pin (45). The insertion of the taper pin should be done with the gear pinion hub held on a soft metal V-block.

12. Insert the long transmission shaft (4) from the front scale housing section side into the first mounted ball bearing (14) carrying it farther through the second mounted ball bearing (14) of the scale ball bearing housing (8). The shaft is a push fit into both ball bearings.

13. Place, the transmission gear pinion (2) on the long transmission shaft inner part (4) and secure it with a taper pin (44).

14. Place the handwheel bracket (6) on the alignment recess of the right side wall of the stadimeter housing center section. Secure the bracket with four lockscrews (37) which are inserted into countersunk clearance holes in the bracket and screwed into tapped holes in the center section right side wall.

15. Insert the handwheel key (1) in the outer part of the handwheel shaft (23), and assemble the handwheel (12) over the inserted key and this part of the handwheel shaft. Secure the handwheel (12) with a lockscrew (35). This lockscrew screws into the tapped hole in the handwheel hub section and extends into the spotted recess in the handwheel shaft.

16. Place the handwheel shaft (23) through the first mounted ball bearing (20) in the transmission center section. The shaft is a push fit in this ball bearing.

17. Place the star wheel (59) with its hub section toward the handwheel (12) on the handwheel shaft (23).

18. Push the handwheel shaft (23) through the second mounted ball bearing (20) of the transmission ball bearing housing (21). The shaft is a push fit in this ball bearing.

 
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19. Place the handwheel shaft bevel gear (3) on the handwheel shaft (23) with its hub section facing toward the handwheel (12).

20. Push the handwheel shaft (23) through the third mounted ball bearing (20) in the transmission ball bearing housing (21). The shaft is a push fit in this ball bearing.

21. Place the transmission shaft bevel gear (5) on the stub section of the handwheel shaft (23) over the inserted woodruff key (31) with its hub section facing toward the handwheel (12). Secure the bevel gear (5) by the insertion of the lockscrew (36), which is screwed into a tapped hole in the hub section and extends into the spotted recess in the handwheel shaft (23). The handwheel hub should be in contact with the hub section of the handwheel bracket (6).

22. Slide the star wheel (59) on the handwheel shaft and line up the taper pin holes. Secure the star wheel with the insertion of the taper pin (44).

23. Reassemble the front scale housing mechanism as follows: Place the index line plate (15) on the scale housing (9) opposite the conical wall clearance hole, and secure it with two lockscrews (38). These lockscrews are inserted into countersunk clearance holes in the plate and screwed into, tapped holes in the scale housing large shoulder flange.

24. Place the length of target scale mount (47) in the counterbored seat in the scale housing (9). Secure the mount with four lockscrews (7). These lockscrews are inserted in countersunk tapped, holes in the scale housing shoulder periphery and screwed into the undercut groove in the mount periphery.

25. Place the scale housing (9) in the front scale housing section counterbored seat, tipping it sufficiently to allow the conical wall clearance hole, adequate clearance over the range scale actuating bevel gear pinion (10). The scale housing is a push fit into its counterbored seat. Secure the scale housing with eight lockscrews (42) which are inserted into countersunk clearance holes in the scale housing and screwed into tapped holes in the scale housing section counterbored seat.

  26. Assemble the range scale mount to the range scale actuating bevel gear (11) recess seat, checking reference marks for proper coincidence of mating reference marks. Secure the mount with four lockscrews (40) which are inserted in clearance holes in the small counterbored shoulder in the mount and screwed into tapped holes in the bevel gear.

27. Rotate the front range scale actuating bevel gear pinion (10) until its reference tooth is down, so that upon the assembly of the range scale actuating bevel gear (11) the reference tooth opening of this bevel gear is upward for its engagement with the reference tooth of the gear pinion (10).

28. Place the range scale actuating bevel gear (11) and the assembled range scale mount (49) in the scale housing (9) tipping it slightly and properly meshing it with the front range scale actuating bevel gear pinion (10) as outlined in Step 27. Ascertain the central position of this assembly by checking the coincidence of the ball bearing race (32) and the small shoulder counterbore of the scale housing (9).

29. The height scale mount (51) should be pushed slowly into the range scale actuating bevel gear ball bearing (32) and farther into the small shoulder counterbore in the scale housing (9). The small shoulder seat of the mount rests against the center ball bearing race and is secured with four lockscrews (39). These lockscrews are inserted into countersunk clearance holes in the mount and screwed into tapped holes in the scale housing lower wall. This retains the small shoulder seat of the mount snugly in contact with the center ball bearing race with sufficient tension to maintain it stationary.

30. Reassemble the rear scale housing mechanism by following Steps 23 to 29 inclusive.

31. Check the reference marks of the range and height scale mounts for the front and rear scale housing mechanisms and note their relation. Should both appear in unison, assemble the range and height scale dials (50 and 52) to their respective mounts of the front and rear scale housing mechanisms over the inserted dowel pins (46). Check the 2.2 numeral graduation on the range scale dial (50). It should appear approximately opposite the value 58

 
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numeral graduation on the height scale dial (52). Values opposite the numbers 2.2 and 58 are found on Figure 2-12. Refer to both sets of dials, noting their proper relation. Should both appear in unison, further assembly is to be continued.

32. With both sets of dials in unison, the handwheel shaft bevel gear (3) is now closely observed for reference marks. This bevel gear has two reference marks on opposite sides to engage with a reference tooth of the transmission gear pinions (2 and 54).

33. Properly engage the handwheel shaft bevel gear (3) reference marks with the reference tooth of each transmission gear pinion. Insert a temporary screw in the hub of the bevel gear which has a tapped hole for this purpose, and secure the temporary screw. Rotate the handwheel (12) and check both sets of scale housing dials through the complete series of range graduations. Should observations denote the unison of both sets of dials, observe the taper pin holes of the handwheel shaft bevel gear (3) and the handwheel shaft (23). They should be in coincidence. However, by releasing the temporary lockscrew and holding the bevel gear in mesh with the gear pinions, the handwheel shaft (23) is rotated for the insertion of the taper pin (44). The taper pin secures the bevel gear to the handwheel shaft.

34. Secure the front and rear range scale dials (50) with six lockscrews (43) each. These lockscrews are inserted into countersunk clearance holes in the dials and screwed into tapped holes in their mounts.

35. Secure the front and fear height scale dials (52) with four lockscrews (43) each. These lockscrews are inserted in countersunk clearance holes in the dials and screwed into tapped holes in their mounts.

36. Place the length of target scale dials (48) on their respective mounts, and secure each with eight lockscrews (43). These lockscrews are inserted into countersunk clearance holes in the dials and screwed into] tapped holes in their mounts.

37. Place the sets of length of target scale knobs (17) in opposite sides of each length of target scale dials (48). These knobs are

  inserted into clearance holes in the dials and screwed into tapped holes in the mounts.

38. Reassemble the front pointer assembly to the front scale housing mechanism as follows: Place the spring washer (77) over the medium shoulder of the pointer shoulder screw (75).

39. Secure the upper pointer (73) to the upper pointer knob (74) with three lockscrews (72).

40. Place the pointer shoulder screw (75) with the spring washer (77) in the upper pointer knob (74).

41. Place the brass friction washer (80) on the pointer shoulder screw (75) aligning the flat part of the broached hole on the undercut shoulder.

42. Place the lower pointer collar (76) on the pointer shoulder screw (75).

43. Place the lower pointer knob (79) on the lower pointer (78) and secure it with a lockscrew (71). Place the lower pointer collar (76) on the pointer shoulder screw (75).

44. Place the felt friction washer (81) on the lower pointer collar (76) and the pointer shoulder screw (75).

45. Place the front pointer assembly at the axis of the height scale dial, and screw the pointer shoulder screw into the tapped axis hole in the height scale mount (51). Check the relation of the upper pointer to the lower pointer. If the brass friction washer is engaged properly on the pointer shoulder screw (75), a proper friction setting for the upper and lower pointers exists.

46. Reassembly of the rear pointer assembly to the rear scale housing mechanism is followed in similar manner to that described in Steps 38 to 45 inclusive for the front scale housing mechanism.

47. Place the transmission shaft pinion thrust collar (66) on the long integral shaft section of the transmission shaft pinion (65) and secure it by the insertion of a taper pin (58).

48. Place the ball bearing (20) on the integral stub section of the transmission shaft pinion (65), allowing the ball hearing to contact the pinion.

 
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49. Place the female tang coupling (68) over the male tang section of the integral stub section of the transmission shaft pinion (65), allowing the female tang coupling to contact the assembled ball bearing (20), and secure the coupling with the insertion of a taper pin (58).

50. With the dials of both front and rear scale housing mechanisms set to the observing position, place the transmission shaft pinion assembly vertically in the center section. It is carried through the ball bearing hole in the semi-circular lug section. The flat tang section in the female tang coupling (68) faces toward the handwheel (12), and the pinion is engaged into the transmission shaft bevel gear (5) as the long integral shaft section is pushed into the mounted ball bearing (20) in the raised semi-circular section of the center section base.

51. Assemble the ball bearing retainer (70) to the semi-circular lug section face of the center section over the female tang coupling (68) and secure with four lockscrews (57).

52. Check the mesh of all pinions and bevel gears for the detection of backlash or shallow depth of the teeth. A careful observation readily determines where shimming is required for a snug working depth of mating pinions and bevel gears.

53. Reassemble the automatic stop assembly into the center section as follows: Place the star wheel key (60) in the star wheel key holder (61), and secure it with the insertion of a taper pin (44).

54. Place the star wheel key (60) and its holder (61) with the star wheel lock plunger spring (63) below the handwheel shaft (23), engaging the key in the star wheel (59).

55. Place the star wheel lock plunger (62) in the star wheel lock plunges housing (64) and assemble them over the handwheel shaft (23). Carefully check the plunger housing as it is lowered to the center boss section. Secure the plunger housing with four lockscrews (33).

56. The automatic stop assembly should be locked at the observing position for its assembly to the base of the eyepiece box (11, Figure 4-29).

  57. Fill the center section with soft mineral grease grade II medium.

58. Place the housing cover plate (69) on the center section, and secure it with six lockscrews (34). These lockscrews are inserted in countersunk clearance holes in the housing cover plate and screwed into tapped holes in the four center section walls.

59 Screw both alemite fittings into the lower part of the front and rear scale housing section walls, filling the housings with soft mineral grease grade II medium.

60. Reassemble the spring handle assembly as follows: Insert the spring handle plunger (26) in the spring handle stud (24).

61. Place the plunger spring (29) over the spring handle plunger (26) and into the large counterbored section in the spring handle stud (24).

62. Place the spring retainer nut (28) over the spring handle plunger (26). Using a special wrench, compress the plunger spring (29) so that the retainer nut engages in the internal threaded section in the spring handle stud (24) until it is flush with the face.

63. Place the spring handle (25) over the spring handle stud (24).

64. To apply the spring handle plunger nut (27), press downward on the spring handle plunger (26), applying pressure with the spring handle (25). Screw on the spring handle plunger nut, securing it with a special wrench.

65. Place the spring handle assembly in the hinge opening in the side wall of the handwheel (12). Insert the two spring handle hinge screws (13). These hinge Screws are screwed into countersunk tapped holes in the handwheel scalloped periphery and extend into reamed holes in each side of the spring handle stud (24).

4J11. Description of the operation of the range and course angle finder. operation of the range and course angle finder is accomplished in the following manner:

The clockwise rotation of the handwheel (12, Figure 4-24) transmits motion to the handwheel shaft (23) to operate the handwheel shaft bevel gear (3). The clockwise rotation of this

 
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handwheel shaft bevel gear (3) transmits counterclockwise rotation to the front transmission gear pinion (2) and clockwise rotation to the rear transmission gear pinion (54) in mesh with this bevel gear at right angles.

The counterclockwise rotation of the front transmission gear pinion (2) carries the long transmission shaft (4) in the same direction as the front range scale actuating bevel gear pinion (10) on the opposite end of this shaft.

The counterclockwise rotation of the front range scale actuating bevel gear pinion (10) in mesh with the front range scale actuating bevel gear (11) transmits motion to this bevel gear, causing it to rotate clockwise. It carries the attached range scale mount (49) and its range scale dial (50) clockwise.

The rear scale housing mechanism operates opposite to the front scale housing mechanism when the observer is located in the front of the periscope. However, relatively speaking, it operates similarly to the front scale housing mechanism, were the observer to be stationed on the rear side of the instrument.

The clockwise rotation of the handwheel shaft (23) operates the transmission shaft bevel gear (5) clockwise. This bevel gear in mesh with the transmission shaft pinion (65) and at right angles to it, operates the pinion clockwise, observing this pinion from the lower end. The clockwise rotation of the handwheel shaft (23) simultaneously operates the front and rear scale housing mechanisms and the transmission shaft pinion (65).

Clockwise rotation of the transmission shaft pinion (65) carries its attached female tang coupling (68) in the same direction. The female tang coupling (68) coupled with the stadimeter transmission shaft (22, Figure 4-27) carries it clockwise, as does also its interconnection with the operating gear pinion shaft (13, Figure 4-23) and its attached operating gear pinion (12).

The clockwise rotation of they operating gear pinion (12) in mesh with the operating gear (1), causes it to rotate counterclockwise. The cam grooves of the operating gear (1) in the counterclockwise rotation looking upward from the lower part of the instrument cause the cam shoes (4) attached to mounting plate guide

  keys and integral shafts (15) to displace the mounting plate halves (5) and the attached lower (split) objective lens and mount halves (see Figure 4-22). The displacement of the lower (split) objective lens halves causes duplicate images to be produced, so that, for example, the waterline of one image may be brought into contact with the masthead or funnel top of the other image. The angle subtended is indicated in terms of yards on the range scale dial (50, Figure 4-24) and against the known height on the stationary height scale dial (52).

The grooves in the operating gear are cut so that the lateral movement of the lower (split) objective lens halves is proportional to the logarithm of the tangent of the angle through which the operating gear is rotated.

With the handwheel (12, Figure 4-24) rotating clockwise, the operating ear is rotated counterclockwise. The operating gear stop (19, Figure 4-23) moves with the operating gear (1) and leaves its contact with the observation position stop (20).

Actuation from the vertical range observing position is accomplished when the (split) lens halves function as a single lens, until the operating gear (1) travels through approximately 147 degrees of rotation and contacts the maximum displacement stop (20), thereby causing the optical axis of each half to be displaced from the periscope axis an amount equal to the movement of each half. The axis of each half remains parallel to the periscope axis, and the principal focal plane of each objective lens half remains in the same plane as before splitting.

Further clockwise rotation of the handwheel (12, Figure 4-24) causes the sliding track (3, Figure 4-23) to which the maximum displacement stop (20) is secured by the operating gear retaining ring (35), to rotate through 90 degrees inside the track sleeve (2). The maximum displacement stop (20) located on the operating gear retaining ring (35) absorbs the torque required to lift the range position detent pawl (7) against spring pressure of the detent pawl spring (6) by the movement of the detent pawl rest (8) attached to the sliding track (3).

The 90 degrees rotation of the sliding track (3, Figure 4-23) counterclockwise is accomplished by the

 
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128 degrees circumferential slot of the track sleeve (2). This 90 degrees rotation ends when the detent pawl rest (8) comes into contact with the end of the 128 degrees slot in the track sleeve (2), and engages a locking device for the course angle position detent pawl (7).

Turning the handwheel (12, Figure 4-24) counterclockwise causes the operating gear (1) and its stop (19, Figure 4-23) to rotate clockwise and make the two lens halves approach each other. The known length of target having been set on the length of target scale dial (48, Figure 4-24) opposite the index mark on the scale housing (9), the course angle is indicated on the length of target scale dial against the previously found range on the range scale dial (50), when the bow of one image touches the stern of the other.

In clockwise rotation, the operating gear stop (19, Figure 4-23) loses contact with the maximum displacement stop (20) and is carried with the operating gear (1) until it contacts the observation position stop (20) in which position the split lens functions again as a single lens. This return movement is approximately 147 degrees traversed previously in the counterclockwise rotation to obtain maximum displacement but giving the course angle single image position.

Further counterclockwise rotation of the handwheel (12, Figure, 4-24) causes the sliding track (3, Figure 4-23) to which the observation position stop (20) is secured to the operating gear retaining ring (35), to rotate through 90 degrees inside the track sleeve (2). The observation position stop (20) located on the operating gear retaining ring, (35) absorbs the torque required to lift the course angle position detent pawl (7) against the tension of the detent pawl spring (6) by the movement of the detent, pawl rest (8) attached to the sliding track (3).

The 90 degrees return clockwise rotation of the sliding track (3) is accomplished by the 128 degrees circumferential slot in the track sleeve (2) This 90 degrees rotation ends when the detent pawl rest (8) comes into contact with the end of the 128 degrees slot in the track sleeve (2), and engages a locking device for the range position detent pawl (7). Thus the observations are resumed as desired from the range position again.

  Collimation of the lower (split) objective lens and mount assembly (Figure 4-22), the objective operating mechanism assembly (Figure 4-23), and the stadimeter housing assembly (Figure 4-24) is described under Section 4V9.

4J12. Steps necessary to obtain range and course angle of a vessel. The range and course angle of a vessel may be found in the following manner:

1. The estimated length and height of the target must be known.

2. Set the length of target on the length of target scale dial (48, Figure 4-24) against the stationary index line mark. Clamp the outer scale by means of the locking clamp screw (16).

3. Set the estimated height of the target with a pointer.

4. Starting with the split objective lens as a whole lens in the observing position, first bring the target approximately into the center of the field of view. Rotate the handwheel (12) clockwise until the masthead of the object or target in one image coincides with the waterline in the other image.

5. Resume turning the handwheel (12) clockwise to the limit of its travel. At this point, the lower (split) objective lens is carried through a 90 degrees rotation.

6. Upon reaching the end of this 90 degrees rotation, the handwheel (12) is reversed or turned counterclockwise, stopping when the bow of the target of one image coincides with the stern of the other image.

7. Read the course angle on the inner scale of the length of target scale dial (48) against the range in yards on the range scale dial (50).

8. Continue counterclockwise rotation until the lens halves again function as a single lens at the observing position.

4J13. Operation of the stadimeter. The following problem illustrates the use of the stadimeter. Figure 4-25 shows the stadimeter setting for a target vessel whose height from waterline to masthead is known to be 60 feet, and whose length from bow to stern is known to be 375 feet. Find the range and course angle of the target.

 
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First set the length of the target on the length of target scale dial against the index mark, and clamp the length of target scale dial and mount by the locking clamp screw. Then, starting with the stadimeter at the observing position, bring the target approximately into the center of the field of view. Rotate the handwheel clockwise until the masthead of the target in one image coincides with its waterline in the other image. At this point, the scale dials are shown in Figure 4-25, and the range (2300 yards) is read on the range scale dial, opposite the height (60 feet) on the height scale dial.

Turn the handwheel clockwise to the limit of its travel; then reverse the direction, stopping when the bow of the target in one image coincides with the stern in the other image. The position of the scale dials at this stage is shown in Figure 4-26. The course angle (20 degrees) is read on the inner scale on the length of target scale dial, against the range (2300 yards) on the range scale dial. The angle thus found is measured from the line of sight of the periscope. Note that the course angle is measured without regard to the direction of movement of the target, and may be either the angle observed, or its supplement, in this case 160 degrees.

Figure 4-25. Operation of stadimeter for obtaining
the range of an individual problem.
Figure 4-25. Operation of stadimeter for obtaining the range of an individual problem.

  Figure 4-26. Operation of stadimeter for obtaining
the course angle of previous problem.
Figure 4-26. Operation of stadimeter for obtaining the course angle of previous problem.

By continuing the counterclockwise rotation of the handwheel to the limit of its travel, restore the periscope to the observing position, ready for the next observation.

The following hints may be of value:

1. Remember that the stadimeter measures only angles, and computes the range on the basis of the known height (and length in the case of course-angle measurements). If the height must be assumed, the range reading can be no more accurate than the estimate of the height. If both height and length are assumed, the course-angle reading thus obtained is subject to a large error.

2. The dimensions selected for these observations should be those which are known, or which can be estimated, with fair accuracy. In addition, the reference points, in so far as possible, should be definite, easy to see, and widely spaced. The masthead and waterline, for example, while affording the greatest vertical dimension, might both be invisible at long range.

3. The stadimeter is graduated up to 11,000 yards. Longer ranges may be obtained by remembering that the angle subtended by 80 feet, for example, at 20,000 yards, is the same as that subtended by 40 feet at 10,000 yards. Thus an object 80 feet high may be set up at the 40-foot line and the range multiplied by two.

 
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4. The stadimeter scale dials are graduated for use with the periscope in high power. When necessary to range on an object more than 130 feet high, the stadimeter may be used with the periscope in low power, and the object set up on the height scale dial at one-fourth its actual height. The range reading is then correct.

5. Difficulty may at first be encountered in centering the eye in order to see the duplicate images with equal intensity. To a great extent, practice overcomes this difficulty. On bright days the use of one of the rayfilters permits the pupil of the eye to expand and intercept a greater portion of the divided exit pupil.

6. A stadimeter range may be taken with a periscope exposure of a few seconds. It is assumed

  that the approximate bearing of the target is known, and that the reference points have been selected. The known or estimated height between the reference points should be set in advance on the height scale dial. Use the pointer if one is provided, or a crayon mark. The periscope may be trained approximately on the target, the power shift placed in high power, and the focus set for the observer's eye. In addition, the estimated range may be set up on the stadimeter. All this may be done with the periscope partially housed. If the periscope is then exposed, no time is lost in focusing, and little in centering the object and bringing the reference points into coincidence. When this is done the instrument may again be partially housed and the range reading taken. Practice is essential to the efficient operation of the stadimeter.
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