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4A2. Shipping, unpacking, and handling. A modern submarine periscope with a reduced section of small diameter is a fragile instrument, especially during handling and shipment. It is shipped in a box of sturdy construction, but to prevent needless stresses it is advisable that the box, whenever possible, be hoisted or supported at more than one point, preferably the quarter-points. During rail shipment, the box should be securely chocked in the car. A reach truck is desirable for highway movement, and in any case the box should be loaded so that the portion overhanging the truck contains the upper, lighter end of the periscope. The name plate of the shipping box is placed at the end containing the lower heavier portion of the periscope.

The periscope is secured in the box by chocks, with brass clamps provided to prevent endwise movement in the box. The clamps should remain with the box for reuse. The cover of the box when inverted, serves as a convenient support for the instrument.

In case of reshipment of the periscope, care should be taken to see that the brass clamps are in place, and that all accessories are either mounted on the instrument or secured inside the box.

In order to be sure that the head window does not crack as a result of the temperatures to

In view of the shocks to which this part of the periscope may be subjected in service, such as a depth-charge attack, an ample margin of strength beyond that necessary to withstand the specified test is most desirable. This is especially true of the head window itself.

The metallic seats for the head window, both in the head and in the bezel frame, should be scraped as necessary to give a true bearing. An approved gasket is inserted between the head window and its seat. Both in the design of the head window, its securing device, and their final assembly in the periscope, all possible precautions are taken to prevent setting up unequal

Figure 4-1. Outer head assembly.

The inner circumference of the head window bezel frame is beveled outward and away from its line of contact with the glass. This increases the effect of wind in clearing drops of water from the glass and reduces the lodgment of water and the deposit of salt by evaporation on the glass near the inner circumference of the bezel frame.

4B2. Outer head assembly. The outer head assembly is composed of the following parts, as shown in Figure 4-1. All bubble numbers in Sections 4B2, 3, and 4 refer to Figure 4-1 unless otherwise specified.

4B3. Description. a. Outer head. The outer head (2) is made of corrosion-resisting steel material. It is designed to meet the service requirements of a covering for the upper part of the skeleton head assembly. The bottom face is counterbored to a nominal depth to accommodate the outer head seat rubber gasket (5). The smaller counterbore is a push fit over a shoulder of the outer taper section (1, Figure 4-15). The machined recess in the outer head is at an angle of 22 degrees from the vertical centerline. This recess receives a head window seat rubber gasket (4) and the head window (7).

The outer face of the outer head has 20 proportionately spaced 6-40 tapped holes to accommodate the head window bezel frame (6). This frame is secured with 20 corrosion-resisting steel lockscrews (8).

A recess of nominal depth, 3/8-inch width, and 5/8-inch length is machined in the rear inner wall of the outer head to provide sufficient clearance for the movement of the skeleton head eccentric arm (21, Figure 4-17).

The inside wall of the outer head is provided with approximately 0.010-inch clearance, so that it does not touch any part of the skeleton head mechanism when assembled to the outer taper section (1, Figure 4-15).

b. Head window bezel frame. The head window bezel frame (6) is made of phosphor-bronze material. Its lower face has a machined irregular recess to fit over the head window (7) with a 45 degrees angle. The 45 degrees angle of the beveled recess is to accommodate a head window bezel frame rubber gasket (3) which compresses to the angle of the head window to form an airtight seal.

The outer flange of the head window bezel frame has 20 proportionately spaced clearance holes with countersunk heads to accommodate the lockscrews (8). These lockscrews extend into tapped holes in the face of the outer head (2). The inner irregular circumference of the head window bezel frame is beveled outward at an angle of 22 degrees away from the line of contact with the glass.

c. Head window. The head window (7) is made of one crown optical glass element with parallel surfaces. It is molded with a 45 degrees angle edge to which a head window bezel frame rubber gasket (3) is applied. It provides a means of sealing without obstructing the entering light rays, and offers a transparent medium through which light is transmitted.

4B4. Disassembly of the outer head. The outer head is disassembled as follows;

1. Rotate the revolving grip of the left training handle assembly (2) so that the zero line of sight graduation of the index ring (6) corresponds to the stationary index line graduation of the fixed grip (29, Figure 4-43). This places the head prism at zero line of sight, offering no obstruction for the removal of the outer head,

2. Remove the AIR OUTLET plug (14, Figure 4-29) and open the AIR OUTLET valve (16) of the eyepiece box (11) to allow the internal gas pressure to be released slowly.

3. Remove the putty from the 12 countersunk holes at the upper part of the outer taper section flange (1, Figure 4-15). This putty covers up the screw heads and permits only personnel familiar with the instrument to break the seal of the periscope.

4. After the nitrogen pressure is released, close the AIR OUTLET valve (16) and replace the AIR OUTLET plug (14, Figure 4-29).

5. Remove the 12 lockscrews (1) from the upper flange of the outer taper section (1, Figure 4-15).

6. Remove the outer head assembly from the outer taper section (1, Figure 4-15) by slowly pulling off the outer head.

7. Remove the outer head seat rubber gasket (5) from the outer taper section shoulder (1, Figure 4-15).

8. Slack off each of 20 head window bezel frame lockscrews (8) several turns.

9. Assemble the outer head seat rubber gasket (5) and the outer head (2) to a special jig with about six lockscrews (1). Apply an internal air pressure of 15 to 30 psi to the outer head assembly to break the seal of the head window (7).

10. Remove the outer head assembly from the special jig.

11. Remove the 20 head window bezel frame lockscrews (8).

12. Lift the head window bezel frame (6) off the outer head (2).

13. Push out the head window (7), placing a piece of clean lens tissue on its bottom face. The lens tissue is applied from the lower base opening of the outer head (2).

14. Remove the head window seat rubber gasket (4) from the seat of the outer head (2) and destroy it.

1. Scrape the seat of the-outer head, if necessary, to give a true bearing. Mark the head window (7) in the position it is scraped so that it cannot be turned end-for-end.

2. Insert the new head window seat rubber gasket (4) of crude rubber of specified drawing dimensions into the head window seat of the outer head (2).

3. Scrape the beveled seat of the head window bezel frame (6), if necessary, to provide a true bearing surface in conjunction with the beveled edge of the head window (7).

4. Clean the inner surface of the head window (7) with clean lens tissue, and use a small air bulb to blow off surface dust.

5. Place the head window (7) in the head window seat of the outer head (2) on the head window seat rubber gasket (4).

6. The head window bezel frame rubber gasket (3) should be approximately 0.072 inch larger than the head window outer irregular circumference, except to comply to drawing dimension as to thickness. Place it in the head window bezel frame (6) in one solid piece. Punch a small hole in the center of the rubber gasket to enable the trapped air to escape.

7. Place the head window bezel frame (6) with the head window bezel frame rubber gasket (3) over the head window (7). Insert the four lockscrews (8) into the tapped holes in the flange of the outer head, and screw each lockscrew down flush with the head window bezel frame.

8. Place a flat wooden block 1 inch thick and slightly smaller than the inner circumference

9. Lubricate the threads of the head window bezel frame lockscrews (8) lightly with a medium grease before insertion, and tighten them evenly. Take each lockscrew down equally in a series of all-around adjustments and use a feeler gage as a check around the head window bezel frame (6).

10. It is desirable to wet the head window bezel frame rubber gasket (3), thereby providing a lubricant for the brass knife-edge, when cutting the crude rubber gasket around the inner irregular circumference of the head window bezel frame (6). The brass blade does not scratch the head window surface.

11. Clean the outer surface of the head window in the same manner as outlined in Step 4 of this section,

12. Use a lens strain testing device to insure that unequal strain is not placed on the head window (7).

13. The outer head seat rubber gasket (5) and the outer head (2) are not assembled to the outer taper section (1, Figure 4-15) with lockscrews (1) until complete disassembly, assembly, and collimation of the instrument have been completed.

1. Place the periscope on V-blocks of the optical I-beam bench. Place it so that sufficient space remains to permit removal of the inner tube.

2. Remove the four axial alignment screws (48, Figure 4-17) located in the small shoulder

3. Remove side plate and pressure gage lockscrews (5, Figure 4-29) from both sides of the eyepiece box (11). It may be necessary to tap out two diagonally opposite holes with an 32 tap in the side plate (9) and the pressure gage

Figure 4-2. Special cord attached to shifting wire spindles and held with both hands.

4. Using two pieces of special cord of 3-foot length doubled, secure one end of each piece of cord to the spindles (1, Figure 4-28) of the power shifting side, and secure the other two loose ends to the spindles (1) of the prism shifting side. Take special care that the end of one cord is secured to the left spindle (1) of the power shifting side, while the other end is secured to the right spindle (1) of the prism shifting side (Figure 4-2). The second piece of cord is secured in like manner to permit one man to hold one set of shifting wire spindles (1) with one hand, while the other set of spindles (1, Figure 4-28) a held with the other hand, using the looped cords.

Figure 4-3. Special spindle adjusting nut adapter.

5. By means of a special spindle adjusting nut removal adapter (Figure 4-3) remove the four shifting wire spindle adjusting nuts (4, Figure 4-28) one by one. The adapter has a short threaded stem which has a clearance hole through its center axis. The clearance hole permits the

6. Remove the shifting wire tape (38, Figure 4-28) from the clamp blocks (16, Figure 4-17) removing and replacing the clamp blocks (16) and clamp block lockscrews (12) to the prism and cube shifting racks (40, 42, 17, and 18) of the skeleton head assembly.

Figure 4-4. The skeleton head assembly is withdrawn.

7. Before proceeding, it is necessary to secure the tapes in place. This is done by using a special metal dowel 1 inch in diameter (Figure 4-5) to which the tapes are tightened sufficiently to pull the dowel into contact with the ninth reduced tube section. (1, Figure 4-18). A larger dowel will not pass through the outer taper section (1, Figure 4-15) while a smaller one may rest on the auxiliary upper eyepiece lens (5, Figure 4-18), in the upper part of the ninth reduced tube section and damage it.

8. After the tapes (38, Figure 4-28) are tightened to the 1-inch metal dowel, and pulled down into contact with the ninth reduced tube section (1, Figure 4-18) by means of the looped cords, the shifting wire spindles (1, Figure 4-28) are free of the prism and power shifting racks (43, 44, 45, and 46) of the eyepiece skeleton assembly.

10. Remove the training handles by taking out the eight hinge bracket bolts (19 and 21, Figures 4-43 and 4-44, respectively) for the left and right training handle assemblies.

11. Remove the focusing knob assembly by taking out the four lockscrews (10, Figure 4-39).

12. Remove the rayfilter by pulling outward on both spring-actuated plunger knobs (24, Figure 4-40).

13. Remove the eyepiece attachments that are secured to the anchor screw pins (19, Figure 4-29) projecting from the eyepiece box itself.

a. Remove the covering lockscrews (4).

b. Unscrew the cover ring (2) with a spanner wrench. Remove the hoisting yoke body (1), phosphor-bronze locating collar (9), lower ball-bearing race (8), ball bearings and retainer (7), and the upper ball-bearing race (6).

c. Remove the split ring (3). All parts of the thrust bearing should be protected from dirt or grit.

d. Remove the cover ring (2).

15. Rotate the periscope on the V-blocks of the Optical I-beam bench so that the eyepiece end is down.

Figure 4-6. Shifting wire tapes attached to 1-inch metal dowel.

Figure 4-8. Eyepiece box and outer tube alignment guide handles in contact.

17. Remove the two lockscrews (7, Figure 4-29) in the main coupling (2) at the eyepiece box (11). Unscrew the main coupling (2), using a special spanner wrench. The main coupling (2) has a right-hand thread on the outer tube and a left-hand thread on the eyepiece box (11).

18. Attach a steel lifting plate (Figure 4-9) to the base of the eyepiece box (11, Figure 4-29) and insert four bolts in the clearance holes in the steel lifting plate and the tapped holes in the

19. Attach a shackle to the lifting projection of the steel lifting plate, and insert the hook of the chain hoist (Figure 4-10). Apply a light lifting strain to this end of the eyepiece box.

22. Attach and secure the hinged clamp (Figure 4-12) over the lower (split) objective lens coupling sleeve (34, Figure 4-23). Locate this hinged clamp at the upper part of the coupling sleeve.

23. Connect the upper part of the lifting spreader bar (Figure 4-13) to the lifting projection of the hinged clamp with a bolt. Connect the lower part of the lifting spreader bar to the lifting projection of the steel lifting plate with a bolt. Place the hook of the chain hoist in the center pad clearance hole of the lifting spreader bar.

24. Take a light strain with the chain hoist on the lifting spreader bar, and remove the adjustable roller stand (Figure 4-11). Resume the removal of the inner tube slowly until the fifth inner tube section (34, Figure 4-20) is clear of the outer tube. The inner tube must be guided parallel with the outer tube and properly centered in it.

25. Attach and secure another hinged clamp (Figure 4-14) over the upper part of the fifth inner tube section (34, Figure 4-20). Attach a shackle in the hole of the lifting projection of the hinged clamp, and with the hook of the chain hoist placed in the shackle, take a light strain with the chain hoist.

Figure 4-14. Hinged clamp attached to fifth inner tube section with shackle and inserted chain hoist hook.

27. Transport the inner tube to the V-blocks of the second I-beam bench. Remove both chain hoist hooks, hinged clamps, and the steel lifting plate.

28. Using canvas-covered galvanized cable slings, each wrapped once around the outer tube, remove the outer tube from the V-blocks of the Optical I-beam bench with both chain hoists and transport it to the periscope rack.

The outer taper section shoulder has a width of 1/2 inch. From this shoulder, the outer taper

The upper end of this flange section is machined with a shoulder which is a push fit in the counterbored portion of the outer head (2, Figure 4-1). The face of the flange is counterbored to a nominal depth to accommodate an outer head seat rubber gasket (5), between the flange and the outer head (2). In this

The upper end of the machined 1.414-inch section is counterbored a short distance with an additional counterbored section to receive the skeleton head assembly (Figure 4-17). A keyway, 0.032 inch deep and 0.124 inch wide, is provided a short distance in the upper part of the counterbored wall. This keyway receives the angular alignment key (19) of the skeleton head assembly and maintains its angular alignment.

Two tapped holes are provided on each side in the overlapping shoulder that projects upward from the flange face. These four tapped holes receive headless lockscrews (48), which retain the skeleton head assembly in the counterbore and extend into mating tapped holes in the cube bracket (45) and the gear train bracket (30) of the skeleton head assembly.

The inside diameter of the taper section does not vary from the calculated diameter at any

The inside section of the lower end of the outer taper section is chamfered at its lower face at a 30 degrees angle. From this point, with a 6 3/8-inch diameter, it tapers upward to a diameter of 5.560 inches in a distance of 6.752 inches, with the shoulder chamfered to a diameter of 4.930 inches.

4D2. Outer tube. The outer tube (2, Figure 4-15) and the outer taper section (1) form the outer shell of the periscope. It is machined cylindrically to fit into a series of bronze steady bearings of the submarine, and is bored cylindrically to receive the assembled inner tube sections, which consist of a series of five telescope system assemblies (Figure 4-16).

The outer tube is machined from a solid forging of corrosion-resisting steel. It is 34 feet 1 inch in length and finished to an outside diameter of 7.497 inches, plus 0.000 inch, minus 0.002 inch.

The inside diameter is ground to 6.375 inches for a distance of 26 feet. The lower part of the outer tube has a counterbore of 6 1/2-inch diameter for 7 feet, with a 15 degrees chamfer to the smaller diameter. This partially counterbored section provides sufficient clearance for the lower (split) objective lens coupling sleeve (34, Figure 4-23).

The external diameter at the lower part has a 5/8-inch undercut section to a depth of 5/32 inch on a side of the vertical centerline. This undercut section starts 2 inches from the bottom face and receives two split ring halves (3, Figure 7-26) of the hoisting yoke assembly. The entire weight of the periscope is carried by the hoisting yoke assembled over the halves of the split ring (3).

The lower external part of the outer tube has a turned shoulder with a threaded section of 12 threads per inch. The threaded section is relieved on each end with a slot, machined for a width of 0.125 inch.

On the lower face of the outer tube, there is a triangular annular ridge on the shoulder 1/64 inch in height and approximately 1/16 inch in width at the base. The angles, including the apex, are filleted. The triangular annular ridge detail is provided to compress a rubber gasket (8, Figure 4-29) into a corresponding triangular annular groove in the large upper face of the eyepiece box (11) joint shoulder. The compression of the rubber gasket (8) into the triangular annular groove of the eyepiece box (11) insures an airtight sealed joint.

A keyway of 3/8-inch width, 1/16-inch depth, and length of 1 1/8 inch is provided in the inner wall of the vertical centerline. This keyway

Two azimuth scale index lines are scribed on the outer tube. The second line is 180 degrees from the first line. Both lines lie in a plane passing through the axis of the outer tube and coinciding approximately with the plane of sight through the vertical centerline of the telemeter lens of the periscope. These lines are in the form of grooves of rectangular section with sides parallel to that radius of the tube which passes through the center of the groove. The width of each groove is not less than 0.015 inch nor more than 0.020 inch. The depth of each groove is not less than 0.010 inch nor more than 0.015 inch. The center of each groove does not, at any point, deviate more than 0.003 inch to either side of a straight line parallel to the axis of the outer tube of the periscope. The angle between the plane in which the grooves are situated and the plane of sight through the vertical centerline of the telemeter lens of the instrument is as small as practicable and does not in any case exceed 15 minutes. The grooves extend upward from the top of the hoisting yoke groove along the outer tube for a distance of 6 feet. In some periscopes the grooves have been extended to a length of 22 feet above the hoisting yoke groove.

Numbers are stamped or engraved on the eyepiece side of the outer tube at intervals of 1 foot for a distance of 6 feet above the hoisting yoke groove, showing the distance in feet from the axis of the line sight through the head window of the periscope to the position of the upper edge of each number. The left edge of the left digit of each number is located 1/2 inch to the right of the azimuth index line, each number is at least 3/8 inch high and is stamped or engraved to a sufficient width and depth as to be easily visible to a person standing 5 feet away from the periscope.

The steady bearings are placed in the submarine periscope supports at intervals to carry the periscope vertically, and also to provide vertical guidance. The periscope can be trained through 360 degrees of azimuth, and raised and lowered.

The raising and lowering are accomplished by one of two systems, electric or hydraulic. With the electric hoisting system, the wire ropes

With the hydraulic hoisting system, the plunger rods are attached to the bracket connectors secured to the hoisting yoke. The hydraulic control valve controls the raising and lowering of the periscope by means of the ship's hydraulic system under high pressure. A safety limit stop serves to cut off the hydraulic pressure when the periscope is at the limit of the vertical travel or the observing position. The weight of the periscope causes the hydraulic pistons to act on the volume of oil in the low-pressure side of the system, and the friction of the oil in the return piping to control the lowering of the periscope. No limit stop is provided in lowering the periscope. The precautions to be taken when elevating and lowering a periscope are:

1. Notify men working around the vicinity to stand clear.

2. Remove the cover plate (if fitted) over the top steady bearing of the submarine.

4D3. Inner tube assemblies. Figure 4-16 shows the inner tube of the periscope divided into five telescope systems. Each telescope system is made up of assemblies as follows:

1. Galilean telescope system: skeleton head assembly.

2. Auxiliary upper telescope system: seventh, eighth, and ninth reduced tube sections.

4. Upper main telescope system.

Part I. First reduced tube section and fifth and sixth inner tube sections.

Part II. Second, third, and fourth inner tube sections.

5. Lower main telescope system.

a. Lower (split) objective lens and mount assembly.

b. Objective operating mechanism assembly.

c. First inner tube section assembly.

d. Eyepiece skeleton assembly.

e. Eyepiece box and miscellaneous assemblies.

1) One stadimeter transmission shaft packing gland assembly, and four spring-loaded packing gland assemblies.

2) Eyepiece window frame assembly.

f. External projections to the eyepiece box.

1) Stadimeter housing assembly.

2) Focusing knob assembly.

3) Rayfilter assembly.

4) Eye buffer and blinder assembly.

5) Variable density polaroid filter assembly.

6) Training handle assemblies.

7) Hoisting yoke assembly.

2. Remove the prism and power shifting tapes (38, Figure 4-28) by slacking off the four shifting wire clamps (2) of the eyepiece skeleton assembly. Remove them from the reduced tube and inner tube sections.

1. Remove the four lockscrews (16, Figure 4-18) from the lower part of the seventh reduced tube section (14). These lockscrews are unscrewed from tapped holes in the upper part of the sixth reduced tube section (1, Figure 4-19).

2. Unscrew the lower part of the seventh reduced tube section (14, Figure 4-18) from the

4E3. Separation of the auxiliary lower telescope system. This consists of the second, third, fourth, fifth, and sixth reduced tube section assembly.

1. Remove the two lockscrews (22, Figure 4-19) from the removable air line strap (21) and remove the air line strap. These lockscrews are unscrewed from tapped holes in the second reduced tube section (19).

2. Pull the air line section (18, Figure 4-20) outward to disconnect the air line coupling (14) and remove the air line section (18) from the air line adapter (11, Figure 4-19) and the attached coupling (14, Figure 4-20) from the bent air line section (17).

3. Remove the four lockscrews (8) from the upper part of the first reduced tube section (1). These lockscrews are unscrewed from tapped holes in the second reduced tube section (19, Figure 4-19).

4. Unscrew the second reduced tube section (19) from the first reduced tube section (1, Figure 4-20). The second, third, fourth, fifth, and sixth reduced tube sections are removed together.

4E4. Separation of the upper telescope system. This consists of two assemblies, Parts I and II.

1. Remove the two lockscrews (22, Figure 4-20) removing the removable air line strap (19) from the lower part of the first reduced tube section (1). Remove the bent air line (17) from this reduced tube section, carrying with it the air line coupling (15) and short air line section (16) from the upper opening of the soldered air line section (30) of the sixth inner tube section (23).

2. Remove the air line section (31) from the lower opening of the soldered air line section (30) of the sixth, inner tube section (23) and the upper opening of the soldered air line section (10) of the fourth inner tube section (1, Figure 4-21).

3. Remove the air line section (21) pulling it outward to free it from the lower part of the soldered air line (10) of the fourth inner tube section (1) and removing it from the upper part of the soldered air line section (20) of the third inner tube section (11).

4. Remove the four lockscrews (35, Figure 4-20) from the lower part of the fifth inner tube section (34). These lockscrews are unscrewed

5. Remove the fifth inner tube section (34, Figure 4-20) unscrewing it from the upper part of the fourth inner tube section upper end coupling (5, Figure 4-21).

6. Remove the two lockscrews (32) from the removable air line strap (30) and remove the air line strap from the lower part of the second inner tube section (22). These lockscrews are unscrewed from tapped holes in the second inner tube section.

7. Remove the two lockscrews (24, Figure 4-27) from the removable air line strap (21) and remove the air line strap from the upper part of the first inner tube section (1).

8. Lift up both air line sections (29 and 18, Figures 4-21 and 4-27 respectively) sufficiently to remove the air line section (29, Figure 4-21) and the soldered air line coupling (28) from the air line section (18, Figure 4-27) of the first inner tube section (1), and remove the air line section (29, Figure 4-21) from its connection with the lower opening of the soldered air line section (20) of the third inner tube section (11).

9. Slide the air line section (18, Figure 4-27) upward to disconnect the air line coupling (17) from the bent air line section (16) located at the lower end of the first inner tube section (1).

10. Remove the two lockscrews (24) from the removable air line strap (19) and remove the air line strap from the lower part of the first inner tube section (1).

11. Remove the bent air line section (16) from its connection with the long air line coupling (15).

12. Unscrew the long air line coupling (15) from the flange of the eyepiece skeleton (42, Figure 4-28).

13. Remove the 15 lockscrews (27, Figure 4-23) from the lower part of the lower (split) objective lens coupling sleeve (34). These lockscrews are unscrewed from tapped holes in the large flange section of the track sleeve (2).

14. Slide the lower telescope system assembly clear of the coupling sleeve (34) about a foot.

15. Remove the four lockscrews (22) from the upper part of the lower (split) objective lens coupling sleeve (34). These lockscrews are unscrewed from tapped holes in the lower part of

16. Remove the split-objective lens coupling sleeve (34, Figure 4-23) unscrewing it from the lower part of the second inner tube section lower end coupling (26, Figure 4-21) and remove the second, third, and fourth inner tube section assembly.

4E5. Separation of the lower telescope system. The lower telescope system is broken into assemblies in the following manner:

1. Remove the two stadimeter collimating lockscrews (13, Figure 4-22) and washers (14) from each of the lower (split) objective lens and mount assembly halves. These lockscrews are unscrewed from tapped holes in each mounting plate half (5, Figure 4-23) of the objective operating mechanism assembly. The straight dowel pins (15, Figure 4-22) are carried out with the mounts (1 and 2) from the mounting plates (5, Figure 4-23).

2. Remove the taper pin (33) from the upper part of the stadimeter transmission shaft coupling (14).

3. Remove the two taper pins (10, Figure 4-27) from the two stadimeter transmission shaft thrust collars (4) located on the stadimeter transmission shaft (22) on each side of the spider (2) of the first inner tube section assembly.

4. Remove the stadimeter transmission shaft (22, Figure 4-27) sliding it out of the stadimeter transmission shaft coupling (14, Figure 4-23) and clear of the track sleeve (2). Remove this coupling from the operating gear pinion shaft (13).

5. Remove the four lockscrews (23) from the lower end of the track sleeve (2). These lockscrews are unscrewed from tapped holes in the upper part of the first inner tube section upper end coupling (11, Figure 4-27).

6. Remove the track sleeve (2, Figure 4-23), unscrewing it from the upper part of the first inner tube section upper end coupling (11, Figure 4-27) and remove the split-objective operating mechanism assembly (Figure 4-23).

7. Remove the stadimeter transmission shaft (22, Figure 4-27) from the first inner tube section assembly, also removing the two thrust collars (4) from each side of the spider bearing projection (2).

9. Remove the six lockscrews (1, Figure 4-36) from the stuffing boxes (5) for the left and right training handle assemblies, and the six lock screws (3, Figure 4-35) from the stuffing box (6) for the eyepiece drive packing gland assembly.

10. Remove the four lockscrews (13, Figure 4-32) from the stuffing box (4) for the rayfilter packing gland assembly.

11. Remove the eyepiece drive and the left and right training handle packing gland assemblies (25 and 26, Figure 4-29) using a special packing gland wrench. Place this wrench over the square section of each shaft. Using a sideward thrust movement, remove the assemblies.

12. Remove the rayfilter drive actuating gear (11, Figure 4-32) from the protruding square section of the rayfilter drive actuating shaft (10). Remove the rayfilter drive packing gland assembly by placing a pair of parallel pliers over the square section of this shaft, and, using a slight sideward thrust, pulling outward.

13. Disassembly of the spring type stadimeter transmission shaft assembly proceeds as follows:

a. Remove the lockscrew (1, Figure 4-30) from the spring retainer (3) and, using a special wrench, unscrew the spring retainer (3) from the stuffing box chamber in the eyepiece box base (11, Figure 4-29).

b. Remove the packing gland spring (4, Figure 4-30), packing, and packing gland (2) from the stuffing box chamber.

14. Where the modified stadimeter transmission shaft packing gland assembly is utilized, delete Step 13 and follow the disassembly procedure as follows:

a. Remove the lockscrew (1, Figure 4-31) from the packing retainer (2).

b. Unscrew the packing retainer from the stuffing box section in the eyepiece box (11, Figure 4-29) using a special wrench.

c. Remove the one packing retainer brass washer (6, Figure 4-31) the three separation brass washers (5), the four Hycar packing washers (4), and the one gland filler piece (3) from the stuffing box chamber in the eyepiece box base (11, Figure 4-29).

16. Remove the four short and eight long lockscrews (2 and 3, Figure 4-38) from the eyepiece window frame (7) of the eyepiece window assembly. These lockscrews are unscrewed from tapped holes in the counterbored recess face in the eyepiece box (11, Figure 4-29). Remove this assembly from the eyepiece box.

17. Remove the eyepiece lens mount (19, Figure 4-28) by unscrewing it from the eyepiece prism front retaining plate (24) attached to the eyepiece prism mount (20). The eyepiece lens mount (19) contains the eyepiece lens (52), eyepiece lens clamp ring (16), and its lockscrew (41).

19. Remove the eyepiece box (11) from the eyepiece skeleton (42, Figure 4-28) carrying it off from the lower end.

20. Move the counterweight to its extreme lower position in order to remove the four lockscrews (37) from the cylindrical bearing surface in the upper part of the eyepiece skeleton (42). These lockscrews are unscrewed from tapped holes in the spider bearing (3, Figure 4-27) of the first inner tube section assembly.

21. Remove the upper part of the eyepiece skeleton (42, Figure 4-28), unscrewing it from the lower part of the spider bearing (3, Figure 4-27).

a. Skeleton head frame. The skeleton head frame (20) is machined of phosphor-bronze material. It forms the necessary framework to carry the prism tilt mechanism, Galilean telescope, and change of power mechanism. The skeleton head is a push fit in the counterbored section in the upper 1.890-inch section of the outer taper section (1, Figure 4-15).

The prism tilt mechanism is composed of numerous mechanical parts in the upper and left hand side of the skeleton head to operate one optical element, the head prism (55).

b. Head prism. The head prism (55) is a right angle prism made of dense flint optical glass material. It is used to reflect the light rays at right angles. The light rays enter from any position of elevation between 90.5 degrees to 26 degrees depression in low power and from 78.5 degrees elevation to 14 degrees depression in high power, and are deflected downward into the instrument.

d. Head prism side plates. The head prism side plates left and right (32 and 33) are attached to the head prism mount (31) with two lockscrews (13) each. These side plates retain the head prism (55) from sideward movement. Attached to each side plate are two head prism shade wire links (38) secured with rivets (59). The opposite ends of each wire link are secured to each bent-over side of the head prism shade (37), so that the shade is carried vertically with the movement of the head prism mount (31).

e. Head prism shade. The head prism shade (37) is made of sheet brass material, and is constructed to conform with the contour of the skeleton head periphery. The sides are bent downward and again at 90 degrees to fit into a vertical recess groove in each of the inner side walls of the skeleton head. Wire links (38) are attached with rivets (59) to each bent side of the shade. As the head prism (55) is elevated or depressed, the head prism shade is carried vertically and is used principally in the elevated position to shade the lower 90 degrees face of the head prism (55), thus preventing a double image.

f. Eccentric arm. The eccentric arm (21) is made of cast phosphor-bronze material. The large section has a reamed hole with a stub section having a sawed slot, and fits over the eccentric of the eccentric shaft (22). The stub section

g. Eccentric shaft. The eccentric shaft (22) is made of corrosion-resisting steel material. The centerline of the eccentric is offset from both shaft stems 0.179-inch. The offset provides the necessary cam movement for the manipulation of the head prism (55) to all the required degrees of elevation and depression. Both of the eccentric shaft stems fit into the lower reamed bearing halves of the skeleton head (20) and are secured radially with the upper two reamed bearing cap halves (23). These bearing caps are secured with two lockscrews (46) each. The axial displacement of the eccentric shaft stems is secured individually on each side. The right side has a thrust collar (35) secured with a taper pin (50), while the left side accommodates a head prism shift actuating gear (24) which also is secured with a taper pin (52). Both the thrust collar (35) and the head prism shift actuating gear (24) are secured snugly against the bearings in the milled recesses of the skeleton head.

h. Head prism shift actuating gear. The head prism shift actuating gear (24) is made of phosphor-bronze material. The large diameter has 20 teeth of nominal width around the outer circumference, to mesh with the teeth of the fourth intermediate prism shift gear (25). The reamed hole of the actuating gear (24) is a push fit on the stem section of the eccentric shaft (22) and is secured with a taper pin (52) through the hub section.

i. Fourth intermediate head prism shift gear. The fourth intermediate head prism shift gear (25) is made of phosphor-bronze material and has 18 teeth around the outer circumference which mesh with the teeth of the head prism

j. Third intermediate head prism shift gear. The third intermediate head prism shift gear (26) is made of phosphor-bronze material and has 32 teeth around the outer circumference which mesh with the teeth of the second intermediate head prism shift gear (27). This intermediate head prism shift gear (26) has a reamed hole in the center axis which is a sliding fit over the first integral upper pin projection and sets in the shallow counterbored section in the gear train bracket (30). It also is provided with two number 60 drilled holes for the insertion of rivets 53) and is secured to the fourth intermediate head prism shift gear (25) and riveted.

k. Second intermediate head prism shift gear. The second intermediate head prism shift ear (27) is identical to the third intermediate bead prism shift gear (26) except in the diameter of its undercut shoulder. The teeth mesh with the first intermediate head prism shift gear (28). The reamed hole in its center axis is a sliding fit over the second integral upper pin projection and sets in the countersunk recess of the gear train bracket (30).

1. First intermediate head prism shift gear. The first intermediate head prism shift hear (28) is made of phosphor-bronze material, and has 18 teeth around the outer circumference which mesh with the second intermediate head prism shift gear (27). This intermediate head prism shift gear (28) has a reamed hole in the center axis which is a sliding fit over the second integral lower pin projection and sets in the countersunk recess of the gear train bracket (30). It is also provided with two number 60 drilled holes for the insertion of rivets (54) and is secured to the head prism shift gear (29) and riveted.

m. Head prism shift gear. The head prism shift gear (29) is made of phosphor-bronze material, and has 21 teeth around the outer circumference

n. Head prism shifting racks. The head prism shifting racks left and right (40 and 42) are made of blued, cold rolled steel, and operate in vertical recess grooves. The left shifting rack (40) is made of nominal width and thickness and is provided with 22 gear teeth in the upper part of the right side in a distance of 1.437 inches to mesh with the teeth of the head prism shift gear (29) on the left side. This shifting rack (40) is offset to the right, and stepped inward toward the center axis. The outer portion of the stepped section is provided with a radius contour of 0.607 inch, and the inside portion has a 0.550-inch radius contour to conform to the counterbore of the skeleton head. The lower end has a 45 degrees radius chamfer conforming to a similar mating radius chamfer of the clamp block (16). Two tapped holes are provided in the radius contour wall of the stepped section to accommodate clamp block lockscrews (12). The flat monel metal tape ends of the shifting wire tape (38, Figure 4-28) of the eyepiece skeleton assembly are secured to the outer radius contour of the stepped section with the clamp blocks (16) and the head prism shifting rack (40). This causes the shifting wire tape (38, Figure 4-28) to be stepped at 45 degrees bevel downward sufficiently to carry it free in the inside radius groove of the skeleton head. Above the stepped section on the outer surface of the head prism shifting rack (40) a protruding stop section of 0.375 inch is located a distance of 1.125 inches from the lower end, and its outer surface has a radius slightly below the contour of the skeleton head periphery. The stop section in contact with the cube bracket (45) restricts the movement of the head prism in the elevated position to the designed limits, thus preventing any damage to the head prism (55) and its operating mechanism.

Both head prism shifting racks left and right (40 and 42) fit into two vertical slots on each side of the vertical centerline of the skeleton head left side wall. Two vertical elongated holes below the groove seats, and offset toward the vertical centerline, provide clearance for the stepped sections of both head prism shifting racks and allow for the attachment of the shifting wire tape (38, Figure 4-28).

o. Gear train bracket. The gear train bracket (30) is made of blued, cold rolled steel material, and serves various functions. It serves to carry the gear train of the first, second, third, and fourth intermediate head prism shift gears (28, 27, 26, 25) and the head prism shift gear (29) by means of four pin projections integral with the bracket. It provides a closed housing by means of countersunk recesses below the three integral upper pin projections for the 1st, 2nd, and 3rd intermediate head prism shift gears (28, 27, and 26) and also serves as a retaining plate for the upper part of the head prism shifting racks left and right (40 and 42). The lower pin projection serves as a pivot for the reamed hole axis of the Galilean eyepiece lens cube (2). All four integral pin projections are a sliding fit into the reamed holes in the left side wall of the skeleton head. The bracket is secured to the flat recess face in the skeleton head with four lockscrews (15) located in the lower part. Two tapped holes are located in the periphery of this bracket on each side of the centerline in the lower part to coincide with the tapped holes of the overlapping section of the outer taper section (1, Figure 4-15) to maintain the axial alignment of the skeleton head with lockscrews (48). The periphery of the bracket when assembled on the skeleton head conforms to its periphery.

p. Cube bracket. The cube bracket (45) is made of blued, cold rolled steel material. It serves to retain the lower part of the head prism

q. Angular alignment key. The angular alignment key (19) is inserted in the vertical centerline in the left side of the skeleton head and is located in the center part. This key is a sliding fit in the vertical keyway in the upper part of the counterbore wall of the outer taper section, and maintains the angular alignment of the skeleton head (20).

The Galilean telescope system is composed of two lenses; namely, a negative Galilean eyepiece lens doublet and a positive Galilean objective lens doublet. It is used in reverse to effect a low power magnification and increase the true field of view.

r. Galilean eyepiece lens. The Galilean eyepiece lens (56) is made of two optical elements, one is a divergent meniscus flint element, cemented to the equi-concave crown element, forming a negative doublet. The divergent meniscus element cemented to the equi-concave element of the Galilean eyepiece lens corrects for spherical and chromatic aberration. It is mounted in a Galilean eyepiece lens mount (3) and burnished in place. The threaded mount can be screwed vertically in the threads of the Galilean eyepiece lens mount housing (4) by using a sharp pointed scribe inserted in any one of a series of eight shallow drilled recesses. This vertical movement provides a means of focusing for elimination of parallax.

s. Galilean eyepiece lens mount housing. The galilean eyepiece lens mount housing (4) is provided with an internal threaded bore to carry the mounted Galilean eyepiece lens (56) and mount (3) movement to eliminate parallax. The housing flange has three equally spaced clearance holes. One hole is used as a pivot hole, while the

t. Galilean eyepiece lens cube. The Galilean eyepiece lens cube (2) is constructed of a suitable framework for holding the Galilean eyepiece lens mount housing (4). By means of integral pin projections of the cube bracket (45) and the gear train bracket (30) protruding in the reamed hole axis in opposite sides of the cube, it can be rotated for change of power. The undercut shoulder of 0.010-inch width and 0.437-inch diameter on each side face provides sufficient bearing wall. All corners are rounded off with a radius of 0.750 inch. The two 90 degrees V-grooves in the right side wall located at 90 degrees, receive the upper pawl (41) attached to the pawl holder (8) with rivets (51). The pawls are held in the grooves with a reinforcing spring (9) to maintain the cube in either the IN or OUT position (low or high power). The 90 degrees rotation of the cube is accomplished by the upper pin projection (60) of the right cube shifting rack (17), protruding into the elongated slot in the right side face. The clearance hole in the upper face of the cube allows the lower undercut shoulder sufficient free movement for collimation of the Galilean eyepiece lens (56). Three equally spaced tapped holes in the upper face receive lockscrews (5) to secure the Galilean eyepiece lens mount housing (4) after collimation. The lower wall is bored out and provided with antireflection threads, and also the front and rear walls, thus offering no obstruction for the entering light rays in either high or low power. The skeleton head (20) is machined out, leaving only the side walls and the center support to accommodate sufficient clearance for the assembly, disassembly, and manipulation of this cube.

u. Galilean objective lens. The Galilean objective lens (57) is made of two optical elements, consisting of a double convex flint element cemented to a divergent meniscus dense crown element, forming a positive objective lens doublet. It is mounted in the Galilean objective lens cube (1) and secured with a Galilean objective lens retainer (6). The retainer is spot soldered to the Galilean objective lens cube (1) to prevent it from unscrewing.

The change of power mechanism is located on the right side wall of the skeleton head frame (20) and is composed of numerous parts to operate the Galilean telescope system.

w. Cube shifting racks. The cube shifting racks right and left (17 and 18) operate in vertical recess grooves, located in the right side wall of the skeleton head. These shifting racks are made of blued, cold rolled steel material, and are constructed similarly to the head prism shifting racks left and right (40 and 42). The right cube shifting rack (17) is wider than the left, and is provided with two assembled and riveted pins (60). These two pins protrude through two elongated slots in the wide vertical recess groove to the right of the vertical centerline and into the elongated slot in the Galilean eyepiece lens and objective lens cubes (2 and 1). These protruding pins (60), by movement of the right or left cube shifting racks (17 and 18), shift the Galilean telescope system to the IN or OUT position. That is, each cube carrying one lens doublet each of the Galilean telescope is

The cubes (1 and 2) are maintained in either position by means of pawls (41) protruding through two elongated slots under spring tension into the 90 degrees V-groove in the right side wall of each cube. The right and left cube shifting racks (17 and 18) are provided with 10 teeth, each located 2 1/2 inches from the lower end in a distance of 11/16-inch, to engage the power shift gear (7) on opposite sides. The left cube shifting rack, (18) is narrower than any of the head prism shifting racks (40 and 42) and the right cube shifting rack (17).

This left cube shifting rack (18) operates in the vertical recess groove to the left of the vertical centerline. When it is pulled downward by the shifting wire tape (38, Figure 4-28) its teeth engage with the power shift gear (7) causing it to rotate. The power shift gear (7), also engaged with the teeth of the right cube shifting rack (17), causes it to be carried upward, and by means of the protruding pins (60) extending through the elongated slots in the skeleton head (20) into the elongated slots of each cube, rotates the cubes to the OUT position and vice versa.

The integral stops of the cube shifting racks protruding outward in each vertical recess groove, contact the lower side face of the lower cube bracket (45) to restrict the movement of each cube beyond the 90 degrees V-groove engagement of both pawls (41).

Both cube shifting racks right and left (17 and 18) are stepped outward from the vertical centerline. The inward stepped sections that tend toward the center axis, for the attachment of the shifting wire tape (38, Figure 4-28) clamp blocks (16), and the clamp block lockscrews (12) are constructed identically to the stepped sections of the head prism shifting racks (40 and 42).

x. Power shift gear. The power shift gear (7) is made of corrosion-resisting steel material, and is provided with 12 teeth in the outer circumference. Both sides of the gear have undercut shoulders, and it sets in the countersunk recess in the vertical centerline and center part of the

y. Power shift pawls. The two power shift pawls (41) are made from tool steel material with an over-all length of 0.375 inch. The detent section is constructed at a 90 degrees angle, to engage in the 90 degrees V-grooves of each Galilean objective lens and eyepiece lens cube (1 and 2) through the elongated slots in the outer left vertical recess groove in the right side wall of the skeleton head.

Each pawl is attached to a pawl holder (8) made of sheet bronze material with two rivets (51). The left vertical recess groove has three enlarged recess sections to accommodate the wider sections of the pawl holders (8) and the reinforcing spring (9) and are secured with two lockscrews (11) each. The reinforcing spring (9) is made of clock spring material, bent to shape, with a wide center section for the insertion of two lockscrews (11). The upper and lower narrow sections of the reinforcing spring (9), overlapping the ends of the power shift pawls (41), provide sufficient spring tension to maintain the detent in the 90 degrees V-grooves for either the IN or OUT position of the cubes.

z. Cube brackets and power shift gear bracket. 1. Cube brackets. The three cube brackets (45) are made of blued, cold rolled steel material, and have integral pin projections. The integral pin projection of the upper bracket is a sliding fit in the reamed hole in the vertical centerline of the skeleton head, and protrudes further into the reamed hole axis of the right side of the Galilean eyepiece lens cube to serve as a pivot for this side. The bracket has a recessed section which fits over the upper part of the reinforcing spring (9) to allow clearance for this part of the spring when the detent pawl (41) lifts on the smooth area between the two 90 degrees V-grooves in the cubes. The bracket is secured on the flat milled recess over the upper part of the cube shifting racks right and left (17 and 18)

The lower cube bracket serves the same purpose as noted above for the Galilean eyepiece lens cube (2) except that it is used for the Galilean objective lens cube (1) minus the tapped holes in the periphery. The lower side of this cube bracket serves as a stop for the protruding stops integral sections of the cube shifting racks right and left (17 and 18), as they contact it alternately for the IN and OUT position of the cubes.

2. Power shift gear bracket. The power shift gear bracket (39) is similar in construction to the cube brackets (45) except for length. It is provided with a pin projection, an integral part of the bracket, which has a countersunk recess to accommodate sufficient clearance for part of the power shift gear (7). The pin projection serves as a pivot for the power shift gear (7) and is a sliding fit in the reamed hole in the vertical centerline of the skeleton head. It is secured over the cube shifting racks right and left (17 and 18) to the flat milled recess of the skeleton head with two lockscrews (15).

4F2. Disassembly of the skeleton head assembly. The skeleton head assembly is disassembled as follows:

1. Move the cube shifting racks right and left (17 and 18), shifting the Galilean telescope system to the OUT position or high power. This allows the Galilean objective lens (57), Galilean objective lens retainer (6), Galilean eyepiece lens (56), Galilean eyepiece lens mount (3), and the Galilean eyepiece lens mount housing (4) to be removed.

2. Remove the three lockscrews (5) from the flange of the Galilean eyepiece lens mount housing (4). These lockscrews are unscrewed from tapped holes in the Galilean eyepiece lens cube (2). Remove the Galilean eyepiece lens mount housing (4) with the mounted Galilean eyepiece lens (56) and its mount (3). Remove the lockscrew (14), unscrewing it from the housing and the mounted Galilean eyepiece lens (56).

4. Remove the four lockscrews (15) from the gear train bracket (30). These lockscrews are unscrewed from tapped holes in the left side wall of the skeleton head (20). Careful attention and skill are required to remove the gear train bracket. Since the gear train bracket (30) has four integral pin projections, it must be lifted evenly.

5. Remove the head prism shift gear (29) and the first intermediate head prism shift gear (28) together.

6. Remove the second intermediate head prism shift gear (27).

7. Remove the third and fourth intermediate head prism shift gears (26 and 25).

8. Remove the two lockscrews (15) from the cube bracket (45) on the left side of the skeleton head (20). These lockscrews are unscrewed from the tapped holes in the centerline of the skeleton head. This cube bracket (45) must be raised carefully in order not to break its integral pin projection.

9. Remove the head prism shifting racks left and right (40 and 42) carrying with them the assembled clamp locks (16) and lockscrews (12).

10. Remove the two lockscrews (15) from each of the two cube brackets (45) on the right side of the skeleton head (20). These lockscrews are unscrewed from the tapped holes in the skeleton head. Remove both cube brackets (45), raising each one carefully in order not to break the integral pin projection of each cube bracket.

11. Remove the two lockscrews (15) from the power shift gear bracket (39). These lockscrews are unscrewed from the tapped holes in the right side wall of the skeleton head. Remove the power shift gear bracket (39), raising it carefully in order not to break the integral pin projection of the bracket.

12. Remove the cube shifting racks right and left (17 and 18), carrying with them the assembled clamp blocks (16) and lockscrews (12).

13. Remove the power shift gear (7).

15. Remove the two lockscrews (11) from the reinforcing spring (9), and remove the reinforcing spring.

16. Remove the two lockscrews (11) from each upper and lower pawl holder (8) and remove the pawl holder (8) and pawls (41). All lockscrews (11) for (8 and 41) are unscrewed from the tapped holes in the enlarged recesses of this outer left vertical recess groove in the right side wall of the skeleton head (20).

17. Remove the two lockscrews (46) from each bearing cap (23), and remove the two bearing caps. These lockscrews are unscrewed from the tapped holes in the top face of the skeleton head.

18. Remove the lockscrew (49), unscrewing it from its contact with the head prism mount pivot shaft (36). Remove the head prism mount pivot shaft (36).

19 Remove the head prism mount (31), head prism (55), head prism mounting clamps (43 and 44), head prism side plates (32 and 33), head prism shade wire links (38), eccentric arm (21), and eccentric shaft (22), in the assembled position, sliding out the head prism shade (37) from the upper part of the skeleton head (20).

20. Remove the lockscrew (49), unscrewing it from its contact with the eccentric arm pin (34), and remove the eccentric arm pin.

21. Remove the eccentric arm (21) from between the two recess side walls of the head prism mount base (31).

22. Remove the two lockscrews (13) from the left and right head prism side plates (32 and 33), and remove both side plates. The head prism shade wire links (38) and the head prism shade (37) are carried assembled with the side plates.

23. Remove the two lockscrews (10) from each of the upper two head prism mounting clamps (43 and 44). These lockscrews are unscrewed from tapped holes in the beveled side faces in the upper part of the head prism mount (31). Remove the head prism mounting clamps and the head prism (5,5). Wrap the head prism in a clean

24. Remove the taper pin (50) from the eccentric shaft collar (35), and remove the collar.

25. Release the eccentric arm adjusting lockscrew (47). Remove the eccentric shaft (22) with the head prism shift actuating gear (24). The lockscrew (47) is unscrewed from the tapped hole in the lower split stub section of the eccentric arm (21). The spacer washer (58) is also removed.

26. Remove the taper pin (52) from the hub section of the head prism shift actuating gear (24), and remove the gear from the eccentric shaft (22).

4F3. Reassembly of the skeleton head assembly. The skeleton head assembly is reassembled in the following manner:

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

2. Place the head prism shift actuating gear (24) on the left side of the eccentric shaft stem section (22). A reference scribed line on the left side of the eccentric designates the proper side for reassembling the above gear, with the hub section of the gear facing the eccentric. Insert the taper pin (52) in the shoulder of the hub section to secure the gear to the eccentric shaft stem section.

3. Assemble the eccentric shaft collar (35) on the right stem section of the eccentric shaft (22). Place the taper pin (50) in the collar to secure it to the eccentric shaft.

4. Place the eccentric arm (21) over the assembled collar (35) and rotate the eccentric shaft (22) sufficiently to slide the eccentric arm over the eccentric. Place the spacer washer (58) in the slot of the eccentric arm stub section, and insert the adjusting lockscrew (47) in the front stub section, tightening it sufficiently to provide a snug sliding fit. It is important to remember that any wear of the eccentric and the eccentric arm bearing surface decreases the designed limits of the head prism travel for elevation and depression.

5. Assemble the complete eccentric assembly into the lower bearing halves of the upper part of

6. Assemble the left and right side plates (32 and 33) to the head prism mount (31) on both sides. Secure the side plates with two lockscrews (13) each in the tapped holes in the head prism mount.

7. Clean the head prism (55) using clean lens tissue; also clean off the surface dust. Place the head prism with its hypothenuse face of the scraped head prism mount (31) sliding the lower part under the 60 degrees prongs of the two lower assembled head prism mounting clamps (43 and 44). Apply two head prism mounting clamps (43 and 44) to the upper beveled side faces of the head prism mount, securing each with two lockscrews (10). Take precautions to note that the 60 degrees prongs touch the 90 degrees faces of the head prism (55).

8. Swing the extended arm bearing of the eccentric arm (21) to the front of the skeleton head (20). Place the recess walls of the head prism mount base over the extended arm bearing section, and insert the eccentric arm pin (34) through the reamed hole in the recess wall into the reamed hole in the extended arm bearing section and through the opposite recess side wall. Secure this pin with a lockscrew (49) which screws into the right recess side wall tapped hole in the head prism mount base, and contacts the spotted recess in the eccentric arm pin (34).

9. Insert the prism shade (37) in the two vertical grooves cut in the inner side walls of the skeleton head (20).

10. Check the reference scribed lines of the eccentric (22) and the eccentric arm (21) on the left side, and rotate them into coincidence. The coincidence of both scribed lines designates the full elevated position of the head prism (55).

11. With the position of the eccentric shaft (22) and the eccentric arm (21) as noted above, the head prism mount (31) is set in place. Insert the head prism mount pivot shaft (36) in the reamed hole in the outer right side wall of the

12. Place the Galilean objective lens and eyepiece lens cubes (1 and 2) in their respective openings in the skeleton head (20). Check the cubes to ascertain that they are located for the IN position or low-power.

13. Place the pawl holders (8) and the assembled pawls (41) in the outer vertical recess groove in the right side wall of the skeleton head. The pawls fit in the elongated slots, and the pawl holders in the enlarged recesses in the upper and lower part of this vertical recess groove. Secure each pawl holder (8) with two lockscrews (11) which screw into the tapped holes in the enlarged recess face.

14. Place the reinforcing spring (9) over the pawls in the center enlarged recess of the above vertical recess groove and secure it with two lockscrews. The lockscrews are inserted in clearance holes in the spring and screwed into tapped holes in the enlarged recess face.

15. With the Galilean objective lens and eyepiece lens cubes (1 and 2) located in the IN position, apply the right cube shifting rack (17), placing the assembled protruding pins (60) through the elongated slots in the outer right vertical recess groove in the right side wall.

16. Place the left cube shifting rack (18) in the center of the three vertical recess grooves in the skeleton head, right side wall (20).

17. Assemble the two cube brackets (45) to the two flat recesses in the right side wall of the skeleton head over the cube shifting racks right and left (17 and 18). Place the integral pin projection of each cube bracket in the reamed holes in the skeleton head and the reamed hole axis in each cube. Carefully push the integral pin projection of the cube bracket down into the reamed hole axis in each cube. Secure each cube bracket with two lockscrews (15). These lockscrews extend into tapped holes in the right sidewall of the skeleton head.

19. Assemble the cube bracket (45) over the head prism shifting racks (40 and 42). The integral pin projection of this cube bracket extends into the reamed hole in the skeleton head and into the reamed hole axis in the Galilean objective lens cube (1). Carefully push the integral pin projection of the cube bracket down into the reamed hole axis in the cube. Secure the bracket with two lockscrews (15) which extend into tapped holes in the recess face.

20. To align the gear train for the head prism shift mechanism, check the scribed line of the eccentric of the eccentric shaft (22) and the eccentric arm (21) for coincidence. This position places the head prism (55) in the full elevated position. In this position move the left head prism shifting rack (40) upward until its integral stop is in contact with the lower side face of the cube bracket (45). Move the right head prism shifting rack (42) downward and measure a distance of 0.875 inch from the lower side face of the cube bracket (45) to the upper shoulder of the stop integral with this head prism shifting rack. This distance is required to shift the head prism (55) to 74.5 degrees elevation and 10 degrees depression.

21. Reassembly of the gear train (Steps 20 to 23 inclusive) proceeds as follows: Place the head prism shift gear (29) and the assembled first intermediate head prism shift gear (28) in the countersunk recess in the skeleton head. Check the reference line on the face of the first intermediate head prism shift gear (28) and place it so that the reference line is in the upper centerline of the skeleton head. The head prism shift gear teeth (29) engage on opposite sides with the head prism shifting racks (40 and 42).

22. Place the second intermediate head prism shift gear (27) so that its reference line tooth meshes with the reference line tooth of the first intermediate head prism shift gear (28) on the flat recess of the skeleton head (20).

23. Place the third intermediate head prism shift gear (26) so that its reference line tooth

24. Make a careful check to see that all bearing holes of this gear train align with the reamed holes in the flat recess face of the skeleton head. Carefully place the integral pin projections of the gear train bracket (30) in the center bearing holes of the gear train and press downward slowly. The first lower integral pin projection enters first, and protrudes into the skeleton head and further into the reamed hole axis of the Galilean eyepiece lens cube (2), while the other three integral pin projections enter the gear train to protrude further into the skeleton head. Secure the gear train bracket (30) with four lockscrews (15) which extend into tapped holes in the skeleton head.

25. With the use of a surface gage and dial indicator attachment, stand the skeleton head on a surface plate. Measure the front and rear sides of the upper face of the Galilean eyepiece lens cube (2). Release the two lockscrews (11) and move the upper pawl holder (8) and pawl (41) axially to obtain a true horizontal measurement. Secure the two lockscrews (11) after the true horizontal measurement is ascertained.

Follow the same procedure for the Galilean objective lens cube (1), using the lower face of the cube for determining the true horizontal measurement. Release the two lockscrews (11) and move the lower pawl holder (8) and pawl (41) axially to obtain a true horizontal measurement. This measurement determination places the mechanical alignment of the Galilean telescope mechanism in a true horizontal position, so that upon the assembly of the lenses, the optical line of sight of this system is parallel to the optical line of sight of the remaining telescope systems. This procedure prevents a pronounced general aberration which results when the IN position of the pawl holders (8) and pawls (41) have a faulty alignment.

26. With the Galilean objective lens and eyepiece lens cubes (1 and 2) located in the IN

27. Assemble the power shift gear bracket (39), placing its integral pin projection in the bearing hole of the power shift gear (7) and further into the reamed hole in the flat recess of the skeleton head. Slowly push the integral pin projection of this bracket into place in the flat recess, and secure it with two lockscrews (15) which screw into tapped holes in the recess of the skeleton head.

28. Check the movement of the Galilean objective lens and eyepiece lens cubes (1 and 2) in the IN and OUT positions to insure that a pronounced and distinct operation of the pawls is obtained.

29 Shift the Galilean objective lens and eyepiece lens cubes (1 and 2) to the OUT position.

31. Assemble the mounted Galilean eyepiece lens (56) and mount (3) in the Galilean eyepiece lens mount housing (4). Attach the housing to the Galilean eyepiece lens cube (2), placing the pivot hole downward, and securing it with three lockscrews (5). These lockscrews extend into tapped holes in the face of the cube. Collimation of this lens doublet is accomplished in the final stage of collimation of the instrument.

32. Clean the Galilean objective lens (57), using clean lens tissue; also clean off any surface dust. Place this lens doublet in the Galilean objective lens cube (1). With the longest radius facing upward in the IN position, apply the retainer ring (6). Spot solder the retainer ring to the cube to prevent its backing off the threaded periphery of the cube.

33. Shift the head prism to the zero line of sight by eyesight and shift the Galilean telescope system to the IN position. Wrap the skeleton head assembly in clean lens tissue and store conveniently to preserve it from damage until the assembly is required for collimation.