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PART III

OUTSIDE MACHINIST TRAINING
INSTALLATIONS, MAINTENANCE, REPAIRS

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PART III

Running a Tight Line

PURPOSE OF A TIGHT LINE

A tight line is used to locate the center line of the line shaft. The line shaft is connected to the propeller at the stern and ends in the engine room, an over-all distance of about 70 feet. This line shaft, see Fig. 218, is made up of four lengths, coupled together to form one continuous length and supported by bearings which are held securely on foundations placed at suitable intervals. The foundations for the bearings must be secured to the tank top of the double bottom. See Ship Terms and Locations, Part I.

Fig. 218--Line Shaft

STERN FRAME

The stern frame is a steel casting which has been welded to the stern plates of the hull, thus becoming a solid part of the ship. See Fig. 219. The opening "a" is cast in the stern frame, and it is through this opening or "eye" that the line shaft turns and thus turns the propeller.

The eye must be bored out, and the center of the bored hole must be exactly in line with the center line of the keel and the correct height above the tank top, mentioned in the first paragraph of this instruction sheet. Check on this height with the leader.

POSITION OF LINE SHAFT

In the engine room, the center of the line may be 3' 1-1/4" above the engine bed. This varies according to the type of ship.

CENTER OF LINE SHAFT

All that now remains to be done is to establish a center line above the deck plates and in line with the ship center line. This is the purpose of a tight line. From this tight line, measurements are taken to locate the spring bearing, the thrust bearing, the supports for the propulsion motor, the circle for the holes in the three bulkheads (see note) aft of the propulsion motor, the stuffing box and the line shaft in the engine-room watertight bulkhead, and the circle for the bored hole in the eye of the stern tube. See Fig. 220.

TIGHT LINE

The tight line used on this job is a piano wire, .018 of an inch in diameter. The same size of wire and the same tension are employed each time a "tight line" is run. On oil tankers, the length of the line is about 70 feet from one end support to the other. On other types of ships this distance will vary. Figure 221 shows these two supports: A "horse" on the outer face of the "eye" and a "line target" at the other end of the line, in the engine room. See "a" and "d".

Fig. 221--Target Stands Set to Center Line of the Ship

SETTING THE TARGET STANDS OR SUPPORTS

The target is a centering device, or metal bar, which is bolted across the two columns of an angle iron support that may be bolted or tack welded to the deck plates or tank top. See Fig. 222. In order to

NOTE: The center line of the ship was located by the shipfitters all along the tank top and on bulkheads with center punch marks as the ship was being built. The outside machinist follows all such center lines when laying out his work.

Figure 221 is a view looking down on the entire line shaft location as in the top view, Fig. 220. A "horse" 'a" is placed across the stern-frame eye. A target stand (See Fig. 222) is set in position as at "d". The chalk line "g" is adjusted until its position is directly over the ship center line which was center punched on the deck by the shipfitters. A plumb bob and line are used to determine the correct position of the chalk line.

The distance from "a" to "d" is about 70 feet, and a target stand is set up, as at "e", every ten feet. The chalk line gives the location for the center of the target stand and the height of the target stand crossbar. When all the targets have been placed, the crossbars are adjusted so that they just about touch the chalk line on the under side. When doing this, make sure the chalk line is stretched TIGHTLY.

PLACING THE TIGHT LINE

The chalk line is now removed entirely. It has served its purpose. The support "a" is relocated for holding the tight line. See Fig. 223. Two brackets, "k", are tack welded in place temporarily. These brackets support two stools "l". "a" is now supported by the stools. The stools and the bar are bolted to the brackets and may be adjusted to bring the tight line into alignment with the ship center line.

Fig. 223--Cross Bars Centered to Hold Tight Line

The reel and supporting bracket, "h", are bolted to the target crossbar in the engine room. See Fig. 224. Check the reel to see that it is well oiled and running free. Check the stop screws on the reel to make sure that the reel is locked in all positions before locating any tram marks. The tight line is unwound carefully and carried back through the several openings in the engine-room bulkhead: the stern-tube bulkhead, the bulkheads between the stern frame and the stern-tube bulkhead, and finally through the eye of the stern frame where the end of the tight line is securely fastened to the crossbar "a". Figure 224 shows that the reel is notched in four or more places. The weight "j" is hung from one of these notches.

TENSION ADJUSTMENT

The piano wire used as a tight line is .018 of an inch in diameter. When this size of wire is supported at two Fig. 224--Tension Weight and Reel places, 70 feet apart, and stretched with a certain tension, the "sag" of the wire will form a long, gentle curve. This curve is always the same if the wire is supported, as above, and tightened the same amount each time.

A 27-3/4 pound weight is used to keep the wire in tension when the over-all distance is 70 feet. See "j", Fig. 224. The amount of sag has been figured very carefully. It is definitely known that a tight line always sags a certain fixed amount, according to the size and length of the line. See illustration, Fig. 225.

Fig. 225--Showing the Sag in a Tight Line

SAG BLOCKS

Inasmuch as it is definitely known how much a tight line sags in ten feet, it is only necessary to raise the wire that much to make the line level. Figure 225 gives the correct amount at every ten feet. Figure 222 shows two small pins in the target or crossbar which is bolted to the target stand. These pins are there to hold the sag blocks in place and to guide the tight line along the center of the target stands. Figure 226 is an illustration of a sag block located in place over the two pins in the crossbar. Sag blocks of the same thickness as mentioned in connection with Fig. 225 are used as long as the distance between tight-line supports remains 70 feet. If this distance changes, sag blocks of a different thickness must be used.

ADJUSTING THE CROSSBAR

With the tight line in tension, the end supports are carefully adjusted to bring the wire directly over the ship center line as was done with the chalk line. This adjustment must be exact. A plumb bob and line are used as before. The height of the tight line at the engine-room-target end must be according to the blueprint. This height is usually 5' 2" from the engine room tank top to the under side of the tight line. Check and recheck the height of the line to provide for a chock thickness of 1-1/2" under all of the bases of the units being installed. Check with the leader.

The crossbars must now be raised and adjusted until a light shows the bar barely touching the wire. Tighten the crossbar bolts and check with the leader. When all the crossbars have been adjusted, place the sag blocks on the pins and recheck at every point to make sure the adjustment is correct for height and center location. Remember the tight line is the center of the line shaft. Measure carefully, tighten all adjusting bolts, and check with the leader.

LOCATING MACHINING POINTS

Before any machining, such as boring and facing, can be permitted, the tight line must be removed. Certain measurements have to be taken from the tight line, and markings made. Figure 227 shows the outer

face of the stern-frame eye. The center of the tight line is plainly marked. Four center punch marks must be made as shown at points "c".

The distance of the center punch marks from the center of the tight line should be about one-half inch greater than the radius of the bore in the stern-frame eye. The reason for this is that after the eye is bored a check may be made from these "register" or tram marks and the accuracy of the work thus assured. A cold chisel is used to mark a small square around the tram marks so that they may be easily located.

Similar measurements and center punch marks are made at every opening through which the line shaft will pass. It should be quite clear that if the tight line is run correctly and if the tram marks are located accurately, the finished job will be satisfactory. The slightest error means serious trouble later.

When taking a measurement from a tight line to a tram mark, "snap" the line to make sure it is on center. Unless this is done there is danger that the line may be slightly to one side. Check this repeatedly.

For any measurements from a tight line set the micrometers to allow for half the diameter of the tight line.

QUESTIONS

1. How much does a tight line 70 feet long and .018" in diameter sag in the center if unsupported?

2. If the tight line is not located directly over the ship center line, how will this affect the alignment of the line shaft?

3. State the precaution which should be taken when locating tram marks with a center punch.

4. How does the mechanic make certain that the tight line is "on center" when taking measurements?

6. What is the correct distance from one target support to the next?

7. Why is a chalk line run before setting the target supports?

8. Explain the reason for burning a hole larger than the stern tube in some bulkheads.

9. How does the diameter of the tight line affect a measurement taken from the center of the tight line to the circumference of any circle scribed about the tight line as the center?

* Removing A Tight Line

INFORMATION

The piano wire used for locating the shaft center line is comparatively expensive, and the slightest abuse can render it useless for further service. The time required to prepare another line would have to be added to its cost in case a second tight line had to be used. If a tight line is kinked, it is of no further use as a tight line.

MATERIALS

Tight line ready for removal

PROCEDURE

1. Unfasten the after end of the tight line from the adjustable bracket.

2. Have one helper hold loose end of line and carry it toward the reel which winds up the line at the other end.

3. Have a second helper apply oil to the line with a rag.

4. Turn the reel crank, and wind the line on the reel neatly until all the wire is wound.

5. Secure the loose end by inserting it under two or three strands of line and then pulling it up tight.

6. Wrap an oiled rag around the line on the reel and place the reel of line in the reel box.

7. When you have finished with the line and the reel, see that they are returned to the tool room.

QUESTIONS

1. Why must care be used in removing the tight line from the shaft center line location?

2. Three men are used in removing the line. What does each man do?

3. What precaution is taken before placing the reel of line in the box?

* Adapted from "Outside Machinist", Alabama State Department of Education.

Setting A Portable Boring Bar

INFORMATION

The illustration at the right, Fig. 228, shows a heavy steel casting, the stern frame, which is welded solid with the stern plates of a ship's hull. The hole in the hub is the stern-tube housing and is called the "eye" by shipyard mechanics.

The lower portion "a" is called the SKFG. The surface "b" is called the outer face of the eye and "c" is called the inner face of the eye. The stern-tube housing must be bored out to a certain size to fit the stern tube. See appendix for definition of stern tube.

Figure 220 shows a longitudinal cross section of a ship's hull in the bottom view. Note carefully the locations of the bulkheads, bearings, stools, and couplings. The stools which support the shaft bearings are welded to the tank top before the tight line has been run. When the construction is complete, the center line of the line shaft must occupy the same position as the tight line occupied before it was removed.

While the tight line was in position, tram marks were accurately located on the outer face of the eye (Fig. 227) and around the rough hole in the stern-tube bulkhead (Fib. 220). Tram marks were located on the engine-room watertight bulkhead and on the two bulkheads immediately forward of the stern frame.

The diameter of the portable boring bar is 5" to 14". A heavy bar is always used on large work. Always use as heavy a bar as possible to avoid spring. See Fig. 229. The diameter of the eye will easily accommodate the boring bar. Other holes in the bulkheads have been burned out small enough for finish-machining and at the right location with the center line.

The eye in the stern frame is to be bored 30".

The hole in the first bulkhead forward of the eye is to be bored 31".

The hole in the second bulkhead forward of the eye is to be burned out 32-3/4" to allow the stern tube to pass freely, but it is not bored. If there are other bulkheads at this location, the blueprint will show which ones are to be bored and which are to be burned.

The hole in the engine-room bulkhead is bored 32-3/4" less about .003 of one inch. The .003 of an inch is to allow for a press fit when pulling in the stern tube.

Study Fig. 229 carefully. The fittings on the main boring bar may all be removed, leaving a bare bar. The entire assembly may be moved backward or forward and secured in any desired location.

Fig. 229--A Portable Boring Bar Assembly

Four stools, Fig. 229, swivel on the yokes and have several bolt holes to allow the yokes to be secured to a support as conditions require.

The yoke on the end opposite to the hand-feed wheel may be removed and the bar slipped into the after end through the hole in the stern-frame eye if the ship has twin propellers. Other parts of the portable boring bar have to be removed while preparing to set the bar in a tight place where one propeller is used. In this case it is lowered into the after peak and run through the eye from the inside.

The boring bar is slung in a chain fall and passed through the eye where a second chain fall is ready to receive it. The bar is located by raising or lowering the chain fall; it is braced sidewise as near to the center of the layout as possible by rough measuring. The yokes are adjusted to a convenient position, and supports to which the boring-bar yokes may be securely bolted are welded to the deck plates and bulkhead. See Fig. 230. These supports are sometimes called "spiders".

After the boring bar is secured to the spiders it may be adjusted to a location exactly central with the tram marks which were located from the tight line.

As the main bar of the boring bar assembly is straight and true, any measurements that may be taken from the outside diameter of the bar will

Fig. 230--Boring Bar Supports, Inside and Outside

be just as accurate as if taken from the actual center of the bar. Fig. 233 shows the boring bar body lined up in the center of the four tram marks which were put on the outside face of the eye while the tight line was still in place. Hermaphrodites may be used to check the distance all around the boring bar until it is exactly in the center. The same procedure is followed at the other end of the bar where it projects through the stern-tube bulkhead. After the bar has been securely bolted in position, the job is checked again to make sure of the alignment.

Figure 232 shows one of the bulkheads with a hole burned through. The four tram marks are measured from the tight line, and the boring bar is lined up with these tram marks. Measurements are taken from the tram marks as shown in Fig. 233, to the side of the boring bar as indicated by the reversed arrows. ----> DISTANCE X <----- The distance "x" between the arrow points is the same all around the boring bar. This measuring must be done very carefully.

Figure 231 shows a boring bar set vertically. The men are boring the top gudgeon on the stern post. Note the strong backs at the upper and lower sides of the gudgeon. The strongbacks are secured to the vertical channels welded to the rounding surface of the gudgeon.

The job of setting up a portable boring bar may be summed up as follows:

PROCEDURE (Applicable in most cases)

1. Clear away all obstructions, tools, and loose materials which might interfere with the handling of the boring bar.

2. Locate chain falls and planking at convenient points for quick and safe handling of the boring bar.

3. Strip the boring bar of the yokes, tool holder, reduction-gear drive, air motor, and hand-feed.

4. Lower the boring bar into the engine room. Wrap with bagging to prevent injury to the finished surface of the bar.

5. Secure the boring bar in the chain fall previously located in the after peak, and balance the bar so that it may be swung forward. Planking is placed to help slide the bar out through the eye in the stern frame. Protect the bar with bagging, if necessary.

6. Support the outer end of the boring bar with planking and chain fall.

7. Reassemble the yokes and other accessories, and get ready to raise the bar into boring position.

8. Estimate where additional spiders and supports should be secured to support boring bar.

9. Have flat or angle supports cut, and welded into position.

NOTE: Measure from outside diameter of boring-bar main body to the tram marks previously Placed on the stern-frame eye and bulkheads. Use a steel scale and hermaphrodites. Keep the hermaphrodite scribing leg to a sharp point. Re careful to hold the tool at right angles to the center line of the boring bar. The measurements must be perfect if the stern tube is to be in correct alignment. Check with the leader.

11. install the tool holder, adjust the air motor, connect the air lines, and recheck all fastenings to make sure the bar will remain in correct alignment. The boring bar should now be ready for boring the eye in the stern frame.

QUESTIONS

1. A heavy boring bar should always be used where there is sufficient room to set it up. Why is a heavy boring bar more desirable than a light one?

2. What is the principal problem involved in setting a portable boring bar?

3. At what points are measurements taken to bring the boring bar central with the diameter to be bored?

4. Explain the reason for removing the fittings from the boring bar before setting through the stern-frame eye.

5. Point out the principal precautions to be taken when getting ready to set the boring bar through the stern-frame eye.

6. What is the purpose of the swivels and yokes on each end of a boring bar?

7. Explain the usual method of providing suitable places to which parts of the boring bar may be

8. State at how many points supports for the boring bar are welded temporarily; explain the purpose of each support.

9. What would be the probable result if a boring bar slipped a little during the boring operation?

10. What is the correct procedure after the boring bar appears to be set central with the eye diameter?

Boring A Stern Frame

ACCURACY OF A BORING JOB

There must be no errors in the boring of a stern frame. The stern frame casting is "welded in" with the hull plates of the ship, after which operation all the pieces become one unit. To ruin a stern frame means a loss of time and materials that is difficult to estimate. Boring a stern frame is a man-sized job which the mechanic must approach with the fixed idea that every move must be carefully and thoroughly planned. Mistakes are absolutely barred.

THE BORING JOB

Full instructions have been given for running a tight line. Full instructions have been given for setting a portable boring bar. The instructions given here are to be followed after the boring bar is in place, ready to bore the stern-frame eye and the bulkheads, which were shown in Fig. 220.

Fig. 234--Portable Poring Par Set Horizontal for Boring a Stern Frame Eye

1. Adjust the tool holder and tool bit to the correct location. Turn the bar slowly to find where the high spots are on the inside of the eye. See Fig. 234.

2. Feed the tool into the full depth of the eye to make sure that there is plenty of clearance and that there are no high spots to foul the tool and throw the "set-up" out of line.

3. When everything seems to be clear, check with the leader.

4. Set the tool to take a 3/16" cut, and feed slowly to get the "feel" of the tool. A faster feed may be used if it is evident that the tool will "hold up" and that there is no "spring" in the "set up." (A cutting speed of 30 to 60 feet per minute is safe in most cases. Check with the leader on this point.)

5. Continue to take roughing cuts until the inside diameter of the eye "cleans up".

6. Check with the leader at this point. Check all spiders, yokes, and stools frequently to make sure there is nothing slipping.

Fig. 235--Checking the Diameter of a
Stern Frame Bore

8. Bore the bulkheads up to this point as outlined above.

NOTE:

Special inside micrometers are used for this job. There is an offset in the micrometer which will clear the boring bar. See Figs. 235 and 236.

MEASURING THE INSIDE DIAMETER OF THE STERN-FRAME EYE.

(d) Now proceed with the finish cut for about 1/8" and check with the micrometer. If the size is correct, proceed. If too large, back off and try again. DO NOT CUT IN LENGTHWISE FOR MORE THAN 1/8" BEFORE TRYING FOR SIZE. See Fig. 235.

Fig. 237--Finish Cut in a Stern Frame

(e) When the bore checks correctly with the mikes, proceed with the finish cut. Watch the tool carefully as the boring proceeds. If the tool begins to burn, STOP. Check with the leader if in doubt as to how to proceed. See Fig. 237.

If the finished hole is bored tapering, the stern tube will likely seize when being "pulled in"; so every precaution must be used to have a straight hole.

NOTE: When finished with boring, do not move the boring bar until the diameter of the hole has been checked and approved by the leader or inspector.

1. When adjusting the tool holder to begin taking a cut, what precaution should be taken to prevent the tool's "fouling" the work?

2. How heavy should the tool be set in for the first cut in a stern-frame eye?

3. At what speed is it considered safe to start a roughing cut?

4. What is understood by the phrase "clean up the inside diameter" of a boring job?

5. Explain the usual causes for the boring bar's getting out of line during a boring operation.

6. How is the rough bore checked for accuracy with the center location before proceeding with the job?

7. How much stock is left for a finish cut in a rough-bored "eye"?

8. State the usual allowance for a press fit between the "eye" and the stern-tube diameter.

9. Explain how the measurement is taken for the finished diameter of the bore in the "eye".

"Pulling in" A Stern Tube

PURPOSE OF A STERN TUBE

The stern tube is the shell for the lignum vitae, tail-shaft bearing. The stern tube varies from 8 to 20 feet in length. The outside diameter is stepped, that is, the end that fits in the stern-frame eye is smaller than the end that fits in the stern-tube bulkhead.

CORRECT FIT FOR A STERN TUBE

When the stern-frame eye and the stern-tube bulkhead are bored to the finished size, the stern tube should "pull in" under pressure, because the stern tube is turned .008 of an inch larger than the stern-frame eye at the stern end (see point "a" Fig. 238), and .003 larger than the stern-tube bulkhead at the bulkhead end (See point "b", Fig. 239). Figure 239 illustrates a tube partially pulled into place.

USING THE CHAIN FALLS

When the bored holes in the stern-frame eye, stern-frame bulkhead, and the intervening bulkheads have been brought to size to allow for a pressed fit as outlined in the last paragraph, the' stern tube is lowered into the engine room. Chain falls are placed in position to take the stern tube off of the crane. Sometimes as many as 8 or 10 chain falls are used to carry the stern tube as it is worked back to its place from one chain fall to another. The stern tube must be protected with bagging to prevent scoring the finished surface while the tube is being handled by the chain falls.

Fig. 238--Stern Tube in Place

PREPARING TO "PULL IN" THE STERN TUBE

Figure 239 shows the stern tube partly drawn in through the stern-frame eye and the stern-tube bulkhead at "a" and "b". A heavy bolt is shown at "c". The bolt extends from the outside of the bulkhead end of the stern tube, through a strong back "d", and all the way through the stern tube and the strong back "e". A hydraulic ram "f" is secured to the outside of the strong back "e". The ram draws the stern tube into place.

Two cradles, Fig. 240, are used under the pull bolt to keep it exactly central in the stern-tube bore. The cradles and made an easy fit for the stern-tube bore and the pull bolt. One cradle is placed at the stern-frame end, and the other is placed at the stern-tube, bulkhead end. See "x" and "y", Fig. 239.

"PULLING IN" THE STERN TUBE

The hydraulic ram works against the washer and nut at "g" and has an effective draw of about 10 inches. When the ram has reached the 10" limit, another washer (10") "h" is placed between the strongback and the first washer under "g" and another 10" section of tube is drawn in. This is repeated until the stern tube is completely drawn into place, making a metal-to-metal joint at the stern-tube shoulder and forward end of eye. See Fig. 238.

Fig. 239--"Pulling In" a Stern Tube

A pressure of not less than 3500 pounds registered on the gauge is standard for a correct fit. This pressure may run as high as 6000 pounds, but it must not be less than 3500 pounds. A pressure gauge is connected to a hydraulic pump which acts on the ram. The gauge should be watched constantly for variations which will indicate too much or too little pressure.

The lock nut, Fig. 241, has in the circumference, several machined notches into which the spanner wrench fits when the nut is being installed or removed. When the lock nut has finally been "snugged home", a hole is drilled in the face of the stern-frame eye and tapped out for a lock stud. The location of this hole brings the lock stud at the bottom of one of the notches. After the lock stud has been secured in place, tack weld it fast. See "a" Fig. 241.

When the stern tube comes to the job, it is packed with sawdust to keep the lignum vitae bearing blocks from drying out and cracking. Never remove the sawdust until ready to null the stern tube into place. While the operation of pulling in a stern tube is proceeding, the job is inspected and criticized by the American Bureau of Insurance, or the Lloyd Insurance Company, and the agent of the shipowner. This is done to make certain that the job will conform to all underwriter requirements.

The operation of pulling in a stern tube may be summed up as follows:

Fig. 242--Inspecting the Progress of the Stern Tube Through the Eye

Fig. 243

1. Lower the stern tube into the engine room.

2. Receive the stern tube in one or more chain falls, and swing to the next chain fall, passing the tube aft.

3. Enter the tube in the bulkhead hole, and pass it through to the stern-frame eye.

4. Apply white lead and oil to the tube, bulkhead, and eye surfaces.

5. Install the pull bolt, and adjust strongbacks and hydraulic ram.

6. Pump pressure until the pull bolt takes hold.

7. Now examine all equipment and fastenings to make certain the tube is entering "fair".

8. Pull the tube in as outlined in the text of this instruction sheet.

9. When the tube is in place, check with the inspector for his approval.

10. If approved, remove strongbacks, hydraulic ram, and pull-bolt; clear the platform for installing the lock nut.

11. Drill through the stern-tube flange for studs, and tap holes to suit.

12. Install studs with grommets and nuts on the after side of stern-tube bulkhead. See Part II, Making a Watertight Joint, Fig. 145 for application of stud and grommet.

13. Place a metal band around the flange of the stern tube in readiness for pouring tight metal.

14. Build up a clay mud seal all around the ring to prevent the tight metal's escaping when it is poured into the joint.

15. Build up (on top of the metal band) a clay mud cup into which the tight metal may be poured.

16. Pour the tight metal into the cup previously prepared. Pour fairly fast to insure a good joint and avoid air pockets.

17. Remove the band and calk the tight metal with a rough calking tool. This procedure will tighten up the joint and make certain there are no gas or air pockets.

18. Install washers and nuts on the studs, and draw up tight. See Fig. 243.

19. Fill up the after peak with water from a shore-line hose to make the necessary test for leakage around the joints between the stern-tube flange and bulkhead and the stern tube and stern-frame eye.

QUESTIONS

1. Why is a forced fit necessary between a stern-tube diameter and the stern-frame eye?

2. How much difference in diameter should there be between the bore in the stern-frame eye and the after end of the stern tube?

3. Explain how a stern tube is carried back into position after 'it is lowered into the hull.

4. What protection should be given a stern tube during the operation mentioned in step 3?

5. What is the purpose of the two cradles which are placed under the pull bolt in the stern tube?

6. State the reason for pulling in the stern tube with a pressure of 3500 lbs. registering on the gauge.

7. When is the sawdust removed from the inside of the stern tube? Why is it not removed sooner?

8. When is the stern-tube job inspected and by whom?

9. What is meant by the word "fair"?

10. Why is a small space left between the stern-tube bulkhead and the stern-tube forward flange? ("c" Fig. 238)

11. Explain in as few words as possible how and why tight metal is poured at the forward end of the stern tube.

12. How are the stern-tube joints tested for leakage after the installation is complete?

Installing A Propulsion Motor

PROPULSION MOTOR DRIVE

The propulsion motor is keyed to one end of the line shaft, and the propeller is keyed to the other. When the propulsion motor turns, the propeller turns at the same speed and so moves the ship through the water. The propulsion motor (See Fig. 244) is electrically operated, very much like any other electric motor except that it is installed on the forward end of the line shaft; the line shaft thus becomes the axle upon which the rotor turns. The foundation is installed according to the location given on the blueprint. Figure 244 shows the motor

Unless the installation of the propulsion motor is correct in the smallest detail it will not be passed by the inspector. The propulsion motor is lowered into the ship by ship riggers, set hack as far off on the foundation as possible to give clearance for installing the rotor, and after the rotor is installed the entire stator unit is shifted to the correct position on the foundation.

PRECAUTION

Every precaution should be taken when installing the stator to make sure that there is no damage caused to either the rotor or the stator. It is advisable to place shims around the inside of the stator to serve as guides when sliding the rotor into place.

INSTALLING THE MOTOR

At the time the final installation is made, the line shaft has already been installed. See Fig. 220. The propulsion motor must be set directly with the line shaft for the line shaft cannot be moved. This calls for extremely careful measuring. The rotor shaft is set in line with the line shaft. As the propulsion motor weighs sixteen tons or more, the entire job must be done carefully.

When the motor is set in position and approved by the inspector or the leader, the job of fitting chocks is begun. When the chocks are fitted, the corners are drilled and reamed for fitted bolts; the bolts are installed and drawn down tightly; and then the rotor shaft is revolved and "indicated" to make sure it is in perfect alignment with the line shaft.

A piece of insulation approximately .125" thick is placed between the top side of the chock and the pedestals of the propulsion motor on the forward bearing. After the chocks are fitted and are found to be satisfactory, they are removed and an amount equal to the thickness of

The fitted bolts through the forward bearing are insulated at the point where the bolts pass through the pedestal and the upper side of the chock. These points are insulated to prevent a ground on the forward bearing. See Fig. 245 and 246.

If an arcing condition should be set up, the shaft and the babbit bearing in the propulsion motor would be scored and both would have to be replaced. Such an arcing condition must be made impossible by proper insulation.

Fig. 246--Typical Insulated Stud Installation

7. Install fitted bolts and draw the nuts down tightly. Be sure to install the insulated bolts correctly.

8. Check the alignment of the rotor shaft with the line shaft to make sure there has been no error.

9. Using jacks or wedges, line the stator up with the rotor and check the spacing between the rotor and the stator with a 12" tapered wedge gauge. See Fig. 247.

10. When the rotor and stator appear to be in perfect alignment all around, check with the leader. If the alignment is correct, fit the chocks under the stator base.

Fig. 247--The Stator is Jacked Up True With the Rotor

11. Drill, ream, and install fitted bolts on the four corners. Pull the nuts up tightly. Use every precaution to insure the nuts being pulled up to the limit.

Fig. 248--Typical Turbo--Generator Unit

13. Call the leader, and have the job inspected up to this point. Figure 248 shows a turbo-generator and exciter set. Several of these units are installed in the engine room or adjacent to the engine room, and they generate power which is used to drive the propulsion motor and numerous other electric motors throughout the ship. The ship lighting system also draws current from the turbo-generators.

QUESTIONS

1. When a propulsion motor is being installed, why is the rotor aligned before the stator?

2. Explain the procedure of aligning the stator with the rotor.

3. How often is the spacing checked between the rotor and the stator?

4. Why is the stator aligned with the rotor in such a way that the center line of the rotor is .005 of an inch above the center of the stator?

5. Describe a diesel side jack.

Installing Fan And Motor For Air Cooler

FAN REDUCES TEMPERATURE

The temperature in the vicinity of the propulsion motor normally varies from 150 to 180 degrees Fahrenheit. As the propulsion motor is installed in the engine room, it is subject to high temperatures caused by heat radiated from the steam lines and absorbed by the surrounding atmosphere. in winter these temperatures are reduced somewhat by cooler weather; but in summer, and in southern climates especially, the temperature around the propulsion motor must be reduced or the motor will run so hot that it may burn the bearings.

An air cooler is installed in a convenient place; a fan and motor are connected to the air cooler by a "circulating duct"; and the air around the motor is drawn through the air cooler continuously, bringing the temperature down to about 115° Fahrenheit. See Fig. 249.

CORRECT INSTALLATION

The importance of correct installation of the air-cooler fan cannot be stressed too much. When the ship is in service, there is an extremely heavy load on the propulsion motor. If for any reason the fan and motor should stop working, the temperature would likely go so high that the motor windings would be in danger of burning out. If this should happen while the ship is at sea, the results may be easily imagined.

FAN AND MOTOR UNIT

The fan-and-motor units are usually mounted on a base as one unit. Sometimes the fan-and-motor units come separate. In either case the work involved in making the installation is much the same.

Fig. 249--Westinghouse Air Cooler Unit

Figure 249 shows two pipe lines through which sea water is circulated for the purpose of cooling the air that is blown through the air-cooler unit installed above the propulsion motor housing. The air duct from the fan to the cooler unit is at the left. The fan and motor (not shown in the photograph) are mounted below and close to the propulsion-motor housing.

The shipfitters build the foundations; and when the unit is ready for installation, the ship riggers place it. The location on the foundation is laid out from the blueprint by the outside machinist. The fan may be anywhere from 38" to 52" in outside diameter. The revolutions per minute may be about 1175 for large motors and about 1400 for small motors. The smaller fans operate at higher speeds. The foundation is installed on the engine-room tank top just aft of the main condenser.

Figure 250 shows a General Electric fan and motor. The motor is indicated at "a", the blower at "b", the intake duct at "c", and the discharge duct at "d".

Figure 251 is a photograph of a General Electric Air Cooler. The blower discharge (hot air) is shown at "a"; the cooler tank (to reduce temperature) is indicated at "b".

PROCEDURE

1. From the blueprint, locate the correct position of the unit on the foundation.

Fig. 250--General Electric Motor and Fan

2. Level the unit on wedges preparatory to bolting down.

3. Drill the corner holes for fitting bolts through the foundation.

4. Fit corner chocks; drill, ream, and install fitted bolts; and draw down.

5. Fit the remainder of the chocks.

6. Have an inspector check the job for accuracy.

Fig. 251--General Electric Discharge Duct and Cooler Tank

Installing A Steam Boiler

DESCRIPTION OF A STEAM BOILER

Tankers and certain types of cargo ships are usually equipped with the boiler which is described here. The boiler is built in the shipyard by the boiler-makers. When completely finished, the boiler is set on the ship by the riggers and bolted down by the outside machinists.

The boiler is known as a Babcock and Wilcox, oil-fired, tubular-header type. This unit weighs approximately forty-six tons when completed. Fig. 252.

Fig. 252--Babcock and Wilcox Oil Fired boiler

THE FOUNDATION

A foundation is constructed in the boiler room. The boiler room in a tanker is located in the after end. The boiler room in a cargo ship is located amidships. The shipfitters build the foundation, which is of heavy construction. It is finished off with two steel channels that support the boiler, back and front. The foundation seat is a channel about 14" wide and 18" high. See Fig. 253.

The channel is welded securely to the foundation plate, and the boiler is bolted down to the channels. The channels are called "stools".

Six 1-1/4" bolts are placed through each of the four bottom corners of the boiler frame and the foundation stools.

LAYING OUT THE BOLT HOLES IN THE STOOLS

The locations of the bolt holes in the stools are taken from the blueprint. Before laying out the holes in the stools, however, boiler-makers check the base of-the boiler to make sure the holes in the base match with the hole locations on the blueprint. If there is any discrepancy, the layout is corrected to agree with the boiler base. Figure 254 is a ton view of a foundation stool on the port side of the ship. A similar foundation is on the starboard side right next to the port foundation. Two boilers are installed with about 3 feet between the adjacent walls.

When the machinist lays out the boiler locations, he takes all measurements from the ship center line, the boiler center line, and the foundation center line.

Fig. 253--Boiler Foundation Setting

SETTING THE BOILER

The boiler is picked up by the shipriggers and set on the foundation under the supervision of the outside boiler-maker leader. This is not done until after the holes are drilled in the foundation stools- A layer of seal tight cement about 1/8" thick is spread on the surface of the foundation stools with a trowel. When the boiler is set on the stools, the cement forms a cushion for the boiler and seals any uneven places on the surface. The cement hardens quickly, and thus a solid, durable joint is formed between the foundation and the boiler base.

Figure 252 shows various valves, gauges, and controls which are installed by mechanics especially trained for this purpose.

PRECAUTIONS

Certain precautions must be observed when installing any of the gauges, valves, and other parts mentioned above.

(a) Examine the fittings closely to find if right-hand or left-hand threads are cut on the connections.

(c) Use a wrench of the correct size on all fittings, and see that the wrench fits closely. (Some wrenches may be "sprung" although they are stamped the correct size.)

(c) Follow the directions given by the manufacturer or the ship-building company's blueprints.

Fig. 254--Plan View of Steam Boiler Foundation

Many of these accessories appear to be simple in form and do not seem to require any special knowledge to install. This is far from true. Each particular piece of equipment requires correct handling and careful treatment.

As an example of the importance of working carefully and correctly, consider the work of installing a Bailey feed-water regulator. The purpose of the regulator is to control the amount of water fed to the boiler so that it will not run dry and cause burning of the tubes. The regulator also prevents an excess of feed water which causes "wet" steam and damages turbine fins or cracks a cylinder head.

* Bailey Feed Water Regulator Instructions
Principal of Operation -- See Fig. 255

The Bailey Thermo-Hydraulic Feed Water Regulator depends for its operation upon the fact that the volume of a given weight of low pressure steam is far greater than the volume of the water from which that steam was made. The water which operates the regulator is sealed in a closed system formed by the annular space between the inner and outer generator tubes, the connecting copper tubing, and the metal bellows of the regulating valve.

When the regulator is placed in operation, heat from steam in the upper portion of the inner generator tube causes the surrounding water to flash into steam. This forces water out of the annular space in the generator through the connecting tubing into the metal bellows which expands and opens the regulating valve.

If the boiler water level tends to rise, cold water from water storage leg J rises up into the inner generator tube. This cold water plus radiation secured from the fin surface of the outer tube causes steam in the annular space to condense, thereby reducing the pressure in the closed system and allowing the spring to close the regulating valve.

In normal operation, the regulation valve adjusts its position to correspond with the rate of steaming as reflected by slight changes in water level and a continuous feed is delivered to the boiler.

How to Fill Generator When Valve is Above Generator

1. Jack valve open by means of handjack K.

2. Disconnect tubing, R from metal bellows D.

3. Remove Guard H from bellows D, and place bellows in large bucket full of water.

4. Compress bellows many times with open end up until all the air is removed and bellows is filled solid with water.

5. Insert end of tubing ft in bucket of water along with bellows.

6. Remove generator plug G, and draw on opening until water syphons from bucket out through generator.

7. Allow water to run until all air is carried out of line, and then insert plug G.

8. With bellows under water, place Guard H over bellows and connect end of tubing R to bellows. Make sure that end of tubing R and bellows are completely submerged during this operation so that no air gets into the system.

9. Replace guard H, and bellows on valve.

10. Release handjack K so that valve spring is free to close valve.

11. Remove generator plug G, and permit excess water to run out.

12. Replace plug G and make sure that connections at both ends of copper tubing, as well as plug G, are made up tight.

* Through the courtesy of Bailey Meter Company, Cleveland, Ohio.

Fig. 255--Principle of Operation of Bailey Feed Water Regulator

13. Open valves F and F, and blow down generator by opening valve P.

14. After generator has had time to cool off, regulator is ready for service.

How to Fill Generator When Valve is Below Generator

15. if practical, remove bellows and tubing to an elevation higher than the generator, and follow same procedure, as when valve is above the generator. If not, jack valve open, remove tubing R, and proceed as follows:

16. Remove bellows from valve, and insert in bucket full of water.

17. Compress bellows many times with open end up until all the air is removed and bellows is filled with water.

18. Place end of copper tubing Q in another bucket of water, and draw on end of copper tubing R until syphon is started.

19. Place end of tubing R in bucket with bellows, and allow water to flow until all air has been washed out of tubing.

21. Replace Guard H and bellows on valve.

22. Connect end of tubing Q to generator.

23. Remove plug G from generator, and fill generator with water until it overflows at plug.

24. Release handjack K, and allow excess water to run out.

25. Replace plug G and make sure that connections at both ends of tubing, as well as plug G, are made up tight.

Fig. 256

26. Open valves F and F, and blow down generator by opening valve P.

27. After generator has had time to cool off, regulator is ready for service.

28. Generator should be blown down periodically; once in 24 hours is good practice. Also generator should be blown down whenever regulator is placed in service after the boiler has been out of service.

29.Spring tension on regulating valve has been adjusted at factory so that valve begins to open when a pressure of 35 pounds per square inch is applied to the metal bellows. This adjustment should not be changed.

30. Do riot make up packing nut tight enough to jam valve stem. Make up only finger-tight.

31. Make sure there is no excessive friction or rubbing of regulating valve parts. A mixture of graphite and oil applied to guides and valve stem is helpful.

32. The water level carried by regulator is determined by location of generator. As will be noted from a curve, the relation between water level and valve travel varies with changes in the

boiler pressure. It may be necessary, therefore, to lower the level of generator with respect to normal boiler water level for higher pressure, and to raise it for lower presses. Under average conditions, generator filling plug is located 1 to 1-1/2 inches above normal water level. When deciding on a generator location, it is well to estimate the gauge glass level which will result when the valve is in a closed position. This may be done by following boiler pressure line to the left-hand edge of curve, and by reading the distance in inches between this intersection and the proposed line of normal gauge glass level which will be somewhere below the level of the generator filling plug.

33. If regulating valve closes completely at too low a water level, this indicates that too little water is in the system and that the system should be refilled.

34. If regulating valve does not close completely until water level gets too high, there is too much water in system and a small amount should be allowed to drain out.

35. Water level carried by regulator under normal load conditions is determined largely by excess of feed-water pressure. Increasing feed-water pressure raises water level, and decreasing feed-water pressure lowers water level. Best results will be obtained if the excess pressure shown on the valve data sheet is maintained.

36. If regulator carries a gradually lower and lower water level, this indicates a leak in system. If leak is not apparent, put a teaspoonful of borax in water and refill. After regulator has run for several hours, a grayish mark will appear at point of leakage.

37. Never paint generator or radiator J.

38. Regulator should operate indefinitely without adding water to generator.

39. When it is necessary to add water, close valves F and E and open valve P. After generator has cooled, remove plug G and

Fig. 258 -- Section through Bailey Feed Water Valve Body showing construction of Tight Seating Inner Valve.

add water to overflowing. Make sure the valve is in closed position when this is done.

40. If there is air in system, completely refill in accordance with previous instructions. (Paragraphs 1 to 14 or Paragraphs 15 to 27.)

Installing Winches

DESCRIPTION OF WINCHES

A winch is a mechanically operated device which, by means of a special arrangement of gearing and drums, pulls a rope, a cable, or a chain at various speeds. (Fig. 259.) These ropes, cables, or chains may be attached to the ship's cargo booms, docking hawsers, or anchors.

The winch mechanism is usually steam-operated.

The operator usually controls the winch by means of throttle and brake mechanisms. The controls are shown clearly in subsequent illustrations.

The drums, or capstans, which are fastened to the drive-shaft extensions are correctly sloped to fit the ropes, or cables, that may be wrapped around the drums. See Fig. 259. The small drum "t", Fig. 259, is grooved to receive a wire cable. This drum and the drum on the port side are sometimes used for emergency steering. When the power is applied to the winch, the rope or cable winds up, and a pull will be exerted upon whatever is fastened to the other end of the rope. The object on the other end of the rope will have a tendency to move toward the winch.

Fig. 259--Starboard Side of After Deck Winch

CLASSIFICATION OF WINCHES

Winches are classified according to their use or location. An anchor winch (Fig. 260), used to raise the anchor, is located within a reasonable distance of the anchor. A stern mooring winch, located at the stern, is used to take on mooring lines. Deck cargo winches are located amidships and on forward decks. As the name implies, cargo winches are used to load and unload cargoes.

Winches are often used for purposes other than those for which they were originally intended; for example, a cargo winch located amidships might conveniently be used as a mooring winch, fore, aft, or outboard. This use is made possible by means of blocks and rollers over which the rope or cable applies its pull in a change of direction.

A WINCH SETTING

Some winches are set on special foundations; others can be set on the foundation or skid just as built by the manufacturer. All setting up and securing of a winch on the foundation must be done in a manner that will not warp or bind the working parts of the mechanism. For this reason the locations for the bearing brackets must all be laid out carefully to the center lines, as shown on the blueprint. A typical bearing bracket is shown in Fig. 261.

The bolt holes for the bracket feet are easily drilled from the outside of the bracket, straight down through the channel filler or base. See "a", Fig. 261. All bracket feet are not the same in this respect.

Fig. 260--Typical Anchor Winch on Forward Deck

An example of another type of bearing bracket is shown in Fig. 262. Notice that in this case the bolt hole is located under the sloping flange of the bearing bracket at "b". The bolt holes for the feet cannot be drilled through while the bearing bracket is in position.

SETTING AN ANCHOR WINCH

The location for an anchor winch is laid off by the shipfitters. Flat bar is correctly placed and welded to the deck so as to form a band around the winch foundation area. Flat bar is also correctly placed and welded to the deck around the chain locker bell mouths. See Fig. 264.

The ship carpenters build a wooden foundation inside of the band area upon which the winch is to be bolted down.

The setting of an afterdeck winch differs in some respects from the setting of an anchor winch and will be explained fully under the heading, "Setting a Deck Winch".

TOOLS AND EQUIPMENT

1. Number 4 corner air-drilling machine

2. Drills
a. 1 full-length
b. 1 half-length
c. 1 12" extension (the sizes of the drills depend on the holes in the base of the winch)

3. Shipfitter's taper reamer (bolt-hole size)

4. Chalk line

5. Center punch

6. Full set of wrenches

7. 1 3/4-lb. hammer

8. 6' tape

9. 50' tape

10. Pocket knife

MATERIALS

2 round steel bars 18" long (These bars must fit the hole in the winch base easily, but snugly.

Red lead
Tarred felt
Tack  Grommets
Studs  Washers
Nuts

Fig. 264--Layout for Chainlocker Bell Mouths

PROCEDURE

1. Find the center between the two chain-locker bell-mouths in the deck.

2. Snap a chalk line "a-a" fore and aft on the wood foundation, parallel with the center line of the ship, and passing through the center between the chain-locker bell-mouths in the deck. See Fig. 264. Distance "W-W" is the same length.

3. Snap a second center line "b-b" at right angles to center line through port to starboard centers of the chain locker openings.

4. Locate a fore-and-aft center line on the base of the winch. Measure from port to starboard on the base of the winch, find the center of the base, and center punch mark the, edge of the base. Do this fore and aft.

5. Measure the distance from the forward edge of the winch base to the center of the chain opening in the base.

6. Lay off this distance on the outboard edges of the winch base and mark with center punch.

7. Have the winch set by the riggers.

8. After the winch has been set by the riggers, go below into the chain locker and inspect the alignment of the winch-chain holes with the chain-locker openings. The centers when checked are equal fore and aft and port and starboard. Adjust the winch if necessary.

9. When the winch has been adjusted to the proper location on the foundation, have the carpenters inspect the wood foundation.

10. Drill all bolt holes, using the holes in the base of the winch as a guide. The holes are drilled through the wood foundation and through the steel deck. Check carefully when drilling to make sure that there are no electric cables immediately beneath the holes. Consult the leader if there are obstructions.

Fig. 265--Cutting the Tarred Felt Around the Bolt Holes

11. Mark through all holes that cannot be drilled through the base of the winch.

12. The riggers lift the winch off the foundation, and the holes that could not be drilled before are drilled now, using the "spotted" points to start the drill.

13. After all the holes are drilled, paint and soak the wood with red lead.

14. Cover the wood foundation surface with tarred felt, and tack it down securely with number ten tacks. Special attention is given to tacking the corner of each sheet of tarred felt. (These tarred felt sheets come in rectangular pieces 2' x 4' x 1/8" thick.)

15. Cut holes through the felt to match the bolt holes bored in the foundation.

16. Have two round steel bars at hand. (See materials)

18. Have the riggers lift the winch and swing it over the foundation. Lower to within three inches of the painted surface.

19. Insert each one of the steel bars in opposite corners of the winch base through an "open hole".

20. Swing the winch until the hole through which the steel bars are inserted correspond with matching holes in the foundation, and enter the bars in the foundation holes.

21. Lower the winch. The steel bars guide the winch to the correct setting.

22. Remove the steel bars.

23. Number each hole in the base of the winch.

24. Measure the length of the bolts required for each numbered hole, and list the sizes on a convenient scratch pad.

25. Order studs from the machine shop. These studs are made of special steel.

26. Go below deck, and with the corner air-drilling machine ream all the bolt holes in order to take care of misalignment and clear the holes of slivers.

27. Install all the studs beginning at the inboard holes. Tighten each stud reasonably tight. Check with the leader.

28. Have the entire job inspected.

SETTING AN AFTERDECK WINCH

An afterdeck winch is located on the poop deck aft of the galley. The outside machinist bolts the foundation angles to the base of the deck winch according to the blueprint. Shipfitters lay out the location for the winch and then set it. The shipfitters tack weld to the deck and then brace the angles which the outside machinist bolted to the winch base. The winch is then lifted from the angles, and the foundation is completed by the shipfitters; brackets and struts are welded in place to stiffen and make the foundation solid.

CAPSTAN SHAFTS

This type of winch is equipped with capstan shafts that extend some distance beyond the winch. Port and starboard couplings connect the capstan shaft to the main driving shaft. These shafts may extend for as much as 4 feet and are supported port and starboard by one or more bearing pedestals. The bearing pedestals (called bearing brackets) are set to carry the capstan shaft in correct alignment with the main driving shaft. Suitable foundations are placed under the feet of the bearing pedestal, and they are welded to the deck. Bearing brackets are bolted to these foundations with fitted chocks between foundations and pedestal feet. See Figs. 252, 266 and 271.

Fig. 266--After Deck Winch Showing Controls

Figure 266 shows the starboard side of an afterdeck winch. The foot pedal "a" controls the brake. The hand lever "b" controls the motive power. The foundations are formed in the blacksmith shop. A flat plate approximately 1/2" thick, and of the correct size, is heated and bent to the channel shape shown in Fig. 263. The flat top of the foundation is then planed off level and true in the machine shop. It is on this machined surface that the locations for the bracket feet are laid out. In Fig. 263 are shown center lines which indicate the center of the foundation lengthwise and crosswise, and the centers of the bolt holes.

The job of setting an afterdeck winch may be outlined as follows:

PROCEDURE

1. Procure from the shipfitter the side angles upon which the winch is to be set.

2. Block up the winch about one foot high all around.

3. Chalk one leg of each side angle for the entire length and clamp the chalked side to the winch base in a fore-and-aft position, one angle to port and one angle to starboard; place the legs of the angles inboard with the edges of the angles extending beyond the winch base about 1/2". See Fig. 267. The ends of the angles project beyond the winch base about 1-1/2" fore and aft. Divide the distance so that the angles project the same amount fore and aft, even if the distance is more or less than 1-1/2".

Fig. 267--Winch Base Blocked Up for Placing Side Angles

5. Mark the angles on one end, and place a similar mark on the winch base above the angles (make the mark with the center punch). This will enable the mechanic to replace the angles in the correct location.

6. Remove the angles, and make four similar punch marks, spaced equally around the circumference of each bolt hold circle. See Fig. 268.

7. With the dividers, find the center of the scribed circle. See Fig. 82 "Removing Broken Studs and Bolts", Part I, for method of procedure.

8. Center punch the center at the intersection of the divider lines.

9. Drill a 3/8" pilot hole through all centers. See Part I, "Reaming Through Holes", Fig. 64, for pilot-hole procedure.

10. Select a drill of the same diameter as the hole in the winch base, and drill through the pilot hole.

11. Measure for the bolt lengths, and allow for a nut, plus 1/2" beyond the actual thickness of winch base and angle.

12. Check for the proper angle location (See step 5), and bolt the angles to the winch base.

13. Have the ship riggers lift and place the winch on the previously laid out location on the deck.

14. Have the shipfitter level the winch and weld the angle edge to the deck. The outside machinist leader checks the job for correct installation at this point.

15. Remove the bolts, and lift the winch off the foundation so that the foundation may be finished by the shipfitters.

16. Grind off the top of the foundation all welding burrs which might interfere with the level fit between the Winch base and the foundation top.

17. Notify the painter, and have the foundation painted with anti-rust solution.

18. Set the winch back on the foundation. Bolt securely, and lock all bolts with half-inch nuts.

20. Check the number which is stamped on the main shaft coupling, and find the matching number on the capstan shaft coupling.

21. Have the riggers block up the capstan. When this operation is complete, line up the capstan as close as possible with the main drive shaft. The capstan should be blocked with two wooden wedges to prevent it from shifting.

NOTE: The inboard end of the capstan shaft is held temporarily by the spigot coupling. One bolt is placed loosely through the coupling to prevent slipping. See Fig. 270.

22. Layout center lines on the top of the channel foundation as shown in Fig. 263.

23. Locate the center of the bearing bracket on the edge of the base, fore and aft, port and starboard. Center punch these centers. See "x" and "y". Fill. 271.

24. Place the bearing-bracket center on the channel foundation center. Center the bracket on the channel foundation fore and aft, port and starboard, to match the center-punch mark and the center lines.

NOTE: Chalk the machined surface of the channel foundation so that the "lay out" lines will stand out clearly.

25. Scribe through the holes in the bearing bracket. Mark the foundations and the base of the bearing bracket so that the locations will not be lost.

26. Center punch the circumferences of the holes as in step 6, and locate center as in step 7.

Fig. 271--Marking the Rearing Bracket Centers

27. Center punch mark at the intersections of the divider lines.

28. Drill 3/8" pilot holes through the centers.

29. Select a drill of the same size as the diameter of the hole in the bearing-bracket base, and drill pilot holes through.

30. Clean up the machined bearing surface on the capstan shafts, and stone any rough spots.

31. Remove the cap from the bearing bracket, and clean any rough surfaces carefully.

32. Apply grease to the shaft-bearing surfaces.

33. Slide the bottom half of the bearing bracket on the shaft, and block up temporarily.

34. Place a piece of garlock packing at the top side of the shaft on the bearing surface. This packing should be the width of the bearing and about 1/3 of the shaft circumference in length.

35. Replace the base cap on the bearing bracket over the garlock packing.

36. Bump the bearing bracket out to the capstan hub to clear the shaft of the hub about .030 of an inch.

37. Tighten the bearing cap on the garlock packing so as to draw the bottom half of the bearing bracket tight to the shaft. See Fig. 272.

38. Check the coupling between the main drive shaft and the capstan shaft. The bottom of the coupling should be lined up at the bottom .003 "open", and about .015 between the faces of the couplings. See Fig. 273.

40. Bolt the foundation to the bottom of the bracket with temporary bolts. Draw the bolts up tight.

41. Chalk the foundation about. 1" above the deck on both sides for the entire length.

42. Re-check the coupling for clearance as shown in Fig. 273.

43. Measure with the square, and level the foundation with the deck fore and aft.

44. Set the "morphs" to 1", and scribe on the chalked surfaces parallel lines on both sides of the foundation.

45. Remove the bolts, and remove the foundation.

46. Center punch mark the foundation along the scribed lines on both sides 1-1/2" apart.

47. Have the foundation burned off to these center-punched lines.

48. Knock off the slag and rough sides of the burned edges with a hammer.

49. Slide the foundation back to the former position under the bracket, but on the deck, leaving a 1" space between the top of the foundation and the bottom of the bracket.

50. Insert two pieces of round stock, easy bolt-hole size, through the bolt holes in the opposite corners of the bracket base and the holes in the foundation. This operation will serve to line up the foundation holes with the bracket holes.

51. With fox wedges, raise one side of the foundation until it is 1-1/16" higher than the other side, thus forming a wedge-shaped space between the foundation and the bracket base.

52. Re-check the coupling for clearance as in Fig. 273.

53. Have the welders tack all four corners of the foundation to the deck.

54. Re-check the wedge-shaped space as in step 51 to make sure that the foundation is 1/16" higher on one side than it is on the other side.

55. If correct, weld the foundation to the deck inside and outside for the entire length.

50. Place heel wedges between the foundation and the bearing bracket, two forward and two aft. The bracket is now supported on the heel wedges.

57. Remove blocking from under the capstan.

59. Weld a piece of flat bar to the deck aft of bearing bracket about 2". A hole is drilled through the plate bar for a bolt. The bolt is used as a backing screw to prevent the bracket's drifting aft. See Fig. 274.

Fig. 274--Using a Flatbar Stop and an Adjusting Screw

60. Check all adjustments for alignment; readjust if necessary.

61. Take chock sizes and order chocks.

62. Fit chocks.

63. Scribe holes in chocks, and have them drilled.

64. Place chocks, install the bolts, and draw down tightly. Lock with the half-nuts.

65. Remove the heel wedges.

66. Re-check coupling. See Fig. 273. If the alignment is the same as it was before, have the inspector approve the job. If the coupling is out of alignment, the chocks will have to be refitted.

67. Drill and install 1/2" dowels on opposite corners of the bearing brackets. See Fig. 275.

Drill the dowel holes with a 31/64" drill. After drilling, ream through with a 1/2" hand reamer. The dowel should drive in with medium force.

68. Remove the bearing-bracket cap, and take out the garlock packing.

69. Clean out the bearing cap. Clean up the shaft.

70. Grease the shaft, replace the bearing cap, and tighten down.

71. Check with the feelers and allow .012 of an inch clearance between shaft and bearing. If more than .012, remove a shim. If less than .012, add a shim.

72. Clean up feed bolts and coupling.

73. Drive fitted bolts through coupling, and draw all nuts down snugly.

74. Drill and dowel the base of the deck winch on the foundation.

75. Grease the entire mechanism, and prepare it for operation.

Installing A Steering Gear and Telemotor For Pilot House Indication

GENERAL DESCRIPTION OF MAIN STEERING GEAR

The main steering gear controls the position of the ship's rudder. A ship's rudder weighs as much as 24 tons and steering the ship by hand as is done in a small pleasure boat is not possible.

A mechanically operated device which is known as a steering gear is installed in the after peak on a deck called the steering-gear flat. Certain motors, pumps, and other mechanisms are installed on the steering-gear flat which control the operations of the steering gear. Control wheels are installed in the wheelhouse and on top of the wheelhouse. The wheelhouse is located on the navigating bridge deck.

Other control wheels are located on the steering-gear flat forward of the main steering gear. The control wheels actuate the steering mechanisms by means of hydraulic power which is transmitted from control wheel to steering gear through a pipe line connecting the wheelhouse with the steering-gear room. Hence, the entire installation is known as the ship's steering gear. The port side of the forward end of the steering-gear engine is shown in Fig. 276.

Fig. 276--Port Side of Steering Gear in Steering Gear Room

ALIGNING STEERING GEAR MECHANISMS

The entire steering-gear mechanism is lined up with the center line of the rudder stock. Hence, the rudder must be placed and the rudder stock installed before the work of installing the steering gear may begin.

Figure 277 shows the rudder (a), the rudder stock (b), the rudder trunk (c), the carrier bearing (d), the bearing disk (e), the carrier and brake drum (f), the tiller (g), and the keeper ring (h), installed in position. All of these parts must line up with the rudder stock center line fore and aft, port and starboard.

The procedure for the installation of these parts up to the point where the installation of the steering gear commences is as follows:

1. Weld the rudder trunk (c) in position as shown.

2. The rudder is placed and the gudgeon pins installed as shown in Fig. 277 at "z".

3. The rudder is raised and a steel block 2" thick is inserted between the upper gudgeon eye and the rudder to hold the rudder in this raised Position. See Fig. 277 at "x".

4. Install the rudder stock (b).

5. Install the carrier bearing (d).

6. Install the bearing disk (e).

7. Install the carrier and brake drum (f), and have the brake hand in position on the brake drum to be connected to the brake lever later.

8. Install the tiller (g).

9. Install the keeper ring (h).

10. Lift the rudder enough to remove the 2" block which was placed to raise the rudder in Step 3.

11. Lower the rudder into position so that the rudder carrier takes the entire weight of the rudder assembly.

12. Tighten the bolts through the two halves of the rudder carrier and brake-drum casting, securing the carrier to the rudder stock.

13. Swing the rudder to port and starboard and check it against the rudder stops for the correct angle with the ship center line. If the angle is not correct, add to or take away from the rudder stops.

14. Bring the rudder to amidship position and secure with chain falls from the tiller to the shell of the ship. 15. Install the packing and the split packing glands shown at "j", Fig. 277.

INSTALLING MAIN STEERING-GEAR RAMS AND CYLINDERS

The foundations for the main steering-gear ram and cylinders are "A" "A" "A", Fig. 279. Figure 281 shows this unit extending athwartships. Note the two heavy bolts, "B" "B" which act as a support for the follow-up gear bearing and pinion. These bolts are shown at "B", Fig. 280 and at "B", Fig. 282. The bolts tie the port and starboard rams and cylinders together and ensure their correct alignment.

The foundation tops, Fig. 279, "A", "A", "A", are rough-leveled off with a portable grinder and finish-ground with a portable surface grinder. The surfaces of the foundation tops are ground level and smooth for a distance of approximately 10" from the edge, fore and aft. This 10" level plane surface slopes from nothing to the outside about 1/64 of an inch, but not more than 1/32 of an inch. A long straight edge is used to check the amount of slope. See Fig. 287.

This procedure is carried out on all the foundation tops shown in Fig. 279, "B"-"B", "C"-"C", "D", "E", "F", and "G".

The shipriggers pick up the main unit and lower it to the foundation "A" "A". The unit is then leveled and brought to the correct position fore and aft, port and starboard. The job is now ready to have the chocks fitted and the bolts installed through the base. This main ram and cylinder unit must be in place before proceeding to install any of the other parts of the steering gear.

Fig. 278--Cast Steel Rudder Trunk

Fig. 279--Foundation Plan for Main Steering-Gear Rams and Cylinders

Fig. 281--Main steering-Gear Ram and Telemotor

16. inspect the position of the ram in the cylinders, and make any necessary adjustment to bring the pivot hole in the ram to the fore-and-aft center line of the ship.

17. Weld angle clips at convenient places to clear the corner chock positions at points shown at "a", Fig. 286. Complete the welding of angle clips to both main ram foundations.

18. Drill holes for 3/4" jacking screws through the base of the unit as shown in Fig. 289 at "b" according to the dimensions given. See Fig. 277.

19. By means of the jacking screws through the unit base and the set screws through the angle clips, adjust the position of the main ram and cylinder until the athwartship center line of the ram is at right angles to the vertical center line of the rudder stock and at right angles to the fore-and-aft ship center line. See Fig. 277, 90° angles. (See Fig. 280).

Fig. 282--Front View of Steering--Gear Looking Aft

center, which is between the top and bottom of the tiller jaws. See Fig. 277 at "g", Fig. 282, and Fig. 290 at "g".

20. Begin at the inboard, forward corners of the port foundation ("d", Fig. 286, Chock #1), and measure for chock sizes. Fill out a chock sheet for each chock.

21. Send the chock sheets to the shop, and order the chocks machined according to dimensions given on the sheets.

22. When the chocks are returned to the job, begin fitting the correct chocks as follows:

Fig. 283--Hele-Shaw Hand--Steering Pump

Fig. 284--Plan and Elevation of Telemotor Copper Piping

See explanation of numbers on page 245

(These chocks are on the port foundation.)

(These chocks are on the starboard foundation.)

Fig. 286--Port Foundation for Main Steering Ram

23. Fit the intermediate chocks.

Fig. 287--Checking Foundation Top with a Straightedge

Fig. 288--Jacking Screws Tack Welded to Foundation Top

24. Scribe through the holes in the unit base on all eight corners, and mark the position of the holes which are to be drilled in the corner chocks.

25. Remove the corner' chocks, and center punch mark the circumference of each hole. Find the center of the holes with the dividers; center punch mark the centers; and send the chocks to the machine shop for drilling. Give the machine shop the size of holes required.

26. When the chocks are returned, place them in position and drill the holes through the foundation, using the hole in the unit base for a guide. See Fig. 61.

BILL OF MATERIALS

A partial bill of materials which goes into the fabrication and assembly of a steering engine is given below. To identify the type and grade of material; compare the key-number on the Figures 284, 297, 299, with the bill of materials.

For example: The number 12 in the circle in Fig. 297 is found in the column at the left in the bill of materials. Reading across from

Fig. 290--Tiller Jaw Center 1/4" Above Ram Center

Follow this same procedure with all the other numbers in the circles in these three figures.

In Fig. 277 the letter "s" is found in one of the circles. This material is 1" square packing.

NOTE: When because of limited working space it is impossible to drill a full-sized hole in the foundation, the workman places a bushing in the hole in the unit base and drills a pilot hole with a small drill. It is then possible to get under the foundation with a large drill and a drilling machine and drill the hole to the full size from below.

27. When the corner holes are drilled, ream them to size as shown on the blueprint.

28. Order 28 fitted bolts to fit the reamed holes. Give the machine shop the sizes of the bolts.

29. When the fitted bolts are ready, install them on all eight corners first and draw up snugly.

30. Scribe through the unit base holes, and mark the hole locations on all the intermediate chocks. Locate the centers as in step 10.

31. Send the chocks to the machine shop to be drilled. Give the shop the size of the hole.

32. When the chocks are returned, install them in the correct location and ream as in step 12.

Fig. 292--Telemotor Foundation

34. Install port and starboard motor and pump units "k" (See Fig. 280, Fig. 281, Fig 282) according to the blueprint.

35. Fit, the chocks and install the fitted bolts as was done with the main cylinder and ram units. See Fig. 291 for location of bolt holes.

INSTALLING THE TELEMOTOR

Figure 284 at "p", shows two small lugs connected by a pin. The pin must he a slip fit through both lugs, and it must slide easily. The forward lug is connected with the follow-up gear and the after lug is part of the telemeter leg which is connected o the telemotor.

The foundation for the telemotor is shown at "e", Fig. 279. The telemotor is shown at "t", Fig. 277, and at "t", Fig. 280. The telemotor must be installed on the foundation and aligned with the follow-up gear. Figure 285 shows the follow-up gear and the pin at "c". See Fig. 292 for location of bolt holes in the foundation.

Fig. 293--Telemotor Rack Foundation

PROCEED

36. Install the telemeter rack and align with the follow-up gear. See fig 279 at "d" for location.

37. Chock the telemotor and bolt down. See Fig. 293 for location of bolt holes.

35. Install the telemeter and align it with the telemeter rack.

39. Chock the telemeter and bolt down.

40. Install the follow-up gear universal control rod "U", shown in Figs. 277 and 280.

EMERGENCY, HAND-STEERING MECHANISM

Figures 277, 280, and 284 show the emergency, hand-steering cylinder and ram. Figure 279 "R" shows the foundation for these parts.

41. Install the emergency, hand-steering cylinder and ram units, and align the center line of the unit in the same manner as was done in step 4 in aligning the main ram and cylinder. See Fig. 294 for location of bolt holes.

42. Chock the unit, and bolt down.

BRAKE-LEVER UNIT

In step 7 the brake band was installed to be connected to the brake lever later on. The brake-lever unit is now to be installed. Figure 279 at "f" shows the foundation for the brake-lever unit. Figure 280 at "v" shows the brake-band connection with the brake-lever. Figure 280 also shows the brake-lever adjusting screw at "w". The adjusting-screw unit must be installed at the same time as the brake lever in order to secure a correct alignment. Figure 303 shows

Fig. 295--Brake Foundation

INSTALLING THE BRAKE LEVER AND SCREW

The brake lever and the brake-lever adjusting-screw units are now installed and aligned with the brake band which was previously placed in position on the brake drum. The brake edges must line up with the flanges on the brake drum and not "cross" the plane of the brake-drum flanges. When the alignment is correct, the bottom edge of the brake should clear the bottom flange of the Crake drum about 1/16 of an inch. The base of each of these units is adjusted to the correct height with jacking screws. When the alignment is correct, the chocks are fitted, drilled, reamed, and bolted down according to standard procedure.

HAND PUMP AND FILLING TANK

Figure 298 shows a hand pump and a filling tank both of which are parts of the telemotor system. The liquid for the hydraulic mechanism is poured into the tank, and the pump is used to circulate the liquid and distribute it throughout the telemotor lines. The foundation for the pump is two 3" angles welded to the deck after the pump has been bolted to the angles. An angle foundation for the tank is welded to the deck, and the tank is strapped down securely.

HELE-SHAW HAND-STEERING PUMP

Figure 280 at "y" shows a hand steering pump which is used for emergency steering when the electric power fails on the main unit. Turning the hand wheel operates the pump which in turn operates the emergency rams "R-R", Fig. 280.

The unit is bolted to the foundation, without chocks. A shim may be used to compensate unevenness in the foundation.

The holes in the foundation are located from the base of the unit which is already drilled when received. See Fig. 297 for the locations of the holes in the foundation. The unit is lined up with the bulkhead.

STEERING-GEAR CONTROL

Figure 299 shows the steering-gear control in the wheelhouse and on the wheelhouse top. Figure 300 is a cross-section view of the base of the steering-gear column in the wheelhouse. Figure 301 is a cross-section view of the base of the steering-gear column on the wheelhouse top. Bosses are welded to the deck as at "a". Studs are screwed into the

Fig. 298--Plan and Elevation of Telemotor System in Steering Gear Room

See explanation of numbers on Page 245

Fig. 299--Elevation of Telemotor Piping System Connected with the Wheel-House Controls

See explanation of numbers on Page 245

The installation is now ready for piping. The coppersmiths connect the piping from the forward telemotor on the bridge to the after telemotor. The coppersmiths also install the piping between the filling, tank and the telemotor.

The installation is now ready for trial operation.

Fig. 302--Steam Operated Steering--Gear

Fig. 303--Brake Lever Unit

See explanation of numbers on Page 245

EXPLANATION OF NUMBERS ON FIGURE 284

EXPLANATION OF NUMBERS ON FIGURES 298 and 299

EXPLANATION OF NUMBERS ON FIGURE 303

Installing A Propeller And Tail Shaft

THE PROPELLER

The propeller, Fig. 304, is usually a bronze casting weighing approximately seventeen tons. The propeller casting is balanced, and the hole in the hub for the tail shaft is bored in the machine shop. A template is used when boring the propeller, the use of which should insure a perfect fit between the tail shaft and the propeller bore.

Fig. 304--Typical Bronze Propeller

THE TAIL SHAFT IS PLACED FIRST

The tail shaft, Fig. 305, is lowered into the engine room by the ship riggers and passed through the stern until flush with the eye. The propeller hub and tail shaft must be free of dirt and grit when placed together.

Fig. 305--Tail Shaft Fitted with Bronze Sleeve

The propeller is lowered into place by the ship riggers. Pads have been welded at suitable locations on the ship shell to port and to starboard. As the crane man lowers the propeller to place, chair falls, hung from the pads, receive it and it is swung into place aft of the stern-frame eye and in line with the tail shaft. Roll the tail shaft until the key in the taper is fair with the keyway in the hub. See Fig.306. The tail shaft is now pushed out and into the hole in the propeller hub. The lock nut is next installed and run onto within three inches of the after end of the hub. See Fig. 307.

FORCING THE PROPELLER ON THE TAIL SHAFT

The approved types of wedges and boxes are then installed between the lock nut and propeller hub for the purpose of forcing the propeller on to the taper of the tail shaft.

A turn of red lead is inserted into the space (about 3/4" deep) between the tail-shaft shoulder and the eye diameter. See Fig. 307.

INSTALLING A PROPELLER AND TAIL SHAFT

The nut is then run up against the after end of the hub by means of a heavy, special spanner wrench. A heavy chain fall is anchored to the skeg and hooked on to the outer end of the spanner wrench. With a steady strain on the chain fall and with repeated blows of a 30-lb. sledge on the outer end of the spanner, the machinist snugs home the lock nut against the after end of the sternframe eye. Check with the leader for his approval.

The chain fall, spanner wrench, and other equipment are now removed and returned to the tool rooms. A special locking device is installed to prevent the propeller lock nut from loosening. See Fig. 308. A hole just large enough to take the pin "a" (Fig. 308) is drilled into the after end of the propeller hub. The hole is located in a convenient notch in the lock nut. See Fig. 309. Holes are drilled and tapped in the lock nut to fit the holes in the locking device, Fig. 309. The pin shown in Fig. 308 is inserted in the drilled hole in the propeller hub, and cap screws are used to fasten the device securely in the lock-nut notch.

Figs. 310 and 311--Fairwater Installed Over Propeller Lock Nut

SEALING THE LOCK NUT

A fairwater is installed over the after end of the propeller hub for the purpose of sealing the lock nut and protecting it from seawater. See Fig. 311. After the fairwater is installed, it is filled with tallow through the hole provided (b), and a pipe plug is screwed in securely. See Fig. 311. A similar hole is provided in the propeller hub through which tallow is poured to seal the tail shaft against corrosion should possible leaks occur. See Fig. 310 at "c".

The job of installing the propeller and tail shaft may be outlined as follows:

PROCEDURE

1. Lower the tail shaft into the engine room.

2. Pass the tail shaft aft until the outer end of the threaded portion is flush with the stern-tube lock nut.

3. Lower the propeller into place on chain falls, fair with the stern-tube bore.

4. Roll the tail shaft until the key in the taper is fair with the keyway in the propeller.

5. Push the tail shaft through the stern tube, and engage the tapered bore in the propeller hub.

6. Install the lock nut, and run it on to within 3" of the after end of the hub.

7. Draw the propeller hub on to the tail-shaft taper by means of wedges and boxes.

8. Insert a turn of red lead between the tail-shaft shoulder and after face of the propeller.

9. Turn the nut home by using the special spanner wrench, chain fall, and 30-1b. sledge.

10. Remove the chain falls and other equipment, and return them to the tool room.

11. Install the lock nut and lock key.

12. Install the fairwater.

13. Fill the fairwater recess and the propeller-hub recess with tallow. Insert pipe plugs and make tight.

14. Cement fairwater bolthead openings.

Launching a Tanker

GENERAL INFORMATION

The outside machinist has several important jobs to perform before a ship can be launched. Docking plugs must be screwed in place; the ship's rudder must be securely locked in a central, fore-and-aft position and the propeller must be firmly held so that it cannot turn when the ship slides into the water. In the bottom of a tanker there are forty-seven docking plugs. See Fig. 312.

Metal flanges are threaded to fit the plugs shown in Fig. 312. The flanges are welded in openings in the ship's bottom.

PURPOSE OF DOCKING PLUGS

The openings are located in the bottom so that every tank in the ship may be drained through them. A docking plug is screwed into the threaded hole in the flange before the ship is launched.

While the ship is on the ways and before the docking plugs area finally screwed in place, lengths of pipe equipped with valves, are temporarily screwed in place and the valves are closed. The tanks are filled with water to test them for leaks. When the tanks have been tested and approved the valves in the pipe lengths are opened and the water is drained. The docking Plug is then screwed in place by means of a wrench which fits the square hole in the plug. See Fig. 312. When a ship is placed in drydock the docking plugs are removed to allow all the water or other liquid in the tanks and bilge to drain. Oil tankers are washed out with live steam and the accumulation of water and oil is drained out through the docking plug openings.

LOCKING THE RUDDER

When the ship slides down the ways, See Fig. 313, there are several thousand tons of, dead weight to control after the ship is in the water. The rudder must be securely locked so that it can not be slammed around by the water pressure as the ship leaves the ways. There are two ways by means of which this is accomplished:

The riggers install cables at the stern of the ship. The cables are fastened from the rudder, port and starboard, to pads which are welded to the ship shell, port and starboard. The cables are drawn up taut and made fast.

Fig. 313--The Ship Sliding Down the Ways

On the inside of the ship, Fig. 314, chain falls are fastened to the tiller jaws; one chain fall to port and one chain fall to starboard. The other end of each chain fall is fastened to the ship's frame, port and starboard. The braces take the strain as the pull of the chain falls is exerted on the tiller jaws. With the braces in place the chain falls are pulled up tight and locked, thus adding extra force inside the ship to assist the force of the cables installed outside of the ship by the riggers.

2. SECURING RUDDER WHEN THE RUDDER STOCK IS NOT INSTALLED

Rudder stops are provided at the stern to prevent the rudder from swinging more than 37 1/2 degrees to either port or starboard. See Fig. 315.

When the rudder is in a central fore and aft position there is a space about 7 inches wide between the rudder stops and the rudder bumpers. The riggers install cables at the stern of the ship as before. With the rudder held exactly fore and aft, R" to 1" thick plates about 7" wide are temporarily welded in the space left between the rudder stops and the rudder bumpers. See Fig. 315. Whichever method is used, the work is supervised and Checked by the outside machinist.

HOLDING THE PROPELLER STATIONARY

The rush of water against the propeller as the ship slides down the ways is sufficient to start the propeller revolving. This must never be allowed to happen. Means must be provided to hold the propeller shaft and thus hold the propeller. Fig. 316 shows a pair of heavy bars of steel which fit around the coupling flanges of the line shaft in the shaft alley. It will be noted that the semi-circular cut-out in the center of each bar is for the purpose of allowing the bars to reach around the line shaft far enough for the bolts in the coupling flanges to pass through the bars.

Fig. 316--Heavy Bars and Struts to Keep the Line Shaft From Turning

After the bars are bolted in place the lower ends of the bars are temporarily welded to the deck and the upper ends are braced by struts welded to the port and starboard sides of the ship shell.

When the ship is about ready for launching the docking plugs are all screwed in and inspected under the supervision of the outside machinist. Leaving a plug out or neglecting to screw a plug in would be equivalent to drilling holes in the ship's bottom. Every docking plug must be snugged home securely to prevent any possible leakage.

QUESTIONS

1. What is the purpose of a docking plug?

2. How is a docking plug flange installed in a ship?

3. Where are docking plugs located?

4. Why are docking plugs inspected carefully before the ship is launched?

5. Why must the ship's rudder be securely blocked in place before the ship is launched?

6. Describe the blocking operation as it is carried through when the rudder is installed.

7. Describe the blocking operation as it is carried through when the rudder stock is not installed.

8. Why must the ship's propeller be prevented from turning when the ship is launched?

9. Describe the method employed to lock the propeller in position while the ship is being launched.

10. Make a list of the accidents and happenings that might take place if any of the duties of the outside machinist, as outlined in this lesson, were left undone.

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