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20
MAINTENANCE
 
A. PRELIMINARY INSTRUCTIONS
 
20A1. General. Extreme vigilance and care should be practiced in the inspection, cleaning, and repair of parts. Personnel performing repair work should use common sense when judging whether or not a part should be put back into service or discarded. If there is any doubt, the part should be replaced. With the exception of bearings and electrical equipment, corrosion should be removed from arts by washing them in clean, fresh water. Dry   the parts thoroughly, and apply a light film of gyro oil to prevent rusting or corrosion. Use Navy-approved cleaning fluid to clean grease and oil from the parts. Keep the bearings oiled and clean by wrapping them in wax paper until needed for assembly. The area in which the repair work is being performed should be kept in a clean condition in order to prevent dust from getting on the parts.
 
B. MAINTENANCE Of RODMETER
 

Figure 20-1. Valves and vent cocks in position
to check for clogged rodmeter.
1. STATIC VENT COCK
2. STATIC SHUT-OFF VALVE
3. BYPASS VALVE
4. DYNAMIC VENT COCK
5. DYNAMIC SHUT-OFF VALVE
Figure 20-1. Valves and vent cocks in position to check for clogged rodmeter.

20B1. Testing for obstruction in the rodmeter. The rodmeter may become clogged with jellyfish, mud, seaweed, or other foreign matter. Consequently the pressure difference will not be normal, and the mechanism will not register correctly. The following test must be performed when the ship is on the surface. Position the valves and vent cocks as

  shown in Figure 20-1. If a full stream of water does not flow from both vent cocks, it is an indication that the line not flowing is clogged.

20B2. Blowing out the rodmeter. This operation should be performed with the rodmeter in its extended, or operating, position. It is a good practice to blow out both lines even if the tests for obstruction indicate only one line clogged, as foreign matter has possibly entered both passages. Blow out the rodmeter in the following manner: Disconnect the static hose from the static pressure pipe nipple at the top of the manometer piping. Pinch the end of the hose to prevent leakage of water. If the line is completely clogged, water will not leak from the hose. Connect the low-pressure air line of the ship to the static hose, and blow the obstruction out of the hose and rodmeter into the water outside the ship. Do not apply the low-pressure air hose to the piping that enters the manometer as the air pressure will blow out the mercury. When a full stream of water is obtained from the static hose, place the end of the static hose over the end of the hose fitting at the upper end of the static piping of the manometer, and install the hose clamp securely. Blow out the dynamic line of the rodmeter in the same manner. Go through the venting routine after connecting the hoses to the manometer. (See Section 19A3.)

 
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20B3. Removing solid obstructions from the rodmeter. If obstructions cannot be removed by blowing out the rodmeter with compressed air, the following operations are necessary. Raise the rodmeter to its fully housed position. Close the sea valve. Unlatch the stop bracket at the top of the hoist assembly by opening and removing the lock that secures the bracket in position above the rodmeter, and swing it to one side. Remove the lower end of the rodmeter from the sea valve extension by raising the rodmeter to the upper sprockets. Using a soft brass wire, dig out the obstructions from the orifices (openings) on the lower end of rodmeter.

Do not use steel wire or a drill to clean out the orifices as they may score the orifices or break off in the openings.

Blow out the rodmeter (as described in Section 20B2) while out of the valve extension. Have one crew member hold his hand near the orifices to detect the flow of air which indicates that the orifice and tubing are clear. Repeat the operation until all passages are

  clear. Align the lower end of the rodmeter with the opening in the sea valve extension and carefully lower the rodmeter to its fully housed position.

Use care in placing the tip of the rodmeter in the packing gland so as not to roughen or remove the packing.

At this point the tip of the rodmeter is approximately 1-inch above the sea valve gate. Connect the tubing from the rodmeter to the manometer. Open the sea valve. Swing the stop bracket to its normal position above the rodmeter and secure it in place with the lock.

It is important that the stop bracket be in position above the rodmeter at all times except during the above operation, or when the rodmeter is being replaced.

Lower the rodmeter to its normal housed position or to the fully extended position as desired. Place the hoist crank in the brackets provided, and replace the deck plate over the sea valve. Vent the system in accordance with the instructions outlined in Section 19A3.

 
C. REPLACING A DAMAGED RODMETER
 
20C1. General instructions. If the rodmeter is bent so that it cannot be drawn up into the ship, it is necessary to install a spare rodmeter. Do not attempt to force the damaged rodmeter up into the ship, as the hoist mechanism may be damaged. The removal and installation operations should be carried out only when the ship is surfaced. If the damaged rodmeter is to, be salvaged, it may be accomplished if a diver is available. Lower the diver over the side of the ship so that he can rig a line around the damaged rodmeter. Secure the other end of the line to the ship so that the rodmeter can be pulled out of the water after it is pushed out of the sea valve.

20C2. Breaking out spare rodmeter. (See Figure 20-2.) Break out the spare rodmeter and place it alongside the hoist mechanism so that it will be immediately available when needed.

20C3. Removing the clamp and guard assembly. (See Figure 20-2.) From 1/2-inch

  diameter dowel pin stock, make up two tapered wooden plugs 1-inch long tapering to 3/8-inch diameter at one end. Loosen the hose clamps and remove the two lengths of hose from the nipples on the upper end of the rodmeter. Unscrew the longest (after) nipple and plug the hole in the rodmeter with a plug. Remove the forward nipple in the same manner, and plug the hole. Remove the two nuts and bolts that secure the clamps and guard to the rodmeter, and remove the clamp and guard assembly. Raise the guard by means of the hoist up against the stop bracket above the rodmeter. Knock out one of the stop pins in the rodmeter.

20C4. Installing the clamp and guard assembly. (See Figure 20-2.) The two clamps and the guard are marked to facilitate reassembly. These marks should be adjacent to one another when the pieces are assembled on the rodmeter. Place the two clamps around the upper end of the spare rodmeter so that

 
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Figure 20-2. Rodmeter.
Figure 20-2. Rodmeter.

the clamps are over the stop pins provided at the top of the rodmeter. Place the guard between the clamps. Align the mounting holes in the three pieces, and install the two bronze bolts and nuts that secure the clamp and guard assembly to the rodmeter. Tighten the nuts securely.

  20C5. Installing the spare rodmeter. (See Figure 20-2.) If the damaged rodmeter is partially raised, push it downward until the remaining stop pin rests on top of the packing gland in the sea valve extension. It may sometimes be necessary to drive the rodmeter downward with a sledge and wooden block. Place the tip of the spare rodmeter on top of the damaged rodmeter, making certain that the dynamic orifice in its leading edge is facing forward. Note the arrow stamped on the rodmeter for facing the spare rodmeter in the proper direction. Remove the cotter pin and clevis pin that secure the old guard to the lifting bar on the hoist chain, and remove the old guard. Align the opening in the lifting bar with the opening provided in the guard on the spare rodmeter, and install the clevis pin and cotter pin that secure the lifting bar to the guard assembly. Place the loose end of the dynamic hose over the nipple provided on the dynamic (short) nipple on the top of the rodmeter. The opposite end of this hose is attached to the lower pipe at the top of the manometer. Secure the hose to the nipple with a hose clamp. Place the end of the static hose on the long nipple on the top of the rodmeter. The opposite end of the static hose is attached to the top pipe fitting at the top of the manometer. Secure the hose to the nipple with a hose clamp. It is a good practice to wire the two hose clamps together with soft brass wire to prevent the hoses from slipping off the nipples at deep submergence pressures. Knock out the pin from the damaged rodmeter and push downward on the spare rodmeter to drive the damaged rodmeter downward and out of the ship. Vent the system in accordance with the instructions given in Sections 19A3.
 
D. MAINTENANCE OF MANOMETER
 
20D1. General instructions. Valves and vent cocks should be kept clean and lubricated with a good grade of waterproof grease. Keep the hose securely clamped to the nipples of the piping of the manometer. The gland on the manometer shaft in the gear chamber is not adjustable and should be kept clean and well   greased by tightening the grease cup on the front of the gear chamber (Figure 20-3). Friction in this shaft is usually due to hardened deposits of salt and grease in the gland. Remove the hardened grease, and clear the gear, roller, and float rack. Fill the gland with fresh grease.
 
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Figure 20-3. Front view of gear chamber.
1. GREASE CUP AND TUBE
2. GEAR CHAMBER
3. DRIVING ARM PIN
4. DRAIN SHIELD AND TUBE
5. GEAR SHAFT DRIVING ARM
Figure 20-3. Front view of gear chamber.

20D2. Testing for loss of mercury. With the bypass valve open, it should be possible to turn the transmitter speed dial approximately 1/4-inch beyond the zero mark on the dial, and when the dial is released it should read zero. If it does not return to zero, it is an indication

  that the mercury level is low, and that the float is hitting the bottom of the float chamber.

20D3. Adding mercury to the float chamber. Add mercury to the float chamber in the-following manner. Close the static and dynamic shut-off valves. Disconnect the three connections on the manometer Y-pressure piping, and remove the piping. Remove the back plate from the gear chamber. Siphon off all the water from the center and side tubes of the manometer. Add mercury to one of the side tubes until the float rises approximately 1/2-inch from the bottom of the float chamber. This is determined by manually pushing the rack and float downward until the float strikes the bottom of the float chamber, then releasing it and noting its rise. When measuring the float rise in this manner be sure that the float hits the bottom of the float chamber, and is not prevented from doing so by the driving arm pin (Figure 20-3) striking the front bracket of the gear chamber. It will be necessary to loosen the drawing arm clamping screw if the pin hits the bracket. Connect the piping to the manometer. Replace the gear chamber cover. Vent the system until all the air is removed from the hydraulic system as described in Section 19A3. Reset the speed dial to zero. (See Section 20E1.)

 
E. MAINTENANCE OF TRANSMITTER
 
20E1 Setting the speed dial to the zero position. Thoroughly vent the hydraulic system, (See Section 19A3.) House the rodmeter. Open the bypass valve. If the driving arm pin has been loosened (see Section 20D3), tighten it while holding the transmitter speed dial on zero. Be sure that the driving arm is so located on the gear wheel shaft that it will not rub on the front bracket, or on the front cover of the gear chamber. Slightly rotate the transmitter speed dial backward and forward from the zero position, pushing the adjusting fork (Figure 20-4). The dial should return to the zero position. If not, set the dial to zero by means of the adjusting screw on the adjusting fork (Figure 20-4).   20E2. Checking integrator timer. There are two types of integrator timing mechanisms used with the mercury manometer log. They are the synchronous motor integrator timer (known as the a.c. clock type), illustrated in Figure 18-5, and the d.c. clock integrator timer, known as the d.c. clock type (Figure 20-5). In the 18- and 20-knot logs, the d.c. clock is used and the integrator operating arm makes 180 strokes per hour. In the 22-knot logs, some having d.c. clocks and some having a.c. clocks, the operating arm makes 240 strokes per hour. The number of strokes per hour for each particular unit is indicated on a marker plate which is mounted over the
 
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Figure 20-4. Adjusting fork.
1. TRANSMITTER CASE
2. CASE MOUNTING STUD
3. GEAR SHAFT DRIVING ARM
4. MAINSHAFT
5. GEAR WHEEL SHAFT
6. ADJUSTING FORK
7. ADJUSTING SCREW
8. DRIVING ARM PIN
9. GEAR CHAMBER
Figure 20-4. Adjusting fork.

timing counter window. Check the integrator timer in the following manner:

Using an accurate stop watch, start the watch and record the indication on the timing counter when the counter number begins to change. Stop the watch and record the counter reading at the exact termination of 1-hour. The timing counter should read the number of strokes indicated on the marker

 

Figure 20-5. Direct current clock integrator timer.
Figure 20-5. Direct current clock integrator timer.

Figure 20-6. Distance repeater contacts adjustment.
Figure 20-6. Distance repeater contacts adjustment.

 
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plate for that particular unit. If the timing of the a.c. unit indicates that the number of strokes per hour is in error, check the constant frequency supply to be sure it is exactly 60 cycles. Also check the gearing for deposits of grease which may prevent the constant speed motor from running at synchronous speed. Clean and lubricate the gear mechanism. On the d.c. clock integrator timer, any error in the clock may be corrected by means of the regulator lever on the escapement (Figure 20-5). Moving the lever down one division on the scale will cause the clock to gain about half a minute per day. Moving the regulator up one division on the scale will cause the clock to lose approximately half a minute per day.

20E3. Installing and adjusting distance repeater contacts. (See Figure 20-6.) Remove the old contact assembly as a unit from the transmitter case bracket. Resolder the wires to the new contact assembly lugs, replace the insulating sleeves on the lugs, and mount the

  new assembly on the bracket with the holding screws. Center the contact springs on the star wheel, and tighten the holding screws. If either contact spring does not press against the star wheel in the open position, increase its tension by bending the spring as shown in Figure 20-6. Heavy spring tension is more desirable than light tension. Rotate the star wheel until the upper (longer) contact spring just drops clear of the tooth. At this instant the upper contact should rest squarely on the lower contact, but the upper contact spring should not touch the star wheel until the lower contact spring drops to the next tooth. This is important for proper, quick, make and break operation. If necessary, bend the tip of the upper contact spring to provide the correct clearance as shown in Figure 20-6. When the contacts are clean and properly adjusted, there should never be excessive sparking. The tungsten contacts must be absolutely free of oil or grease. If the contacts are pitted, they may be cleaned with fine sandpaper or a contact stone. Do not oil the star wheel.
 
F. MAINTENANCE OF MASTER SPEED REPEATER
 
20F1. Follow-up motor. The follow-up motor used in the master speed repeater is the same as the lead screw drive motor used in the master speed indicator of the Pitometer rotary balance type log. Test, removal, and installation operations are covered in Sections 5M3, 5M4, and 5M6.

20F2. Calibrating the master speed repeater. (See Figure 20-7.) In order to make the speed indication of the master speed repeater agree with the speed indication of the transmitter speed dial, calibrate the master speed repeater in the following manner: Remove the interior mechanism from its case and place it on a convenient surface. Connect the jack of the case to the plug on the back of the mounting plate by means of the plug-jack cord furnished for this purpose. Do not energize any circuits. Remove the pointer and dial from the master speed repeater. Manually turn the gearing of the follow-up motor until the cam and roller are within approximately 0.005

  inch of seating in the hollow of the pointer cam as shown in Figure 20-7. Use care in turning the gears as excess motion may bend the supporting arm of the cam roller.

At this point, the limit switch which prevents over-travel of the follow-up motor should operate. If necessary, reset the limit switch operating screw. Replace the dial and pointer without the pointer hub cap, and set the pointer at exactly 22 knots by loosening the three screws clamping the pointer to the hub; then replace the pointer hub cap. The speed pointer is now in correct relation to the cam (Figure 20-7). Now rotate the followup gearing by hand until the master speed repeater indicates about 5 knots. Energize the 1Y circuit. If the master speed repeater speed indications do not agree with those of the transmitter, it will be necessary to align the self-synchronous repeater with the self-synchronous transmitter.

This is accomplished in the following

 
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Figure 20-7. Cam positioned for setting pointer at 22 knots.
Figure 20-7. Cam positioned for setting pointer at 22 knots.
  manner: Close the dynamic and static shutoff valves and open the bypass valve. Loosen the clamping screw of the gear shaft driving arm (Figure 20-4). Slowly turn the dial in the transmitter to 15 knots and secure the dial in this position to the fixed pointer with a small C-clamp. Loosen the clamps that secure the self-synchronous repeater to the mounting plate of the master speed repeater, and shift this repeater until the speed pointer reads 15 knots as indicated on the master speed repeater dial. Tighten the clamps to secure the repeater in this position on the mounting plate. Remove the C-clamp from the transmitter dial. Slowly turn the speed dial of the transmitter back to the exact zero. If the master speed repeater does not indicate zero, or approximately zero, clamp the transmitter dial at zero and make further very slight adjustments of the self-synchronous repeater in the master speed repeater. Tighten the clamping screw of the driving arm (Figure 20-4), and remove the C-clamp.
 
G. SYNCHRONIZING SPEED AND DISTANCE REPEATER
 
20G1. Resetting the speed pointer of the speed and distance repeater. If the speed indications of the speed and distance repeater do not agree with the speed indications of the master speed repeater, shift the repeater of the former in the following manner: Remove the speed and distance interior mechanism from its case. Connect the plug jack cord to   the case and interior mechanism. Loosen the clamps that secure the repeater to the mounting plate. Shift the repeater from until the speed indications agree with those of the master speed repeater, then tighten the clamps to secure the repeater in position. Install the speed and distance interior mechanism in its case.
 
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