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PART I
 
PITOMETER UNDERWATER LOG-
ROTARY BALANCE TYPE


2
DESCRIPTION
 
A. GENERAL DESCRIPTION
 
2A1. General. The Pitometer underwater log, rotary balance type, is made by the Pitometer Log Corporation, New York, New York. This system, illustrated in Figure 2-1, consists of five major components. Each instrument is watertight, and is designed for either panel or bulkhead mounting.

2A2. Rodmeter. The rodmeter, commonly called the sword, is located in the forward torpedo room below the light draft water line. It projects through the hull of the ship, into the water, and is the unit in which static and dynamic pressures are produced and transmitted to the other units of the system. When in use, the rodmeter extends into the water for a distance of about 3 feet. Being located in the forward part of the ship, the rodmeter contacts water that is least affected by the movement of the ship or by the turbulence of the water created by the action of the propellers.

2A3. Sea valve. The sea valve forms a support for the rodmeter and provides a means of closing the opening through which the rodmeter passes when the rodmeter is withdrawn, or fully housed. It is located in a well below the deck in the forward torpedo room, and is bolted to the inner hull below the light draft water line. A tube extends from the underside of the inner hull to the outer hull where it is welded to a flange and guide bushing. The guide bushing forms the lower support for the rodmeter. When the rodmeter is withdrawn, closing of the sea valve prevents sea water from flooding the forward torpedo room.

2A4. Control unit. The control unit is mounted in the forward torpedo room and is suspended on a gimbal bracket which tends to keep the unit in an upright position regardless of the pitching or rolling of the ship. This unit provides a means of automatically controlling the operation of the rotary distance transmitter. It consists of a sensitive

  bellows enclosed in a watertight housing, and a set of electrical contacts. The inside of the bellows is hydraulically connected to the pump of the rotary distance transmitter, while the outside of the bellows is connected to the static orifice of the rodmeter. The electrical contacts control the supply of current to the rotary distance transmitter pump drive motor.

2A5. Rotary distance transmitter. The rotary distance transmitter is located in the forward torpedo room, below the light draft water line. It is the unit that develops the force applied to equalize the dynamic pressure produced within the rodmeter. It consists of an electrically driven transtat assembly, an electric motor which drives a centrifugal-type pump, and a distance transmitting unit. By means of these components, rotary motion is transmitted to the master speed indicator, and to the speed and distance indicator.

2A6. Master speed indicator. The master speed indicator (Figure 2-3) is mounted on a panel near the control room steering station. Revolutions, the number of which are proportional to the distance traveled, are received by this unit from one of the self-synchronous transmitters in the rotary distance transmitter. These revolutions are registered on a counter and, by means of a time element, are converted into a speed indication in knots. This indication is transmitted to the speed and distance indicator.

2A7. Speed and distance indicator. The speed and distance indicator, commonly called the repeater, is mounted in the conning tower. It repeats the speed and distance readings of the master speed indicator.

2A8. Constant frequency supply unit. Some installations of the Pitometer underwater log system include another unit known as the constant frequency supply unit. This unit is designed to supply a constant 60-cycle current at 115 volts to the system.

 
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Figure 2-1. Components of Pitometer underwater log-rotary balance type.
Speed and distance indicator. (Repeater) Located in Conning tower.
Master speed inicator. Located on foreward bulkhead of control room.
Control unit, Rotary Distance Transmitter, Rodometer and Sea Valve. Located in aft section of Forward Torpedo Room.
Figure 2-1. Components of Pitometer underwater log-rotary balance type.
 
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Figure 2-2. Operation of Pitometer rotary balance system.
Figure 2-2. Operation of Pitometer rotary balance system.
 
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Figure 2-3. OPERATION OF THE MASTER SPEED INDICATOR

 
B. DESCRIPTION OF OPERATION
 
2B1. Sea valve and rodmeter. While the ship is stationary, the water pressure in the rodmeter is static and the log system is in balance. As soon as the ship is underway, the forward motion creates additional pressure through the dynamic orifice in the rodmeter, while the pressure through the static orifice remains the same. This creates an unbalanced condition in the control unit, and causes it to operate. (See Figure 2-2.)

2B2. Control unit. As the dynamic pressure increases, it is transmitted through the pump of the rotary distance transmitter to the inside of the bellows in the control unit. The pressure on the outside of the bellows (static pressure) has not changed, and because of this, the increased pressure inside the bellows causes it to expand. Movement of the bellows actuates the external contact arm, forming an electrical contact through the contact points at the outer end of the arm. Current then flows to the follow-up motor in the rotary distance transmitter.

2B3. Rotary distance transmitter. The follow-up motor operates the transtat, an electric transformer which supplies current to the pump drive motor. As the pump drive motor operates, the pressure produced by the pump opposes the dynamic pressure created in the rodmeter, reducing the pressure inside the bellows in the control unit. The bellows then contracts, returning to its former position. The contracting movement of the bellows draws the external contact arm upward,

  breaking the flow of current through the contact points. The pump continues to operate at a constant speed until a variation in the speed of the ship causes a variation in the pressure inside the bellows. The pump motor is geared to a distance counter, and is so designed that for every 14,400 revolutions of the pump, 1 mile is recorded on the distance counter, regardless of the speed at which that mile is covered. The distance reading is electrically transmitted to the master speed indicator and to the repeater.

2B4. Master speed indicator. The master speed indicator (Figure 2-3) receives the distance reading from the rotary distance transmitter, and registers it on a counter. This reading is of distance traveled, and bears no relation to the rate of speed. Through suitable gearing that connects the mechanism recording the known revolutions per mile with a mechanism that is operating at a known number of revolutions per minute, speed in knots is computed and registered on the dial of the master speed indicator. This reading is electrically transmitted to the speed and distance indicator, or repeater, in the conning tower.

2B5. Speed and distance indicator (repeater). The speed reading of the master speed indicator, and the distance reading of the rotary distance transmitter are transmitted electrically to the mechanism in the speed and distance indicator, and are registered on the dial and counter of that unit.

 
C. RODMETER AND SEA VALVE
 
2C1. Rodmeter. The rodmeter is made of manganese bronze, and is 8 feet 3 inches long this length is necessary because the rodmeter projects through the inner and outer hulls of the submarine. It is of oval, cross-section construction, with a fiat tip at its lower end. Two water passages are formed in the rodmeter (Figure 2-4). The upper ends of these passages terminate in nipples to which a rubber hose is attached by means of a clamp. Some types of rodmeter are equipped with valves so that these passages can be closed   when the ship is submerged to a depth greater than 200 feet, to prevent damage to the sensitive bellows in the control unit (Figure 2-5). The lower end of the forward passage in the rodmeter terminates in an opening or orifice in the forward edge, and is known as the dynamic tube and orifice. The lower end of the after passage terminates in two openings (one on either side of the tip), which are known as the static tube and orifices. These two orifices are not placed diametrically opposite each other, and therefore, cross pressures
 
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Figure 2-4. Cutaway view of rodmeter.
Figure 2-4. Cutaway view of rodmeter.

which would affect the accurate operation of the system do not develop. A lifting yoke and guard are attached to the upper end of the rodmeter by clamps, serving as a means of raising or lowering the rodmeter, and also forming a protection for the nipples. When lowered, the rodmeter projects about 3 feet through the hull into the water. A lifting device is provided in the ship for raising and lowering the rodmeter, and for replacing it in the event of damage. The rodmeter must always be raised, or housed, when the submarine docks or when, for tactical reasons, the submarine is allowed to rest on the ocean floor.

2C2. Sea valve. The sea valve is the mechanism that supports the rodmeter when the rodmeter is extended into the sea and that

  Figure 2-5. Radmeter with valves attached.
Figure 2-5. Radmeter with valves attached.

prevents water from entering the ship when the rodmeter is removed. The valve is a 3inch gate type, operated by means of a handwheel on an operating rod which in turn is bevel-geared to the valve stem. The sea valve is bolted to the inner hull of the ship. A 5inch valve extension with a packing land is mounted on the top flange of the valve. This extension provides an upper support when the rodmeter is projected into the sea, and also provides a leakproof joint around the rodmeter.

2C3. Rodmeter hoist. Submarines are equipped with either one of two types of rodmeter hoist (Figure 2-7) for raising and lowering the rodmeter. One type consists of a double sprocket and roller chain arrangement, and the other type is a single chain and

 
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Figure 2-6. Sea valve.
Figure 2-6. Sea valve.

single sprocket assembly. The upper sprockets are mounted either on the side of the hull or on a suitable panel near the installed rodmeter. The lower sprockets are mounted in the sea valve and rodmeter well. Sprockets are connected by roller chains. Operation is by means of a hand crank through a worm gear drive. In the single chain hoist assembly, the chain is connected to the clamp and guard assembly of the rodmeter by means of a connecting link which is pinned to the chain and to the clamp and guard assembly. In the double sprocket and double roller chain type of hoist, the chains are connected to a lifting bar which in turn is pinned to the lifting yoke and guard of the rodmeter. As the hand crank is operated, the chains rotate around the sprockets, thereby raising or lowering the rodmeter. The hoist crank normally is stowed in brackets in the rodmeter and sea valve well. To operate the hoist, a deck plate is first raised and the

  Figure 2-7. Rodmeter and hoist installed.
Figure 2-7. Rodmeter and hoist installed.
 
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crank is lifted off its brackets and placed on the hoist operating rod. When in the lowered, or operating, position, the clamp and guard on the upper end of the rodmeter are flush with the top of the extension on the sea valve. Approximately 32 turns of the crank are required to raise the rodmeter to the normal housed position. The normal housed position of the rodmeter is defined as the position that will permit the tip to just clear the outer hull; In this position, approximately half of the length of the rodmeter is above the extension   on the sea valve. This point is marked by a plate which is mounted on the hull side of the hoist bracket. The rodmeter is fully housed when the tip clears the sea valve gate. Approximately 82 turns of the crank are required to raise the rodmeter to the fully housed position. Approximately 90 turns of the crank are required to raise the rodmeter to its extreme raised position for inspection. The sea valve should be closed whenever the rodmeter is raised to the fully housed position.
 
D. CONTROL UNIT
 
2D1. Control unit case. The control unit case (Figure 2-8) is mounted on a gimbal bracket, and is suspended above the rotary distance transmitter in the forward torpedo room. Tapped openings which contain pipe plugs are located on the upper and lower sides of the case to permit access to the upper and lower adjustable stop rods. A third opening is provided in one end of the case to permit access to the inner contact arm clamp. The case cover, equipped with a rubber seal, is doweled in position on the case and secured to the case with cap screws.

2D2. Valve and pipe assembly. A valve and pipe assembly is mounted above the control unit case to permit venting, or bleeding, of air from the hydraulic system. Two vent cocks are provided to vent the bellows chamber; one vent cock is connected to the piping that terminates inside the bellows; the other vent cock is connected to piping that terminates in the bellows housing outside the bellows. The inside of the bellows is hydraulically connected to the nipple fitting on the center of the pump; the outside of the bellows is connected hydraulically to the nipple fitting on the static tube of the rodmeter. A control valve is mounted at the control unit end of each of these hydraulic lines. A bypass valve is mounted between the static and dynamic control valves.

2D3. Bellows assembly. The primer bellows assembly used on submarines consists of a hydraulic bellows which is mounted in a cast bronze watertight housing to protect the bellows from the high pressures caused by

  submersion. The primer bellows is mechanically, connected to an external contact arm which actuates electrical circuits through a lever. The upper end of the bellows is secured to the bellows housing by a bellows ring. The lower end of the bellows is connected to a seal bellows mounting stud by means of a cap screw and bellows extension post. The seal bellows mounting stud passes through the bellows housing and is secured to the contact lever shaft by a bellows shoulder screw. A water seal is provided between the bellows mounting stud and the pressure bellows housing by a seal bellows. The seal bellows is attached to the pressure bellows housing by means of a bellows seal cap and gasket. The contact lever shaft is supported in ball bearings which in turn are mounted in a pillow block.

A Y-shaped external contact arm is mounted on the ends of the contact lever shaft by adjustable clamps. Upper and lower adjustable stop rods are provided to limit the motion of the bellows, thereby preventing damage to the interior parts at times of excessive pressure differences in the bellows. As the ship moves forward, the dynamic pressure in the bellows causes the bellows and its attached linkage to move downward, establishing electrical contact at the lower end of the external contact arm.

2D4. Electrical contacts. Upper and lower platinum contacts are attached to springs on an extension of the external contact arm. A pigtail wire connects the inner arm of the external contact arm with the right-hand

 
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Figure 2-8. Control unit, cover removed.
1. DYNAMIC HOSE (FROM PUMP)
2. DYNAMIC PRESSURE VALVE
3. VENT COCK
4. BYPASS VALVE
5. GIMBAL BRACKET
6. STATIC PRESSURE VALVE
7. ELECTRIC CABLE (FLEXIBLE)
8. STATIC HOSE (FROM RODOMETER)
9. UNION
10. TEST LAMPS
11. LAMP SOCKETS
12. ADJUSTABLE THUMB SCREW
13. CONTACT BRACKET
14. CONTACT SCREW
15. MAGNET CORE
16. MAGNET SPOOL
17. CONDENSER 0.5 MICROFARAD 18. 1000-OHM RESISTOR
19. 100-OHM RESISTOR
20. EXTERNAL CONTACT ARM
21. LOWER ADJUSTABLE STOP SCREW (SHORT)
22. GLAND NUT
23. HOUSING END CAP
24. CONDENSER 0.5 MICROFARAD
25. OUTER CONTACT ARM CLAMP
26. BELLOWS HOUSING COVER
27. BELLOWS HOUSING
28. DRIP TUBE DRAIN HOSE
29. BELLOWS HOUSING CAP
30. DRIP TUBE FITTING AND GIMBAL SUPPORT
31. UPPER ADJUSTABLE STOP SCREW (LONG)
Figure 2-8. Control unit, cover removed.
 
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terminal of the auxiliary center contact block. This so-called pigtail wire is a light wire and is coiled to prevent any drag on the contact arm. The pigtail is connected from the auxiliary center contact block through a resistor to the center terminal of the terminal block located in the upper right side of the control unit. Upper and lower stationary contact points are mounted in brackets in the control unit, and mate with the contact points on the end of the external contact arm. The upper stationary contact is connected to the upper terminal of the terminal block, and thence to one shading coil of the follow-up motor in the rotary distance transmitter. The lower stationary contact is connected to the lower terminal of the terminal block and thence to the other shading coil of the follow-up motor. Magnetic coils mounted one above and one below the external contact arm are   known as antihunting coils. Their function is to assist the operation of the contact by causing a rapid break of the contacts when the bellows pressures are equalized. When the ship begins to move forward, or to increase speed, the bellows and its attached linkage move downward. The contact arm also moves downward, establishing contact between the arm and the lower stationary contact. Current then passes to the transmitter mechanism in the rotary distance transmitter, actuating the pump to equalize the pressure in the bellows. Conversely, when the ship slows down or stops, the contact arm moves upward to make contact with the upper stationary contact. Current then flows through the transmitter mechanism in the rotary distance transmitter, and causes the pump to slow down to a point at which the pressures in the bellows are equalized.
 
E. ROTARY DISTANCE TRANSMITTER
 
2E1. Rotary distance transmitter. The rotary distance transmitter (Figure 2-9) consists of four major units: the pump, the pump drive motor, the distance transmitting unit, and the motor-driven transtat assembly. The pump and the pump drive motor are mounted beneath the rotary distance transmitter case. The case contains the motor-driven transtat assembly, rectifiers, two electrical transmitters, a counter, and a gear train which connects the transmitters with the pump drive motor. The functions of the rotary distance transmitter are to control the speed of the pump, to equalize the pressures in the bellows of the control unit, and to transmit the rotary motion of the pump (14,400 revolutions per mile) to a counter in the master speed indicator, to the speed and distance indicator, and to the dead reckoning analyzer.

2E2. Motor driven transtat. The transtat assembly derives its name from the fact that it functions as a combination transformer and rheostat. Electric current from the control unit, actuated by the control unit external contact arm, flows through a shading coil of the follow-up motor in the rotary distance transmitter, and causes this motor to operate. When the contact arm moves downward, the follow-up motor runs in a counterclockwise

  direction. This motor, through a gear train at the right side of the transtat assembly, then moves the rotating brush arm of the transtat toward its high voltage end. Alternating current starts flowing through the rectifiers, which change the current to d.c., and on to the pump drive motor armature. When the current becomes approximately 15 volts, the pump starts to turn over slowly, gradually increasing in speed until the pump pressure equalizes the pressures in the bellows, at which time the contact arm centers and shuts off the flow of current to the followup motor. The pump continues to operate at a substantially constant speed until such time as the ship's speed either increases or decreases. When the ship decreases its speed, the opposite action occurs. The opposite shading coil of the follow-up motor is energized, causing the motor to turn in a clockwise direction. The transtat brush arm moves toward its low voltage end, and the pump slows down until the pressures in the bellows are again equalized.

2E3. Pump. Figure 2-10 shows a centrifugal-type pump. The pump shaft is coupled to a pump-driven motor shaft, which drives a radially bladed impeller. Hydraulic pressure developed by the pump is used to oppose

 
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Figure 2-9. Cutaway view of rotary distance transmitter.
1. ARMATURE RECTIFIER
2. SELF-SYNCHRONOUS TRANSMITTER TO DRT SYSTEM (360 R.P. MILE)
3. FOLLOW-UP SWITCHES
4. LIMIT SWITCHES
5. TRANSTAT
6. TRANSTAT ARM
7. PRESSURE HOSE TO CONTROL UNIT
8. DYNAMIC PRESSURE HOSE FROM RODMETER
9. PUMP
10. PUMP MOTOR
11. FIELD RECTIFIER
12. SELF-SYNCHRONOUS TRANSMITTER TO MASTER SPEED INDICATOR (60 R.P. MILE)
13. COUNTER MOUNTING PLATE WITH MOTOR TERMINAL BLOCK.

Figure 2-9. Cutaway view of rotary distance transmitter.
 
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the dynamic pressure which is transmitted through the rodmeter. The pump is so designed that it turns 14,400 revolutions for every mile the ship travels. The pump is equipped with two hydraulic nipples. The outer nipple is hydraulically connected to the dynamic nipple of the rodmeter. The center nipple is hydraulically connected to the left-hand nipple of the control unit. When the ship moves forward, the pump drive motor drives the pump impeller, producing a pressure at the outer nipple which opposes the dynamic pressure from the rodmeter. When the pump impeller reaches a speed sufficient to produce a balance between these opposing forces, the external and internal pressures of the bellows in the control unit are" equal. The contact arm in the control unit is in its central position, the transtat brush arm maintains its approximate position with a slight hunting, motion, and the pump drive motor drives the pump at an approximately steady speed until the ship's speed increases or decreases.

2E4. Pump drive motor. The electric motor that drives the pump receives its power from rectifiers in the rotary distance transmitter, which change the a.c. supply to d.c. Direct

  current is used because speed regulation of a d.c. motor is superior to that of an a.c. motor. The field rectifier (small rectifier) supplies a voltage to the motor field which is constant regardless of motor speed. The armature rectifiers (large rectifiers) supply a variable voltage to the motor armature. This voltage is controlled by the position of the transtat brush arm. With the field voltage constant, the motor will not operate until the armature voltage reaches approximately 15 volts. Above 15 volts, the greater the armature voltage, the greater will be the pump motor speed. The motor also drives a shaft and a slow speed gear train which is connected to a counter and two self-synchronous transmitters. The gear train is so designed that for every 14,400 turns of the pump drive motor shaft, one mile is registered on the counter. The left-hand transmitter turns at the rate of 60 revolutions per nautical mile. These revolutions are transmitted to the master speed indicator and to the speed and distance indicator. A second transmitter located in the left center of the case is turned at the rate of 360 revolutions per nautical mile and transmits these revolutions to the dead reckoning analyzer.
 
F. MASTER SPEED INDICATOR
 
2F1. Master speed indicator. The master speed indicator (Figures 2-3 and 2-11), located near the control room steering station, consists of the following components: self-synchronous repeater, self-synchronous transmitter, slip ring and contact assembly, differential assembly, lead screw drive motor, counter, roller and disk assembly, and a constant speed (synchronous) motor. These components are mounted on a main mounting plate in such a manner that the whole assembly can be removed from the case as a unit for inspection and tests.

2F2. Self-synchronous repeater. The self-synchronous repeater receives rotary motion at the rate of 60 revolutions per nautical mile from the self-synchronous transmitter in the rotary distance transmitter. This rotary motion of the repeater shaft is transmitted through a worm and worm gear to a counter in the master speed indicator which registers

  the distance traveled. The shaft extension of the self-synchronous repeater also carries a spiral gear which meshes with the spiral gear fastened to the upper shaft of the differential. When the repeater shaft is turned, the upper differential gear is also turned.

2F3. Differential. The upper end of the differential shaft is connected to the slip ring and contact assembly. The lower differential gear is meshed through a spur gear with the roller shaft and pinion of the lead screw assembly. The upper differential gear is free to rotate on the differential shaft. The small differential pinion gear is free to rotate on the differential spider, and is in mesh with both differential bevel face gears. If the speeds of the two bevel face gears are not equal, the spider, which is rigidly attached to the differential shaft, will rotate in a direction corresponding to that of the faster running gear. This turns the slip ring and contact

 
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Figure 2-10. Cutaway view of rotary pump.
1. IMPELLER SHAFT
2. PUMP FAN
3. ROTARY SEAL INSERT
4. SEAL RING
5. ROTARY SEAL BELLOWS
6. VENTING COCK
7. HOSE CONNECTING NIPPLE, TO CONTROL UNIT
8. PUMP IMPELLER
9. HOSE CONNECTING NIPPLE, TO RODOMETER
10. DRIP FITTING

Figure 2-10. Cutaway view of rotary pump.
 
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Figure 2-11. Cutaway view of master speed indicator.
1. SELF-SYNCHRONOUS TRANSMITTER
2. FOLLOW-UP CONTACT ASSEMBLY
3. SLIP RING AND CONTACT ASSEMBLY
4. SELF-SYNCHRONOUS REPEATER
5. UPPER DIFFERENTIAL GEAR
6. DIFFERENTIAL SPIDER
7. LOWER DIFFERENTIAL GEAR
8. CONSTANT SPEED MOTOR AND DISK
9. FRICTION ROLLER AND PINION
10. LEAD SCREW DRIVING MOTOR
11. YOKE
12. LEAD SCREW

Figure 2-11. Cutaway view of master speed indicator.
 
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assembly which is mounted on the differential shaft.

2F4. Slip ring and contact assembly. The slip ring and contact assembly turns with the spider and the differential shaft. This causes one of the contact points to push up against one side of the contact of the follow-up contact assembly, which is frictionally mounted on the follow-up shaft. Closing this contact shorts out one of the shading coils of the lead screw driving motor, causing the motor to run in one of two directions, depending on which shading coil is shorted out.

2F5. Lead screw driving motor. The lead screw driving motor is geared to the lead screw. As the motor turns the lead screw, the yoke assembly which is meshed with the lead screw, moves upward or downward on the lead screw, depending on which way the screw is turning. The friction roller and roller shaft and pinion which are mounted in the lead screw yoke also move with the yoke.

2F6. Constant speed motor and friction disk. The constant speed (synchronous) motor is energized, by a 60-cycle controlled frequency a.c. The current is obtained from the constant frequency supply unit in the ship. Through gearing, this motor operates a slow speed shaft on which a spider and disk assembly is mounted. The disk turns at 100 rpm. A spring arrangement keeps the disk in positive contact with the friction roller. When the roller is at the center of the disk it will not revolve, because of its central position. As the roller is moved away from the center of the disk by the action of the lead screw, it rotates at

  an increasing speed. Its revolutions are transmitted through the roller shaft and pinion to a spur gear which carries the lower differential gear. When the speed of the lower differential gear equals the speed of the upper differential gear, the spider stops revolving. This causes the follow-up contact to open, and the lead screw driving motor stops. The roller stays in one position on the disk until a change occurs in the ship's speed.

2F7. Anti-hunting mechanism. When the two differential gears are revolving at the same speed, and the differential spider and shaft stop moving, the contacts are still closed lightly. This would cause the lead screw motor to move the roller beyond the desired point, and hunting of the pointer would result due to the contact arm hitting first one contact point and then the other. To control this, a gear driven by a pinion at the extreme top end of the lead screw, drives the center contact very slowly in the same direction as the differential shaft. This will open the contacts just before the differential: shaft stops moving, allowing final adjustment to the exact balance point.

2F8. Speed transmission. A full revolution of the pointer measures the speed of the ship from 0 to 25 knots. As the lead screw turns, the worm at the upper end of the lead screw turns a worm gear which moves the pointer to indicate- speed in knots. The rear end of the pointer shaft is connected to a self-synchronous transmitter which electrically transmits the speed in knots to the speed and distance indicator, the torpedo data computer, and the gyrocompass speed corrector.

 
G. SPEED AND DISTANCE INDICATOR
 
2G1. Speed and distance indicator. The speed and distance indicator (Figure 2-12) is located in the conning tower. The unit consists of two self-synchronous repeaters, a counter, a dial and pointer. Speed is received from the master speed indicator self-synchronous transmitter, and distance is received from the transmitter in the rotary distance transmitter. The shaft of the large   repeater self-synchronous motor carries the speed-indicating pointer. The function of the counter is to repeat the number of nautical miles traveled. The indicator dial is illuminated by three Navy type TF 53 lamps, which are rheostat-controlled by an exterior knob. The complete mechanism can be removed from the case as a unit.
 
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Figure 2-12. Cutaway view of speed and distance indicator.
Figure 2-12. Cutaway view of speed and distance indicator.
 
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H. CONSTANT FREQUENCY CONTROL UNIT
 
2H1. Constant frequency supply unit. Older type submarines are equipped with a constant frequency supply unit (Figure 2-13). Recently commissioned submarines derive their constant frequency supply from the ship's regular a.c. supply. The Pitometer rotary balance unit is composed of two parts: the converter which changes d.c. to a.c. of a constant frequency of 60 cycles per second at 115 volts, and the control unit which controls the output of the converter to maintain a constant frequency. Constant frequency voltage is supplied to the constant speed motor which drives the friction disk assembly in the master speed indicator, and to the shaft revolution indicator.

2H2. Converter. The converter consists of an armature having its d.c. and a.c. windings in the same slots of the armature core. The d.c. windings connect to the commutator on one end of the armature, and the a.c. windings connect to two collector rings on the opposite end of the armature. The converter is prevented from rotating more than 1750 rpm until speed control is taken over by the control unit by a speed regulator assembly. This speed regulator consists of a rotating disk on which are mounted two electrical contacts. When the disk tends to rotate more than 1750 rpm, the contacts are opened by centrifugal force, and the converter slows down. When the converter begins to drop slightly below 1750 rpm, the contacts close. This action tends to keep the converter operating at a substantially constant speed. When the control unit takes over control of the speed of the rotary converter, it holds it at 1800 rpm.

2H3. Control unit. The control unit consists of an electrically driven tuning fork, an amplifier circuit to amplify the tuning fork frequency, a phonic wheel motor assembly which is driven at a constant speed by the tuning fork impulses, a differential gear assembly, a rheostat, a synchronous motor, and an electric clock.

2H4. Electric clock. The clock operates on 60-cycle a.c. supplied by the converter, and is a means of checking frequency.

  2H5. Rotor (stroboscope). A neon light is mounted beneath the rotor in the phonic wheel motor. This light flashes each time the tuning fork vibrates. Visual inspection of the rotor, when operating, should show the white marks on the rotor clearly and distinctly. This indicates that the impulses from the tuning fork are being amplified correctly and that the rotor is rotating in frequency with the fork frequency.

2H6. Operation of constant frequency supply. When the constant frequency supply unit is energized, the starting magnet starts the tuning fork vibrating. These impulses are amplified and picked up by the pick-up phone, where they are further amplified and fed to the driver phone. These amplified impulses keep the fork vibrating. The impulses are also picked up by the amplifier tubes, power tubes, transformers, chokes, and condensers which further amplify the impulses. They are then fed to the phonic wheel motor. This motor is attached through gearing to the upper differential gear, which is free to rotate: on the differential shaft. Two differential pinion gears attached to the spider are meshed with the upper and lower differential gears, and are free to rotate with these gears. The spider is rigidly attached to the differential shaft. The lower differential gear is also free to rotate on the differential shaft, and is driven by a synchronous motor which rotates at the same speed as the converter armature. The lower end of the differential shaft is connected through spur gears to a rheostat shaft. The rheostat shaft controls the rheostat contact arm, which in turn regulates the converter field current, increasing or decreasing the speed of the converter armature, and thereby the output frequency of the converter. If the frequency of the controlled 60-cycle a.c. supplied by the converter should drop, the speed of the synchronous motor driving the lower differential gear would also drop. The upper and lower differential gears would not be rotating at the same speed. Consequently the spider and shaft would turn in the direction of the faster moving gear. The rheostat

 
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Figure 2-13. Constant frequency control unit, cover removed.
1. CLOCK
2. 50,000-0HM RESISTOR
3. RECTIFIERS
4. CHOKE
5. CONDENSER 2-MICROFARADS
6. 1000-OHM RESISTOR
7. GRID TRANSFORMER
8. SPRINT POST, ASSEMBLY
9. STARTING MAGNET, ASSEMBLY
10. 2250-OHM RESISTOR
11. PICK-UP PHONE UNIT
12. DRIVER PHONE UNIT
13. TUNING FORK
14. TUNING FORK BASE
15. AMPLIFIER TUBES, NO. 6J5G
16. POWER TUBES, NO. 25B6G
17. SUSPENDED PLATE
18. CONDENSOR, 0.005-MICROFARAD
19. TRANSFORMERS
20. PHONIC WHEEL MOTOR, ASSEMBLY
21. 190-OHM RESISTOR
22. 2000-OHM RESISTOR
23. DIFFERENTIAL, ASSMEBLY
24. STARTING CONDENSER
25. CONSTANT SPEED (SYNCHRONOUS) MOTOR TERMINAL BLOCK
26. MAIN MOUNTING PLATE
27. CONSTANT SPEED (SYNCHRONOUS) MOTOR
28. TERMINAL BLOCK
29. RHEOSTAT, 450-OHMS

Figure 2-13. Constant frequency control unit, cover removed.
 
20

arm is turned so as to insert more resistance in the converter field circuit, thereby increasing the speed of the converter and of the synchronous motor. When the lower differential gear is rotating at the same speed as the upper differential gear, the spider and   shaft stop turning; the rheostat arm remains stationary until further change in frequency occurs. When the upper and lower differential gears are rotating at the same speed, the output frequency of the converter is exactly 60 cycles.
 
21

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