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PART 2

BENDIX
UNDERWATER LOG


10
DESCRIPTION
 
A. GENERAL DESCRIPTION
 
10A1. General. The Bendix Underwater Log is made by the Bendix Aviation Corporation, Marine Division, Brooklyn, New York. This system (Figure 10-2) consists of four major components. Each instrument is watertight, and is designed for either panel or bulkhead mounting.

10A2. Rodmeter. The rodmeter (Figure 10-1), 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 about 3 feet into the water. Being located in the forward part of the ship,

Figure 10-1. The Bendix rodmeter.
Figure 10-1. The Bendix rodmeter.

  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.

10A3. Sea valve. The sea valve and extension form a support for the rodmeter and provide a means of closing the opening through which the rodmeter passes when the rodmeter is withdrawn, or fully housed.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 When the rodmeter is withdrawn, the closing of the sea valve prevents sea water from flooding the forward torpedo room.

10A4. Master transmitter indicator. The master transmitter indicator (Figures 10-3 and 10-4) is mounted inside the ship in the forward torpedo room, 4 feet or more below the light draft water line of the ship. The instrument consists of electro-mechanical linkages, known as the log mechanism, mounted inside the case, and a bellows assembly mounted below the case. The bellows assembly is divided into chambers. The upper part of the bellows chamber is hydraulically connected to the static tube in the rodmeter by means of flexible hose and copper tubing. The lower part of the bellows chamber is connected to the dynamic tube in the rodmeter in the same manner. Flexible tubing permits lowering the bellows assembly from the case without disconnecting the tubing. The movement of the bellows rod, caused by dynamic pressure, actuates a spring-loaded balance arm mechanism which develops the force applied to equalize the dynamic pressure produced within the rodmeter. The movement of the balance arm operates electrical contacts which control a main drive

 
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Figure 10-2. Components of Bendix underwater log system.
Speed and distance indicator located in control room and conning tower
Master transmitter indicator and rodometer and sea valve located in aft section of forward torpedo room
Figure 10-2. Components of Bendix underwater log system.
 
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Figure 10-3. Master transmitter indicator.
1. SELF-SYNCHRONOUS DISTANCE TRANSMITTER
2. DIFFERENTIAL ASSEMBLY
3. FOLLOWER
4. ROTATING DISK
5. LEADS TO CONSTANT SPEED MOTOR
6. RHEOSTAT
7. FOLLOW-UP MOTOR (TORQUE AMPLIFIER)
8. SELF-SYNCHRONOUS SPEED TRANSMITTER
9. CAM
10. MAIN FORCE ARM
11. A ADJUSTMENT ASSEMBLY
12. AUXILARY BALANCE ARM
13. MAIN BALANCE ARM
14. B ADJUSTMENT ASSEMBLY
15. POWER MOTOR
16. CONTACT ARM ASSEMBLY
17. CONTACT ASSEMBLY
18. POINTER
19. MAIN FORCE ARM COUTNERWEIGHT
20. C ADJUSTMENT ASSEMBLY
21. MAIN BALANCE ARM COUNTERWEIGHT
22. ROTATING CONTERWEIGHT
23. STATIC DRAIN COCK
24. DYNAMIC DRAIN COCK
25. BELLOWS CHAMBER
26. STATIC MANEUVERING COCK
27. DYNAMIC MANEUVERING COCK
28. BELLOWS
29. DRAIN MANEUVERING COCK
30. DIVE ERROR COMPENSATING ASSEMBLY

Figure 10-3. Master transmitter indicator.
 
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Figure 10-4. OPERATION OF THE MASTER TRANSMITTER INDICATOR

Figure 10-5. Speed and distance indicator.
1. ILLUMINATION INTENSITY CONTROL KNOB
2. RINGLIGHT SECTOR
3. SELF-SYNCHRONOUS SPEED REPEATER
4. SELF-SYNCHRONOUS DISTANCE REPEATER
5. DISTANCE COUNTER

Figure 10-5. Speed and distance indicator.
 
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motor. Through mechanical linkage a speed pointer is turned to indicate the speed of the ship in knots. This speed indication is electrically transmitted to the speed and distance indicators, or repeaters. By means of a controlled time element, the motion of the mechanism is transposed from a speed indication to a distance indication, and this distance indication is electrically transmitted to the repeaters where it is registered on a six-place odometer, or counter. The log mechanism is mounted on a single brass plate which permits the removal of the entire mechanism from the case as a unit. The case and mounting plate are equipped with plug and jack units so that electrical connections need not be disturbed when removing the mechanism from the case. The complete instrument is rubber shock-mounted.

10A5. Speed and distance indicators. One of the two speed and distance indicators (repeaters) (Figure 10-5) is mounted in the control room and one in the conning tower. These units are housed in watertight cases equipped with glass windows through which the speed dials and the distance counters are visible. Each unit consists of a speed repeating self-synchronous motor, and a distance repeating self-synchronous motor which are connected electrically to speed and distance self-synchronous transmitters in the master transmitter indicator. Speed is indicated on a dial graduated in tenths of a knot from 0 to 25 knots. The counter is a six-place odometer. The first two right-hand number wheels are colored white with black numerals, and represent hundredths and tenths of nautical

  miles. The four other number wheels are colored black with white numerals, and indicate nautical miles. A transformer is mounted within the instrument to convert the 115-volt 60-cycle current to a lower voltage for the lighting circuit. A six-position tap switch is connected to the transformer and permits the selection of variable voltage to control the intensity of light for the instrument. Four lamps furnish illumination which is carried around the dial by a ringlight.

10A6. Sea water lines. The water lines system consists of copper tubing, flexible rubber tubing, an air collector, and two pressure snubbers. The fixed tubing consists of 3/8-inch seamless copper tubing connected with standard 3/8-inch flared-type screw connections that may be easily disconnected or replaced. Flexible rubber tubing is connected at the rodmeter nipples to permit the raising and lowering of the rodmeter. Flexible rubber tubing is also provided at the master transmitter end of the fixed lines to permit the lowering of the bellows assembly without disconnecting the lines. An air collector is mounted in the static line. The air collector consists of a glass tube protected by a metal casing, and is provided with two shut-off valves. One shut-off valve is mounted at the bottom of the air collector to control the flow of water into the collector. The upper shut-off valve permits the release of air from the lines. Two pressure snubbers, or shock absorbers, are mounted one in each line to protect the bellows from any sudden shock or increase in pressure due to an explosion or a sudden surge of water.

 
B. DESCRIPTION OF OPERATION
 
10B1. 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 gets underway, the forward motion creates additional pressure through the dynamic orifice in the rodmeter, while the pressure through the static orifices remains the same. This creates an unbalanced condition in the master transmitter   indicator, and causes it to operate (Figure 10-4).

10B2. Operation of master transmitter indicator. a. Derivation of speed. As the ship begins to move forward, the bellows rod rises because of a pressure difference within the bellows. The rod movement is transmitted through the C-adjustment mechanism to a pivot on the main balance arm, causing the

 
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main balance arm to rotate to the right. The contact arm mounted on the main balance arm first closes the slow speed contact and then the high speed contact, depending on whether the acceleration is small or great. When contact is made on the forward velocity side of the contact assembly, the power motor turns, and this action is transmitted through the gearing and the transmission shaft assembly to a helical gear on the cam and bracket assembly. The helical gear, cam, speed transmitter drive gear, and pointer are fixed to the same shaft so that when the helical gear is turned, the cam and pointer are also turned. As the cam turns, it moves the cam follower of the main force arm extension downward. This action moves the main force arm and causes the A-spring, attached at its upper end to the main force arm and at its lower end to the main balance arm, to stretch. When the load on this spring just overcomes the force of the bellows rod, the contact arm is returned to its central, or neutral, position and the power motor stops turning. When the power motor stops turning, the cam, pointer, and speed transmitter drive gear also stop turning, thereby maintaining this set position of the cam and pointer assembly until the ship changes speed. The speed transmitter drive gear is geared to the speed transmitter driven gear in such a relation that a 240-degree turn of the pointer in the master transmitter indicator will turn the pointers in the speed and distance indicators 360 degrees, thereby transmitting speed indications to the speed and distance indicators. In addition to driving the cam assembly, the power motor transmission shaft assembly also drives a lead screw in the component frame assembly which positions the B-adjustment slide downward from the zero position. When the B-adjustment pointer is turned away from zero on the scale, the motion of the slide moves the auxiliary balance arm which causes the B-spring to stretch between the auxiliary balance arm and the main balance arm. This B-spring aids the A-spring in overcoming the force of the bellows rod and in returning the contact arm to its neutral position.   b. Derivation of distance. The lead screw in the component frame assembly is geared to the lead screw in the follower assembly. The follower assembly lead screw positions the follower radially across the rotating disk. The rotating disk, driven by the constant speed motor, is turning at a constant speed or 60 rpm. The position of the follower on the disk is dependent on the pointer indication, or speed indication. The follower is caused to turn by the rotation of the disk and, by its position on the disk, turns at the rate of 360 revolutions per nautical mile. The follower, through the universal joint, therefore, turns the right-hand side of the differential at 360 revolutions per nautical mile. Since the torque required to drive the distance transmitter is greater than the torque that can be obtained from the follower, a torque amplifier is used. The torque amplifier (follow-up motor) consists of a shaded pole induction motor, rheostat, slipping clutch, differential, and suitable gearing. The shaded pole induction motor (follow-up motor) turns the distance transmitter and the left-hand side of the differential. If the left-hand and right-hand sides of the differential turn at different speeds, the spider rotates in the direction of the faster moving differential gear, and turns the rheostat brush arm through a slipping clutch. This action changes the voltage across the main field of the follow-up motor. The change in voltage changes the torque which the motor can supply, thereby changing its speed so that the distance transmitter rotates at the same speed as the follower and disk, that is, at 360 revolutions, per nautical mile. The self-synchronous distance transmitter transmits the distance indications to the speed and distance indicators.

10B3. Speed and distance indicators (repeaters). The speed and distance indications of the master transmitter indicator are electrically transmitted to the mechanism in the speed and distance indicators, and are registered on the dial and counters of those units.

 
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C. RODMETER AND SEA VALVE
 
10C1. Rodmeter. The Bendix rodmeter (Figure 10-1) is made of manganese bronze, and is approximately 8 feet long. This length is necessary in order that the rodmeter may be projected through the inner and outer hulls of the submarine. It has a streamline cross-section, with a flat tip at its lower end. Two water passages are formed in the rodmeter; the upper ends of these passages terminate in tapped openings, protected by pipe plugs. Standard pipe fittings are installed in these tapped openings in order that the flexible hose may be attached to the rodmeter. The lower end of the forward passage in the rodmeter terminates in an opening in the forward edge, called the dynamic orifice. The lower end of the after passage terminates in three openings, one on each side of the tip and one in the bottom of the tip. The latter openings are called the static orifices. A handle and two straps are mounted at the top of the rodmeter to serve as a means of raising and lowering the rodmeter. When lowered, the rodmeter projects about 3 feet through the outer 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 rests on the ocean floor.

10C2. Sea valve. The sea valve assembly (Figure 10-6) supports the rodmeter when the rodmeter is projected into the sea, and prevents water from entering the ship when the rodmeter is removed. The valve is a 3-inch gate valve, operated by 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 valve extension with packing gland is mounted to 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 gland around the rodmeter.

10C3. Rodmeter hoist. Submarines are equipped with either one of two types of rodmeter hoists (Figure 10-7) for raising and

  lowering the rodmeter. One type consists of a single sprocket and chain arrangement, and the other type is a double sprocket and chain assembly. The upper sprocket is mounted either on the side of the hull or on a suitable panel near the rodmeter. The lower sprocket is mounted in the well containing the sea

Figure 10-6. Sea valve.
Figure 10-6. Sea valve.

valve. The sprockets are connected by a roller chain. Operation is by means of a hand crank through a worm gear drive. The roller chain is connected to the strap and handle assembly of the rodmeter by means of a connecting link which is pinned to the chain and to the strap and handle assembly. As the hand crank is operated, the chain rotates around the sprockets, thereby raising or lowering the rodmeter. The hoist crank normally is stowed in brackets near the sea valve. To operate

 
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Figure 10-7. Rodmeter and hoist installed.
Figure 10-7. Rodmeter and hoist installed.
 
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the hoist, a deck plate must be raised and the crank lifted off its brackets and placed on the hoist operating rod. When in the lowered or operating position, the straps on the upper end of the rodmeter are close to the top of the sea valve extension gland. Approximately 32 turns of the crank are required to raise the rodmeter to the normal housed position, that is, the position that permits the tip just to clear the outer hull. In this position, approximately half the length of the rodmeter is above the sea valve extension. This point is usually   marked by a plate mounted on the 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. The sea valve should then be closed. About eight additional turns are required to raise the rodmeter to its extreme secured position for inspection. Care should be exercised when lowering the rodmeter from this latter position to see that the packing is not pushed out of the gland.
 
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