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CHAPTER 8, THE TRIPPING LATCH AND TORPEDO STOP BOLT

The Tripping Latch Mechanism106
The Torpedo Stop Bolt109
 
105

THE TRIPPING LATCH AND TORPEDO STOP BOLT
 
THE TRIPPING LATCH MECHANISM
 
The tripping latch is the device which, when the torpedo starts out of the tube, engages and trips the starting lever (a trigger-like projection from the torpedo) to start the torpedo's engine.

The tripping latch is a hammer-shaped lever, about six inches long and five-eighths of an inch thick. It is so arranged and placed that it engages the torpedo starting lever when the torpedo has moved forward three-fourths of an inch after the firing charge has started it out of the tube.

When a torpedo is being loaded into the tube, the tripping latch must be raised, or retracted, from the barrel, so there will be no interference with the

Figure 199 The breech door hinge bracket
Figure 199 The breech door hinge bracket, showing the tripping latch am. (A) Tripping latch arm, which connects with operating shaft as shown in Figures 200 and 201; (B) Roller; (C) Tripping latch cam; (D) Key which rotates cam when engaged by (E) Free end of upper arm of breech door.

  free movement of the torpedo as it is moved forward into place in the tube.

However, the mechanism is so designed that the tripping latch is raised out of the tube as the breech door is being opened, and it is lowered back into position as the breech door is being closed. This is done by means of a cam attached to the upper hinge pin of the breech door, a key on the cam being engaged by the end of the upper arm of the breech door as it is being opened, thereby rotating the cam, as illustrated and described in Chapter 3 (see especially Figures 24 to 30, on pages 26 and 27). The cam is also shown here in Figure 199.

Figure 200 shows the linkage between the cam on the breech door, the operating shaft, and the tripping latch housing, in the position when the breech door is closed. Figure 201 shows the linkage in the position when the breech door is open. Another view of the tripping latch housing and the linkage with the breech door is shown in Figure 202, this illustrating the position of the tripping latch housing with relation to the poppet valve and other operating units.

An interior view of the tripping latch housing is shown in Figure 203, illustrating the latch lowered into the barrel to contact and trip the torpedo starting lever.

The curvature of the cam, shown in Figure 199, is such that the tripping latch is in the extreme down position before the breech door is entirely closed. Hence, this position of the tripping latch can be verified by sighting into the barrel before fully closing the breech door. During the opening of the breech door, the tripping latch cam remains in neutral position for the first 45 degrees of the opening of the door, so that the latch can also be observed by sighting down the barrel as the door is being

 
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Figure 200
Figure 200 Linkage between cam on breech door hinge, operating shaft, and tripping latch housing, in breech door closed position. (A) Cam and roller; (B) Latch arm; (C) Operating shaft; (D) Tripping latch housing.
 
Figure 201 Tripping latch linkage in breech door open position.
Figure 201 Tripping latch linkage in breech door open position.
 
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opened. It is considered good operating policy to observe carefully the position of the tripping latch both on opening and on closing the breech door when loading a torpedo.

The starting lever on the torpedo, which is engaged by the tripping latch to open the torpedo starting valve and set the operating mechanism in the torpedo in action, is shown in Figure 204. Here, the operator is removing a safety stick from the starting lever preparatory to loading the torpedo into the tube. This safety stick is inserted to protect the starting lever, and to prevent it from being tripped unintentionally or accidentally while the torpedo is being handled up to the time of loading into a torpedo tube.

There are certain differences between the tripping latch as installed on some of the earlier submarines and those on vessels of more recent construction. This is due to the fact that the somewhat limited movement of the tripping latch in the original design was found, after moderate wear, to be insufficient to insure proper adjustment by means of the turnbuckle arrangement provided, so as to permit the latch to project the required amount within the bore when down but with all lost motion taken out

  in the up direction, and, at the same time, not project within the bore when up but with all the lost motion taken out in the down direction.

This last condition has no effect in connection with torpedoes, as the slope of a war or exercise head on a torpedo will push the latch up out of the way. It is likely to cause interference, however, when mines are being loaded into the tube.

In some installations, therefore, a crank arm, having provision for adjusting its length, will be found substituted for one of the crank arms of the earlier design. In some other installations, especially those of later construction, the throw of the tripping latch has been increased by changing the relative lengths of crank arms, without altering the operating cam, so as to allow for the development of a considerable amount of lost motion due to manufacturing tolerances and service wear, without resulting in any objectionable projection of the tripping latch within the bore when up.

It will be noticed, particularly in Figures 202 and 203, that a turnbuckle attachment is connected in the link leading directly from the tripping latch housing to the operating shaft. This turnbuckle attachment is provided for the purpose of adjusting

Figure 202
Figure 202 Showing position of tripping latch housing, operating shaft, and linkage, in position on barrel and its relation to other mechanisms. (A) Operating shaft and linkage; (B) Tripping latch housing.
 
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Figure 203 The tripping latch housing
Figure 203 The tripping latch housing, interior view, showing tripping latch extending down info the tube in position to trip starting lever on torpedo. Dotted lines show position of latch when raised.

the tripping latch as required.

Tripping latch linkages should be examined carefully at regular intervals to make certain that there is no deformation of any of the parts, also that there is no lost motion in operation. These linkages should also be tested carefully for correspondence between actuation and response, to make certain, for example, that when the tripping latch is raised by the opening of the breech door it does not project within the 21.125 inch bore of the tube, in which case it would interfere with the loading of a mine, as previously stated; also, that when the tripping latch is lowered by the closing of the breech door, it projects into the tube the required amount as shown by the drawings which apply specifically to the particular installation in the submarine.

  The projection of the tripping latch within the bore is best tested by the use of the barrel center line gauge, which is specially fitted to indicate whether this projection (as well as the projections of the stop bolt, and depth, speed and gyro setting spindles) is accurate. Do not close the breech door with the barrel centerline gauge in place to test the projection of the tripping latch, since the tripping latch is forced down by the closing of the breech door, and the tripping latch linkage will be de formed if the tripping latch is then prevented by the barrel centerline gauge from taking its "down" position.

Figure 204 The starting lever on the torpedo
Figure 204 The starting lever on the torpedo, operator removing safety stick which protects the starting lever and prevents it from being tripped accidentally up to the time the torpedo is loaded into the tube.

 
THE TORPEDO STOP BOLT
 
The purpose of the torpedo stop bolt is to fix the position of the torpedo in the tube so the depth, gyro, and speed setting sockets in the torpedo will be in the proper location with reference to the setting mechanisms, so that the spindles of the setting mechanisms will engage the sockets in the torpedo readily. It also fixes the position of the starting   lever with relation to the tripping latch.

On the top of the torpedo is a guide stud which slides in the guide slot in the top land of the interior of the barrel, keeping the torpedo in its proper position and preventing it from rotating in the tube. The torpedo stop bolt engages this guide stud as the torpedo is being slid into the tube.

 
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There are two housings for torpedo stop bolts, attached on the top of the middle section of the barrel, as shown in Figure 18 on page 20, also in the large fold-out chart between pages 22 and 23. Only one of these housings is used, however, depending upon the type of torpedo being used. For torpedoes such as the Mark 14, or others having a distance of 141.44 inches from the tail to the front of the guide stud, the housing nearest the muzzle end of the tube will be used. For torpedoes such as the Mark 10, Modification 3, or others having a distance of 109.0 inches from the tail to the front of the guide stud, the housing nearest the breech end of the tube is used.

The stop bolt housing, detached from the tube, is shown in Figure 205, a side view being shown in Figure 206. In Figure 207, a view of the under side of the housing, the stop bolt is shown in the down position, while in Figure 208 the stop bolt is shown in the up position. Figure 209, in which the housing has been broken away, shows the interior mechanism and its operation. Figure 210 is a view of the parts disassembled.

Each of the two housings includes the stop bolt lever, the stop shaft, and the lever attached to the stop rod which lifts or retracts the stop bolt at the time-of-firing. Only one stop bolt, stop bolt gib, and stop spring are installed, however, these parts being interchangeable from one housing to the other.

Referring to Figure 207, the stop bolt, as well as the stop bolt gib, and the stop spring, can easily be removed from the stop bolt lever and the housing by simply removing the gib screw. Care should be taken to observe the position of these pieces as they are removed, so they can be placed in the other housing in the same order and without difficulty, the procedure for assembling these parts, or for putting them in the housing, being the reverse of that for removing them.

The stop bolt is lifted or retracted from the tube by means of the stop rod, which is connected with the lever (A in Figure 207). The stop rod extends, through a stuffing box, to the retraction slide (by means of which the stop piston retracts the gyro setting spindle) which in turn is connected to the piston of the torpedo stop cylinder (as in Figure 211, which forms a part of the firing

 

Figure 205 The torpedo stop bolt housing.
Figure 205 The torpedo stop bolt housing.

Figure 207
Figure 207 Torpedo stop bolt housing as seen from underneath, showing (A) Lever to which stop rod is attached; (B) Stop bolt, in down position; (C) Stop bolt gib; (D) Gib screw; (E) Stop shaft; (F) Stop bolt lever.

 
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Figure 206 Side view of torpedo stop bolt
housing.
Figure 206 Side view of torpedo stop bolt housing.

Figure 208 Showing stop bolt in up position.
Figure 208 Showing stop bolt in up position.

  mechanism, as described in Chapter 5 (see pages 52 and 53). As the firing lever is pressed, opening the stop cylinder valve and admitting air into the torpedo stop cylinder, the piston of the torpedo stop cylinder is forced toward the breech end of the tube, drawing the stop rod with it, thereby (after first taking up the designed lost motion between the lever A of Figure 207 and the stop shaft E of Figure 207) lifting or retracting the stop bolt and disengaging the gyro setting spindle in the same operation.

As the stop rod is drawn toward the breech end of the tube it pulls the lever (A in Figure 207), which is attached to the stop shaft (N in Figure 210). This stop shaft enters the stop bolt housing through a stuffing box, which must be kept tight to prevent leakage, yet not so tight that it will prevent rotation of the shaft and thereby interfere with the proper operation of the stop bolt.

Figure 209, which shows the interior of the housing, gives a better idea of the operation of the stop bolt. Studying this with Figure 210, which shows the parts disassembled, the following steps should be noted: The stop shaft connects with the stop bolt lever (Q in Figure 210), the rounded projection at the end of this lever engaging a slot in the stop bolt (V in Figure 210).

The action of the stop bolt lever, as the stop rod is pulled by the piston of the torpedo stop cylinder, raises the stop bolt vertically, the stop bolt gib (S in Figure 210) and the shape of the housing acting as a guide for the vertical movement of the stop bolt. A lug on the stop bolt gib determines the position of the bolt when it is down.

The length of the slot in the stop bolt which is engaged by the rounded end of the stop bolt lever permits a slight overtravel of the top rod. This feature is carried over from the tube design as it existed before the adoption of automatic gyro setting spindle retraction. The overtravel was originally provided so as to allow the stop rod to make a portion of its stroke without lifting the stop bolt, in case air pressure should, by leakage or malfunction, come on the stop cylinder while the firing interlock shutter bar is in position to block the stop

 
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Figure 209 Interior view of
torpedo stop bolt housing.
Figure 209 Interior view of torpedo stop bolt housing.
Figure 211
Figure 211 The torpedo stop cylinder, a unit of the firing mechanism, showing (A) Threads for connection to gyro setting spindle retraction slide; (B) Stop rod spring; (C) Electric firing solenoid; (D) Stop cylinder valve; (E) Firing handle; (F) Stop cylinder; (G) Pilot valve.
 
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Figure 210 Torpedo stop bolt housing and parts disassembled.
Figure 210 Torpedo stop bolt housing and parts disassembled. (A) Cotter pin; (B) Nut for shaft; (C) Washer; (D) Castellated nuts with cotter pins; (E) Lever plate; (F) Lever; (G) Actuating block; (H) Lever plate; (I) Bolts; (J) Nuts; (K) Gland; (L) Stud bolts; (M) Housing;, (N) Stop shaft; (O) Washer; (P) Plug; (Q) Stop bolt lever; (R) Gib screw; (S) Stop bolt gib; (T) Spring seat; (U) Stop spring; (V) Stop bolt; (W) Tap bolts; (X) Taper dowels; (Y) Gasket.
 
rod. (In such a case, the end of the stop rod will engage in a recess in the shutter bar, as explained in Chapter 4, under "Firing Interlocking Mechanism.") When automatic gyro spindle retraction was adopted, additional overtravel of the stop piston extension was considered necessary in order that the engaging end of the spindle should be clear of the socket in the torpedo before the stop bolt started to lift. This additional overtravel is provided by the clearance between parts F and G in Figure 210.   After a torpedo has been fired, and the air pressure on the piston of the torpedo stop cylinder is released, the spring on the stop rod where it connects with the piston of the torpedo stop cylinder (See Figure 211) forces the stop rod back toward the muzzle end of the tube, and this action of the stop rod combined with the stop bolt spring (U in
 
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Figure 210) allows the stop bolt to drop back into place to engage the guide stud of the next torpedo to be loaded into the tube.

The stop bolt has three grooves, two of which extend the entire length of the bolt. The purpose of these grooves is to allow free passage of air and water from the barrel, and thereby prevent any obstruction to the upward movement of the stop bolt which might be caused by air and water be coming trapped in the upper part of the housing.

It is important that the connections between the stop rod and the lever which operates the stop shaft to raise the stop bolt be carefully inspected regularly, and that it be maintained in proper adjustment at all times. An adjustment spacer is provided for adjusting the stop bolt lever, this spacer being located

  at the end of the stop rod proper, where the stop rod connects with the slide that retracts the gyro setting spindle, as shown in Figure 212. The adjustment should be made so that when the stop bolt is all the way down, in which position its end should be 10.563 inches, plus or minus .015 inch, from the center line of the barrel, it should not be possible to push the stop bolt up more than .045 inch before it contacts the stop bolt lever.

When loading a torpedo into the tube, extreme care should be taken to ease the torpedo gently against the stop bolt to avoid bending the stop bolt or binding any of the parts of the stop bolt assembly. Should the stop bolt become bent, or in any way mutilated so it does not function properly, it should be immediately replaced.

Figure 212
Figure 212 Showing (A) connection on stop rod for adjusting stop bolt lever.
 
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