Author Topic: Torpedo arming questions?  (Read 14226 times)

Offline Lance Dean

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Torpedo arming questions?
« on: September 07, 2008, 06:29:28 PM »
So I understand that WWII era torpedoes armed themselves after so many revolutions of their props.  I've read the arming distance to be 500 to 700 yards.

So what about the torpedoes that had two different speeds/ranges?  For example, the Mark 14 could be set to go 4,500 yards at 46 knots or 9,000 yards at 31 knots.  Was the arming distance the same for either setting?

Offline JTheotonio

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Re: Torpedo arming questions?
« Reply #1 on: September 07, 2008, 07:09:22 PM »
The Mark 14 had a series of problems with the contact exploder, but your question is simple to answer.  During the first part of the torpedo run, an 8mfd capacitor is charged by the output of a DC generator driven by the impeller shaft.  The generator output passes through a voltage regulator tube, which keeps its voltage nearly constant regardless of generator speed.  Therefore, no matter what the speed of the torpedo, the arming would be uniform to the solution required.
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Offline Lance Dean

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Re: Torpedo arming questions?
« Reply #2 on: September 07, 2008, 09:36:00 PM »
Thanks a lot John.  I'd been wondering how they did that for a long time now.  +1 BZ to you!

Offline Paul Farace

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Re: Torpedo arming questions?
« Reply #3 on: September 07, 2008, 11:13:59 PM »
What Mod Mark 14 does this relate to? Maybe a post-war mod of the 14... I didn't think the WWII 14s had an electrical system... I was told the warhead arming of a 14, like that of the 18, was achieved via a water feed tube on the forward lower portion of the warhead... water was driven past an impeller which mechanically drove the primer into postion... I sometimes play with the the impeller on the Mark 18 aboard COD... as did some crewmen!  The hold in the nose is about the size of your index finger.. the impeller is sort of like a water wheel on a paddle wheel steamer... the water blasting through the tube and out the exit portion of the tube turned the impeller... and the run out was about 400 yards to arm the fish. 

The Mark 14 handbook is now on line via Rich Pekelney, yes?  It should provide the answers!

Let's look!

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Offline Lance Dean

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Re: Torpedo arming questions?
« Reply #4 on: September 07, 2008, 11:18:42 PM »
Well, what I was getting at was that if the arming mechanism was tied directly to propeller speed, then I wondered how they kept the arming distance constant when the torpedo had 2 different speeds available.  But apparently a capacitor was in the mix.

Offline JohnG

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Re: Torpedo arming questions?
« Reply #5 on: September 08, 2008, 01:13:55 AM »
What if a target was closer than the arming distance? What then?
"If crime fighters fight crime and fire fighters fight fire, what do freedom fighters fight?" ~George Carlin

Offline Lance Dean

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Re: Torpedo arming questions?
« Reply #6 on: September 08, 2008, 08:10:41 AM »
What if a target was closer than the arming distance? What then?

From what I understand, it either a) ran under without the magnetic detonator going off or b) hit the side of the target and made a loud THUD scaring the fool out of the Japs onboard.

Offline Darrin

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Re: Torpedo arming questions?
« Reply #7 on: September 08, 2008, 09:12:51 AM »
 Or the CO would open the firing solution up so his weapon would go off like advertised ;)

Offline Mark Sarsfield

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Re: Torpedo arming questions?
« Reply #8 on: September 08, 2008, 10:10:30 AM »
The arming distance was installed for safety reasons.  You didn't want the warhead denoating against a target at 300 yards from your boat.  Talk about a depth charge.  As Darrin said, you'd get the boat into position to take the proper shot or you'd wait for the target to pass and then do an "end around" attack and set up for another shot.  Getting into position sometimes required a lot of time.

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Offline JTheotonio

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Re: Torpedo arming questions?
« Reply #9 on: September 08, 2008, 01:38:02 PM »
I hope this works - right from the Mk 14 Mk 23 manual.  I will attach the word document so you can see the diagrams - they do not come through with copy and pastge.

War heads for the Torpedoes Mk 14 and Mk 23 Type are fitted with Exploder Mechanisms Mk 6 Mod 5, which are fired by direct impact with the target.
The exploder mechanism is mounted on a flange in a rectangular cavity (exploder-mechanism casing) in the forward part of the war head. The exploder-mechanism base is rectangular in shape to fit the war head cavity, and its exterior surface is curved to maintain the contour of the head.
A channel in the exploder mechanism base provides a path for the stream of water that drives the impeller wheel which furnishes the driving power for the various mechanisms within the exploder mechanism (Fig. 6A). The rotation of the impeller is transmitted to the interior of the exploder-mechanism base by means of a shaft passing through a watertight packing gland.
A direct-current generator driven from the impeller shaft supplies the electrical energy necessary for firing the detonator. A voltage regulator tube controls the output of this generator, limiting it to a nearly constant value, regardless of the speed of the generator. This generator charges a large condenser, which then becomes a reservoir of electrical energy. When this energy is released by closing an impact switch, it fires the detonator and detonates the war head.
hen the torpedo is fired, the exploder mechanism must be inoperative for the first part of the run in order to protect the firing vessel from possible premature action of
 
Figure 6A-Exploder Mechanism Base, showing Impeller, Channel, and Impeller Guard (removed)
the exploder mechanism. This is the function of the arming mechanism, the essential features of which are as follows:
1. The safety chamber, in which the detonator is housed during the first part of
 
 
Figure 7A-Exploder Mechanism Mk 6-5-Unarmed
 
Figure 8A-Exploder Mechanism Mk 6-5-Armed
 
 
Figure 7B-Exploder Mechanism Mk 6-5-Ball Switch Open
 
Figure 8B-Exploder Mechanism Mk 6-5-Ball Switch Closed (Fired)
 
________________________________________
19
  the run and within which it can be fired without detonating the war head.
2. The delay device, composed of a switch which grounds the generator of the exploder mechanism during the first part of the run, thus temporarily preventing current from passing into the condenser and detonator.
A self-cocking impact-operated switch provides the means for firing the detonator upon impact of the torpedo with the target. This impact switch is installed in the exploder-mechanism casing above the exploder mechanism, and is connected by wire leads to the electric terminals of the condenser and the detonator, which are mounted in the exploder-mechanism base.
The operation of the exploder is as follows:
Upon launching of the torpedo the impeller of the exploder begins to rotate. The rotation of the impeller drives a gear train (Fig. 7A) which rotates the delay-device worm wheel and the arming gear. The delay device renders the generator inoperative by grounding its field circuit until the delay wheel has made nearly a complete revolution, at which time the wheel stops, breaking the ground, thus activating the field circuit and allowing the generator to build up operating voltages. In the meantime the rotation of the arming gear has run the detonator up out of the safety chamber into the booster cavity (firing position). The generator charges the large condenser, mounted on the firing-mechanism base plate, which supplies the electrical energy necessary for firing the electrical detonator.
Upon impact with the target, the ball in the impact switch (Fig. 8B) is displaced,
  and as a result the spring contact of the switch is forced down, making electrical contact with the fixed contact. As soon as electrical contact is made, the condenser is discharged through the electric detonator (Fig. 8A), setting it off, thus detonating the booster and the main charge in the war head.
Note: The exploder mechanisms are issued to the service with a pick-up coil and thyratron tube installed on their base. These devices are applicable to the influence feature only and will not be described in this publication.
Booster
Above the exploder mechanism, when installed in the war head, is a thin sheet-copper container holding a charge of tetryl. This is known as the booster. It is so shaped that it fits inside the pocket at the top of the exploder casing, and rests snugly upon the top of the safety chamber.
The detonator, during the arming operation, is moved up out of the safety chamber into a recess in the bottom of the booster; thus, the detonation of the detonator can set off the booster. Before the exploder is fully armed, the detonator holder is within the safety chamber, where it can explode without detonating the booster. It is not until the detonator holder is well extended from its safety chamber that it can detonate the booster; thus any accident which might cause the detonator to explode while the torpedo is still aboard, or close to its firing vessel, cannot cause detonation of the war head, since the torpedo must travel about 350 yards through the water before the detonator can fire the booster.
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John

Offline Paul Farace

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Re: Torpedo arming questions?
« Reply #10 on: September 10, 2008, 09:45:04 AM »
Wow, torpedo arming class, 101!  Is this cool or what?  We can look up answers in the WWII manuals!  I didn't know the arming system involved electrical circuits...  now I know a lot more than I did yesterday, and the minimum arming range is 350 yards!   

Good work everyone!
 :smitten:
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Offline JTheotonio

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Re: Torpedo arming questions?
« Reply #11 on: September 10, 2008, 10:05:42 AM »
If I can get my hands on an OCR (Optical Character REader) program, I'd like to run the manual through it to create a PDF file that is searchable.  So much easier.

Likewise I had forgotten about the impeller. 
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Offline Darrin

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Re: Torpedo arming questions?
« Reply #12 on: September 10, 2008, 04:20:32 PM »
The Mk 14 Torpedo manual is online already and that is on the HNSA website, a LOT of usefull information on that site is there and some of it may come in VEERY usefull during the school of the boat.... hint hint wink wink ;)

Offline JTheotonio

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Re: Torpedo arming questions?
« Reply #13 on: September 10, 2008, 05:36:15 PM »
on-line yes I know - but it is a scanned image and not a document such as a PDF document that can a person can search - off line.  It's a wild idea and I'm not going to go out a buy software to have my personal copy of any of these manuals. Converting documents like this is time consuming because you need to proof the entire document to clean up the characters that were not read correctly.  OCR will even pick up spots and try to insert into the text.  I did a lot of this a few years ago when all we had were paper copies - some pretty bad off old copiers.  But I got it done and they turned out good.
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Offline Darrin

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Re: Torpedo arming questions?
« Reply #14 on: September 10, 2008, 06:27:21 PM »
Good luck JT ;)