BULLETIN NUMBER 30

Dear webmaster:

Looking over this bulletin on the MK 14 Mod 3a torpedo and its MK 6 exploder mechanism, I am somewhat disappointed in what was published.
"Operation of the Mk 6 Exploder"

You wrote: "The exploder is really two exploders in one." Not really! This should read as follows:

"Properly, the exploder is the entire MK 6 assembly. It has a magnetic-influence feature and a contact feature. This leads to awkward verbiage, so we refer to the magnetic-influence exploder and the contact exploder. Both are parts of the MK 6, which weighs approximately 92#, and some elements of the exploder function in both modes. The exploder also contains important safety features. This complex arrangement was presumably designed so that an exploder, MK 5, without the magnetic-influence portion, but otherwise identical to the MK6 exploder could be produced and issued to the fleet in peacetime. Security was the overall motivation for this convoluted approach."
source: US NAVY TORPEDOES by Frederick J. Milford - Part two.

You wrote: "The contact exploder consists of an inertial ball and electric contact." This type of contact exploder is not the one that was issued the fleet at the start of WWII. It was issued as a last resort, makeshift substitute for the original MK 5 contact exploder that was mounted on the same baseplate. It was a totally unnecessary feature added by BUORD, in order to save face. After the modification of the MK 5 contact exploder by the Torpedo Shop personnel at Pearl Harbor, (by fabricating a firing-pin block assembly from aluminum, and strengthening and re-positioning the vertical brass guide posts), successful firings resulted. This was named the (PHM) Pearl Harbor Modification, accomplished by field personnel, and not by BUORD.

Btw, where did the electricity for operating this "contact switch" and the magnetic-influence feature come from? 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. The magnetic-influence feature was disabled by removing the "pick-up" rod from the warhead (coil assembly) by removing a plug from the forward underside of the warhead. When the new brass ball contact switch was used, an electrical "squib" attached to the 65-grain fulminate-of-mercury detonator, started the chain reaction, by detonating the theTetryl booster and the main charge of TNT or TORPEX.

You wrote: "The problem is the sensitivity of ball to shock. If the shock is too much it destroys the mechanism before the ball can do its job." The MK 15 Mod 3 surface type torpedo used the same MK 6 exploder mechanism with the brass ball contact switch, and it was launched from the 02-level of a destroyer, and this "shock" problem was non-existent. Incidentally, there is no electrical current available to "destroy" the mechanism at launch, because the output of the generator is shorted out until the impeller has turned about 481 turns, and the detonator has been screwed in the cavity of the Tetryl booster.

I have ten torpedo related questions for you.........

What is the arming distance of the exploder mechanism on a MK 14 or MK 15 torpedo?

Why are the warheads made of phosphor bronze on MK 14 and MK 15 torpedoes and steel on the MK 13, MK 18 and MK 23 torpedoes?

What type of exploder mechanism is installed in a MK 23 torpedo?

Can a MK 15 (surface to surface) torpedo be used in a submarine?

What prevents a torpedo from rolling over after it is launched?

How does the anti-countermining feature on a MK 6 exploder mechanism work?

How does the anti-circular run feature work on a MK 6 exploder mechanism?

What is the maximum depth for opening a fleet submarine's torpedo tube for launching a torpedo?

What successful post-WWII modifications were made to the troublesome MK 6 exploder mechanism?

What is the difference between a run-down gyroscope and a constant-spin type?

On page two you wrote: "The movie "Operation Pacific" showed John Wayne as a submarine captain who had his torpedomen dropping MK 14s from the roof of the Pearl Harbor Sub Base torpedo shop......." I know that torpedomen can do almost anything, but they can't drop MK 14s off the roof of the Sub Base torpedo shop at Pearl Harbor.......... Run that movie over again and you'll notice that John Wayne used a "cherry-picker" to drop those plaster-filled warheads (on MK 14s) on a steel plate on a pier. Also, refer to: Robert Gannon's "Hellions of the Deep", on page 90, 3rd paragraph.

On page 3 you wrote: "Disposition: The concept of exploders was abandoned in favor of acoustic guidance. The MK 14 continued using a greatly modified contact exploder through the sixties."

Passive-acoustic guidance was first in the MK 24 "Fido" aerial ASW torpedo on May 14. 1943, destroying the U-266. Then the 19" diameter MK 27 "Cutie" was sent to the Pacific in the summer of 1944. The 21" diameter Mk 28 was sent to the Pacific Fleet in the summer of 1945.

The MK 27" passive-acoustic torpedo used a MK 142 nose-mounted contact exploder mechanism.

The whole point of my requesting information, in the first place, on the post WWII modification of the Mk 6 exploder mechanism, was to confirm the fact that I viewed a B&W 16-mm training film (at the Naval Torpedo School in early 1950) of a surfaced fleet boat launching a stern shot MK 14 at an AKA/APA in Long Island Sound, using a MK 6 Mod 10 magnetic-influence exploder mechanism, with devastating results.
Again, do you have any info on this Mk 6 Mod 10 exploder mechanism?
Respectfully,
Robert F. Marble TMCS(SS) USN (Ret)
relbram@earthlink
Port Charlotte, FL