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Sub-Munitions with Volute Spring stabiliser.

Sprockets

Well-Known Member
One of our best known contributors used an avatar showing such a device, which I believe he had seen being used on an experimental project.(I cannot locate said avatar now, so perhaps it has been altered). I have now found, by chance, three US patents using the device. It had the virtue of compactness for stacked items, and also was very "draggy", due to air-flow between the layers. It also could be used to revolve an arming feature, due to its helical form. The three US patents are US 3710715, US 3792662 & US 3891162, and form a particularly neat use of this device. If anyone has problems accessing these, let me know, and I will explain how they can be found on "google advanced patents", espacenet or USPTO.

Does anyone know if such a "tail" was ever used? Thanks.

Martin.
 
As far as I can remember (less every day) the only one I've seen it on is the XM54 Rook submunitions. As you mention it was one of my old avatars. On 20 Dec I posted a couple of pics of the carrier projo on the museum photo thread, which I'll place again below, along with one of my XM54's. According to a project engineer I spoke with (Aerojet Ord), the project was dropped for fuze safety reasons after a test worker was accidentally killed at Yuma Proving Ground.

ICE-CP-82-4.JPGICE-CP-82-6.JPGDSC_7253.jpg
 
Thanks, US-subs, for the interesting information. It seems that one approach that was being worked upon was to have a bounce charge ignited upon impact, with the initial flash operating a small bolt-cutter like device to discard the tail, which was found to otherwise retard the upward projection of the bounce charge. Interesting looking fuze on your picture, fluted on outside for interference fit. Also the carrier shell expulsion charge is intriguing, seeming to be activated in stages, perhaps to minimise expulsion shock. No sign of anti-rotation splines for the projectiles?

Best regards,

Martin
 
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The submunitions are mounted in a "birdcage" which slides into longitudinal slots in the projectile body. This acts as the anti-rotational splines.
 
Sorry, my bad, XM53E2, to be precise.

Here is a factory shot of the projo and the birdcage to make up for it.

Untitled-2.jpgUntitled-3.jpg
 
I suspect that the XM53 was developed by Aerojet, it was an Aerojet engineer that told me the history. He had been working on the project, but I cannot say for certain that he was an Aerojet employee at the time. I do know that the patent for the M42 sub was in his name - as an Aerojet employee. They were pretty good about locking things down.
 
Thanks for the picture of the "birdcage"-Now I see why staged expulsion of the subs was required, as otherwise the "cage" would probaly buckle and jam. Any idea about the fuzing, as the volute was not used in this case to activate. Probably an axial pin was allowed to be expelled after separation of the submunitions, so perhaps the accident happened when a gap opened between subs during expulsion?
1989rjb- US 3710715 to Wayne E Hoofnagle, covers the tail stabiliser. The other patents given refer to a sub with a "bounce", which does not seem to be provided in this case. Was Hoofnagle the M42 inventor?

Martin.
 
It was a team effort, but my understanding was that the patent was in Wolterman's name.

The fuze had a small plate on the base that would push away on arming, compression would result in detonation. The explanation given to me was that the space necessary to make ejection work correctly allowed for too much movement within the birdcage. This resulted in arming of a submunition within the round, one bump during handling and it was all over.
 
There were actually a couple of different variants of the rook. The one you see in the photos, and a shorter one.
 
There were actually a couple of different variants of the rook. The one you see in the photos, and a shorter one.

Some examples. The BLU-25 (L) is separate, but it's similarity in size and shape could cause some confusion.

IMG_0761.jpg
 
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