churchill AVRE effectiveness

[Michael Emrys]

Originally posted by MikeyD:

Geepers, it's frustrating trying to research the Petar motar on-line. Every site seems to repeat the same useless description over-and-over (Grrrr...).

Heh. I had that same frustrating experience two days running trying to google something definite for this thread.

But I thought I had read once the big mortar was indeed hollow charge.

And I am equally certain that I read in more than one place that it was not. In fact, I almost want to call it a "mattress charge", but that's not really it either. I think it works on a similar principle though.

I guess it's just a Mexican standoff at this point.

Michael

[Michael Emrys]

Originally posted by Kingfish:

My guess is that is the mortar bomb on the right. Can't tell if it had a standoff spike, or if it a HEAT or HESH round.

Looks like it to me. BTW, I suppose everyone realizes that it is front side down in these photos.

I've never seen a spike or a standoff cone on any of the cutaways or other illustrations I have seen, and as best I can recall, they all had solid charges.

Michael

[JonS]

I had a look through some stuff I have here at home. The best I could come up with was 'demolition bomb', which isn't terribly descriptive, or helpful.

[Simon Fox]

Here's a question: is the calibre 290mm or the barrel length?

Also, I have a picture of one loaded and the front of the dustbin definitely does not have any kind of standoff although the centre is slightly recessed.

I understand that the proper designation is "mortar, recoiling, spigot, MkI and Mk II".

[ruf9ii]

wow, thanks for the reply's

[Stalin's Organ]

290mm is hte calibre.

Re HESH: the round cannot have been HESH according to Hogg's "British and American Artillery of WW2".

HESH was developed after the war, from the "Wallbuster" round developed for the British recoilless guns. This round (which was essentially HESH), was designed by Sir Dennis Burley for his range of RCL's as an anti-concrete round - the 7.2" Wallbuster was trialed against a 5 foot thick concrete wall, and blew fragments 60 feet beyond it, cut the reinforcing rods and "severely bulged hte wall backwards" - however the success of hte Petard mortar removed the requirement for it and only a handful were built.

In August 1944 the 7.2" gun was trialed against 6" (150mm) armour plate -

.....the shell blew a 117 lb scab, 19" x 24" off the back of the target plate at an estimated 600 feet per second, and this led to research into defeating armour plat which, several years later, was to lead to the squash head shell.

Page 237

[MikeyD]

I searched all my standard Churchill references and to my horror I could not find any reference to the AVRE's HEAT round. Basically, none of my references went beyond the vague line or two in Chamberlain & Ellis.

I still want to say the Spigot mortar round was HEAT but I've got absolutely nothing on-hand to backup that assertion

- I posted this question on another armor forum yesterday in the hope of getting some confirmation... and didn't. No mention of HEAT, no mention of HESH. So (to quote someone on the other forum) "it's possible they did it the old-fashioned way. 40 pounds of HE can still ruin your whole day, even if it isn't HEAT or HESH."

[ September 09, 2005, 07:42 AM: Message edited by: MikeyD ]

[DEY]

What little info I can find seems to indicate that the ammo type was only HE, I read an account from a veteran that stated that this AFV could disable a Tiger tank, but only if it was in close proximity.

I would think a 40lb heat round would do more then disable a Tiger.

Also the mortar had to be loaded as any mortar is loaded, meaning someone had to expose themselve outside to load the thing.

http://www.mapleleafup.org/forums/showthread.php?s=8e63e5ac92cf52e6a7842da71bb420b1&threadid=4007

http://www.armourinfocus.co.uk/a22/

According to this site the Brits didn't have HESH ammo until after WW2

http://members.tripod.com/~nigelef/ammo.htm

[flamingknives]

Originally posted by DEY:

Also the mortar had to be loaded as any mortar is loaded, meaning someone had to expose themselve outside to load the thing.

Negative. i've definately seen a picture of the barrel of the Petard mortar open, the hatch above the drivers' position open and a dustbin being loaded. Unfortunately I can't think where I've seen it.

[flamingknives]

Loading the Petard mortar:

http://www.perthmilitarymodelling.com/reviews/vehicles/resicast/resicast35170.htm

Modellers are notoriously picky in their detail.

http://www.d-daytanks.org.uk/exhibits/churchill-avre.html

Look at the second last picture - you can see the pivot and also that the loader couldn't get out the 'loader hatch' if the gun was near it.

[Private Bluebottle]

Yea gods! Someone claiming that the Petard fired a HEAT round or that HESH is a "type of HEAT round"?

This is pretty basic stuff. Its been in all the publications for over 30 years that I know of.

It fired HESH.

HEAT functions by exploding when it contacts the surface (or rather it is best if it explodes just before it contacts the surface) of its target, creating a jet of liquid metal formed from the inverted cone of usually copper which lines the face of the explosive charge. This jet then basically burns its way through the armour, melting it as it goes.

HESH, on the otherhand, explodes after it makes contact with the surface of the target. It is contained in a soft metal round, which allows the plastic explosive contained inside to flatten out, over the surface of the target, where a base fuse, behind it, then explodes, detonating the plastic "patty" of explosive, creating massive shockwaves which then penetrate the target and cause "scabs" of armour or concrete to break away from its inner surface and shoot around inside. The shockwave is often enough to kill the occupants of AFVs and bunkers.

Even Wikepedia has entries on both types of round. I'd suggest you do a bit of basic bloody research.

http://en.wikipedia.org/wiki/HEP-T

http://en.wikipedia.org/wiki/HEAT

[Private Bluebottle]

Originally posted by DEY:

According to this site the Brits didn't have HESH ammo until after WW2

http://members.tripod.com/~nigelef/ammo.htm [/QB]

Actually, Nigel makes the point that HESH wasn't developed for the 25 Pdr, until after WWII. He doesn't say that British didn't have HESH or that it wasn't developed until after WWII.

[roqf77]

err bluebottle? it has already been stated hesh was not developed until after ww2. so it didnt fire hesh.

[roqf77]

Original posted by stalins organ.

"Re HESH: the round cannot have been HESH according to Hogg's "British and American Artillery of WW2".

HESH was developed after the war,"

[flamingknives]

Mr. flamingpicky would like to point out that while the HEAT jet is fluid, it isn't liquid, and that any burning/melting is a secondary effect as the jet is moving at up to 8km/s.

Also on the list of pedantry for today, HESH sets up shockwaves within the armour plate that can be severe enough to break large scabs off the reverse face as they reflect off air/armour interfaces and superpose. Furthermore, if the shockwave alone is sufficient to kill, the risk from secondary projectiles is substantially greater. AIUI, surprisingly few people are killed by blast alone.

One final thing, the Blacker Bombard was also a spigot mortar and intended for anti-armour use. That had a regular HE round.

[stoat]

Originally posted by flamingknives:

HEAT jet is fluid, it isn't liquid

Gotta love plasma.

[flamingknives]

Plasma is very cool (not in the temperature sense), but a HEAT jet isn't plasma either*. It's a solid that has been pushed past its hydrostatic yield strength.

*Plasma being gas heated to the extent that all the electrons are stripped from the constituent molecules. I'm not sure wether plasma is actually a fourth state of matter or ionised gas. At atmospheric pressure gas needs to be exceptionally hot to become plasma.

[John D Salt]

Originally posted by MikeyD:

I searched all my standard Churchill references and to my horror I could not find any reference to the AVRE's HEAT round. Basically, none of my references went beyond the vague line or two in Chamberlain & Ellis.[snips]

My collection of references is almost as unhelpful, but the Bovington Museum booklet "British Tanks 1939-1945" (published in 1978) says, on page 63, under the heading "Particulars Petard (Churchill IV AVRE)":

Designed in May 1942

Spigot demolition mortar: 9in bore

Bomb: 27 in long

Weight: 40 lbs containing 26lbs hollow charge HE

However, PRO document WO 291/598, "Attack of Concrete Walls by Petard", gives the filling as 23 lbs, and fails to mention anything about hollow charge. The main text of the Bovington booklet entry also says HE without mentioning a hollow charge, although it does mention General Wade "bee-hive" (hollow-charge) demolition charges being carried by AVREs for placement by hand. I am therefore a bit suspicious about the hollow charge claim.

I make the volume of the charge something like 0.028 cubic metres, and mass of explosive 11.8 Kg (if one believes the higher figure), so if someone knows the likely density of the explosive filling (and I don't know what it is, but I imagine RDX/beeswax would be likely) then we might be able to guess whether there is room for any significant amount of emptiness in the warhead.

The Bovington booklet also has a photo of the projectile that magically contrives not to show the nose, but I'd also suggest that the apparently very blocky nose-shape of the projectile would make fuzing for a HEAT round (which must have a point-initiating, base-detonating fuze) a bit awkward.

All the best,

John.

[flamingknives]

The only one I know off-hand is 1170kg/m²

11.8kg thus fills 0.01m² which is 228mm diameter by 244mm long.

The explosive isn't 27" long. Surely that's from nose to tail?

The white bit in the picture, which I presume contains all the explosive, looks about those proportions.

[Buq-Buq]

I think that one thing that might be getting in the way of this discussion is the terminology in use. Be aware that while a High Explosive Anti-Tank (HEAT) warhead is a Hollow Charge device, a Hollow Charge device is not necessarily a HEAT warhead.

HEAT warheads (i.e., a warhead using the hollow charge principle) are purpose-built for defeating armor. They are built using a metallic cone (a concave surface) surrounded by explosive; the proper detonation of said explosive converts the metallic cone into a fluid kinetic energy penetrator, moving at a velocity upwards of 5 kilometers per second.

On the other hand, a Hollow Charge can be almost any type of explosive device that is built with a concave surface. The Monroe Effect dictates that an overwhelming portion of the blast from the explosion of said device will be directed towards that concave face. These Hollow Charge explosive devices do not have to be sophisticated: when I was in the Army, our Cavalry Scouts were trained to build Hollow Charges for cratering roads by filling locally-procured better-quality wine bottles with C4 — the sediment-trap in the bottle served to form a nice concave surface to direct the blast.

I have done a quick search amongst my material on the Churchill AVRE and the Spigot Mortar here, and have come up with little more information than has already been presented. The weapon from which the Flying Dustbin (the projectile launched by the AVRE's Spigot Mortar) was developed, the Blacker Bombard, was originally intended as an anti-tank weapon, but I believe that it destroyed its target strictly through the sheer brute force of its 10-20 pound explosive charge, enhanced by being concave to take advantage of the Monroe Effect.

As others have stated above, the Spigot Mortar had a hefty amount of explosive (Patrick Delaforce, in Churchill's Secret Weapons, says 26 pounds of explosives) in a 40 pound projectile. Delaforce continues: "This could be fired up to a range of 230 yards but the most effective range was about 80. Practically any target of steel, brick or concrete could be destroyed . . ."

I think that it is quite safe to say that the Flying Dustbin was not a HEAT warhead; I think, however, given its reputation at destroying fortifications, that it must have employed a Hollow Charge of some sort. Someone will discover a cut-away of the Flying Dustbin in a month or two — once this discussion is long-forgotten — that will prove (or disprove!) the theory.

Mark

[John D Salt]

Originally posted by Buq-Buq:

I think that one thing that might be getting in the way of this discussion is the terminology in use. Be aware that while a High Explosive Anti-Tank (HEAT) warhead is a Hollow Charge device, a Hollow Charge device is not necessarily a HEAT warhead.

Nonsense.

"Hollow charge" and "HEAT" are almost as freely interchangeable as warhead descriptions as "Monroe effect" and "Neumann effect".

All the best,

John.

[ September 11, 2005, 03:21 PM: Message edited by: John D Salt ]

[Guest Mike]

He's right tho - there are hollow charge/monroe-effect blasting charges to cut steel - you see them used on demolition sites all the time and they are not HEAT.....in that they are not anti-tank!!

But I don't think the difference is of any importaance in this context.

[Guest Mike]

Originally posted by Private Bluebottle:

Yea gods! Someone claiming that the Petard fired a HEAT round or that HESH is a "type of HEAT round"?

No - IIRC the claim was that HESH is a type of shaped charge - if you stretch the point.

Which is true - at a stretch!!

In the case of HESH the "shape" is flat agaisnt the target, and is achieved only after the round strikes, as opposed to hEAT which is removed from the target and which is shapped at manufacture.

[Buq-Buq]

John: ~ No comment ~

Mike: Go back and have a look at the first page of this topic to see why the difference between a Hollow Charge and HEAT is important. It took less than a dozen posts after Kingfish said "shaped charge" for the acronyms to start flying.

Mark

[Guest Mike]

BB - yes I was part of all that - perhaps that's why I dont' see the difference as being particularly important!