Chieftain Questions

[Stuart Galbraith]

 

Well HEAT is a focused cone of high explosive that burns through armour.

 

You've been here long enough to not use that "Burns through" language Stuart.

 

Go sit in the corner for 10 minutes.

 

 

Like I say, im more familiar with HESH. All this HEAT is all furriner stuff to me.

[rmgill]

Hopefully the ghost of Lieutenant-Colonel Blacker does not decide to haunt you.

[Ken Estes]

Plastically deforms sounds enough like melt to me. It's not a function of temperature of course.

 

pp 6-7 of the first ref I linked:

 

Early German reference to the hollow cavity effect, after von Foerster and Bloem, occurred in 1911–1912 patents in the United Kingdom (U.K.) and Germany by Westfalische Anhaltische Sprengstoff Actien Gesellschaft (WASAG). The WASAG patents clearly demonstrated the unlined-cavity effect and the lined shaped-charge effect. Also, M. Neumann in 1911 and E. Neumann in 1914 (who are often confused in the literature) demonstrated the unlined-cavity effect. M. Neumann shows a greater penetration into a steel plate from a cylinder of explosive with a hollow, conical cavity (247 g of Trinitrotoluol) than from a solid cylinder (310 g of Trinitrotoluol). This clearly illustrates what is known in the U.S. and U.K. as the Munroe effect and in Germany as the Neuman effect. The depth of the crater in the target is increased by utilizing a lined shaped charge and the penetration can be further increased by displacing the shaped charge some optimal distance from the target. To illustrate this effect, in Germany in 1941 a hollow cavity charge, a lined cavity charge, and a lined cavity charge detonated at a certain standoff distance above an armor plate were compared. The target plate was ship armor steel and the explosive mixture was 50% TNT and 50% cyclonite. The hollow cavity was a hemisphere with a cylindrical extension at its base equal to one-half of the diameter of the cavity (D). The liner was made of iron. The explosive contour was of the same geometry as the cavity, and the explosive thickness at the base of the liner was 0.15 times the cavity diameter. For the unlined hollow charge, the penetration (P) = 0.4 D at zero standoff. For the lined cavity, P = 0.7 D at zero standoff and P = 1.2 D for standoffs between 0.5 and 1.5 D. For the iron-lined shaped charge, D represents the inside diameter of the liner. These formulas are not universal laws, but they illustrate the increase in penetration in going from hollow charges, to lined cavity charges, to lined cavity charges with a nonzero standoff distance.

 

 

There is no 'slug' with an unlined cavity. The term 'jet' remains an insufficient descriptive. The high velocity explosive wave thus focused breaks down the molecular structure of the target material.

[Stuart Galbraith]

Well im on friendly terms with Lieutenant General Henry Shrapnel.

[Ken Estes]

Has he stopped spinning in his grave yet from the everyday use of the term 'shrapnel' to describe all shell fragments?

[Stuart Galbraith]

He is jolly thrilled about it I can tell you.

 

Just learned an interesting thing, he was born in Bradford on Avon, just down the road from me. Perhaps not one of the achievements the West Country is comfortable with, which is probably why Id not realized it before. As usual I digress.

[bojan]

Plastically deforms sounds enough like melt to me. It's not a function of temperature of course.

 

No, plastic deformation is not same as melting, not even close in how process works.

 

 

...There is no 'slug' with an unlined cavity. The term 'jet' remains an insufficient descriptive. The high velocity explosive wave thus focused breaks down the molecular structure of the target material.

 

With unlined cavity working medium is gas. It still does not melt metal, metal behaves same as hit with other metal, it is just that effectiveness of such interaction is very low so low penetration of unlined charges. It is possibly do do liquid liner shaped charges, they work the same, by plastically deforming target material.

[Sovngard]

Out of interest I always thought the PISH designation was the much simpler Product Improved Squash Head. Your designation works as, if

 

I've found the meaning of this acronym on the web, I'm not even sure that it's the right one.

 

But, like you said, Product Improved Squash Head is mentioned in the text accompanying the pictures of the 1976 British Army Equipment Exhibition.

 

I remember correctly, the aim was to be able to fire at a somewhat higher velocity then the existing shell to reduce time of flight and to be able to partially penetrate layered/spaced armour before functioning. The higher performance would also help reduce the in-bore disparity between the primary and secondary natures helping to alleviate some of the fume extractor (bore evacuator) performance problems.

That's a shame that no data has been published.

 

This concept could have provided a second life to this type of ammunition.

 

BTW, the British 120 mm HEAT round was a rather long projectile, I wonder if it could fit properly in the racks of a Challenger 1 or a later mark Chieftain.

Edited December 31, 2017 by Sovngard

[DB]

Just in case you didn't know, "pish" as in "pish and tosh" is a term of general disparagement in Scots. Meaning "rubbish" or "nonsense". I find it hard to believe that whomever originated the acronym wouldn't be aware of this.

[Stuart Galbraith]

Pish a very old English word. Its used at least twice in 'Henry V'.

[Przezdzieblo]

 

any guess from which document this diagram is?

 

AFAIR it is from briefing on the first official release of information on Chobham armour, from 1976. The presentation was prepared with some slides as illustration. Nothing that looks good in paper form

I will post here TNA reference when I am home.

.

 

 

 

UK 120 mm HEAT, that was made in hope that USA will choose British gun, was said to be a failure. There is one experimental projectile, probably from that programme, exposed in Bovington.

Edited January 1, 2018 by Przezdzieblo

[Stuart Galbraith]

 

any guess from which document this diagram is?

 

AFAIR it is from briefing on the first official release of information on Chobham armour, from 1976. The presentation was prepared with some slides as illustration. Nothing that looks good in paper form

I will post here TNA reference when I am home.

 

 

 

UK 120 mm HEAT, that was made in hope that USA will choose British gun, was said to be a failure. There is one experimental projectile, probably from that programme, exposed in Bovington.

 

 

 

That explains a hell of a lot, thank you!

 

Perhaps the illumination round and the HE Frag were for the same reason?

[Przezdzieblo]

Ok, that is DEFE 13/1372, slides 2 and 3 for proposed presentation on special armour to NATO, 10 May 1976.

Slide 1 was a comparison of RHA and Chobham armour needed to stop 105 APDS and 6 inch HEAT. Slide for was just image of FV 4211 standing along Chieftain. Unfortunately, the remaining 4 slides with target samples were not included in the file.

 

Something more from that file:

 

Proposed press release

 

A NEW BRITISH ARMOUR FOR TANKS AND OTHER ARMOURED VEHICLES

 

A new armour has been developed by the UK. It is our great significance since it represents a major step forward in protection against all forms of anti-tank weapons. The uniqie feature of the armour is the exceptional level of protection it affords against the Chemical Energy warhead used in all guided weapons as compared with any other conventional armour system.

The armour has undergone extensive practical tests, so that it is now possible to design a tank with greatly improved protection against both anti-tank guns and anti-tank guided weapons. This is an important step forward in armoured fighting vehicle design at a time when guided weapons have assumed greater prominence on the battlefield. It is no exaggeration to say that it represents the single most significant development in the design of armour since World War II.

Information on this new development has been freely shared with the United States of America and the Federal Republic of Germany in the course of mutual discussion on future tank systems; and a general presentation has recently been given to NATO.

Edited January 1, 2018 by Przezdzieblo

[Wiedzmin]

thanks interesting, i have some reports about Chobham on PC, IIRC in terms of "APDS/APFSDS protection" it says something like "if someone require data on APFSDS protection, try not to show real data... it better to get some test with PPL64/L64 APFSDS later for France(?)"

 

if interesting i can try to find report and text

[rmgill]

Plastically deforms sounds enough like melt to me. It's not a function of temperature of course.

 

 

Go to your fridge. Get out a stick of butter.

 

Take out your largest knife and cut the stick of butter with a very hard, fast downward swing. You'll see plastic deformation in that cutting effect.

 

Now, stick a knife you don't mind losing the temper on in the heat of the stove for 10 minute on high. Now, cut the stick of butter with the hot knife That's melting.

 

 

[Ken Estes]

Go to your fridge. Get out a stick of butter.

 

Take out your largest knife and cut the stick of butter with a very hard, fast downward swing. You'll see plastic deformation in that cutting effect.

 

Now, stick a knife you don't mind losing the temper on in the heat of the stove for 10 minute on high. Now, cut the stick of butter with the hot knife That's melting.

 

 

Just saving this for the record, Mr Science.

Edited January 1, 2018 by Ken Estes

[Paul Lakowski]

French studies on shaped charges recorded temperature of 480oC , which is enough to melt aluminum and soften steel...given enough time. However since the entire penetration event lasts only 1/2 millisecond - I can't see melting being a factor.

[Jim Warford]

French studies on shaped charges recorded temperature of 480oC , which is enough to melt aluminum and soften steel...given enough time. However since the entire penetration event lasts only 1/2 millisecond - I can't see melting being a factor.

I'm glad you're still around Paul...

[Loopycrank]

 

 

any guess from which document this diagram is?

 

AFAIR it is from briefing on the first official release of information on Chobham armour, from 1976. The presentation was prepared with some slides as illustration. Nothing that looks good in paper form

I will post here TNA reference when I am home.

.

 

 

 

UK 120 mm HEAT, that was made in hope that USA will choose British gun, was said to be a failure. There is one experimental projectile, probably from that programme, exposed in Bovington.

 

 

 

Does anyone have pictures of the 120mm HEAT for the L11? I had heard it was also pitched to Chieftain export customers.

[rmgill]

Just saving this for the record, Mr Science.

Would you prefer a cartoon with crayons?

[Panzermann]

French studies on shaped charges recorded temperature of 480oC , which is enough to melt aluminum and soften steel...given enough time. However since the entire penetration event lasts only 1/2 millisecond - I can't see melting being a factor.

 

exactly. If you could move the hot knife similarly fast through the butter, it would not really melt either and just displace the butter in its movement to penetrate the stick of butter.

[Ken Estes]

WTF???

[Loopycrank]

WTF???

 

 

The heat only flows so quickly from the hot knife into the cold butter. It's a function of the conductivity of the knife, the conductivity of the butter and how much hotter the knife is than the butter.

 

Similarly, the thermal energy of a shaped charge jet, can only conduct into the armor of a tank so quickly.

[Dreilide]

Probably a dumb question, but can the fuzes on HE/HEAT/HESH rounds be set off by dropping/bumping the nose into something i.e. clumsy loading?

[Ken Estes]

It's getting weird.