Author Topic: Explosive Devices  (Read 2323 times)

Offline kitnut617

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Explosive Devices
« on: December 12, 2014, 04:20:33 AM »
D'oh... I posted this already in the Trumpeter section, forgetting we had a HB thread here.

Anyhoo, Leopard 2A4M CAN:




I have noticed the tread for vehicles to have this grill type surrounding, what purpose is it for ?

Offline LemonJello

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Re: Explosive Devices
« Reply #1 on: December 12, 2014, 05:07:40 AM »
Slat/bar armor to defeat EFP warheads, I believe. 

Offline Jeffry Fontaine

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Re: Explosive Devices
« Reply #2 on: December 12, 2014, 05:15:08 AM »
I have noticed the tread for vehicles to have this grill type surrounding, what purpose is it for ?
Robert,

That grill work is what used to be called an RPG (Rocket Propelled Grenade) Screen.  The Russians used bed springs on their tanks during WW2 to defeat the Panzer Faust (early RPG) and it was introduced later during the Vietnam conflict by the troops using chain-link fence sections in front of their positions to detonate the HEAT warhead (shaped charge) before it could strike the vehicles or bunkers.  This latest version is performing the same duty as the bed springs and chain-link fence sections but is now a production item instead of some battlefield expedient.  The stand off barrier works best when it is further from the target so the shaped charge (HEAT) warhead detonates and the energy from that blast in the form of a high-velocity jet of metal is negated due to the distance it has to travel to strike the target. 

Shaped charge weapons usually work best when the stand-off distance to the target is one to one and a half times the diameter of the warhead.  So a six-inch (152 mm) diameter warhead would be effective at six to nine inches (152 mm - 240 mm) from the target.  Any further than that reduces the effectiveness of the warhead and the jet formed by the warhead will not be as effective. 

The Leopard 2A4M CAN in the above image is protected by the Chobham armour system in the front and to reduce weight the RPG screen system is used at the rear where penetration is less likely to create catastrophic vehicle kill. 

These screen systems can defeat or reduce the effectiveness of most man-portable anti-tank systems but all bets are off when it comes to larger vehicle and aircraft mounted weapons that have much larger warheads and greater penetration provided by explosive weight or in some cases tandem warheads that are designed to defeat this type of defensive system. 
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Offline kitnut617

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Re: Explosive Devices
« Reply #3 on: December 12, 2014, 10:20:19 AM »
Thanks guys --  :)

To me though, it just looks like a natural climbing frame for any would-be attacker to climb up on top of the vehicle --

Offline Rickshaw

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Re: Explosive Devices
« Reply #4 on: December 12, 2014, 11:16:08 AM »
Thanks guys --  :)

To me though, it just looks like a natural climbing frame for any would-be attacker to climb up on top of the vehicle --


They shouldn't be getting that close if the accompanying infantry are doing their job (and the argument should be they shouldn't be necessary, if the infantry are doing their job, as well).   The reason why they've gone for a bar design is because they need to not only defeat hollow-charge warheads but also EFP (Explosively Formed Penetrators) which are a variation on the hollow-charge principle.   Hollow-charge warheads work on turning the metal (usually copper) liner which covers the face of the hollow-charge warhead into a liquid which is projected forward at high speed and high temperatures, to literally burn it's way through the armour plate, like a knife through butter. 

In the 1970s, some smart fellows in the US worked out they could use this to project a thicker plate which instead of being liquified forms a semi-plastic penetrator, which works like the dart of a long-rod APFSDS round to force it's way through the armour at incredibly high speed.  Whereas, as has been pointed out, merely making the warhead go off, beyond it's optimum distance from the target's armour was sufficient to degrade it's penetrative ability significantly and so protect the vehicle, with an EFP you need to basically not only make it explode away from the armour but you also need to degrade it's penetration by forcing it to go through some serious metal work.  So, while anti-HEAT protection could be made of, as has been noted bed springs and mesh or thin plate steel (WWII Schutzenplatte), you need something more substantial against an EFP and the bars are made of hardened steel (usually nearly as tough as the armour plate itself).

This is a good diagram of how an EFP works:



This is a good picture showing an EFP disk and a penetrator:


Offline Nexus1171

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Re: Explosive Devices
« Reply #5 on: December 27, 2015, 04:41:54 AM »
Rickshaw,

So the mesh reduces the penetrator's effectiveness?

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Re: Explosive Devices
« Reply #6 on: December 27, 2015, 04:58:25 AM »
Rickshaw,

So the mesh reduces the penetrator's effectiveness?

That's not what he said.  Read it again, focussing on the following part:

So, while anti-HEAT protection could be made of, as has been noted bed springs and mesh or thin plate steel (WWII Schutzenplatte), you need something more substantial against an EFP and the bars are made of hardened steel (usually nearly as tough as the armour plate itself).

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Offline Volkodav

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Re: Explosive Devices
« Reply #7 on: December 28, 2015, 08:41:03 PM »
I read a piece a while back on perforated armour, basically full thickness plate lightened with laser cut holes, and how it retained the same level of protection and strength as the original plate.