M113G3 Serrated, Holed Add-On Armor

[Ssnake]

The M113 has been updated with serrated, holed, comparatively thin metal sheet add-on armor. Is this just to protect against small-arms fire, or even against 12.7mm NSVT?

 

Example:

 

 

 

 

(I suppose that the effect is similar to the Leo 1A5's Deisenroth add-on armor to protect the turret flanks and hull against lateral 30mm AP shots, just for smaller calibers).

[CV9030FIN]

Good question,

I am in the same linbe as I've been for a long time interested in AAVP-7A1 appliqué armor kits. AAVP-7A1 add on armour are interesting as vehicles has to retain its ability to swim (more protection with less weight than for example ERA/NERA). For example in case of M2/M3 Bradley A2 model born in the same time frame but got "regular" steel ad on armour and lost the ability to swim.

 

To my knowlege there has bee at least two different appliqué armor kits in AAVP-7A1 AAK (P900, Rafael made?) and EAAK (type? manufacturer?)

 

Against what AAVP-7A1's AAK (P900) was designed?

Then again I suppose AKK wasn't it sufficient enough as Marines bought EAAK? Against what it was designed?

 

Photo of P900 AAK:

 

Photo of EAKK:

[Exel]

RPG screens?

[CV9030FIN]

RPG screens?

...I doupt that...RPG's wasn't "hot topic" in 1991...I mean that any extra protection or device creating more stand off helps against RPG's too, but I doupt that at least AKK is not optimised against RPG's, but small arms.. BTW it surely seems that M113G's add on armour is from the same company that made EAKK (or then it is just a knock off...)

[Simon Tan]

Is the M113 Uparmor the Danish ones?

[CV9030FIN]

Is the M113 Uparmor the Danish ones?

 

If you mean one on the Ssnake's photo, that is a Danish M113G3DK.

Edited October 25, 2012 by CV9030FIN

[Simon Tan]

HMG and limited HEAT protection. Spall liner on the inside probably does more for the latter.

[TTK Ciar]

Does anyone know the size of the holes? This would tell us the diameter of the threat the applique is intended to meet, assuming it is using the edge effect.

 

The distance between hole edges would be nice to know, too.

[Burncycle360]

There's a pic of the CVR(T) with perforated steel addon armor too

 

http://tinyurl.com/9p5773t

Edited October 25, 2012 by Burncycle360

[Ssnake]

I wouldn't be surprised to find polyurethane foam behind the serrated sheet metal, just like what was done to the YPR / AIFV, although that would probably require yet another metal layer to keep it away from rain water.

 

It seems to be important that the holed/slotted surface is presented to incoming fire at an angle, to explain the serrated look of the whole array.

Edited October 26, 2012 by Ssnake

[Max H]

It seems to be important that the holed/slotted surface is presented to incoming fire at an angle, to explain the serrated look of the whole array.

 

Maybe it's because angling means the projectile interacts with more of the plate, and so has more chance of encountering a hole? It can't be essential, as the CVR(T) burncycle360 found has flat plates.

[Galen.Wright]

Didn't the Israelis field something similar to this in Lebanon on their M113s - TOGA I believe it was called? Now the Iranians seem to be using it as well.

[Ssnake]

While I can't say anything about the hole diameter, the M113G3 apparently meets the STANAG 4569 Level 4 requirements (14.5mm proof for distances > 200m / impact velocity 911m/s or lower).

[Guest Jason L]

I'm pretty sure all those perforated systems are designed to shear the ballistic/incindiary tip, strip the jacket and tumble the penetrator from the various HMG rounds with full/mostly full caliber hardened penetrators. Probably works for both 14.5 KPV and the .50 BMG rounds.

 

You can see one particular take on that system in the following patent for the P900 AAAV applique:

 

http://www.google.co...tents/US5007326

 

The point of the angled channels is that the tip and jacket strips and the penetrator then travels through a whole series of yaw inducing perforations. The angle of the plate isn't important, it's the angle of the perforations that matter. P900 puts angled perforations in a vertical plate. The other systems probably use additional surface deflection plus angled perforations or use harned louvers in addition to perforations:

 

http://www.google.co...epage&q&f=false

 

You can probably get away with a vertical plate and straight holes too but it's evidently not as good. Base armour obviously matters too.

Edited October 26, 2012 by Jason L

[Leo Niehorster]

Is it possible that the holes are merely a weight-saving feature?

[Simon Tan]

Bingo!

[Ssnake]

"Possible": yes - "likely": no.

 

I remember that Paul Lakowski dug out an article that pointed out that holes slightly smaller than the caliber of the attacking projectile were particularly effective, but only against that matching caliber. Hence the Deisenroth add-on armor for the Leo 1A5 (and Leo 1V) were specifically designed against the BMP-2's 30mm AP rounds but wouldn't help much against anything else, and it's probably the same here for 14.5mm protection (which is pretty impressive for an M113, actually).

[Guest Jason L]

"Possible": yes - "likely": no.

 

I remember that Paul Lakowski dug out an article that pointed out that holes slightly smaller than the caliber of the attacking projectile were particularly effective, but only against that matching caliber. Hence the Deisenroth add-on armor for the Leo 1A5 (and Leo 1V) were specifically designed against the BMP-2's 30mm AP rounds but wouldn't help much against anything else, and it's probably the same here for 14.5mm protection (which is pretty impressive for an M113, actually).

 

I would categorically say "no". It is well accepted (and explicitly stated in all patent literature availlable, like say, the ones I linked to) that edge effect interaction between projectile and some sort of perforation dramatically increases effective ballistic resistance of plates. It is a desired design feature.

 

The P900 patent includes images of the design with exceptional clarity (slots, mounting, perforation obliquity, etc, etc) as well as defeat mechanism. I think it's pointless to entertain other hypothesis (weight saving) when the answer is written in plain english if anyone actually bothered to read it.

 

The sensitivity to hole size vs defeat ability isn't as great as you make it out to be though, the issue is really that a too-large hole will basically admit too much of the penetrator from a smaller calibre but a too small hole doesn't provide enough edge to penetration area for a large penetrator. But the range isn't like 1mm (ie something can probably handle 12.7mm and 14.5mm etc You can correct those issues with oblique holes, slots and multiple pannels with interfering perforations. The other issue is simply that as you move to large L/D, >> 1 km/s rounds there are better array designs.

[Ssnake]

Thanks for that clarification.

[Leo Niehorster]

Indeed.

[dejawolf]

armor looks identical to the swiss schützenpanzer 63/89:

http://preservedtank...e=2&PhotoID=287

 

http://www.panzerbaer.de/models/87_mr_spz63-a.htm

Edited November 1, 2012 by dejawolf

[methos]

I remember that Paul Lakowski dug out an article that pointed out that holes slightly smaller than the caliber of the attacking projectile were particularly effective, but only against that matching caliber. Hence the Deisenroth add-on armor for the Leo 1A5 (and Leo 1V) were specifically designed against the BMP-2's 30mm AP rounds but wouldn't help much against anything else, and it's probably the same here for 14.5mm protection (which is pretty impressive for an M113, actually).

 

The Leopard 1A5 was just a mere FCS upgrade, it never received newer armour. In case of the Germans and the Dutch the Leopard 1A1A1 was used as base for the Leopard 1A5 (hence it had the same applique armour as Leopard 1A1A1), while the Danes used newer production vehicles with welded turret (also designated Leopard 1A5).

The applique armour is also not made, simply because there was no IBD Deisenroth (the company didn't exist). According to literature the armour was made by Blohm & Voss, the fact that the patent can be found after a quick search online (under the name "doppelte Panzerung") pretty much validates this information. According to the author Frank Lobitz the applique armour was designed to resist small shaped charges like RPGs or the 2A28 Grom gun of the BMP-1, one explanation of how the armour works against them can be found in the patent - the rubber-coated bolts on which the armour is fitted work like coil springs, but better.

The BMP-2 - and subsequently the 30 mm 2A42 autocannon in ground use - was not existing at the time the Leopard 1A1 was upgraded to 1A1A1, which makes it impossible that the armour was designed against the BMP-2.

 

So: Leopard 1 armour = no connection in design to M113 perofrated applique armour.

[Guest Jason L]

Which patent? Do you have link or patent number?

[Sardaukar]

Would those serrated armours have any connection with Israeli "Toga" armour?

[Guest Jason L]

Would those serrated armours have any connection with Israeli "Toga" armour?

 

Yes, Toga, like the systems previously described, is meant to defeat 14.5mm by the means I mentioned.