This has been bothering me for awhile. How does sloped armour gain me
anything?
If I take the same mass of sloped armour and make armour perpendicular to the
ground I gain the same thickness you would gain from the slope. Space would
remain the same (If I pivot the slope about the center everything I lose from
the bottom reappears on the
top.)
The only thing I can think is maybe you increase your chance of a "glancing"
hit.
Where am I off? I'd think my reasoning would be obvious to any engineer.
No matter how you cut it, if the shell glances (bounces/slides) off, it
carries a big part of the kinetic energy with it.
And since war is essentially the consumption of resources, the less steel you
can use to bleed off the enemy's weaponry without losing your tank in the
process, the better. So you would rather use 1 ton of armor and get
glancing hits than 10 tons of armor and take them all head-on.
> on 02.5.1 1:22 PM, Roger Books at books@jumpspace.net wrote:
> This has been bothering me for awhile. How does sloped armour gain
Sloping armour increases the effective thickness of the armour, depending on
the angle of impact. It doesn't increase the effective of mass of the armour.
> On Wed, 1 May 2002, Roger Books wrote:
> This has been bothering me for awhile. How does sloped armour gain
It's just geometry, AFAIK, in two ways.
1. Rounds are more likely to bounce off upward, rather that 'stick'.
2. (the more important one) If you've got a round coming in parallel to the
ground, it's got to go thru MORE of an angled plate to reach the squishy bits
of the vehicle inside.
Say we have a 10cm sheet of armour - if it's perpendicular to the
round's path, the round only has to go thru 10cm.
Tip the armour back a bit - or a lot - and your round has to go through
more actual thickness of armour on it's parallel-to-the-ground impact
path. Slope the armour back 45 degrees and your 10cm armour is effectively
12-14cm thick or so, without adding anything to the weight of your
vehicle.
> If I take the same mass of sloped armour and make armour perpendicular
Nope, you're just reduced the *effective* thickness of your armour by the
percentage (roughly) that it used to be sloped. Do a bit of scribbling on
scrap paper, and you'll see what I mean. Draw two parallel lines for the inner
& outer surfaces of your hypothetical armour plate, and then measure
lines passing thru at differing angles - non-perpendicular lines are
naturally going to be longer, equalling 'thicker' armour when it's sloped.
> Where am I off? I'd think my reasoning would be obvious to
I'm nothing even remotely resembling an engineer, and my math bites too, but I
think I've got the gist of it above.
Anyone who can give a better explanation - or correct me if I'm totally
off - please do!
I think what he was saying (putting words in his mouth) was that at an angle
you have to cover a lot of area with a sloped plate. If you take the same
volume (not area, volume!) of steel, you can make a very thick front plate
standing vertically. Your point remains true, of course.
> on 02.5.1 3:14 PM, Brian Burger at yh728@victoria.tc.ca wrote:
> Brian Burger wrote:
> On Wed, 1 May 2002, Roger Books wrote:
There's a diagram on this page that illustrates the idea:
http://members.surfeu.fi/stefan.allen/strf9040.html
As a matter of fact you got what I was saying exactly. It's a bit late for me
to work out the math (I'm doing an emergency restore of on of my unix servers
that croaked) but it should be just as thick as it would if sloped if you use
an equivalent mass of armour.
On 1-May-02 at 02:26, Edward Lipsett (translation@intercomltd.com)
wrote:
> I think what he was saying (putting words in his mouth) was that at an
/ |
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/ | 1M
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/ 30 degrees |
If the only benefit were the extra thickness provided by the sloped
cross-section, then ceramic armor wouldn't have much to offer over a
lump of steel, would it? If there is a hole punched in the ceramic, a Bad
Thing happens. If the ceramic is hard enough to turn a potential punch into a
bounce, with the help of sloping, a Bad Thing may not happen.
On the third hand, I have been on neither end of a shell aimed at a tank, so I
may be wrong.
> on 02.5.1 3:50 PM, Roger Books at books@jumpspace.net wrote:
Quoting Edward Lipsett <translation@intercomltd.com>:
> If the only benefit were the extra thickness provided by the sloped
Ceramic armour fragments. You can embed a metal mesh in the ceramic to retain
the fragments - because ceramic fractures along fractal surfaces,
retaining the large fragments will effectively lock in the smaller fragments.
This is the basis behind "Chobham" armour, I believe.
So a lot of the shell's energy is spent in making cracks. Now obviously, this
isn't good long-term (probably don't want to get hit again in the same
place),
but in the short-term, the energy is absorbed.
Steel armour bends (which absorbs energy), but bends enough to transmit energy
to the interior surface, which is flaked off at high speed into the tank
interior...[1] this is because metal deforms and then delaminates fairly
easily along crystal boundaries.
{Annoyingly we discover ceramic composite armour doesn't seem to be covered in
the rules for Robot Wars. Mind you, the powerplant we've been looking at using
isn't in there either...}
[1] Why isn't the tank interior coated with something to retard these?
[quoted original message omitted]
Actually you do gain thickness from a horizontal shot:
: :
======> : :
: :
vs.
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=====> / /
/ /
The more the slope, the the greater the apparent increase. Think of an extreme
case where the plate is 60 or 80 degrees from vertical, the horizontal hit is
then spread over a large, oval shaped area rather than a nice small round area
and since it had to have enough energy to penetrate over the entire area, it
takes a whole lot more energy. APFSDS tries to negate this by having a really
pointy missile to concentrate the force. Sloping also has the additional
benefit of
increasing the chance of deflection - if the incoming shot is a little
wobbly or off horizontal, it might just glance off.
The down-side is that shots from a higher elevation will partially or
totally negate the slope of your armor so it's not a totally free advantage.
--Binhan
> -----Original Message-----
That phenomenon is known as "spall" and most armoured vehicles are equipped
with spall liners to catch such fragments. I believe that this a big problem
in APC's with aluminum armor vs. steel armor in that aluminum spalls worse
than steel and so is a big debate in the weight savings vs. armor protection
arena.
--Binhan
> -----Original Message-----
Chobham armor is a mixture of ceramic/laminate/depleted uranium. It used
the shear inertia of the DU, the inherent strength of ceramics, and the "spall
catching ability" of laminates to defeat kinetic and chemical (HEAT)
penetrators. It is in layers to decrease the "fracturing along fractal
surfaces" as it was crudely (yet most accurately) stated. The layers are
like a thatch weave (each in a different direction) so as to break up the
actual thickness of any particular "slab" of armour. It also serves to allow
the sliding of slab in differnt directions as a penetrator penetrates,
basically shearing it (slug/jet/etc.) off; drastically reducing the
penetrive power of the incoming object. LOTS of power is expended in sliding
slab in (relatively) lateral directions instead of actually penetrating the
armor. If you have ever seen chobham hit by a warhead, it looks like a carcass
that has been shot with buck shot, until you realize how shallow the
penetrator actually made it into the armor. Joe
----Original Message Follows----
From: "B Lin" <lin@rxkinetix.com>
Reply-To: gzg-l@csua.berkeley.edu
To: <gzg-l@csua.berkeley.edu>
Subject: RE: [OT]Stupid question about sloped armour
Date: Wed, 1 May 2002 10:24:37 -0600
That phenomenon is known as "spall" and most armoured vehicles are equipped
with spall liners to catch such fragments. I believe that this a big problem
in APC's with aluminum armor vs. steel armor in that aluminum spalls worse
than steel and so is a big debate in the weight savings vs. armor protection
arena.
--Binhan
> -----Original Message-----
> Edward Lipsett wrote:
> I think what he was saying (putting words in his mouth) was that at an
I think an advantage may be that the sloped plate does double duty. Not only
does it protect things behind it, things underneath it are also protected.
Sloping allows more volume to be protected by the same area of armor. Spheres
are best, but we are only considering ground vehicles that are primarily
armored against weapons that will not strike the top or bottom (although that
is
> Roger Books wrote:
> / |
But you need less top armor. Unless the vehicle is open topped, you will need
something on top of the vertical plate, but the sloped plate provides its own
top armor.
> It must be the glancing that makes it worthwhile, but we get