Re: [FYI] World's Longest page on tracks vs wheels

Tomb wrote:

>I call it the world's longest because it includes lots of facts, a
fairly 
>liberal sprinkling of bias to boot (but if you just pick out the facts 
>you're okay), ...
>
>http://www.geocities.com/lavdanger/

Geez. With friends like this, the M113 doesn't need any enemies... you
need 
to be pretty careful when you pick out the facts here, or else you'll
fall 
into the same traps as the author of this page (in the following called 
"the ranter" :-) ).

To summarize, the ranter has three main gripes with the LAV-III 8x8:

1) It is too heavy to carry in a C-130, at least for long distances.
True. 
How the former Swedish Coastal Artillery (they've changed their name
after 
a recent reorganization, but I always forget their new name) manage to 
transport their LAV-III 10x10 up and down the length of Sweden in the
old 
RSwAF C-130s I don't know; I suspect they're cheating somehow <g>

2) Wheeled vehicles don't have the cross-country mobility of tracks.
Also 
true, though I find the ranter's repeated comparisons of the LAV-III's 
mobility with that of French armoured cars from the early 1950s quite 
amusing. Technology has advanced somewhat during the past half century, 
even in the wheeled-vehicle transmission field <g>

3) The gripe which gets the most attention on the page is the claim that

the LAV-III has vastly inferior protection than the vehicle the ranter
pits 
as its rival, the M113A3. Here he is quite wrong, and presents an 
impressive array of misleading data; I hope that he is being misled by
them 
rather than attempting to mislead others. Let's take a closer look at
this 
gripe:

Relevant quotes from the page:

"The LAV-III is only 14mm THICK in its body
Proof:
http://autonet.ca/DriverSource/Stories.cfm?StoryID=867"

"www.snipersparadise.com/equipment/ammunition.htm
The 5.56 AP round penetrates 12mm armor plate of 300 HB at 100 m. The
7.62 
AP round penetrates 15mm armor plate at 300m"

"The LAV-I is designed primarily to defeat the "7.62mm x 39mm" Ball 
cartridge projectiles (aka: M1943 Soviet Short) fired typically by the 
"AK-47" weapon."

"In regard to #2, defeating artillery fragments, aluminum alloy armor is

superior to steel armor on a weight-per-sq-ft basis. "Back spall" can be
a 
serious problem when armor is perforated, AND HIGH HARD STEEL ARMOR IS 
ESPECIALLY PRONE TO BACK SPALL."

"Compared to the LAV-III's measley 14mm thick steel (little more than
0.5 
of an inch), the M113A3 has rolled 5083/5086 H32 aluminum armor that
varies 
from 1.5 to 1.75 inches (38.1mm to 44.45mm thick), not to mention spall 
liners inside the hull. We have not even talked about adding applique' 
armor to it yet.
http://afvdb.50megs.com/usa/m113.html
So the M113A3 as-is has armor that is 3 times thicker and is thus much 
stronger and lighter than the LAV-III's thin steel. "

Finally there's a reference to a book by Foss&Sarson:

"Page 22 describes how a Warrior AFV was hit in the CHOBHAM plate by a 
Challenger 120mm tank round and all that happened was a small dent!

Amazing what you can do with a TRACKED armored vehicle with reserve
power 
and low pressure..."

The total impression is that the LAV-III can be shot through by small
arms 
AP ammunition, whereas the three times thicker M113A3 armour is proof 
against such ammo.

Let's take a look at the quotes again:

"The LAV-III is only 14mm THICK in its body
Proof:
http://autonet.ca/DriverSource/Stories.cfm?StoryID=867"

The link leads to a driver's magazine. The only mention of metal
thickness 
in the article is this description from the factory:

"A computer-controlled laser cuts the 14-mm (just over ½-inch) steel
plate 
that goes into the LAV III's "hull." "

In other words, all it tells us is that somewhere in the LAV-III hull
there 
is at least one steel plate which is 14mm thick. It doesn't say *where* 
this plate is, nor does it say that the entire hull is made from a
single 
thickness of such plate. In fact, this *proof* doesn't tell us
*anything* 
about the armour configuration of the LAV-III.

But OK; let's assume that the entire LAV-III hull *is* made of a single 
thickness 14mm steel plate. It could be true, though personally I
suspect 
that the front plates are thicker than this. The next quote says:

"www.snipersparadise.com/equipment/ammunition.htm
The 5.56 AP round penetrates 12mm armor plate of 300 HB at 100 m. The
7.62 
AP round penetrates 15mm armor plate at 300m"

If you follow the link you'll find that these AP rounds are made by a 
company called "Bofors Carl Gustaf". Hm, wonder where I've heard that
name 
before... <g> These rounds were designed by some of the guys sitting
down 
the corridor from my office, though we no longer produce small arms ammo

ourselves - Nammo does that nowadays. But I digress.

A penetration of 12-15 mm sounds rather scary when you only have a 14mm 
plate protecting you, doesn't it? Trouble is, you can't compare these 
numbers straight away.

Armour penetration is usually measured in mm RHA, ie. the distance which

the projectile penetrates into a standard Rolled Homogenous Armour plate

with a Brinell hardness number in the 350-380 range - I've seen several 
definitions :-/ The higher the number, the harder the metal; the harder
the 
metal, the harder a bullet has penetrating it - very simplified, but 
essentially correct for the plate thicknesses and projectile calibers
we're 
talking about.

But look at the above quote: "...penetrates 12mm armor plate of 300
HB..." 
Not sure why the page says "HB" rather than "BHN", but according to my 
collegues these AP rounds were indeed tested against steel plates with 
Brinell hardness 300. Against harder steels, they don't penetrate as
far.

So, how hard is the steel used in the LAV-III hull? 300 BHN, 380, or...?

Well, according to Jane's Armour & Artillery the LAV-III is built of
"high 
hardness steel", but it doesn't say exactly which steel. Doesn't matter
all 
that much; high hardness steels typically have a BHN around 550. This is

quite a bit harder than than the 300 BHN the AP rounds were tested
against, 
reducing the penetration by at least 15% - so the 5.56 round only 
penetrates ~10mm, and the 7.62 round only 13mm into this harder plate. 
Suddenly the margin is on the LAV's side... still narrow against the
7.62, 
but on the right side.

Next quote:

"The LAV-I is designed primarily to defeat the "7.62mm x 39mm" Ball 
cartridge projectiles (aka: M1943 Soviet Short) fired typically by the 
"AK-47" weapon." ...

Here the ranter seems to have forgotten which vehicle he is critizising.

The above quote refers exclusively to the LAV-*I* - a design which is at

least 15 years older than the LAV-III we're discussing! According to
Jane's 
the LAV-II was up-armoured compared to the LAV-I, and the LAV-III was 
further up-armoured compared to the LAV-II... so the LAV-I specs have 
nothing whatever to do with the LAV-III specs. On to the next quote:

"In regard to #2, defeating artillery fragments, aluminum alloy armor is

superior to steel armor on a weight-per-sq-ft basis. "Back spall" can be
a 
serious problem when armor is perforated, AND HIGH HARD STEEL ARMOR IS 
ESPECIALLY PRONE TO BACK SPALL."

This quote is quite correct. In fact, spalling can be a serious problem 
even when the armour *isn't* penetrated. However, the armour thickness
is 
determined by the threat which is hardest to defeat - and in this case
the 
hardest threat is bullets, not artillery fragments, so the fact that 
aluminium alloy armour is better than the steel armour against the 
artillery threat is irrelevant.

High hard steel armour is especially prone to back spall, but that's why

all modern AFVs have spall liners (soft but strong materials on the
inner 
face of the armour which catches the spall fragments). For some reason
the 
ranter seems to believe that the LAV-III doesn't have a spall liner
(unlike 
the M113A3, which is explicitly mentioned as having a spall liner), but
he 
never states why he believes this. (OK, the driver's magazine doesn't 
mention the spall liner, but a) I don't think that the average reader
(or 
writer!) of a driver's magazine knows what a spall liner is, and b) the 
scene from the factory where the plate thickness is mentioned is far too

early for the spall liner to have been fitted!)

In other words, the statements quoted above are all entirely correct -
but 
they're not very relevant for the discussion! Next quote:

"Compared to the LAV-III's measley 14mm thick steel (little more than
0.5 
of an inch), the M113A3 has rolled 5083/5086 H32 aluminum armor that
varies 
from 1.5 to 1.75 inches (38.1mm to 44.45mm thick), not to mention spall 
liners inside the hull. We have not even talked about adding applique' 
armor to it yet.
http://afvdb.50megs.com/usa/m113.html
So the M113A3 as-is has armor that is 3 times thicker and is thus much 
stronger and lighter than the LAV-III's thin steel. "

Having 38-44.5mm armour sounds a lot better than having a mere 14mm, 
doesn't it?

The devil is in the details, as the saying goes. Remember what I wrote 
about armour plate hardness above? Aluminium alloys are *much* softer
than 
high hardness steel, which means that they're correspondingly easier to 
penetrate. While I don't have exact data for the alloy used in the
M113A3, 
I know that you need twice the thickness of the best aluminium armour to

stop a bullet than you need RHA, and you need ~15% less high hardness
steel 
than RHA to stop said bullet. Taken together, this means that you need
2.3 
times as thick top-grade aluminium armour as high hardness steel armour.

The M113A3's armour translates to a mere 16-19mm of LAV-III steel.

Still, 16-19mm is still better than 14mm, isn't it? Well...

...this is where the shape of the vehicle comes in. The M113A3 has
vertical 
sides and a front which slopes quite steeply, whereas the LAV-III has 
sloped sides (IIRC ~30 degrees from the vertical, but don't quote me on 
that - I didn't get to measure it last time I stood beside a LAV-III :-(
) 
and a front glacis which is far more sloped than that of the M113A3. 
Unfortunately I don't have the angles for the glacis on either vehicle.

Now, if a projectile doesn't strike the armour at right angles it takes
a 
longer path through the armour. At a first approximation, the effective 
armour thickness is increased by a factor 1/cosine(angle to the 
perpendicular). This means that a round hitting horisontally will find
the 
sloping side armour of the LAV-III "thicker" than the actual 14mm; if my

estimate of a ~30 degree slope is correct it'll have to go ~16mm through

the armour.

...oops! The M113A3's thinnest armour was only equivalent to16mm when 
translated into the LAV-III steel... all of a sudden the M113A3's 
comfortable armour advantage (38mm vs 14mm, with rifle AP rounds 
penetrating up to 15mm) has melted down to a virtually dead heat (16mm
vs 
16mm, with rifle AP rounds penetrating only about 13mm)! Not quite the 
impression you get from the ranter's page, is it?

Of course the actual thickness of armour the round has to go through 
depends on the exact angle from which the round hits. If the enemy can
fire 
from above, the LAV-III's sloped armour isn't as good, etc. However, 
without exact numbers on the armour thickness - as noted above, there's 
virtually no data on how thick the LAV-III armour really is. 14mm high 
hardness steel plus spall liner looks like a reasonable minimum.

The last quote, about the Warrior incident:

"Page 22 describes how a Warrior AFV was hit in the CHOBHAM plate by a 
Challenger 120mm tank round and all that happened was a small dent!

Amazing what you can do with a TRACKED armored vehicle with reserve
power 
and low pressure..."

The Warrior is, of course, a tracked vehicle; the implication seems to
be 
that tracked IFVs can be armoured enough to survive a direct hit from a 
tank gun.

However, the ranter doesn't tell the entire story. What happened was
that 
the Challenger hit the Warrior with a HESH round (HEP to you Americans)
- 
the Brits used HESH quite a bit during ODS, among other things scoring
the 
longest-ranged tank-on-tank kill ever recorded (a bit over 5km IIRC).
Now, 
the HESH round doesn't kill AFVs by penetrating the armour; instead it
sets 
up a shock wave in the armour which causes scab to spall off the inner
face 
of the armour and fly off to cause general havoc inside.

The trouble is, if the armour consists of two successive plates with a 
space inbetween (so-called "spaced armour") the scab spalls off the
outer 
plate and is stopped by the inner one. There's a space between the 
Warrior's applique and main armours... IIRC the dent in the
above-mentioned 
Warrior's hull was caused by the scab from the applique armour.

Some other things to note are:
1) The Warrior weighs 28 metric tons (without the applique armour, which

IIRC adds another 3 tons), compared to the LAV-III's 17 tons. The
majority 
of those 11 extra tons consists of thicker armour.
2) If the Challenger had fired an APFSDS round (ie., a long rod 
penetrator), the above-mentioned Warrior would have been very, very dead
in 
spite chobham applique armour.

Finally, some comments about the Chechen video clip:

The ranter implies that the BTR ran into the ambush only because it was 
wheeled, implying that a tracked vehicle wouldn't have suffered this
fate. 
However, he ignores that:
* the cliffs on either side of this particular road are too steep for a 
even tracked AFVs to move over
* according to at least some analyses I've seen of this video the BTR
was 
the lead vehicle of a convoy guard - the trucks it was escorting
couldn't 
have moved off road even if the BTR had been capable to do so. (I can't 
find those analyses now, though - they seem to be just as dead as the 
kavkaz.org site where the video was originally published :-( )
* judging from the size of the explosion in the video the
command-detonated 
mine consisted of 100+ kilos of high explosive. That's enough to throw
even 
an MBT into the air.

In other words, while the ranter does have a point about the
cross-country 
capabilities of the LAV, the Russians in the above ambush wouldn't have 
been any better off if they had been riding in a heavily armoured
tracked 
MBT than they were in their thin-skinned wheeled APC...

"Will they [LAVs] stay mobile after enemy fires hit their tires? Why
should 
we be
any different? Because we have a computer screen inside?"

Yes, the LAVs will stay mobile over most types of terrain after enemy
fires 
hit the tires. Why? Because the modern western run-flat tires are vastly

better than the older Russian no-run-flat tires. The LAV is capable of 
moving even if you blow some of the wheels clean off and puncture the
rest; 
if you break even a single link on the track of a tracked vehicle it 
becomes immobilized. Against smaller mines (ie., not the 100+ kg command

detonated variant shown in the video clip), the LAV is actually less
likely 
to be immobilized than a tracked vehicle is. (I've seen a demonstration 
where a Piranha-III 8x8 (ie., a Swiss-built LAV-III) with three wheels 
*removed* and the other five flat completed a rough-terrain course... it

didn't go as fast as its "undamaged" comrades, but it didn't get stuck
either.)

And a final musing:

In the middle of the description of the destruction of Mobile Group 100,

the ranter suddenly injects the bit inside [square brackets] below:

"The B-26 bombers arrived from Nha Trang to strafe and drop napalm but
the
fighting was at close quarters now and they were ineffective [So much
for a
LAV-III/IAV computer screen's "situational awareness" calling in an air
strike to save you--we still live in a PHYSICAL WORLD where you cannot
just
"mouse-click" reality to conform to your fanciful plans]."

The ranter seems to have missed a couple differences or three between an

IAV with modern C4I and the 1950's French:

1) The situational awareness you get from the modern C4I system and IR 
sights makes it harder for the enemy to ambush you, allows you to call
air 
support earlier, and also allows you to provide much better targetting
data 
to the supporting aircraft

2) A B-26 isn't *quite* as accurate as a modern a/c dropping
laser-guided bombs

3) Year 2000 rough-terrain wheeled vehicles are quite a bit more mobile 
than their year 1950 ancestors...

Kind regards,

Oerjan
oerjan.ohlson@telia.com

"Life is like a sewer.
  What you get out of it, depends on what you put into it."
-Hen3ry