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

Took me a while to dig through the old Armor mags... fortunately I could
do 
so at work claiming that I was looking up references for some of the 
projects I'm working on and have people think it was work-related
projects ;-)

Ryan Gill wrote:

>>Kinda-sorta. The ground pressure problem hasn't disappeared
completely, 
>>but with centralized tyre pressure control (you can adjust the
pressure 
>>of each individual tyre from inside the vehicle) etc. it has been
reduced 
>>quite a bit for modern wheeled vehicles.
>
>The Argies couldn't get their Armored cars to go anywhere in the
Falklands 
>but on the roads. Dropping the tire pressure or not.

The armoured cars (AML-90) the Argentines used in the Falklands were 
designed in the late 1950s, and didn't have any centralized tyre
pressure 
control.

In other words, this example says no more about the capabilities of
modern 
armoured cars than the 1954 An Khe ambush described on the "world's
longest 
page" webpage :-/

>>An interesting article from Armor magazine some time ago (don't
remember 
>>which issue offhand, but can check): During the UN operation in 
>>Macedonia, some of the US posts guarding the Serbian-Macedonian border

>>were supplied by the neighbouring Finnish troops during the snowy
period 
>>- because the Finnish SISU wheeled APCs were able to negotiate the
snow 
>>and get to the posts, while the US tracked M113s either got stuck or 
>>turned into gigantic sleighs (and the weather was too poor for helos
to 
>>fly out to the posts) :-/

Hm. My memory is slipping :-( The article doesn't mention the Finns
doing 
the resupply runs to US outposts; that part I heard from some of the 
Swedish members in the Macedonian NordBat. (Swedish UN forces are 
mission-trained by the armoured regiment on the other side of the hill
from 
where I live, so ex-NordBat soldiers are quite common in the bars around

here :-/ ) Sorry 'bout that; "I heard that..." isn't nearly as
compelling 
evidence as printed matter!

What the Armor article does say is that the SISUs (XA-180s) could drive 
when even the US M113s were immobilized. (The US Bv206/SUSVs were still 
operating, of course! :-) ) The article can be found on-line at:

http://knox-www.army.mil/center/ocoa/ArmorMag/ja96/4wheeled96.pdf

>The Fins probably did something specific to get those to work in the
cold 
>weather and in snow.

They added snow chains, but that's it. I would've thought that tracks
gave 
better traction than wheels+chains, but appearently this isn't always
the 
case <shrug>

>That is their environment. Likely they are very very light.

A bit heavier than the M113 IIRC... not particularly light, no. The
XA-200 
has an empty weight of 14 tons, but it is somewhat bigger than the
XA-180 
discussed in the above article.

>>Could be the front as well - it is much better sloped than the sides
and 
>>rear, so would give better protection against horisontal hits even
with 
>>the same thickness. After all, the glacis plate on an M1A2 Abrams is
only 
>>55mm thick ;-)
>
>On the ferret, it is thicker to the front. On the Abrams...well....you
go 
>on thinking that...I suspect its likely thicker.

It's not just me thinking that <g> The upper glacis (ie., the nearly 
horisontal expanse in front of the turret) is only 55mm thick, but it is

very heavily sloped - 80 degrees from the vertical - which makes its 
*effective* thickness somewhere in the 350mm RHA range against
horisontal 
hits. The fuel cells on either side of the driver are designed to absorb

hits that penetrate the glacis, too, and the *lower* glacis (the 
inwards-sloping bit below the headlights) and the turret front are both 
much thicker.

However, if you can attack the M1 from above it is quite easy to punch 
holes through it... aim for the engine deck if you can, otherwise go for

the center of the glacis plate to kill the driver and wreck the
controls. 
Yes, even M1A2s are vulnerable in built-up areas...

>>Agreed. But see the SISU vs M113 anecdote above in this post <g>
>
>Hmm. Why the SISU would be able to get through and US HEMMTs and other 
>things wouldn't is a good question. I'd like to see the anecdote in 
>greater detail.

See reference above.

>>If it is light and air droppable, then it is fairly easy to make float

>>(floating also requires a relatively light vehicle). AFAIK the Bradley
is 
>>neither airdroppable nor amphibious, though - OK, they used to say
that 
>>it can swim, but the swim gear was withdrawn from service to prevent 
>>anyone from actually trying to use it <g>
>
>Bradleys don't swim because the whole project suffered from design
bloat. 
>They kept adding things to it that they went over their allowable
weight 
>for amphib operation.

*Why* the Bradleys are too heavy to swim isn't very relevant, is it? All

that matters to the users is that they can't swim. (The Bradley isn't 
air-droppable either, but AFAIK no-one has ever claimed that it is <g>)

Later,

Oerjan
oerjan.ohlson@telia.com

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