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QUESTION:Regarding the M1 tank, or tracked combat vehicles in general, I
would like to offer some information on their design and employment
based on my dealings in this area for many years.
70mph - Several reasons combat vehicles are not made to go much
greater than 45 mph:
- They also have to be able to climb steep hills and have
high torque-low speed capability for sand/mud/muck/etc.
By adding on additional speed requirements complicates the
final drive gearbox and gear range selection. Every additional
gear assembly/clutch pack is added complexity and cost.
- Where ever the tanks go, the IFVs, fuel trucks, APC's, ammo
reloaders and the rest of the logistics train has to follow.
We saw in Desert Storm that the tanks were starting to out
run the logistics train due to their great cross country
speed.
- When top speeds like this are mentioned, it is for hard level
surface. When you talk cross country mobility, one also
has to specify the terrain being traversed and a ride quality
criteria (power absorbed by the driver/troops).
ANSWER: John Deere 16 speed transmission - This would not work in a tracked
vehicle by the nature of how the vehicle is made to steer. Tanks and
other tracked combat vehicles use skid steer (make one track go faster
or slower than the other and skid in the turn). The 16-speed transmission
would only have one input shaft (from engine) and one output shaft (to
differential), whereas in a tracked combat vehicle, there is a need
for one input shaft (from engine) and two output shafts (one for each
track/final drive). In addition, current tracked combat vehicle transmissions
have regenerative steering so that in a turn, the energy absorbed by
the inboard track is pumped to the outboard track to help with the increased
power demand. All-in-all, todays tracked combat vehicle transmissions
(the XGT-1100 on the M1A1 and the HMPT-500-3 on the Bradley) are very
refined pieces of machinery that perform their functions quite well.
The XGT-1100 is made by Allison Transmissions who do know what they
are doing, and similarly the HMPT-500-3 is made by General Electric
who is equally competent. As for the "bow-tie" maneuver mentioned in
"King of the Killing Zone" that caused the XGT-1100 problems, this is
what Operational Testing is designed to flush out. Developmental Testing
measures how far, how fast, how reliable - Operational Testing is where
the hardware is put in the hands of the operators (privates, corporals,
and seargents) and they say how good it is.
Putting a log in the tread of a moving tank - as mentioned before,
infantry move with the tanks (at least in good Armies and Marine Corps
they do). It would be very difficult to do this and stay alive. Secondly,
tanks have machine guns (the M1A1 has three) to defeat soft targets
and personnel who mean to bring them harm (as in this case). Third,
when a tank is moving, it is very unhealthy to be close by, lest one
gets tangled in the tracks, and in this this case the tank will certainly
win. And lastly, most tanks have side skirts that make it difficult
to stick things into the suspension system.
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