Re: DS2 Another armour\mobility idea

Dances With Rocks wrote:

>
>
> This just feels...wrong. I'm not able to see how you can have
something
> that's nominally "slow tracked" be cooking along at just about the
same
> speed as "fast tracked". The way I understand engines (and I'll be the
> first to admit I'm no mechanic ;-) is that they have a certain torque
and
> mobility output and whatnot (the "whatnot" part is my non-mechanic
lack-
> of-jargon portion of the understanding ;-), and you can't make 'em go
> faster than they are designed to go. I mean, a bulldozer is not going
to
> go much faster than it already does if you strip off all the heavy
weight
> attached to it. My Indymobile is not going to keep up with Nascar
vehicles
> no matter how much I strip off the car (I can get up to 90 mph on a 7%
> grade and 7 miles of uncontested road in front of me - 95 if there's a
> stiff wind at my back ;-). I think the "mobility" factor is a limit to
> how much an engine on a particular vehicle can move said vehicle.

Transmission is everything.  The bulldozer is damn slow, because it is
required to

move rubble and earth.	To accomplish this task, it worries more about
torque and
traction, than speed.  Stripping the weight off of a bulldozer will
improve its
acceleration, but the top speed will only change slightly, because the
final drive
ratio was only intended for moving the vehicle at a walking pace.  The
bulldozer
tops out at nearly the same speed as before, because the engine is
running at the
end of its powerband (why construction equipment howls as it drives by
at roadway
speeds, the engine is pushed against its rev limiter).

Some american muscle cars had similar limitations.  The engine and final
drive
were optimised for maxing out the speed achieved by flooring it for a
quarter-mile
from a stop.  Topping out at 120mph was useless if you were not going
that fast
after the quarter mile.  Some of these vehicles had the perverse
combination of
over 400hp and a top speed of only 110mph.

It also works the other way.  If I do not need as much torque, I can
change the
final drive ratio to go faster for the same power.  The lighter vehicle
has less
rolling resistance, so a taller gear ratio can overcome drag at a higher
speed.
Aerodynamic drag will be similar, so the new speed will depend on
whether the old