Per (GRMPer@aol.com) wrote:
> Anybody out there know if you just replace the DRIVE wheels with lighter
> pieces, how much advantage this is?
> Are the drive wheels 50% of the rotational inertia from the wheels...or
is it
> more?
Imagine you have a tank - you know, big-ass metal thing with a big gun -
and you turn it upside-down so the track is in the air. Drive wheels are in
the back, all the bogies are just along for the ride.
Run the engine, watch all the wheels turn, driven by the track - so each
wheel is causing an inertia penalty.
Now separate the track (one long strip, instead of a continuous loop) and
lay it across the wheels. Run the engine. Watch all the wheels turn until
you run out of track and it falls off.
Now consider that the "ground" is really a drive belt of infinate length,
and as long as the non-drive wheels of your car are in contact with the
ground, the drive wheels are driving the non-drive wheels, just like the
upside-down tank.
So, assuming similar wheel size front and rear, and assuming 2 drive
wheels, the drive wheels make up 50% of the rotating inertia from the
wheels. QED.
Funny tank story: A tank is really a locomotive, where the "rails" are
continuously picked up after they've been driven over and placed up front
again. Of all the wheels on a tank, only the drive sprocket (one per side)
is actually connected to anything - like brakes. I once saw a crew, who had
to replace some track sections and thought they could cut corners, break
both sides of the track (explicitly forbidden!) and as soon as the track
was free of both drive sprockets, 45 tonnes of tank rolled down the
now-flat track sections like a big ol' roller coaster, down a hill, and
into a swamp. Doh!
DG
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