jon e prevo <tcbracer@juno.com> wrote:
> dg, your hyperbole
I believe the word you want is "analogy"
> of the ground being the track on a tank is incorrect.
No, it's not.
> On a tank, the drive wheel not only has to support the (ground) track but
> also has to overcome the friction between (ground) the track, the ground
> and the other wheels. Friction is applied three times in this scenario,
> always to one place, the drive wheel.
Uhhhh... no. The track is stationary with respect to the ground, so for all
intents and purposes, the part of the track in contact with the ground IS
the ground. The non-driven wheels (the bogies) ride along the track exactly
the same way a train runs along rails (in fact, the initial patent for what
we call today "catapiller tracks" called them "self-laying railroad
tracks")
There is friction between the drive sprocket and the track, and friction
between the bogies and the track, but this is no different than the car
situation.
The only penalty a tank pays is the added inertial weight penalty of
sending the returning half of the track "forward" to be run over again. If,
however, we assume our track has zero mass, then we're OK.
Lemme put it this way - on a tank with 4 wheels (2 drive, 2 return) and a
massless track, the rotational inertia is *exactly the same* as a car with
similar wheels, so long and the non-driven wheels on the car remain in
contact with the ground.
> In a car, friction
Incidently, all this talk about "friction" is a complete red herring.
Assuming that the wheel profile is unchanged, making them lighter will not
affect friction in the least. What you *are* affecting is rotational
inertia, and from an inertia standpoint, it makes no difference if you
drive the wheels direct from the crankshaft, or via the ground. You still
have to pay the inertia penalty.
DG
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