Thread: The Game Floor
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Unread 03-01-2009, 18:12
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Re: The Game Floor

Quote:
Originally Posted by smartkid View Post
I have to ask this, the rules state that we can buy and use additional official 2009 first wheels. I suggested that making a bot with multiple wheels (12 wheeled beast) would give us an edge however someone said that it would just redistribute the weight.

What I'm asking is (to someone who knows more physics) will more wheels (more surface area) give any real increase in traction? If so (or not) how is this calculated?

Thanks,
-Cody
Under normal circumstances, the "surface area" is irrelvant to traction. Friction is proportional to the
normal force (that is the force perpendicular to the surface, usually the weight supported by the wheel.
You can calculate friction from the dimensionless coefficient of friction multiplied by the Normal force on the
wheel. Do remember that forces (including friction) are vectors.

As in past years, a driven wheel cannot impose greater torque than that which occurs just before the wheel
breaks traction. The ability of a drive train to supply more torque than this is not very useful, although
it looks like the there is an 18 inch carpet border which will yield quite different characteristics and some
serious pushing may still be possible around the edges.

The main difference this year is that with a coeeficient of friction of approximately 0.06 rather than the
typical 1.0 - 1.2 or so, the peak torques on the FRP will be about 1/6th of those of past years.

Having 4 driven wheels will increase your pushing force (and acceleration) because all wheels will be able
to push (before any of them start of to slip). As in past years, 6 wheel drives will still be useful because
with a raised center wheel, you will always have two wheels slightly off the floor (or with very low normal
force) and the effective wheelbase will then be about half that of a 4 wheel drive without the center wheels.
This may be quite important with the required wheels. Note that (assuming the supplied information is correct)
the transverse coefficient of friction of the wheel/FRP interface is more than twice that of the inline
coefficient. Do not assume that it will be easier to skid steer on this surface. It may actually be much
harder. You will have to do the physics and the math and it might be best to get some input from your engineering
mentors on this.

I think that some of the interesting challenges of this year's game comes from deciding which "rules of
thumb" to throw away and which ones to keep.
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