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Unread 11-01-2009, 23:15
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VEX Robotics Engineer
AKA: Arthur Dutra IV; NERD #18
FRC #0148 (Robowranglers)
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Re: What r possible drive systems under these circumstances?

Quote:
Originally Posted by Cartwright View Post
However, It is important to point out the specific case of multi-wheeled robots or robots with multiple contact patches between the wheel and the surface. This is what this engineering book I have says: If the normal force is increased, per given area of contact patch, the COF decreases. As the normal force decreases, the COF increases. If this were not true, then lowering tire air pressure in cars or installing wider tires, which both increase the area of the contact patch, would have little effect on traction.

The traction force is equal to the acceleration times the mass. Therefore, wouldn't the wheel's contact patches matter?
In perfect physics, contact area has no relation on total traction force, which is just coefficient of friction times normal force.

In the real world, things like rubber on asphalt or roughtop treading on carpet are different, because they have some measure of "interlocking" between the wheel and the carpet, as none of the listed things here are perfectly flat and smooth.

However, the playing field surface this year is probably about as close to perfect physics (friction wise) as we'll ever get in FRC, because there isn't any "interlocking" between smooth acetal wheels and nearly smooth FRP flooring.
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Art Dutra IV
Robotics Engineer, VEX Robotics, Inc., a subsidiary of Innovation First International (IFI)
Robowranglers Team 148 | GUS Robotics Team 228 (Alumni) | Rho Beta Epsilon (Alumni) | @arthurdutra

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