6WD Pros and Cons

[Madison]

Originally Posted by Daniel_LaFleur

Kevins comments about being able to turn better are a function of wheelbase and not traction or CoF. Because of this I commented on shortening the wheelbase of a 4WD system would (by driving 36" wide rather than 36" long), in effect, create an equivelent wheelbase on a 4WD robot, and thus the same turning advantage of the 6WD system.

Wheelbase, while taking about turning, acts only as a short hand description of considerations of friction, coefficient of friction and torque. The behaviors described by Kevin's comments are absolutely a function of coefficient of friction and resulting traction. There are a handful of ways to make your robot turn more easily -- one is shortening the distance between the center of mass and a wheel's contact point, reducing the torque required to rotate the robot as a result of reducing the distance variable in your torque equation. Conversely, you might reduce the force variable in the equation by using wheels with a lower coefficient of friction; it is by this principle that omniwheels work. You could, with more difficulty, also increase the available torque.

I'm sure you understand this, but some of the folks coming down the line later may read this without some of the inherent assumptions I think you're making -- namely, considerations for all other things being equal. I just want to be sure that we avoid having someone think that they can use wheels with a higher coefficient of friction and simultaneously shorten the wheel base and have everything come up roses.