Quote:
Originally Posted by brennonbrimhall
I'm pretty sure that I'm misunderstanding something here. Ff = mu*Fn. While I could see that more bumper-bumper contact would make the t-bone more stable (greater chance of maintaining contact as Robot A wiggles and tries to escape Robot B), there should not necessarily be a frictional force increase as the bumper-bumper contact area increases.
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You also shouldn't see a frictional force increase as a robot's wheels get wider, but you do. (Cue angry theorists.) I'll do my best to explain why; I would think it's the same explanation for both.
In the case of the wheel, the rubber on the wheel interacts with the carpet on a microscopic scale, digging into the nooks and crannies like Velcro sticking together. The wider the wheel, the more rubber there is to do that (even if nothing else on the robot, including weight, changes). So mu appears to be higher by some amount.
Applying to the bumpers, there is some digging in fabric-to-fabric. If you've got fabrics that are really rough-ish, they'll dig in more than smoother fabrics (like sailcloth). Even a sailcloth bumper cover will see this, but it'll be less noticeable than a Cordura bumper cover will because the sailcloth already has a much lower mu.
The theoretical value of mu and the actual value of mu will almost certainly be different in such cases; not by much, but by enough to make a noticeable difference.
This also doesn't take into account the various variances in bumper mounting and configuration that can affect apparent mu, like bowed bumpers, corner-only bumpers, height of the bumpers, stuff like that.
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