Coefficient of Friction Testing

[Siri]

We don't do this routinely (being both somewhat limited and somewhat naive in wheel choices), but with the bridge this year we did several true experiments, including using the full robot and bridge with various wheels and other surface texture changes. We used both tipping and dragging (as our CG meant tipping sometimes preceded slipping). With all our off-season drivetrains, we're setting up weighted testbed chassis and switching in wheels/treads on carpet, polcarbonate and polypropylene (approximation for polyethylene).

Originally Posted by ttldomination

Some years ago, we actually had to find the COF between a rough-ish sponge and a piece of wooden board (relatively smooth), for a physics lab.

The situation you describe is not strictly Coulombian, because of inconsistency both in approximating contact area as proportional to normal force and in the angle(s) of the contact planes(s) in general. (Leaving the sponge's contact with the wood and the wood's own imperfections to prevent constant behavior in both time and space).

Weighing down the surface (higher but constant normal force) gets you past some of that initial "noise". However, beware both the "pull slowly" difficultly JVN describes and the failure of Columbian models when contact area isn't proportional to normal force (below saturation) and/or frictional force isn't proportional to normal force (independent of contact area).