Going over 6 inch step with 12 inch wheels

[Al Skierkiewicz]

Originally Posted by Joe P

The set of front wheels go over with no problem but the back set of 12 inch wheels get hung up and start spinning a lot. We eventually get up to the top of the platform but it takes great effort for the driver to get up there.

Joe,
I think if you watched closely, the robot front tires are actually being pushed into the step edge. The resulting force combined with the turning ability of the tire results in the tire climbing the edge. The robot front wheels would climb even if they weren't powered. (Think of a bike going up a curb.) There is just more point friction on the front tires. Lowering the air pressure in the rear tires should help quite a bit. Some teams have added some friction enhancers, i.e. teeth or grippers, to the tires. These grip the edge during climbing and do not allow the tires to slip on the platform edge. I have seen grippers mounted right on the tire and on a wheel attached to the tire.