Joe with
Ramming Speed at BattleBots in Nov '01

Mike and Joe with Ramming Speed at BattleBots in May '01

Their has been great debate on the BattleBots Forum about traction. Does more width give you more traction? Do the Black Colsons have better grip than the Grey ones? Does that grip compound actually work? Time to find the answers.

I am building a rig that will allow the mounting of a loaded wheel for the purpose of testing the amount of torque that can be applied to the wheel shaft before the wheel breaks traction. The rig will be general purpose, to accommodate a wide variety of wheel sizes, with the idea that a chart can be formed to compare wheels to each other.

In general, the rig will include a base that contains a piece of tempered glass (the driving surface), a platform that floats over the base (through guide bars) and has a test wheel mounted to it such that the wheel sits freely on the base. The platform can then be loaded so the weight the wheel is applying can be altered.

The data gathered will be added to a spreadsheet available from this page. The data will include:

I first looked at using an ordinary torque wrench to measure the torque. The smallest torque wrench I found could only measured down to 50 in-lb increments. I have a feeling we'll need to get down to 10 in-lb increments to tell a performance difference between wheels.

The next option is to extend a lever from the hub and hang a  weight from the end (probably 12" from the center of the hub to make conversion to ft-lbs easy. I'll add ballast to something hanging off the end of the lever, and when the tire breaks traction, weigh the ballast. 1lb of weight breaking the wheel free=1ft-lb of torque (12 in-lbs)

To measure the surface area, I will use a Pyrex casserole dish as the driving surface. After the traction testing is done, I will add a colored liquid to the dish, which will make it easy to see the foot print of the wheel from the bottom of the glass.