Posted by Ted Jones at 1/15/2001 12:33 PM EST
Engineer on team #486, Positronic Panthers, from Strath Haven High School and Drexel University / Boeing Company.
In Reply to: hehe, wanna bet?
Posted by Anton Abaya on 1/13/2001 9:03 AM EST:
Our team discussed tank treads vs. wheels this weekend, and I came to a realization. Since friction is relatively independent of surface area, it appears tank treads would not buy you much in this competition. Friction is based on the normal force (weight) multiplied by the static friction coeficient. The static friction coef. is based on the nature of the two materials that are interacting, in this case the wheel/tread and the low-pile carpet that is the playing field. So, if surface area is not a factor, then I don't see how tank treads gain much over wheels in terms of maximizing traction. So why does the US Army have tank treads? Because Army tanks are designed to drive over soft, unprepared surfaces. The tread distributes the vehicles weight over a larger area, which deforms the ground less. This keeps the vehicle from getting bogged down in the mud. Think of a car in the snow, or mud, or sand, essentially any soft surface. For the competition then, I can't really justify using a tank tread system, unless you want to climb over obstacles that are lower than the top of tread. That, BTW, is another benefit of treads.
Given the time we have to design/build/test/fix and ship, I would spend more time finding an optimum wheel treatment to maximize traction. I plan on having our team conduct some experiments using a wheelchair wheel, a known weight, and the sample carpet, to find experimentally the static friction coefficients of various configurations. Once the coef is found, you can estimate the maximum pulling power of your robot, given its weight and power available.
Hope this helps,
Ted