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Originally Posted by KenWittlief
because the friction of the tread is a function of the downward force on it - so if you have two wheels, with a tread running between them, you wont get anymore friction that if you simply wrapped the tread material around the wheels separately (like a tire)
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Just a clarification of friction in terms of physics:
In an ideal situation with constant coefficient of fricions, and simple, constant surfaces, the surface area of the wheel (or tread) does not matter. Though a tread has more surface area, the weight is distributed over that wider area, and it cancels out.
However...
When a wheel (or tread) has grooves, knobs, etc. it is quite different. The ability of a wheel to dig into the carpet, greatly improves it's traction.
The soft, tready rubber wheels they gave us are really good a)because those rubber skyway wheels have good traction both on the carpet and on the HDPE, and they are large enought to easily go over the small steps. (I suppose that with a large enough wheel (>12in) you could go directly over the 6in step.)
Treads will only help if they can get you over the steps easier, because they provide traction over the whole length of the robot. We saw how wheeled robots can get hung up on the edge of the steps. Caveat Builders!