pic: Traction test

[meaubry]

A few thoughts about this -
Given a perfectly level surface and a rigid chassis - how many contact points would there be on the 4 wheels vs 8 wheel? 3 points determine a plane.

So, given that the chassis and wheel assembly might very well flex a bit, and the surface may not be perfectly flat - the # of contact points and the amount of force could vary between the 4 wheel and the 8 wheel.

As stated earlier, the normal force will be divided among the number of contact points - contact points are more relavent in this case than surface area.

I believe the difference that made the 4 wheel win, is due to the 4 wheel having more contact pressure per wheel in contact, and that the gearing reduction caused that machine to slip less than the 8 wheel. I know you indicated that both machine slipped right away, but I don't think that both slipped at the same rate. My guess is that the 4 wheel slipped slightly less.

Just my 2 cents worth,
Looks like you're having fun

Mike Aubry