[daltore]

Looks like 10 wheels.

Do the double wheels actually help at all with traction, or are they just for stability? Because friction force is dependent on an inverse relationship between coefficient of friction and normal force, if you add more wheels, adding to the over all friction coefficient, you're decreasing the normal force on each wheel by the same amount, so the effects cancel and you end up with the same amount of friction force. The reason more wheels are used for more traction is mainly an issue of distributing the force evenly to reduce the event of too much load on one particular part of the robot, which CAN result in slipping. Not too much problem with distribution this year because there's very little back-force on the wheels. Might as well use fewer wheels and use that spare weight to put some small steel bars a little closer to the floor.

By the way, if I'm wrong, please do correct me.