4wd vs 6wd?

[Andy Baker]

Originally Posted by Yov

dropped down?
meaning the two middle wheels are lower than the others?

Yes, in most cases. For many FIRST robots that have used 6 wheel drive bases or tank tread drive bases, the middle wheel (or tread roller) is about 2-3mm (1/8") lower than the other wheels.

This has been the case if the robot has it's wheels positioned along the long dimension (36 inches~914mm) of the robot. On the other hand, if the robot is wider than its length and the wheels are positioned along the short dimension (30 inches~762mm), then that middle wheel may not need to be lowered at all.

Lowering the middle wheel allows the robot to turn easily. The front and rear wheels skid sideways easier when there is a lower middle wheel (some folks call this middle wheel a "bogey wheel").

Andy B.

<edit: wow... 4 posts, all written at the same time, all giving Yov the answer he needed>