[RyanCahoon]

Originally Posted by squirrel

I suppose someone who wants to use an extra wheel for instrumentation could calculate how much force it needs to contact the floor with, to prevent it slipping under maximum robot acceleration conditions (it would slip if it takes more torque to overcome it's own inertia, than will be transfered to it by the frictional force of it's contact with the arena). I expect it won't take (much) more than it's own weight.

The point being, any normal force used to creating friction between the instrumentation wheel and the ground is normal force that's not able to be used to create friction between the drive wheels and the ground.

On a different note:

Our team is still considering different drivetrain options, but we've nearly decided on a six-wheel, dropped center wheel method if we follow a differential drive design, as the ability of the robot to rock slightly will allow the robot to not be as affected by transverse friction when trying to turn. We've tested a 4-wheel differential drive and while accelerating was not as difficult as one might think, turning was not as responsive as we would like. We're waiting for two more rover wheels to test out the 6-wheel drive.

--Ryan