(Mid)west coast drive?

[Dan.Tyler]

As long as you are on ONLY the center wheels... You should have similar traction to the situation in which all of your wheels are driven.

The moment one of the blob driven sets of wheels touches the ground and stays carrying weight, you have less traction than if all were powered. The reason being that your weight is now being split between the two sets of wheels. So your coefficient times weight goes down, because that only refers to the weight on driven wheels.

[PAR_WIG1350]

There are 2 interactions occurring at the wheels that determine traction: 'simple' friction, and the more complex interaction of the engagement of the carpet and the tread. The former is dependent on the normal force applied on the driven wheels and the coefficient of friction. The latter is dependent on, among other things, contact area of the driven wheels.

The driven contact area will roughly be the same for both configurations (six wheels worth of contact), so the maximum traction from that interaction with only the centers driven is AT MOST as high as that as when all wheels are driven. Traction from friction will (almost) always be less when only the centers are driven. So, as far as traction is concerned, all wheels driven is preferable.

I don't know how it would help with turning, but you could test it if you have time to see if there is any improvement.

Now, traction and turning aren't the only factors involved. Weight, reliability, and maintenance should also be considered. When all factors are accounted for, it might benefit you, or it might not.

Another option is to only drive the middle and back, and shift your weight rearward. Assuming the center wheels are lowered, the front wheels would usually be off the ground so your traction would normally be the same as it is with all wheels driven. there would be brief periods where the traction is reduced, but it during forward acceleration and pushing (when it is particularly important) it would be maxed out.

[Pault]

Think about it this way: if you don't power the outside wheels, they will spin freely. So when someone pushes you from the front, they won't resist, they will just spin. However when somebody pushes you from the side, they will resist in the same way that a power wheel would. However, this also means that you will have more trouble turning, because when you turn the force is perpendicular to your wheels, resulting in the same effect of having it not matter if the wheels aren't driven. On the other hand, if your robot is light and you don't weigh it down, that will hurt your pushing power in all directions significantly and increase your turning ability.

It's up to you to decide how this info will affect your decision.