[Mark Sheridan]

Your pulley will probably will get damaged from ground debris.

We ran 3.5" colson wheels this year with a west coast drive. with the 1" by 2" box tubing frame, we had 0.5" of ground clearance. For us this was right at the threshold of getting hung on debris or the steel plates under the carpet at the pyramid corners. So if there was a wad of tape or a piece of broken #35 chain at the pyramid corner, we usually would get hung up on it.

So if you want to run 3" wheels, you need this on some low profile pillow block or something to create space for the frame. Also, you will have the pulley touching objects on the ground. I think you will risk unnecessary wear and tear on you pulley and belt from running over debris. Lastly, I think your wheel will compress the carpet a bit so the flange of the pulley will touch the carpet. Colson wheels wear a bit to, so the gap will be reduced. So you may find your self your supporting the robot with your pulley more than your wheel.

Going up to and 3.5" to 4" wheel should solve most of these issues. Personally, I would stick with 4" but there are several teams that run 3.5" wheels effectively.