[daltore]

Our team has been looking at Colsons. Last year we had 4-inch IFI wheels with wedge-top for low-weight and low center of gravity, but we also wanted to go fast, so our wheels ended up rotating at about a thousand RPM, and we had to replace a set of treads (that's 6 treads for us) at lunch on practice day, and we've had to replace them again since then. The Colsons are a great solution, at about $5 a wheel, they're MUCH cheaper than almost any other good robot wheel, and they offer a pretty good amount of traction if you get the Performa rubber type, and they also last a LONG time. Two other companies that offer similar wheels are NPC, which are made for battle bots, but are much more expensive and don't have quite the life of Colsons, and Banebots, but their treads wear off like a Firestone tire. These wheels are used in the battle bots world more than almost any other wheel, and most of the people I've talked to love them. If you make a custom hub in the middle out of delrin or aluminum, you can put a key between it and the wheel, and then key it so it fits on a 1/2" or 5/8" shaft, to which you can connect a sprocket. Simple, fewer moving parts (bearings) than the IFI wheels, about the same weight, and very rugged.