The wheels and motor mounts for the Bucket Bot are homemade, and were created before these kinds of parts were more widely available. The next rev of this project will probably use off the shelf parts for this. The following approach worked well, though, and could save some money.
The motors came from Jameco
, but they are available in many places like Lynxmotion
now too. It uses 12v DC brushed motors, around 200rpm, but you can choose a voltage/speed/power combination to suit your application.
The motor mounting brackets are made from angle aluminum - getting those three motor mount holes lined up was the trickiest part. A cardboard template is useful for that. The aluminum angle was 2"x2", and was cut to 2" wide. These were built for a different robot, but for this one the wheels are under the platform, so they need a 1/8" spacer (made from plastic that was around).
The tires are Dubro R/C airplane wheels, and the center part was drilled out to use a big old 3/4" tap to thread that hole.
Next, use a 3/4" bolt, and drill a hole for the shaft along the length of the bolt from the head in. Getting that straight and centered is key. The higher grade bolts have marks on the head that help find the center, and a drill press was used to make that hole. On the side, a hole was drilled for the set screw. It was tapped with something like a #6 size tap.
Then, you screw the bolt into the wheel and mark where the bolt sticks out the other side of the wheel, remove it, and cut off the bolt with a Dremel tool to remove the excess. The bolt then fits in the wheel, and the set screw holds it on the motor shaft. The friction of the wheel on the big bolt was enough to keep it from slipping.