Much like Sanddrag, our team used keyed shaft on our competition robot, though we did use 5/8th shaft instead of the lighter 1/2, it wasn't a strength issue, we just had the extra weight and had 5/8th keyed on hand when we built the chassis, so the robot got a little heavier drivetrain. On our practice robot (which is a 30 by 36 in square of 1x1 (1/8 in thick) aluminum angle. For those axles, sice we were just messing around with it, we bought sprockets, drilled them out, and bolted them to some skyway wheels. for the actual axle, we used some scrap barstock (I mean scrap...it was anywhere from 1/4 to 5/8 diam. because it was in a former life a practice piece for lathework), and we just drilled little 1x1in blocks of extruded alum. to act as pillow blocks (yes that bound up often, I don't advise it, it was just make-shift). In previous years, certain (not the drivetrain, but other axle-d items) parts have used brass bushings instead of bearings and pillow blocks, but we generally stay with pillowblocks on the robot.