[ConKbot of Doom]

3/8" shaft must be supported on both sides, you can probably do without the extra support with 1/2". In 2005 we used 3/8" shaft with the skyway wheels, and slowly the axles bent upwards. They would be fine if it was just our robot driving around on the flat surface, but it had to content with other robots weight some of the times, and being leaned back onto 2 wheels for getting it up onto the cart, etc... Luckily, we just had to undo some bolts, take off some shaft-locks, and slide out the old axles, put new ones in, put wheel and shaft locks on, tension up the chain, and tighten the bolts back up.