Bearing, shaft, etc.

Without knowing your exact design, it is difficult to discuss bearing and shaft. However, there are generally two approaches to attach the wheel to the chassis.

The first approach involves a stationary shaft. This works well for slowly rotating wheels. This approach is easier to implement because the shaft can be a bolt fixed on the chassis by nuts and washers.

The second approach involves a rotating shaft that is mounted onto the chassis via sleeves or ball bearing. This approach is more common with faster rotating wheels. It is more difficult to implement.