Omni Wheel Configuration

[Madison]

Originally Posted by thursam

Is that everything, or is there anything else that we would need? We found a diagram for a basic drive system, but we don't need some of it.

Okay, generally --

You need a gearbox with appropriate gearing for 8" wheels. You probably want something in the 12:1 range.

You'll probably need form of power transmission between the gearbox output and your wheels. This is usually chain and sprockets or belt and pulleys. It could also be gears. The power transmission component that turns your wheel's axle will have to be bored appropriately.

In FRC, a live axle is either a hex shaft or a keyed round shaft in nearly all cases. If you're using a hex shaft, you just need a hex bore in your sprocket or pulley and a hex hub attached to your wheel. If you're using a keyed shaft, you'll need a keyed bore on the sprocket and a keyed hub for the wheel. You'll also need a machine key -- a square piece of steel that sits between the shaft and the hub and transmits the torque between the two of them.

You'll probably need shaft collars or some form of retaining rings to stop the wheel and sprocket/pulley/gear from sliding around on the shaft axially. You want to use spacers for this as well.

Folks don't usually use a drive made entirely from omniwheels because it offers almost no resistance to be pushed sideways by a defender. If your strategy relies upon constant mobility around the field, being susceptible to defense may not be a big tradeoff. If any function of your robot requires you to stop in place (to aim, to score, to collect, to catch), an omniwheel drive may be a large liability.

The upside, of course, is that you can swap in a pair of traction wheels for a pair of omniwheels pretty easily and that'll give you some additional resistance to being pushed, spun in place, etc.