Pulley gears & timing belts

Here are a couple websites that have them:

Small Parts has a good selection and a friendlier website. MSC has lower prices. If you order from MSC, ask for the "Big Book". It is a goldmine of robot parts. The Small Parts catalog is pretty good too. Sometimes I thumb through it looking for nothing in particular, just to get inspired.

I don't know of anyplace that sells kits. But they come in standard pitch sizes and widths, so as long as the wheel and belt have the same pitch size and width, you should have no problem. Another option is flange or no-flange. In in doubt, get the flange, it will help keep the belt from slipping off the wheel.

Some of the wheels are metal (usually aluminum, but sometimes steel) and some are plastic or fiberglass. For robotics applications you probably want fiberglass or plastic. It will be strong enough, but will cut down on the weight, and lower the inertia for stopping and starting. The heavier metal wheels are better for machines that run continuously at a constant speed.

What size are your stepper motors? Is this for driving the wheels, or some other part?

Stock Drive Products.

Good stuff. Some times you have to request a price quote but the prices are actually pretty low. Dollar or two for plastic w/metal insert timing pulleys, depending on size.