Robot Wheels

There are all sorts of wheels available for small robots online. But you can also just make wheels yourself. And then you can make them to different sizes and widths.

A few hints:

They work better with something rubbery around the outside. Like a rubber band. And the rubber band(s) will stay on if you make the wheel just a little bit larger than the rubber band is at rest. So look for fat, wide, rubber bands that are about 2 to 4 inches. Weatherstripping also works. Or slices off an old bike inner tube. If all else fails, you can try for an even bead of hot glue.

Assuming they are going on a continuous rotation servo, the servo feed horns have special castilations and shapes to lock in to the servo shaft. Don't make a wheel for the servo shaft, make a wheel for the feed horn.

Standard elmers or other glues make cardboard and paper really, really strong. Especially if you use multiple layers and alternate the "grain".

Cutting a really round circle can be difficult. You can also spin them before you attach them to the servo and sand off the outside edge to make them more round.

Smaller wheels make the robot move slower, but it will pull more and be easy to control. Larger wheels are fast, but not strong, and it can be difficult to run.

Other ideas include

lego wheels (kind of hard to get centered and well attached to the feed horns.)

Bottle caps (again something rubber around them helps)

Old / broken toys can donate wheels.

If you can find something round to mold it in (bottom of a small water bottle?) you can try this cool stuff called oogoo