These instructions show you how I attach a Lego wheel like this to a motor like this (We call these motors Sanyo copies, because are all similar to the first ones of this type that we saw which were made by Sanyo). Warning: before you go any further, I use a lathe to make the part, so if you don't have a lathe it's going to be very difficult to replicate my technique. Many roboteers just glue their wheels on.

1: Here's a typical Sanyo copy. It's best to get one that rotates at about 300rpm at the voltage that you're going to run it at for (in my opinion) the best balance of speed with control).

2: Here's what to do in reverse order (!) with everything attached.

3: A different angle. The wheel is known as a "Black Tire 30.4 x 14 Offset Tread" and bricklink.com is an excellent way to buy small quantities of spare Lego parts at reasonable prices.

4: Just the wheel this time. In later versions of this design I use a grub screw, which seems to be better at getting very tight: Allen keys let you apply more torque than a Philips screwdriver will.

5: Another angle. I cut the wheel with two slots using a junior hacksaw and then just wiggle the resultant piece of plastic until it breaks off. I then drill a 2mm hole into the plastic and mark the steel collar, so I know where to drill my 1.5mm hole into it later.

6: Finally the collar that does most of the work. I make these on my lathe. External diameter 5mm to fit inside the wheel, inside diameter 3mm to fit over the motor shaft. I then drill a 1.5mm hole and tap an M2 thread. I used to machine these out of aluminium but they were too soft and the thread used to strip, so these days I use M8 steel bolts and machine them down.

Disclaimer: Building robots can be dangerous, any damage caused by following these instructions must be your own responsibility. Please take care.

Also note that Lego and Sanyo are trademarks of their respective owners. This site has no affiliation to either Sanyo or Lego.