These instructions show you how to attach a featherweight robot wheel (in this case a 125mm diameter wheel) to a drill motor. It's just my made-up technique and it may be far from the best method. We'll see how good it is once the robot's been in a few fights.

1: A 16mm diameter aluminium bar

2: Machine off the rough end

3: Use a centre drill to start the hole off right in the centre

4: The centre hole drilled

5: Time to drill a 12mm hole to about 10mm, this will fit over the collar of the drill.

6. Hole drilled.

7. Then drill another hole 8.5mm diameter a further 18mm deep into the alumnium bar.

8. Tap the hole with a 3/8 UNF thread

9. Screw the bar onto the drill.

10. A look at the end of the drill motor.

11. Punch a hole at the side of the aluminium rod. Make sure you have at least 2mm (plus the 2.25mm diameter of the hole you're about to drill) between the edge of this new hole and the edge of the rod.

12. Drill a 4.5mm diameter hole

13. The hole drilled.

14. Machine the rod down to 0.2mm larger than the internal diameter of the wheel.

15. Part the piece from the rod (cut the thing you've just machined off the bar), tidy up the end and put some fairly deep scores in the aluminium. This should stop it turning when it's in the wheel.

16. place the piece in the wheel and with something not made of metal (I used a delrin bar) between the piece and a mallet, firmly persuade it to slide into the wheel.

17. Stop before the transverse holes in the aluminium get too close to the wheel: you won't be able wo screw a nut on if there's not room.

18. Nearly complete. I need to get some nyloc nuts to make sure the bolt doesn't fall out. I hope this stands up to the rigors of robotic combat.

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