Step 7: Motors & Wheels
The drill's chuck is held on its thread and in the centre there is a bolt, that is screwed but in the other direction.
The same method is used in my project, but you won't be able to central bolts. The wheels and the bronze bushes are unseparable now after some riding :D
The motors are held to the side caps using two screws each. It all depends on the type of drill you buy and may vary.