Direct drive minibot - output diameter?

[philso]

We did something similar to what Roy's team did. Instead of drilling out the motor shaft hub, we hooked the motor up to a bench DC supply and held a file against the pinion gear until it fit in the motor shaft hub.

We put two of the motor shaft hubs back-to-back. We were able to find a pair of holes where the threads on the two hubs for the 6-32 screws matched up without binding on the second hub.

You can then use that to hold pieces of the gear box you have cast aside.

Phil