The swing drive consists of a drive motor, a milled bevel gear and a set screw:
The drive motor is a 12V 50RPM gear motor. The set screw is M4. I'm going to use one that is slightly longer in the final version (10mm long).
Ebay links:
- Motor:
http://www.ebay.com/itm/321622024429
The gear is milled from a 12mm aluminum sheet, where 6mm is the gear and the other 6mm is the part where the set screw sits. The set screw hole was drilled with a 3.5 mm drill and the tapped to M4 thread.
I 3D printed a test plate to find the right fit for the gears before milling the real bottom plate of the excavator:
