I have two largish (15 cm) surplus Pittman motors, which I'm trying to cram into a circular shell 24 cm across in order to power the two primary wheels (for a differential-drive robot). Obviously I can't just lay them out side by side; I'm going to have to have one motor in the front, and the other in the back, which means connecting to the wheels via gears, chains, or belts.
Of these options, I like gears best and chains least. But now I'm at a loss -- where would I find reasonably-priced gears beefy enough to suit these motors? I'm expecting this to be a fairly heavy robot, which is why I'm glad to have such strong motors. The axle-to-axle span of these gears only needs to be about 4 cm, but it's no good if they're skinny little axles that introduce an obvious weakness compared to the rest of the system -- the gears built into the motor assemblies are all 5 mm thick or more.
So, in brief: I need (for each wheel) a pair of gears with a total radius of 4 cm or so, and a thickness of 5 mm or more. (I'll also need fitting shafts and bearings, but presumably those are easier to find than the gears themselves.) Any suggestions?