pic: Vex Face Bearing Gusset Gearbox

[aldaeron]

Originally Posted by asid61

The largest reduction could even be 70:14 if you use 3/8" hex bore gears.
If there was a way to easily align these across a tube, like some kind of C-channel acting as a square, you could just make a gearbox with oversized holes made with a step drill and a piece of versaframe.

Originally Posted by s_forbes

If you are going from a CIM, you can have a 12/72 reduction, or even an 11/72 reduction using vexpro's 11 tooth pinion gear (link).

The original design used 8mm to 1/2 adapters and was supported by a hex bearing and therefore required a hex bore gear. As Adam pointed out, using a bushing is a better idea and allows you to use CIM gears.

If you want a less aggressive first stage, you can still use the adapter and a hex bore gear.