pic: DeWalt Gearbox with two CIMs

[dlavery]

This is a gearbox for a direct drive system I have been working on. It was inspired by team 1097s direct drive system (http://www.chiefdelphi.com/media/photos/20620). The gear ratio between the CIMs and the dewalt replaces the "final drive" ratio in a standard system. The gearboxes will be mounted on one end of the robot and a .5" drive shaft will run the length of the robot. The wheels will get power from the shaft through a several sets of miter gears. To avoid using U joints like team 1097 did I plan on using different thicknesses of tread or different sized wheels to get the center wheel offset.

OK, not to be too pedantic about this, but "direct drive" and "gearbox" are oxymoronic when used to describe the same system. A direct drive system is, by definition, one in which the load is coupled directly to the output shaft of the motor with no intermediate gear box or other torque/speed modification in the linkage.

Other than the terminology issue, this looks like a nice design. If you are going to go with the idea of a 0.5" drive shaft running the length of the robot, I would suggest that you consider using a torque tube rather than a solid shaft. A 0.1" wall torque tube 24" long with a 0.5" bore will save approximately 40% of the mass of a solid 0.5" shaft made of the same material (and even more if the torque tube is aluminum vs. a solid steel shaft).

-dave