I've been avoiding designing with bevel gears due to the complexity of modeling them but my latest design for the weapon transmission on my 30-lb combat robot (MegatRON) called for a right-angle transmission so I said "why not, let's learn". The goal was to replace the direct-drive hubmotor solution with a right-angle gearset driven by slim inrunner brushless motor nestled between the arm and the blade. A 4:1 reduction of 1.5 Mod gears fit within the existing volume and allowed me to maximize my bearing sizes for the rotor.

I started planning the interfaces as most engineers would; download a CAD model from McMaster-Carr or KHK, import into SolidWorks, and begin adding features as desired. When I was about to finalize my design, I realized the 3d model tooth profile was less than ideal, a trapezoidal approximation of the involute profile. This assembly would be rotating nearly 50,000 RPMs on the pinion side and I was fearful for excess vibrations and tooth chipping on impacts. To make better gears, I had to model my own gears using Tregold's approximation. Gears machined from prehard 4140.

The fabricated result was phenomenal; smooth running and tunable backlash using 100 micron shims. Testing video linked here.

I took MegatRON to the National Havoc Robot League (NHRL) June qualifying event. The field was stacked with competitors from across the world but I began the day with quick win and solid test of the new right-angle drive. See the match here and the rest of the competition from their Youtube channel!