Engineering360: "Conic systems offers zero backlash harmonic gearing to replace planetary gear drives"

These may be very good motors, but I would like an explanation of how they can have zero backlash (and for life!).

My guess is it uses some some sort of spring-loaded tapered gear arrangement. If so, the gearbox may not be as efficient as a planetary drive because of the greater friction on the gear contact surfaces.

Harmonic drives have a wave generator ellipsoid on the driving side that slowly push around a flexible geared spline against an inner gear (like the one in a planetary gear). So, there are no traditional set of gear teeth that directly drive another set of teeth, so there's no blacklash.

https://en.wikipedia.org/wiki/Harmonic_drive