Hello PierongiaPete,

I have a multi-branch parallel shaft reduction gear design that I am patenting.  You might be able to use it.  The trick is to balance the loads on the shafts.  I have a way to do this without springs, flexible shafts or gears, etc.  With a triple reduction unit you can get a very high ratio.

Windward

PirongiaPete;

Every drive  type has its advantages and dissavantages. Harmonic drives have big ratios in one step, but are not very stiff, and somwhat inefficent. Harmonic drives are typically used for low HP service, often with servo motors. Ordinary, parallel shaft drives have efficency of 99% per stage. For 20:1, you need 2 stages and get 98% efficency.

Parallel shaft drives are a safe first choice. For special constraints, and ecconomics, other types may be better.

Multi-path systems, such as planetaries and split power path drives have higher power density and make more efficent use of mass and space.

There are always new ideas comming out, but nothing currently happening to sweep choices in a new direction.

This is a promising two stage gear train that will split the load and drive the output gear with two pinions. It was used to allow all plastic gears, whereas the single load path version demanded metal gears in the last stage:

1- Motor drives worm, which drives two opposite gears top and bottom.
2- Bottom gear (1) goes thru an additional spur stage to the ouput gear.
3- Top gear (2) is an idler that meshes with another gear (3). This gear goes thru another stage to the same output gear above.
4- Gear 3 needs to be synchronized to the output gear so that it works together with gear 1. A detail layout of center distances is needed to produce a synch relationship between gear 1 and gear 3. When gear 1 pinion is centered on the output gear, gear 3 pinion will be some fraction away from centered. Gears 1 and 3 need to synch marked.