pic: Experimental VP drive gearbox

[Deke]

Another thing to consider when going through these exercises is that generally a planetary gear system will be less efficient than a spur gear system.

This may not always be the case, but there are usually more interfaces and bearing surfaces that create more friction in the planetary system. The planetary shines with its packaging for high reduction instances, where a spur gear system will take up more room for the same reduction.

A side note for the VP load cases. If you use a 3, 4, or 5:1 as the output stage is the VP, the hex shaft will fail before the stage will. Those are the three strongest stages, we did some rough solid mechanics calculations on it this year for our intake rotation. However, the gears are more brittle and if we twisted the hex shaft, the gears exploded due to the hardness, but usually the hex shaft twisted before the gear box exploded. The shaft is more ductile than the gears. I would be concerned about shock loads in a drive train if you are geared too high with the ratios. If the gearing is low enough, it should reduce that concern.