Would it be feasible to design a passive CVT gearbox that converted input rpm into an output of always N by splitting the input (such as is split in a helicopter transmission) then inverting the speed from one split-torque gear to merge with the input from the other (both inputs undergoing several transformations) for instance in the ring of a planetary gearset?


1 Answer 1


If I understand correctly what you are looking for (and provided that I translated it correctly), then a power-split transmission or power-distributed transmission should get pretty close to it.

It's a common transmission in tractors. Basically the rotation from the engine gets split into a mechanical part that ends in a planetary gearset and a hydraulic CVT that drives the ring gear of the planetary gearset. Via appropriate settings of the hydraulic CVT, you can control the RPM of the mechanical driveshaft continuously down to 0 RPM, that is, the ring gear turns against the sun gear and exactly cancels it out.

Your application sounds to me like looking for the reversed process, but maybe the concept is helpful.

I don't have a picture at hand right now, but can add one later.

  • $\begingroup$ Great answer. I see the Vario and Bosch Rexroth: A41CT are more or less similar to what I had in mind. Would you hazard how much hiring en engineer to design it would cost, and if this is a task for a freelance engineer or a team? Say input is 15 kN•m at 1500 rpm. $\endgroup$ Oct 15, 2022 at 15:27
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    $\begingroup$ To be honest, I lack the experience to estimate the cost of such a project. But considering that the torque range you are looking for by far exceeds that of some of the largest tractors (Fendt Vario 1050: 2400 Nm) or construction machines (Liebherr L586: 2000 Nm) in the world, this would probably be a development from scratch, done by a large, experienced team, costing millions. $\endgroup$ Oct 15, 2022 at 17:59

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