Planetary Hydraulic Winches vs. Worm Drive Winches:
The diagram shows planetary-type reduction is a very efficient type reduction since there is very little sliding friction between the teeth of the gears. By comparison, worm drive reduction has a lot of sliding friction between the worm and the main gear. Planetary gear reduction is limited in the amount of reduction in one set of gears relative to a reasonable diameter size. Hydraulic gear motor: In the diagram, red indicates hydraulic oil pressure pumped to the motor which is caused by the shaft resistance or torque required to do the job. The blue indicates the return pressure it takes for the oil to flow back to the reservoir. Winch manufacturers may use 2 or more sets of planetary reductions in series to get the amount of overall reduction they want without the drum being too large in diameter. By putting planetary reductions in series there would be a multiplying of the 2 reductions. Since this explanation is about planetary reduction you can see how a hydraulic motor with its RPM and torque can be used to drive the drum on hydraulic planetary winches. The shaft of the hydraulic motor is attached to one of the gears in the motor diagram above. The theoretic torque on the drum to do the job 10,000 lbs. x 5″ radius which is 50,000 in. lbs. of torque. If we have an overall planetary reduction of 40:1, then the input torque from the hydraulic motor would be 50,000 in. lbs. / 40 = 1250 in. lbs. torque. This example does not take in to account the frictional losses in the planetary gears and the inefficiencies of the hydraulic motor. Some hydraulic winch manufacturers use the theoretic calculations for the publicized drum torque.