The Model 22S/GM Series dc servo "true planetary" gearhead is
about half the length of most conventional gearbox designs in
the same frame size and ratio. It typically puts out only 50 to
60 dB of noise, compared to >85 dB that is typical of
conventional gearhead designs. The 22S/GM, from Dynetic Systems
Corp., Elk River, Minn., sells for less than $100 per stage,
including the motor, at the 100-unit level. Its gear meshing is
such that no-load current draw is about a third of what is
typically required to turn ordinary gearboxes. Little torque is
wasted turning the gears, resulting in a system that runs
smoothly and efficiently.