Comer Industries Planetary Drive Wheel Hubs, The use of planetary gear units in the field of power transmission is the modern answer to the demand for compactness, constructive simplicity and product reliability. PG/PGA planetary drives are made of 60% steel, about 35% cast iron and a lower percentage of aluminum, copper, rubber and brass. These percentages vary depending on the product configurations. PG planetary gear units are divided into 2 basic groups depending on the different torques that are to be transmitted to the out put shaft, which can vary from 0.5 to 65 kNm. In fact, the Planetary Drives product modular construction permits the coupling of bevel gears, worm gears, hydraulic brakes and a variety of input shafts to the planetary units, as well as providing for a wide choice of coupling flanges for hydraulic or electric mo tors. An other advantage of the planetary drives' modular construction is that various stages, in different sizes, can be mounted in series to offer a wide range of reduction ratios. Planetary Drive reduction ratios range from 3:1 to 7:1 on single-stage drives up to 10,000:1 and more on 5-stage drives. The wide selection of out put shafts and flanges simplifies the reduction unit mounting op er a tion on industrial machinery or plants.