A maker of hand-operated movers for boats and airplanes needed a motor drive able to provide a high power density. A quarterhorsepower parallel-shaft gearmotor proved too large and a servodrive was considered overkill.
The solution came through use of a new planetary gear reducer from Groschopp, Sioux Center, Iowa. It operates at input speeds to 4,000 rpm for servolike performance at about the same cost as a parallel-shaft gearmotor. In another application involving an RV slide out, the 377:1 ratio planetary gearmotor routinely operates (intermittently) at output torques to 1,200 lb-in.
The new planetary units target uses where less precision is acceptable but cost is important. The design meshes a sun gear with three planet gears. Such configurations tend to last longer than parallel-shaft spur geartrains and better handle larger continuous and peak torque. Tough involute gears are pressed net shape from a sinter-hardened, powder metal which eliminates secondary machining and the associated cost.
Another important design consideration is heat management because the amount of heat generated in a gearbox is proportional to transmitted power, gear ratio, and mechanical efficiency. The Motion Master 7300SA planetary unit is lubricated for life with an advanced synthetic-blend lubricant that remains stable at extreme temperatures. The lube lets the gearbox run cooler than those filled with grease but still permits operation at temperatures to 150F (60°C). A low internalfriction and high oil-viscosity index combine to reduce frictional power loss by 5% in some cases. No breather vent is required provided the reducer operates within specified thermal limits.
Groschopp engineers also specified a relatively higher gear-contact ratio as a means of lowering noise and boost torque capacity. Continuous-duty torque ranges from 90 to 700 lb-in. with corresponding peak torques three to five times these levels. This makes the reducer ideal for intermittent or slower applications at high torque levels.