Gearboxes, also known as gear drives, speed reducers and gear reducers, are mechanical devices that control a load at a fixed ratio of motor speed. The output torque is also raised by the same ratio but the horsepower remains the same hence less efficiency losses. Right-angle gearboxes are often made with worm or bevel gearing. Worm gearboxes feature mating gear on the output shaft and a gear type known as worm on the input shaft. They can change the drive by 90 degrees. Helical gears
, on the other hand, have slanted tooth traces on the spur gear making them stronger and more efficient than spur gears
for power transmission. The helical worm gear reducer reduces input speed from the motor to the worm-gear set thereby keeping the worm gear reduction ratio and size low enough for maximum efficiency. The combined efficiency of worm and helical gears ranges from 79% (300:1 speed reduction ratio) to 90% (5:1 ratio). Helical worm gear reducers have parallel axes between the small contact areas and the gear teeth which keeps the heat and friction low.