Large reduction gearboxes are made to channel high torque by lowering the high input speed to the wanted output speed. This is the reason gearboxes are commonly used for heavy industry driving conveyors, crushers, mills and pumps. The gears in a gearbox are manufactured with high accuracy. Because of the high accuracy, professional technicians with training experience are required for gear assembly and install the gearboxes. It is common for simple reduction gearboxes to have multiple stages that includes bevel and pinion gears for both drive and input direction changes, along with multiple helical gears with differing ratios to reach the desired output.
The main objective is to have the gearbox function as quietly as possible. To help reach this goal, helical gears are usually used preferably over cross-cut gears to cut down the audible gear mesh noise. Helical gears are a great for power transmission as well as durability and a quiet operation. However, a downside to this design is the angle of the gears. There will always be a resultant axial force that needs attention because of the angle.
When in operation, the gear design will not create axial loads. For the more common helical and bevel pinion gears, the resulting axial needs to be borne by the bearings supporting the gear. The most common choice of bearings is determined by the load carrying capacity and theoretical bearing life. There are several different bearings available. Each has their own unique, load carrying characteristics. It is important for these characteristics to be understood as well as the application load characteristics before installation.
Bearing loads can be solely radial, axial, or a combination of both. Bearings are designed to handle different loads, with most of them holding the ability to accommodate a combination of loads. For example, a ball bearing is designed to support radial loads, but it is also able to accommodate axial loads. This makes a ball bearing a great option for electric motors. Another bearing example is a cylindrical roller bearing, which can eliminate cross location.