Overview of Various Gear Types, Part 2

Technically speaking, a cluster gear isn’t a specific type of gear, but an assembly of multiple gears. Typically, it consists of two spur gears of different proportions being pressed onto each other to create a change in gear ratio. They move in the same direction at the same time. More than two gears of differing sizes may be used as well. Cluster gear configurations require less space since they fit multiple gears within smaller envelopes. They are also flexible, as the variety of gear ratios allows for better customization. Cluster gears can be found in many applications where space is a precious commodity such as manual transmissions, industrial machinery including pumps and mixers, and medical equipment.

This configuration consists of two components, the worm and worm wheel, that function as a meshing set. The “screw-like” worm consists of a shaft with a spiral thread that engages with and drives the toothed worm wheel, which is similar in appearance to a helical gear. Typically, they transfer power via perpendicular axes, but can only be driven in one direction. They can not be back driven, as this will cause them to lock up. The biggest benefit of worm gears is their high reduction ratio. They also run smoothly and quietly. When coupled with the fact that they can’t go in reverse, they are ideal for applications such as elevators, doors, hoists, lifts, and other uses where locking is needed. 

These conically shaped gears contain angled teeth and are used on perpendicular axes that will rotate in opposite directions.  Both gears in a pair have the same number of teeth, yielding a 1:1 gear ratio. As such, they are used to change axial motion/radial direction but not speed. This makes them ideal for applications where right-angle power transmission is needed such as robotics and drive train mechanisms.

Also conically shaped gears where the axes of the two shafts intersect or are used on perpendicular axes. Unlike miter gears that are two identical mating gears, bevels can have different features. Examples are number of teeth, diameters, and mating angles as long as the two gears remain perpendicular to each other axially. The teeth must have the same pitch and hold the same orientation restrictions as a miter gear set would.

With bevel gears, the direction of motion can be changed like other perpendicular axes gear sets. The torque and speed outputs can be changed too, and they are reversible. Since they can perform all these functions, bevel gears are found in applications such as car differentials, gearboxes, and power tools.