12.25 Number of contacts per revolution

For a single pinion in mesh with a single gear, each member has one contact per revolution. Some gears have more than one cycle of load contact per revolution. An epicyclic gearset (planetary or star gear) is shown below:

PIC

PIC

In this example, if the pinion is the driver or is driven, it has 2 contacts/rev. If the pinion is an idler, it has 1 contact per revolution and reversed bending. The mating gears each have 1 contact/rev.