GEAR

GEAR DIRECTION

Gears can be used not only to multiply torque, but also to change the direction torque is applied. When two gars are in mesh, the direction of rotation is reversed. That is, if one gear turns clockwise the meshing gear turns counter clockwise.

If we want the direction of rotation to be the same, we must use three gears. If we place a gear between two gears as shown in, we can get the outside gears to turn in the same direction.

The gear in the middle is called an idler or floating gear. It is free to turn on an idler shaft. When gear A is turned counter clockwise, the idler gear turns clockwise and drives gear B counter clockwise. Since the idler gear “floats” it does not affect the gear ratio between gear A and B. Any number of gears can be used in a transmission. An even number of gears (1,4,6, etc.) always reverses the direction of rotation. An odd number (3,5,7, etc.) will keep the same direction of rotation.