V. Ryan © 2001 - 2009

When faced with three gears the question can be broken down into two parts. First work on Gears A and B. When this has been solved work on gears B and C.

The diagram above shows a gear train composed of three gears. Gear A revolves at 60 revs/min in a clockwise direction.

What is the output in revolutions per minute at Gear C?

In what direction does Gear C revolve ?

 GEAR A GEAR B GEAR C 20 TEETH 60 TEETH 10 TEETH

First work out the speed at Gear B.

(Remember B is larger than A therefore, B outputs less revs/min and is slower)

Next, take B and C. C is smaller, therefore, revs/minute will increase and rotation will be faster.

What direction does C revolve ?

A is clockwise, B consequently is anti-clockwise and C is therefore clockwise.

Gear A revolves at 90revs/min. What is the output and direction at Gear C.

 GEAR A GEAR B GEAR C 30 TEETH 90 TEETH 15 TEETH

First work out the speed at Gear B.

(Remember B is larger than A therefore, B outputs less revs/min and is slower).

Next, take B and C. C is smaller, therefore, revs/minute will increase and rotation will be faster.

What direction does C revolve ?

A is clockwise, B consequently is anti-clockwise and C is therefore clockwise.