Engineering Mechanics

Chapter 34 : Transmission of Power by Gear Trains „„„„„ 699

2. Internal gears. Sometimes, the gear of the two shafts
   mesh internally with each other as shown in Fig. 34.4.
   Such a type of gear is called internal gearing. The
   larger of these two wheels is called annula wheel and
   the smaller one is called pinion.
   In an internal gearing, the motion of the two wheels is
   always like as shown in Fig. 34.4.


3. Rack and pinion. Sometimes, the gear of a shaft
   meshes externally and internally with the gears in a
   straight line* as shown in Fig. 34.5.

Fig. 34.5. Rack and pinion.

Such a type of gear is called rack and pinion. The straight line gear is called rack and the

circular wheel is called pinion. A little consideration will show that with the help of a

rack and pinion gear, we can convert linear motion into a rotary motion and vice versa

as shown in Fig. 34.5.

34.6. SIMPLE GEAR DRIVE

A simple gear drive consists of two shafts, containing wheels, with similar teeth, geared
together as shown in Fig. 34.6.

Fig. 34.6. Simple gear drive.
The wheel A is keyed to the rotating shaft, and is known as driver (since it drives the other
wheel). The wheel B is keyed to shaft, intended to be rotated and is known as follower or driven
(since it is driven by the wheel A). When the driver rotates, its teeth drive the teeth of the follower,
which rotate it in the opposite direction of its motion as shown in Fig. 34.6.

Fig. 34.4. Internal gearing.

* A straight line may also be defined as a wheel of infinite radius.