Engineering Mechanics

Chapter 34 : Transmission of Power by Gear Trains „„„„„ 701

34.9. TRAIN OF WHEELS

Sometimes, two or more gears are made to mesh with each other, so as to operate as a single
system, to transmit power from one shaft to another. Such a combination is called gear train or train
of wheels. Following are the two types of train of wheels depending upon the arrangement of wheels :

1. Simple train of wheels, and


2. Compound train of wheels.

34.10.SIMPLE TRAIN OF WHEELS

Sometimes the distance between the two wheels is great. The motion from one wheel to
another, in such a case, may be transmitted by either of the following two methods :

1. By providing a large sized wheel, or


2. By providing intermediate wheels,
   A little consideration will show, that the former (i.e., providing large sized wheel) is very
   inconvenient and uneconomical; whereas the latter (i.e., providing intermediate wheels) is very
   convenient and economical.

It may be noted that when the number of intermediate wheels is odd, the motion of both the
wheels (i.e., driver and follower) is like as shown in Fig. 34.7. (a). But, if the number of intermediate
wheels is even, the motion of the follower is the opposite direction of the driver as shown in
Fig. 34.7. (b).

Fig. 34.7. Simple train of wheels.

Now consider a simple train of wheels with one intermediate wheel as shown in Fig. 34.7 (a).

Let N 1 = Speed of the driver

T 1 = No. of teeth on the driver,

N 2 , T 2 = Corresponding values for the intermediate wheel, and

N 3 , T 3 = Corresponding values for the follower.

Since the driver gears with the intermediate wheel, therefore

2

1

N

N

=

1

2

T

T ...(i)

Similarly, as the intermediate wheel gears with the follower, therefore

3

2

N

N

=

2

3

T

T ...(ii)