Thus it appears that there is more sliding action upon the teeth of the smaller than upon those of the larger wheel, and this is a condition that will always exist.
Fig. 44.
In [Fig. 44] is represented portion of a pair of wheels corresponding to those shown in [Fig. 42], except that in this case the diameter of the generating circle is reduced to one quarter that of the pitch diameter of the wheels. v is the driver in the direction the teeth of v that will have contact is c n, which, the wheels, being of equal diameter, will remain the same whichever wheel be the driver, and in whatever direction motion occurs. The amount of rolling motion is, therefore, c n, and that of sliding is the difference between the distance c n and the length of the tooth face.
If now we examine the distance c n in [Fig. 42], we find that reducing the diameter of generating circle in [Fig. 44] has increased the depth of flank that has contact, and therefore increased the rolling motion of the tooth face along the flank, and correspondingly diminished the sliding action of the tooth contact. But at the same time we have diminished the number of teeth in contact. Thus in [Fig. 42] there are three teeth in driving contact, while in [Fig. 44] there are but two, viz., d and e.
Fig. 45.