400 APPLIED MECHANICS 
follower for the cam shown in Fig. 642 has angular motion about the axis 
O, and would have the form shown in Fig. 628. | 
AB, the path of the end of the follower in contact with the cam, is 
first divided into parts, which are the displacements of the follower for 
Fig. 640. Fia. 641. 
equal angular displacements of the cam. The parts of AB are deter- 
mined, as explained in Art. 334, to suit the particular kind of motion 
which the follower is required to have. The cam is now supposed to 
remain at rest, while the path AB of the follower is revolved about the 
axis C of the cam into as many 
equidistant positions as there 
are points of division on AB. 
It should be noted that two 
or more points of division on 
AB may coincide. The next 
step is to swing round, from 
the centre C, the various points 
of division on AB to intersect 
the corresponding positions into 
which AB has been placed round 
the fixed cam, as is clearly shown 
in Figs. 640, 641, and 642. A 
fair curve drawn through the 
points determined in this way 
is the pitch line of the cam. 
If the follower is provided with 
a pin, or a pin and roller, the 
outline of the cam is determined from the pitch line exactly as described 
in the latter part of the preceding Article. 
Figs. 643 and 644 show how a plane rotating cam is designed to 
work against followers. of the form shown in Figs. 631 and 632 respec- 
tively. As in the three cases just considered, the cam is supposed to 
remain at rest, while the follower is made to revolve about C, the axis of 
the cam, into as many equidistant positions as there are points of 
