398 APPLIED MECHANICS 
move over equal distances, starting from A at the beginning of the 2nd 
interval and reaching B at the end of the 5th, interval, and during 
the remaining intervals the follower is to have harmonic motion, return- 
ing from B to A. _ It is required to find the positions of the follower 3 
corresponding to the positions of the cam at the end of each of the equal 
intervals of displacement of the cam. The construction is clearly shown 
in the figure. DE is a straight line. FHC is a sine or harmonic curve 
constructed in the usual way, as shown. The ordinates of ADEFHC give 
the positions of the follower corresponding to the abscissze which give the 
displacement of the cam. Considering AC as a time base, the diagram 
ADEFHC is a space-time diagram for the follower. 
Fig. 634 shows in a similar manner the case where the tallesiene is to 
rise half the distance AB with uniform positive acceleration, and to 
complete its travel to B with 
uniform retardation or uni- . 6B 6B 
form negative acceleration. 4 7) 5 
The curve AED is made up , x 
of two parabolas, AE and A 24 E 
ED. The parabola AE has 2) C2a oh : 
AB for its axis and A for its 9X12 43.6. °A 12845 91 6 
vertex, and the parabola ED 
has CD for its "ie and D ee se 
for its vertex. The usual and most convenient construction for drawing 
the parabolas in this case is shown in the figure, 
In Figs. 633 and 634 the movements of the follower have been found 
for equal movements of the cam, but from the same diagrams the move- 
ments of the cam for equal movements of the follower can be found as 
shown in Fig. 635, which is the case illustrated in Fig. 634. 
When the follower has angular motion, as in Figs. 628, 630, and 632, 
the length of the straight line AB in Figs. 633, 634, and 635 must be 
equal to the length of the arc AB in Figs. 628, 630, and 632, and the 
subdivisions of the are AB in Figs. 628, 630, and 632 must be 
equal, each to each, to the subdivisions of the straight line AB in Figs. 
633 and 634, that is, the are AB must be divided similarly to the line ae 
on the space-time diagram. 
335. Plane Sliding Cams.—The flat plate AC (Fig. 636) has a re- 
ciprocating horizontal motion in its own plane, and its upper edge works 
in contact with the lower end of the follower AB. The follower is guided 
fat a ) 
12345678 9 10 '| 2.3 205 6.9 8 Sl10s6 
~w 
wo 
; Ty 
4 
i 
T 
| 
i} 
1 
DU JUDUOUENUAUUUOCOLORESUCSUUUUASEONTURERMBEODEDIORIS  TEOUUVEEEUSULOUUORURTOCUGUUAUDUCUGDSOORENUITUSOHUUREGDEDBOREDIOOE 
Fig. 636. Fig. 637. 
in a vertical direction, and rises and falls as the cam plate reciprocates. 
The foree to lift.'the follower comes from the cam plate, but in this 
example the force which brings the follower down is independent of the 
cam, and may be the action of a weight or spring. The cam, however, 
———- oe 
ee 
