Page 49 - Cam Design Handbook

THB2 8/15/03 12:48 PM Page 37

BASIC CURVES 37

2.7 SKEWED CONSTANT
ACCELERATION CURVE

The asymmetrical constant cam acceleration curve (follower motion) is shown in
Fig. 2.5. The acceleration curve is made up of two parts, the positive and negative
acceleration periods 1 and 2 connected at the transition point
y = Cq 2 ( 0 £ £ ) (2.25)
q
b
1 1 1
- )
-
q
hy = C (bq 2 (b ££ ) b (2.26)
2 2 1
where
C 1 and C 2 are constants
h 1= displacement at the transition point, in.
b 1 = angle of rotation for rise h 1, radians
Substituting in Eqs. (2.25) and (2.26) yields
h = C b and (2.27)
2
1
1 1
-
- )
hh = C (bb 2 (2.28)
1 2 1
Combining Eqs. (2.27) and (2.28) yields
(
2
-
C b + C b b ) = h (2.29)
2
11 2 1
Jerk y''' = • Velocity, y' Transaction point Dwell

Displacement, y

Acceleration y"

y, y', y", y''' h

h 1

0
Cam angle q b
Dwell b 1

Jerk, y''' = • Jerk, y''' = •

FIGURE 2.5. Skewed constant acceleration curve—DRD cam.