This curve of the polynomial family (n=1) is the simplest of all. It has a straight-line displacement curve at a constant slope giving the smallest length for a given rise of all the basic curves. The displacement is uniform, the velocity is constant and the acceleration is zero during the rise. But, at the ends where the dwell meets this curve, we have an impractical condition. That is, as we go from the dwell (zero velocity) to a finite velocity we have an instantaneous change in velocity, giving theoretically infinite acceleration .This acceleration transmits a high shock throughout the following linkage-the magnitude depending on its flexibility. In other words, we have a “bump” in the contour which neither a roller nor other follower could follow. With a dwell-rise-dwell cam, this curve is therefore not practical.
Characteristics:
Let h=maximum displacement of follower.
β=cam angle rotation for rise h, radians.
The displacement of follower
y=hθ/β
Differentiating in the range of the curve for the velocity and acceleration, we find
v=dy/dt=hω/β=a constant.
a=dv/dt=0.
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