Question

Find the ratio of the time of cutting to the time of return stroke from the following information: In a crank and slotted lever quick return motion mechanism, the distance between the fixed centres is 0.240 m and the length of the driving crank is 0.120 m.

(a) 3

(b) 4.5

(c) 3.2

(d) 2

I got this question during an internship interview.

My question is taken from Single Slider Crank Chain and its Inversions in section Simple Mechanisms of Machine Kinematics

Answer 1

Correct choice is (d) 2

For explanation: In a crank and slotted lever mechanism, symmetry can be observed. Using this symmetry and trigonometric ratios we find that vertical inclination of slotted bar is

angle = 30 degrees.

now 90- α/2 = 30

α=120 degrees

therefore ratio = 2.