Question

In a crank and slotted lever quick return motion mechanism, the distance between the fixed

centres O and C is 200 mm. The driving crank CP is 75 mm long. The pin Q on the slotted lever,

360 mm from the fulcrum O, is connected by a link QR 100 mm long, to a pin R on the ram. The

line of stroke of R is perpendicular to OC and intersects OC produced at a point 150 mm from C.

Determine the ratio of times taken on the cutting and return strokes.

Answer 1

Quick return ratio = Time of cutting/time of return = $\dfrac{a}{b} = 360-\dfrac{a}{a}$

OC =200 mm ,CP = 75mm

$\cos \dfrac{b}{2} = \dfrac{CP}{OC} = \dfrac{75}{200}$

$\dfrac{b}{2}= 68°$

$b = 136°$

QRatio = $\dfrac{360-136}{136} = 1.647$