Answer to Question #301072 in Mechanical Engineering for Pawan

Question

In a crank and slotted lever quick return motion mechanism, the ratio of maximum

velocity at return stroke to the maximum velocity at cutting stroke is 2. If 25cm is the

stroke length, find (a) slotted lever length, (b) the ratio of time of cutting to return

strokes, (c) If the crank rotates at 30rpm, what is the maximum cutting velocity per

sec.

Answer 1

$(a)\ \dfrac{x}{25} = 2$

$x = 50\ cm$

$(b)\ \sin\dfrac{25}{50}= \sin({90-\dfrac{\theta}2)}$

$30° = 90 -\dfrac{\theta}2$

$\theta= 120°$

ratio of time of cutting to return strokes = $\dfrac{180-\theta}{\theta}$ = $0.5$

$(c)\ 30\ rpm × 2 = 60\ rpm$