Mechanical Engineering - Theory of machines - Discussion

Option D is correct because in Whitworth quick return mechanisms the smallest link is fixed which lead to turning pair.

Smallest link will be fixed (crank). So answer D is correct.

Its correct what @Rahul said. Whitworth quick return mechanism is the 2nd inversion of slider crank mechanism. So, in 2nd inversion fixed link is the crank which is the smallest link in the mechanism.

Yes I agree with @Rahul its wright Whitworth return motion mechanism is formed when crank or smallest links fixed.

Whitworth quick return motion is a 4 bar mechanism i.e. crank, slider, coupler, slotted bar. In this mechanism slider can slides into the slotted bar while the crank makes 360" rotation.

So, here the crank (input rotation) is not fixed as well as slider (slides) and slotted bar (oscillates) also not fixed because these are all having motions with respect to each other therefore the only link we must fix to rotate crank 360" is coupler.

In whitworth quick return motion mechanism crank(smallest link) is fixed. In Crank slotted lever mechanism Coupler link is fixed. So The ANSWER given is WRONG.

Coupler/smallest link i.e. crank is fixed, as it is second inversion of four bar linkage.

The right answer should be (D) - Smallest link is a fixed link.

With-worth quick return motion mechanism is a inversion of simple single slider mechanism with lower pair when we fixed the shortest link which is known as crank.

Because in single slider mechanism inversion there are two mechanism is possible when we fixed the crank one is with-worth QRMM and second one is rotary IC engine (GNOME engine).

Therefore according to the question given answer is wrong and correct answer is when shortest link is fixed.

Crank and slotted lever - connecting rod fixed.
Whitworth QRM - crank is fixed.