In the Whitworth quick-return (crank-and-slotted lever) mechanism obtained as an inversion of the slider–crank chain, which link must be kept fixed to produce unequal cutting and return strokes characteristic of quick return?

Question

Solve this multiple-choice question and choose the correct option.

Curioustab · Accepted Answer

Introduction / Context Quick-return mechanisms allow the tool (or ram) to spend more time on the cutting stroke and less on the return stroke, improving productivity. The Whitworth mechanism is a classic inversion of the slider–crank chain using a crank and a slotted lever. Given Data / Assumptions A slider–crank chain is the parent mechanism. We need the inversion that yields a crank driving a slotted lever about a fixed pivot. Goal: unequal forward and return stroke times. Concept / Approach In the Whitworth arrangement, the slotted lever oscillates about a fixed pivot on the frame, while a rotating crank drives a slider (block) that runs within the slot. This configuration is obtained by fixing the link opposite the slider, i.e., the frame that houses the lever pivot. The geometry causes non-uniform angular motion of the lever for uniform crank rotation, delivering the quick-return effect. Step-by-Step Solution 1) Start with the slider–crank chain and identify links: frame, crank, connecting rod (coupler), and slider.2) To form a slotted lever pivoted to the frame, fix the link opposite the slider so the lever has a stationary center.3) Rotate the crank; the slider (block) in the lever slot converts rotation to oscillation with unequal forward/return timing. Verification / Alternative check Textbook kinematic inversions list the Whitworth mechanism as the inversion where the frame opposite the slider is the fixed link, creating a slotted lever pivot. Why Other Options Are Wrong Coupler fixed: yields other inversions (e.g., oscillating cylinder) but not the Whitworth quick return. Slider fixed: produces different layouts (e.g., crank and guide) without the characteristic slotted lever geometry. Smallest link fixed or longest link fixed: size is not the defining criterion; the correct inversion is specific to which link is the frame opposite the slider. Common Pitfalls Confusing the Whitworth inversion with the crank-and-rod quick return (drag link or slotted disc types). Thinking link length alone determines inversion; it is the fixed link choice that matters. Final Answer Frame opposite the slider is fixed

In the Whitworth quick-return (crank-and-slotted lever) mechanism obtained as an inversion of the slider–crank chain, which link must be kept fixed to produce unequal cutting and return strokes characteristic of quick return?

Answer

Explanation