Topic: Theory of Machines
The configuration of a planar four bar mechanism with frictionless joints is shown in the figure below. The length of the links are L1 = 40 mm, L2 = 15 mm, L3 = 35 mm and L4 = 30 mm. The suffixes 1, 2, 3 and 4 represents the fixed, input, coupler and output link respectively. If Ti and To are the torque to the input and output link, what is the mechanical advantage (To/Ti) of the mechanism?
- A. 2
- B. 0.5
- C. Infinity
- D. 0
Answer: C. Infinity
Explanation: In the given configuration, links 2 and 3 are collinear (180 degrees). This is a toggle position where a finite input torque creates an infinite output torque (theoretically) because the mechanical advantage becomes infinite. The ratio of output torque to input torque (To/Ti) approaches infinity.