Question
Download Solution PDFWhich of the following mechanisms is NOT associated with a four-bar linkage?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFExplanation:
According to Grashof’s Law:
"A four-bar mechanism has at least one revolving link if the sum of the lengths of the largest and shortest links is less than the sum of lengths of the other two links".
- The mechanism in which no link makes a complete revolution will not be useful.
- In a four-bar chain, one of the links, in particular, the shortest link, will make a complete revolution relative to the other three links, if it satisfies Grashof ’s law. Such a link is known as a crank or driver i.e. AD (link 4 ) is a crank.
- The link BC (link 2) which makes a partial rotation or oscillates is known as lever or rocker or follower and the link CD (link 3) which connects the crank and lever is called connecting rod or coupler.
- The fixed link AB (link 1) is known as the frame of the mechanism.
- When the crank (link 4) is the driver, the mechanism is transforming rotary motion into oscillating motion.
There will be at least one complete revolution between the two links.
- If the shortest link is fixed: Double Crank Mechanism
- If any of the adjacent links of the shortest link if fixed: Crank rocker mechanism
- If the link opposite to shortest link is fixed: Double Rocker Mechanism
(2) S + L > P + Q (Class II mechanism)
- Only a double rocker mechanism is possible.
Hence, the Crank-shaper mechanism is NOT associated with a four-bar linkage.
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