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Four bar linkage 9a




A special case of the 4-bar linkage.

Input: pink crank.

Output: oscillating green crank.

The unusualness: a working cycle of of the mechanism corresponds 2 revolutions of the input. Output oscillating angles are larger than 180 deg., a thing that is hard to get by using an ordinary 4-bar linkage. It happens because:

1. The sum of the lengths of the two opposite links is equal to the sum of the lengths of the other two links.

A + B = C + D

A: length of pink crank (=10)

B: length of green crank (=40)

C: length of yellow conrod (=35)

D: distance between fixed axes of cranks (=15)

2. There are measures to overcome dead positions (when green crank is in line with yellow conrod). For example, inertia of the green crank must be big enough.




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