Mécanismes à barres trajectoires et conception.pdf


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Solutions to Chapter 6 Exercise Problems
Problem 6.1:
Design a double rocker, four-bar linkage so that the base link is 2-in and the output rocker is 1-in
long. The input link turns counterclockwise 60˚ when the output link turns clockwise through 90˚.
The initial angle for the input link is 30˚ counterclockwise from the horizontal, and the initial angle
for the output link is -45˚. The geometry is indicated in the figure.
A2
60˚
O2

A1
O4

30˚

45˚
B2

90˚

B1

Solution:
Invert the motion and solve the problem graphically. Draw a line from O2 to B2 and rotate it
clockwise 60˚ to locate the position of B'2 . Draw the perpendicular bisector of B'2 B1 and locate the
intersection of that line with the line O2 A1 . This will locate A1 . The solution is given in the first
figure. Measure the lengths os 02 A1 and A1 B1 . This gives the linkage shown in the second figure.
The link lengths are:
r1 = 6"
r2 = 3.72"
r3 = 7.29"
r4 = 4"

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