1. ME321 – Kinematics and Dynamics of Machines Introduction (Continued)
Steve Lambert
Mechanical Engineering,
U of Waterloo
12/7/2018

2. Simple Mechanisms – 2 links
Consider 2 links: M = 3(2-1) = 3
A single pin or slider joint (or 2 roll-sliding joints) can reduce the mechanism to 1 dof
not very useful 1 2 1 2
12/7/2018

3. Simple Mechanisms – 3 links
Consider 3 links: M = 3(3-1) = 6
2 pin/slider joints plus 1 roll-sliding joint are necessary to limit it to 1 dof
Useful as cam mechanisms 1 2 3 2 3
12/7/2018

4. Four-Bar Mechanisms
4 links and 4 pins/sliders gives M = 3(4-1) - 2(4) = 1 dof
This is a particularly useful mechanism 2 3 4 2 3 4
12/7/2018

5. Four-bar mechanisms
By extending the coupler, a four-bar mechanism can be used to generate a wide variety of functions 2 4 3
Coupler curve
(artist’s impression)
12/7/2018

6. Six-Bar Linkages
Six bars and 7 pin/slider joints give M = 3(6-1) - 2(7) = 1 dof
However, now at least 2 links must be ternary
For a Watt linkage, the two ternary links are adjacent
1 1
Watt I 2 3 5 6 4
Watt II 2 3 4 5 6
12/7/2018

7. Six-Bar Linkages
For a Stephenson linkage, the 2 ternary links are separated by a binary link
Stephenson II 2 3 4 6 5
Stephenson I 2 3 4 5 6
12/7/2018

8. Six-Bar Linkages
Stephenson III 2 3 4 5 6
12/7/2018