ME 321 Kinematics and Dynamics of Machines Introduction
- Slides: 8
ME 321 – Kinematics and Dynamics of Machines Introduction (Continued) Steve Lambert Mechanical Engineering, U of Waterloo 3/6/2021
Simple Mechanisms – 2 links l Consider 2 links: M = 3(2 -1) = 3 Ô A single pin or slider joint (or 2 roll-sliding joints) can reduce the mechanism to 1 dof 2 2 1 Ô not 3/6/2021 1 very useful
Simple Mechanisms – 3 links l Consider 3 links: M = 3(3 -1) = 6 Ô 2 pin/slider joints plus 1 roll-sliding joint are necessary to limit it to 1 dof 3 2 1 Ô Useful 3/6/2021 3 1 2 1 as cam mechanisms 1
Four-Bar Mechanisms l 4 links and 4 pins/sliders gives M = 3(4 -1) - 2(4) = 1 dof 3 2 4 2 1 l 3/6/2021 3 1 1 This is a particularly useful mechanism 4 1
Four-bar mechanisms l By extending the coupler, a four-bar mechanism can be used to generate a wide variety of functions Coupler curve (artist’s impression) 3 4 2 1 3/6/2021 1
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 l l 5 5 6 3 3 4 2 1 1 Watt I l 3/6/2021 4 6 2 1 1 Watt II 1 For a Watt linkage, the two ternary links are adjacent
Six-Bar Linkages l For a Stephenson linkage, the 2 ternary links are separated by a binary link 6 6 5 3 3 4 4 2 5 2 1 1 Stephenson I 3/6/2021 1 1 Stephenson II
Six-Bar Linkages 5 3 4 2 1 3/6/2021 1 Stephenson III 6 1
