ME321 Kinematics and Dynamics of Machines Introduction Continued

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ME321 Kinematics and Dynamics of Machines
Introduction (Continued)

• Steve Lambert
• Mechanical Engineering,
• U of Waterloo

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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

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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

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Four-Bar Mechanisms

• 4 links and 4 pins/sliders gives M 3(4-1) -
  2(4) 1 dof
• This is a particularly useful mechanism

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Four-bar mechanisms

• By extending the coupler, a four-bar mechanism
  can be used to generate a wide variety of
  functions

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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

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Six-Bar Linkages

• For a Stephenson linkage, the 2 ternary links are
  separated by a binary link

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Six-Bar Linkages