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Kinematics of Machine Lab Experiments

To draw velocity diagram of four bar mechanism



Aim

To draw velocity diagram of four bar mechanism.

Problem:

The dimensions and configuration of the four bar mechanism, shown in Figure, are as follows:

P1A = 300 mm; P2B = 360 mm; AB = 360mm, and P1P2 = 600 mm. The angle AP1P2= 60°. The crank P 1A has an angular velocity of 10 rad/s and an angular acceleration of 30 rad/s 2, both clockwise. Determine the angular velocities of P2B, and AB and the velocity of the joint B.

PSolution:Given:ωAP1= 10 rad/s; α AP1= 30 rad/s 2; P1A = 300 mm = 0.3 m ; P2B = AB=360 mm = 0.36 m. We know that the velocity of A with respect to P 1or velocity of A, V AP1= V A= ω AP1 × P 1A = 10 × 0.3 = 3 m/s.

diagram

Velocity Diagram:

  1. Choosing appropriate scale; draw vector ap (VAP1=3 m/s).
  2. Draw fixed point P1& P2 by single point in velocity diagram.
  3. From point a, draw vector ab perpendicular to AB to represent velocity of B with respect to A.
  4. From point P2 draw vector P2b perpendicular to P2B to represent the velocity of B with respect to P2 or velocity of B.
  5. The vectors ab and p2b intersect at b.
  6. By measurement, we find that p2b = 2.2 m/s
  7. We know that angular velocity of P2B,and angular velocity of AB:
equation
velocity-diagram

Conclusion

The velocity diagram of four bar mechanism was drawn and analysed.