Four bar mechanism | Four bar linkage | Transmission angle

 Four bar mechanism | Four bar linkage | Transmission angle

Four bar mechanism / Four bar linkage transmission angle equation derived using analytical method. Equations for maximum and minimum transmission angle equations also derived.

In the below picture shown a typical four bar mechanism (Crank rocker), L2 is crank length, L3 coupler length, L4 follower length and L1 is fixed link (frame) length. Angle between crank and horizontal axis is theta 2, angle between coupler link BC and follower link CD is gamma, called transmission angle.

In the below picture described the procedure to calculate transmission angle gamma for any given crank angle theta 2.

Minimum transmission angle occurs when theta 2 is zero degrees, Maximum transmission angle occurs when theta 2 is 180 degrees, In the below pictures described the procedure to calculate maximum and minimum transmission angles.

In the below picture, a problem is solved using Microsoft excel. In which fixed link length is 8 cm, crank length is 3.5 cm, coupler length is 10 cm and follower link length is 9 cm. In the first column crank angle is taken 0 to 360 degrees at an interval of 15 degrees. In the second column transmission angle gamma is calculated using above described equation. in the right side graph crank angle theta 2 along horizontal axis and transmission angle gamma along vertical axis is plotted.