Watt Linkage Mechanism

Watt linkage is also known as the parallel Linkage. James Watt invented Watt's mechanical Linkage. In Watt's Linkage, the central moving point is constrained to travel on an approximation to a straight line. Watt's Linkage can be found in some automobile vehicles at suspensions, which allow a vehicle's axle to move vertically while preventing sideways motion.

Application of Watt's Linkage:

Watt's linkage mechanism is used in the rear axle of some car suspensions as an improvement over the Panhard rod. This mechanism prevents relative sideways motion between the axle and the car's body. It approximates a vertical straight-line motion more closely while locating the center of the axle rather than toward one side of the vehicle, as commonly used when fitting a Panhard rod.

Panhard rod consists of two horizontal rods of equal length mounted on each side of the wheels of an automobile. At the center of the Panhard rod, a vertical bar is connected. The center of this vertical rod, the point which is constrained to move in a straight line motion, is mounted to the center of the axle. All pivoting points are free to rotate in a vertical plane.

Watt linkage can be seen in the rear suspension of the above animation as two Panhard rods mounted opposite each other.

Advantages:

• Simplifies design while achieving near-linear motion.
• Reduces friction and wear compared to sliding mechanisms.

Limitations:

• Watt's linkage mechanism motion only approximates a straight line, not perfectly linear.
• Limited range of motion before a deviation from straightness increases.