Watt, grasshopper, modified scott russel are appr. strightline mechnisms....

Watt Mechanism for an Approximately Straight Line Motion
The Watt mechanism is a type of four-bar linkage that is commonly used to convert rotary motion into approximate straight-line motion. Here's why the Watt mechanism gives an approximately straight line:

1. Linkage Configuration:
- The Watt mechanism consists of four bars connected by revolute joints.
- The input crank and output rocker are connected by two intermediate links.

2. Parallel Motion:
- The Watt mechanism is designed in such a way that the end point of the rocker moves in an approximate straight line.
- This is achieved by carefully positioning the joints and links to create a parallel motion.

3. Slider-Crank Mechanism:
- The Watt mechanism can be seen as an inverted slider-crank mechanism, where the slider corresponds to the end point of the rocker.
- The slider-crank mechanism is known for converting rotary motion into linear motion.

4. Straight-Line Approximation:
- While the motion produced by the Watt mechanism is not perfectly straight, it is a close approximation over a limited range of movement.
- The Watt mechanism is often used in applications where precise straight-line motion is not necessary but where a simple and efficient mechanism is required.
In conclusion, the Watt mechanism is known for providing an approximately straight-line motion due to its specific linkage configuration and parallel motion design.