Model: S06 Approximate Four-bar Straight-Line Linkage of the Second Kind After Evans

This mechanism uses three moving links and one grounded link to create an approximate straight-line linkage. The crank and connecting link are not essential to this device nor is the vertical guide to the right of center. The use of the four-bar linkage to produce an approximate straight-line coupler curve was pioneered by James Watt around 1780 as one of his four major improvements of the steam engine. (See models S-24 and S-25). At the time there were no large machine tools precise enough to create accurate guides for linear sliding motion of the pistons. Interest in the mathematics of straight-line mechanisms grew into the 19th century as the need for them declined. However, the subject of kinematic synthesis of linkages to produce special mathematical curves for application to machines continued to evolve into the 20th century.

Francis Moon 2004-07-00

#### Reference :

- Ferguson : Kinematics of Mechanisms from the Time of Watt (U.S. Nat'l Museum Bulletin, Vol. 228,, 1962)

#### Resources :

- Interactive Simulation : S06. Angenäherter Ellipsenlenker II. Art Evans
- Tutorials and Descriptions : Brief Description of the Mathematics Behind the Peaucellier-Lipkin Linkage
- Tutorials and Descriptions : How to Draw a Straight Line