This is an example of a six-link (one fixed) and seven-joint compound mechanism with one degree of freedom invented by the mathematician Pafnutii L. Chebyshev (1821-1894) as an approximate straight-line mechanism. He has another straight-line mechanism in model S-19. Chebyshev spent several decades trying to find a theorem that would establish whether a linkage mechanism could draw an exact straight line. It was a French engineer, Peaucellier, and Chebyshev’s student, Lipkin, who found an eight-line exact straight-line mechanism. (See tutorial on straight-line mechanisms.) Reuleaux discussed briefly compound mechanisms in his Kinematics of Machinery (1876), but it was a follower of Reuleaux, Grübler, who wrote extensively on the criteria for degrees of freedom in a linkage given the number of links and joints.

Francis Moon 2004-07-00