TABLE OF CRANK TRAINS. 323
similarly placed in the chain, as are also & and d, it gives us there- fore only two mechanisms. In all these mechanisms the centroids
have only infinitely distant points. The single crossed slide has sometimes been used in machinery.
74. Recapitulation of the Cylindric Crank Trains-
The number of important mechanisms which we have formed or derived from the chain (C") has been so large that in order that their mutual relations may be more clearly surveyed it will be well to place them together in a tabular form. This has been done in the Allowing pages, with the addition of a small schematic out- line of each mechanism, the fixed link being in every case shaded. The higher pairing, where it occurs, is omitted.
A. Quadric Crank Chain (<7' 4 ')*
1. Lever-crank ...... (C 4 ') d=b
2. Double-crank ..... (C 4 ') a
- In this table I have put in brackets words which, although they form an
essential part of the name of the mechanism, might yet very often bo omitted without indistinctness in referring to it.