THE KINEMATICS OF MACHINERY. 



97 



link d as before, we have the mechanism^) 6 . It does 

 not essentially differ from (Cl) d . .<- The crank now revolves 

 about the pin 2 wh&h was formerly the crank-pin, and the 

 pin 1, which formerly represented the crank-shaft, is now 

 the crank-pin, but there is nothing changed in the nature of 

 the mechanism. By this inversion therefore we have got 

 nothing new. 



Let us now fix the link a, which was formerly the crank 

 (Fig. 11). We have now the mechanism (CQ*; it contains 



FIG. 11. 



precisely the same elements as before, and the relative motions 

 of the links are unaltered, but as a mechanism it is entirely 

 different. It is now a combination frequently enough used 

 in mills and' elsewhere, known by the name of a " drag-link 

 coupling." The links b and d have become cranks, and one 

 drives the other by means of the link c. 



By fixing the remaining link of the chain, the link c, 



