Page:The Kinematics of Machinery.djvu/356

 334

KINEMATICS OF MACHINERY.

coupler with a radius equal to its length, for the slots which would be required as envelopes for pins further from the centre 1 have forms much more troublesome to deal with, such as the path

FIG. 266.

(shown dotted) of the point 2'. If the link I be removed and the

chain afterwards closed in this simple way, its complete formula, (placed on d), will run :

a ' c d

We must find means for distinguishing this chain from the former

As it gives us no new motions, but only fewer motions than before, we shall not make a new class for it, but shall treat it as a derived form of the four-linked chain, obtained from it by

FIG. 267.

the removal of one link, in this case &. We shall call this removal of a link from a complete chain and its replacement by higher pairing areduction of the chain by that link, and shall