Page:The Kinematics of Machinery.djvu/594

572 last considered combined chains,* and the former class mixed chains. The consideration of the combined chains forms an essential part of kinematic synthesis, while that of the mixed chains is not in every case necessary.

§ 161.

Examples of Combined Chains.

The compound chains having a larger number of links than the simple ones, the mechanisms formed from them have a proportionately greater number of applications than those from the former. Their investigation, therefore, to be in any degree complete, would far exceed the space here at our command. Our object here, too, is rather to point out the existence and nature of problems than to attempt any complete treatment of them. I must therefore limit myself to a few examples.

FIG. 427.

An immense number of compounds can be formed from chains of the class (C" 4 ') and its modifications. Among these compounds some of the mixed chains also give us something new if they be placed upon certain links. The chain shown in Fig. 427 is a combined chain. It consists of two chains of the form (C') the first is a b c d, the second aefb.

When it is remembered that the lengths of the different links can all be changed, and also that they can be increased to infinity, it will be recognised what an enormous number of special cases arise out of the general one shown in the figure. If, for example, we


 * Prof. Reuleaux uses the expressions ächt and unächt zusammengesetzt,—real and apparent compound,—for what I have called combined and mixed chains. I think I am justified in using the latter much shorter terms, especially as a very closely analogous use of them is familiar in chemical terminology.