Page:The Kinematics of Machinery.djvu/473

 HOPES, BELTS AND CHAINS. 451

which these matters have hitherto been looked at has made many things appear simple and self-explanatory which in reality are com- plex and require proof, while others have been considered specially remarkable which are only conclusions directly deducible from definite propositions. In the latter circumstance we can recognise the power we possess in having at our command an exact logical system.

Many other examples could be mentioned, which show, like those cited, the want of a distinct perception of the function of

FIG, 312.

those parts of machines and structures of which we have been speaking. Eedtenbacher's attempt to treat those machines in which the frames are in one piece as a class by themselves seems to have been due to the same cause.* We have seen that the right treat- ment of the problem is very simple and intelligible, and does not indicate the existence of any such separation it will not, therefore, be well to perpetuate it.

Ropes, Belts, and Chains.

We have already found ( 41) that ropes, belts and chains are kinematic elements. They are the tension-organs T T p and T z. If they are so used that by the help of hooks, screws, rivets, etc., they are either made endless (that is, returning upon themselves), or are united with other bodies, they represent links of certain kinematic chains which we shall consider in the next paragraph. The flat-link chains are essentially combinations of numerous kinematic links each of the form C^ ... l| ... C~ t the closure of the whole being effected by the insertion of a frame between the chain-wheels.


 * Redtonbacher gave these the name of Mobel-inaschinen.

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