516 KIN EM A TICS OF MA CHINEE Y.
into the separate trains we have enumerated, so that the existence of these is not necessary that a machine may be complete, and, secondly, that (as already said) there may sometimes be employed in the machines arrangements for special purposes which do not fall exactly under any of the subdivisions spoken of.
136.
Examples of the Descriptive Analysis of Complete Machines.
It will be useful to give here a few examples of descriptive analysis, in order to show more distinctly by particular instances what the nature of the problem is, and how far its results extend. Let us first take a few prime-movers.
A breast-wheel used for driving a manufactory has for its main- train a mechanism of the formula (C'C s iV\)l, as we found from 62, that is, a toothed- wheel having a liquid pressure-organ guided (in the breast) by a portion of the frame which carries the wheel, in place of a rack, The motion is continuous, the main-train is therefore a running train. The driver is the pressure- organ, water. Neither director nor supply exists ; the work of the supply gear is performed in a physical or meteorological operation which furnishes continually fresh portions of driving material with- out any action of the part of the machine. A regulator may exist, as a governor acting on the sluice-valve.
Jonval turbine. The main-train here also is running gear, it is a screw-train with the place of the nut taken by the water which forms the driver of the machine. There is no director, a regulator may be arranged as in the water-wheel. Stop-gear may be employed, as for instance in the turbines at Schaffhausen, where in case of one of the driving ropes breaking the regulator suddenly allows a sluice-valve to fall.
Steam-engine. Let us examine a high-pressure engine such as is shown in outline in Fig. 360. Here, besides, the main-train we have both a director and regulator. The steam is the driver, the work-piece being the fly-wheel shaft. A is the main-train (in the form of a cylinder with suitable ports and piston, cross-head, con- necting-rod, crank, shaft and frame), a reversed and double-acting
