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Fig. 3.

Main line belts come high, and the more they are used the sooner will they wear out. By changing the clutch from shaft B to A and the pulley D from A to B, belt C will be at rest whenever B is not in use. Where, however, these shafts are each in a separate room or on a different floor (the belt running through the wall or floor and ceiling, as the case may be) the clutch, despite belt wear, should be placed directly on the driven shaft (as B), so as to provide a ready means for shutting off the power in cases of emergency.

Figs. 4, 5 and 6 represent a dangerous mode, much in vogue, of driving an overhead floor. An extremely slack belt connects the driving shaft A and the driven shaft B; when it is desired to impart motion to the driven shaft the belt tightener C is let down and belt contact is thus secured.

Fig. 4, Fig. 5, Fig. 6.

This tightener system is called dangerous advisedly, for few are the shops employing it but that some employee has good cause to remember it. Unlike a clutch—where control of the power is positive, instantaneous and simple—the tightener cannot be handled, as in emergency cases it has to be.