Page:Motors and motor-driving (1902).djvu/228

196 which oil is also occasionally applied during use. The wider and longer the belt, the larger the pulleys, and the faster their speed of rotation the better will the results be, so that narrow or short belts and small pulleys in positions of no great speed should be avoided. If a belt slips unduly its under surface may be treated with Sternoline belt dressing, which very much increases the grip, and Mr. Buttemer has a good word to say for Collan oil for this purpose; but if this is not effective, it is evident the belt has stretched, and it must be taken off, half an inch or more, as required, cut off one end, and the two ends joined up again with a belt fastener, which consists of a small malleable iron casting carrying rows of teeth which are driven into the belt with a hammer. Failure of these to hold is generally due to their having been flattened out by hammering. In joining up a belt see that it is cut square across and the two parts joined in accurate alignment. The belt may also be joined by lacing the two ends together with a strong leather lace, a method which Mr. Buttemer advocates when using new unstretched belts, as then the stretch may be taken up by tightening the lacing without taking off the belt again. 'The secret of success with belt driving,' writes that gentleman, 'is to have belts as large as admissible, of sufficient substance and good leather, protected from wet and mud and well dressed with castor or Collan oil, and under these conditions they should never give trouble beyond the occasional taking up of slack.'

The usual arrangement provides two speeds only, and to get a third speed for surmounting excessive gradients the loose pulley of the lower gear is furnished with what is termed a 'Crypto' gear which, however, is not a true Crypto, but what is known as a lathe back-gear action, fitted to a revolving drum, the holding of which by a brake tightened around its surface and put into operation by a handle causes the gear to come into action, and so effect a still further reduction of speed.

But although the Benz gear is not a true 'Crypto,' as such gears are used upon several machines a few words about the peculiarities of this class of variable gearing may not be amiss.