A Manual of Petrol Motors and Motor Cars; Comprising the Designing, Construction, and Working of Petrol Motors (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 edition. Excerpt: ...increasing the size of their gear boxes. If a powerful engine, a direct drive and three speeds only are used, the top speed being sufficiently low for all ordinary hills to be taken on it, the wear on the gear is necessarily much smaller than when more speeds are used and the drive is more often through the gear. Further, the oftener the gear is changed the more is the wear on it. Thus, not only have the gears been increased in size but they are less used. If speed is the main object, gears are often made exceedingly small for the power they transmit and yet are sufficiently efficient and durable. Putting in wide gear, therefore, is not a matter of safety, but a matter of wear. Very narrow gears wear more than the wider ones, and when worn are very noisy. It would appear that with the gate plan of changing the gears might be much wider than is customary, as the increase in weight and cost is very slight. To show the variation there is in practice in this matter, it may be mentioned that 80 horse-power cars have been built with gears-f inch wide and 10 horse-power cars with gears 1 inch wide. The latter is probably the narrowest that should be used for a car of, say, 15 horse-power or upwards, while for the larger sizes the width should be 1J inches or li inches. The wider wheels give more margin of wear and run more quietly, particularly after some use. The distance the centres of the shafts in the gear box are placed apart varies nearly as much as the width of gear. Some makers who use very narrow gears make them large in diameter to compensate for this. Roughly speaking, the centres vary from four to six times the width of the gears, though some makers exceed these proportions. The proportions adopted depend on the general arrangement...