Arizona republican., 1918-08-04

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 to slip and the differential allows it to absorb most of the power. with the re- suit that it spins uselessly in the slip. pery mud and the car stays just where it is. If the power were distributed equally to both wheels. the car would readily climb out of almost any hole it got into. unless. of course, neither wheel could get traction.
 Another condition which brings out the inherent failure of the ordinary diff ferential is when the wheels of the car bounce up in the air In this case the wheel which leaves the ground is per mitted to spin at high speed, with the result that when it strikes the earth again the tire receives a scraping blow that is not very different from filing off part of the tire tread.
 Its Part In Skidding
 Further. the present type of differ ential contributes largely to skidding. that least enjoyable mishap. which sometimes becomes tragedy. When the brakes are applied on a slippery pave ment. it is the usual thing for one wheel to hold. while the other revolves. If each wheel had equal power all the time this tendency would be largely ob- viated.
 Naturally some attempts have been made to improve on the commonly ac cepted type of differential. It cannot be said that at the present time any of these attempts has met with striking success. One of the most successful in- novations is what is known as the spiral gear differential. This differs from the ordinary differential only in the form of gearing employed. With the spiral differential both wheels get equal power when pulling ahead, yet it allows of differentiation on turns as a result of friction between the spiral gears. The salient faults of the ordin- ary differential unit are overcome. but at the present time the spiral gear is in use only on few trucks in this coun- try. though I believe it has been ap- piled to few Ford cars with satisfac- tory results. Later on we shall hear from this form of differential. Differential Novelty
 Not long ago a form of dfferential substitute was offered. which embodied a solid rear axle. having a thread cut | on each end. Double tapered cone clutches were attached to each end. so tldl WueH power was dpplleu 10 tue axle the threads pushed the clutches over to the left or the right, where they 1 gripped a cup on the wheel, thereby 1 transmitting the power. In making d turn the outer wheel was automatical- | ly disconnected and ran free.
 | This idea of permitting the outer wheel to run free has been the basic l idea in a number of differential sub stitutes. In one particular instance two cams were used, being fastened to the solid axle. When the car was run ming in straight line these cams pushed rollers against drum, alta ched to the driving wheels. thereby locking axle and wheels insuring equal power ] to each wheel But in turning cor ners the connection between cam and drum was released so that the outer wheel ran perfectly free.
 Some Even Do Without
 Some builders have even held that the differential was non- essential The cyclecars of a few years ago were | seldom equipped with a differential Some racing cars get along without this part. However. the average drive, would resent being asked to go withou, a differential, because instead of the sort of turns he has been used to mak- ing. he would have to make very wide