Page:Popular Science Monthly Volume 91.djvu/46

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Differentials for Motor Vehicles

��Comparisons which illustrate the merits of various types By Marius C. Krarup

��HP 1

��left pick-up plate Left ratchet



��IHE Bailey is the name of a new differential gear for motor vehicles. It transmits power to both driving- wheels when these can rotate at the same speed, but only to one wheel when the other runs faster. The power is divided at the rate at which the wheels can utilize it for trac- tion if the wheels have the same speed but one is inclined to slip. Traction from one of the wheels is thus sacrificed on all curves, wheth- er the going is good or not, in order to con- centrate power and traction on one of the wheels when traction from the other is lost for lack of fric- tion with the

road surface from slippery mud or snow. The casing is rotated by a bevel gear or worm drive, as usual. To the casing are secured two heavy pawls, of which one holds the left and the other the right wheelshaft by engaging notched disks fixed upon the ends of the shafts. The pawls are pressed against ball-pivots by coil springs. Their seats in the disks are shaped so as to make the engagement hold in either direction of movement, for backward as well as forward driving; but if one of the disks is forced around by the road contact of its wheel faster than the casing and the pawl are rotated by the power, this movement is permitted by means of a cam plate that lifts the pawl out of its seat. This action seems to be as follows : The pair of cam plates is mounted on a sleeve as a rigid unit that turns around with' the casing, and opposite to each pawl one of the plates has a semi- circular recess that limits sideways turning of the pawl on its ball pivot, while the other plate here has a straight-line contour passing obliquely under the active end of the pawl but coming to a point directly




���A differential which concentrates power on one wheel when the other has lost traction on a bad road

��before it This gives the lifting action. When both pawls drive, they stand at right angles transversely, balanced one against the other, but when one of the disks, actuated from the road, begins to push its pawl, the latter begins to turn a little on its pivot, allowing the disk the same small movement,and thereby the relatively im- movable cam plate gets a higher point of support under the pawl, rais- ing it and per- mitting the disk further unhindered rotation.


��A compari- son with other differentials illustrates the merits of each. In the ordinary balance gear differential of the type still used in a majority of motor vehicles the four small bevel pinions revolve on the plan of freely balancing the pres- sures on all teeth engaged. The engine power turns the casing which carries with it the two pivot pins on which two of the pinions are mounted. The two wheel- shaft pinions, each in mesh with both of the power-transmitting pinions, can con- form with the turning of the casing by revolving, taking the wheelshafts with them. If one wheelshaft resists as much as the other, one side of the actuating pinions is resisted as much as the other, and these pinions remain balanced and un- moved in relation to their pins. The teeth engaged become mere lugs gripping the wheelshaft pinions and forcing them to follow, by revolving. But, the moment one wheelshaft resists more than the other, from any cause whatsoever, the pressure on the teeth on one side of the actuating pinions becomes greater than that on the other side. These pinions are no longer


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