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Page:Popular Science Monthly Volume 90.djvu/376

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A New Ball Differential for Automobiles

It will enable a car to get out of a hole when only one wheel grips

���ANEW differential for automobiles has just been put on the market which differs from all previous types in that the differentiation is secured not through gears but through the friction of steel balls running in grooves. It has an advantage over former de.- signs in that while the power of the motor is differentiated between the two wheels in the usual manner for corner turn- ing, it will still The center plate is allow a car to pull

of chromo-nickel q^^. ^f ^ h^ig ^^^^

steel into which are . 111

fitted steel balls only one wheel has traction. As shown in the accompanying views, the device con- sists of a con- V e n t i o n a 1 different ial casing at the center of which is a plate carry- ing eight steel balls arranged on two concen- tric circles. These balls move in cres- cent-shaped grooves in two

��The power shaft of the automobile turns the ball-plate

��The differential in position and the relation of the work- ing parts to each other

��disks, one on each side of the plate. The disks carry the ends of the axle shafts. Each groove is deep and wide at its middle, tapering off to points at the ends. The deepest part of the groove and the thickness of the center plate are each one-half the diameter of the balls. When any one ball is at the deepest part of the groove on one disk, it is at the end of the corresponding groove on the other.

The transmission of the motor power through the large differential

���The balls move in crescent- shaped grooves in two disks

��ring gear to the plate carrying the balls creates a thrust which tends to force the disks apart, causing them to press against grooved washers in the ends of the casing. When the car is running ahead, the plate and the disks revolve as one piece, like any differential, the thrust ex- erted by each disk and the torque on each wheel being equal. In turn- ing a corner, the power delivered to the wheels is un- equal, due to the tendency of one wheel to turn faster than the other. This permits the balls to revolve from the grooves of one disk into those of the other, causing one disk to move faster than the other and similarly allowing the outer wheel to turn faster than the inner. I f one wheel is spinning, the friction induced by the disks arrests the spinning wheel and converts its motion to torque on the stationary one, the spreading of the disks acting as a brake on the spinning wheel because only on that side is there relative motion be- tween the disk and its case. As it is the inner wheel which usually slips when an automobile turns around a corner, the action of the new ball differential is considered an improve- ment over the old type bevel gear. It is being used on a number of cars.

���The gearless dif- ferential which gives a positive pull at all times


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