Page:Popular Science Monthly Volume 92.djvu/96

 Using Oil Instead of Gears

Hydraulic transmission does away with most of the present day gearing of automobiles

��HYDRAULIC transmission for auto- mobiles is not new. But the type of hydraulic transmission described here is both new and revolutionary. It has been simpHfied, and then simplified further, until it does away with the clutch, change-gear, differential and brake on the automobile.

��no oil is pumped over to the hydraulic motors. But begin to tip this collar, and back and forth go the pistons, forcing streams of oil into the motors.

The more the collar is tipped, the greater is the amount of oil forced over. To take up this oil and to send it back again into the pump

��Moreover, as it is now applied to cer- tain makes of motor trucks, it is per- forming the func- tion of an ideal speed control.

Among those who were instrumental in developing it, are the Chief Mechani- cian of the Navy, and two mechani- cal engineers, Charles R. Pratt and H. F. J. Porter. In its original form, this transmission is now used on many battleships of the different navies of the world. Because of its ability to im- part a very large number of speeds, it has been found excellent for re- volving turrets and for maneuver- ing guns which have to be trained upon an enemy's ship, dashing here and there over a zig-zag course.

The large number of speeds is obtained in this manner: The pump cyhnders of the system are always driven around at the constant, full speed of the engine. The collar of the pump pis- tons is pivoted about the diameter and remains station- ary. With the collar in the "dead" posi- tion, the pistons cannot reciprocate and

���Why Gears Are Unnecessary

The oil between the hydraulic pump and the motors, being imcompressible, forms a rigid gearing which takes the place of the clutch, change-gear, differential and brake. To start, the driver throws over the controlling lever to full speed. _ The auto- mobile gains speed gradually and without the slightest jerk. This is accomplished by an attach- ment which permits the pump collar to incline slowly as the automobile runs faster. Should the automobile be stopped abruptly, the collar is immediately brought back to its neutral position and the engine power is shut off automatically

���taken care into the outer wheel.

��chambers, the pis- tons of the two motors start recip- rocating. In other words, since the motor collars are stationary, the con- stant-stroke motor pistons start turn- ing.

The motor cylin- ders that revolve are connected with the rear driving wheels. The rate at which the cylin- ders rotate depends upon the quantity of oil they handle in a given time. Since this quantity is in- creased by tipping the pump collar, it is obvious that the speed of the auto- mobile is made to pick up by the same means. Thus, the three- speed change-gear now generally used can be substituted by a fluid gear capable of producing any speed whatever, depending upon the exceedingly large number of angles at which the pump collar can be tipped.

When turn- ing a corner, the difference in the rotation speed of the rear wheels is of by more oil going over motor connected with the

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