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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