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Another Hydraulic Transmission Gear.

7th March 1912, Page 11
7th March 1912
Page 11
Page 11, 7th March 1912 — Another Hydraulic Transmission Gear.
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The latest development in the direction of hydiaulic gears hails from America. This is the Manly gear. It is now being fitted as a standard part of their equipment by both the Remington Truck Co. and the La France Fire Engine Co., neither of which is an inexperienced firm. The gear appears to be quite simple, consisting in the main of a pump and either one r two hydraulic motors,the latter in their main details being duplicates of the pump, the chief difference between them being that, whereas the pump pistons are provided with a variable throw, those of the motors have no variation. Both pump and motor units are multi-cylinder affairs, five cylinders with trunk pistons working on a single crank being employed. The variable throw of the pump pistons is obtained by mounting dem eccentrically around the shaft, in such a way that the centre may be moved into a position concentric with the driving shaft, or to any point to the maximum of eccentricity allowable from it, the result being that, with the centres concentric with each other, there is no movement at all of the pump pistons and no power is transmitted, but the whole outfit operates as a fluid brake of great power. The slightest movement from dead centre causes the pump to operate the length of the stroke, and consequently the volume of oil put into circulation increases with the eccentricity. From the pump cylinders, the fluid employed—ordinary lubricating oil— is passed to the motor cylinders, the pistons of which are journalled upon a crank on the transmission shaft, which, as the motors are fixed, is turned in accordance with the movement of the pistons. By means of suitable valves, the flow of oil can be reversed through the motors, and the car driven

backwards when required. With the exception of a small auxiliary piston, operated by a pilot or control valve which is controlled by a small finger lever on the steering wheel, the rest of the outfit consists only of connecting ways and control valves for the passage and regulation of the oil. The outfit has been adapted for employment in conjunction with either shaft or chain final transmission. The outfit is not unduly heavy, when the weights of the conventional parts which it replaces are considered, although it is not light. The weight of the pump for a 3-4-ton vehicle weighs 375 lb., and that of each motor 2251b.

The question naturally arises as to its efficiency, and in this respect it would seem to possess quite exceptional merit, as, in a paper recently read by the inventor before the American Society of Mechanical Engineers, the results were recorded of a series of tests, working through a single motor, taking the power from an electric motor and measuring it at the other end by a Prony brake, the series showing results varying from 83.1 per cent. to 91.9 per cent., the average of all the figures of efficiency given working out at 87.7 per cent., which, if correct—and I have no reason to doubt it—is a very remarkable showing. These tests were made with the oil at a freely-flowing temperature, and it is admitted that, as temperatures fall and the fluidity of the transmitting system decreases, the efficiency falls off somewhat. Such a transmission system would appear to possess tangible advantages over any of the conventional systems, and at any rate it opens up a very promising field for investigation.


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