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Hydraulic-Mechanical Transmission

25th April 1958, Page 66
25th April 1958
Page 66
Page 66, 25th April 1958 — Hydraulic-Mechanical Transmission
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Which of the following most accurately describes the problem?

DATENT No. 791,903 gives details of

a novel form of transmission in which the rear wheels are driven via gearbox and back axle in the conventional manner whilst the .front wheels are individually powered by hydraulic motors. An engine-driven pump provides the power for this. (The Rover Co., Ltd., Meteor Works, Lode Lane, Solihull, Warwickshire.)

The drawing shows a layout in which the front wheels each have a hydraulic motor (1). The two motors are connected in series with the engine-driven pump (2). Control is provided by a two-way valve

(3) which can divert the fluid either to the motors or to an idling by-pass pipe (4) if the front wheels are not required to be driven.

A by-pass pipe (5) across the two motors contains a one-way valve which allows the motors to overrun when the load is light. This valve, therefore, acts as a hydraulic free-wheel.

In an alternative scheme, the two motors are connected in parallel histead of series; in this case the scheme provides an automatic differential gear. Loss of drive through the total slippage of one wheel can be prevented by providing a restriction in the piping.

A NOVEL TWO-STROKE OIL ENGINE

CRANKCASE compression is a simple means for charging a petrol-driven two-stroke, but the available pressure is far too low to enable it to be used on a compression-ignition engine. A method of boosting crankcase compression by an additional pumping cylinder is described in patent No. 791,714. (P. August, Directorio 130, Bernal, Buenos Aires, Argentina) The drawing shows an opposed-piston engine according to the invention. Air is drawn into the crankcase through ports (1) by the outward movement of the pistons. The suction effect is intensified by the presence of a third piston (2); this is set at a phase angle of about 90°, which results in air being drawn into the crankcase for practically the whole time that the intake ports are open. The converse applies on the instroke, during which the compressed air in the crankcase is moved to the working cylinders by conventional transfer ports (3).

The working cylinders are of • normal design, and both are water-jacketed, as shown on the right-hand one. This not only cools the cylinder sides, but also functions as a steam-raising boiler, being externally exhaust-jacketed as shown at 4. The aim is to recover some of the heat losses, and the steam so generated is applied to the top side of the pump piston in the normal steam-engine manner. No details are given of the associated valve gear for this, but condenser and circulating pump are mentioned.

CARBON DEPOSITS IN OIL-ENGINE I N a compression-ignition engine. carbon incrustations often occur both on the nozzle tip and in the immediate vicinity, and to prevent this is the object of a combustion head modification shown in patent No. 790,996. (Mondial Piston Company, Corso Bramante, Turin, Italy.) The drawing sho.ws the basic principle Of the device, which can be applied to any design of combustion head and is not limited to that shown. In all cases the requirement is that at top dead centre a cavity in the piston crown shall approach the nozzle very closely, as shown at 1.

The theory behind the scheme is that the gases are partially trapped in the cavity as the piston ascends and the compression wave so created causes the carbon to be scrubbed away on each compression stroke. The presence of the piston cavity is said also to have a favourable dispersive effect on the jet of fuel.

AUTOMATIC COUPLING FOR • TRAILER BRAKES QM/II-TRAILERS of the type that automatically couple when the trailer is backed up to them are the subject of

patent No. 791,951 The patent is concerned with a means for coupling the brake mechanism at the same time. (B. Farrington and H. Hands. Hands (Letchworth), Ltd., New Icknield Way, Letchworth, Herts.)'

The tractor brake-operating gear comprises a pull-rod (I) which lifts a spadeended lever (2) to apply the brakes. In assembly, the spade is positioned under a vertical plunger (not shown) on the trailer, and the brake effort is transmitted via the plunger.

During coupling, the spade must be depressed clear of the plunger, and the method of doing this is the subject of the patent. On the spade-lever spindle is a pair of arms (3) and on the trailer a pair of levers (4). As the roller (5) climbs the ramp, small rollers (6) ride on the levers and depress them. The motion is transmitted by the arms to the spade, which is then pushed downwards to clear the approaching mechanism. After the rollers have passed the levers, everything returns to the normal operative position. The scheme enables the brake mechanism to be coupled tight without any lost motion in the linkage.

A RICARDO COMBUSTION HEAD

A COMBUSTION head, suitable for .1-1 high-speed oil engines and capable

, of being easily produced, is disclosed in patent No. 791,388. (Ricardo and Co., Engineers (1927), Ltd., 21 Suffolk Street, Pall Mall, London, S.W.1.) Essential features of the design are that the combustion chamber shall be axially located in the piston crown (as shown at 1) and the valves shall lie on a diameter of the cylinder. The injector (2) is centrally placed and its nozzle is closed by a part-conical plug-valve which is largest at the lower end. When forced open by fuel pressure, the plug moves to a definite stop-face, so that the annular gap thus formed is always of the same dimensions.

Another feature is the use of a conical deflector plug (3) screwed into the bottom of the piston cavity. When the fuel jet impinges on this, it spreads to reach the largest diameter of the cavity.

The cylinder-head shown is air cooled, not only by the fins around the lower part but also by passages (4 and 5). The cooling system has been covered by an earlier patent numbered 720,644. The combustion system may however be used with liquid-cooled engines.

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