Engineering Wonders of the World
Volume III

AERONAUTICAL ENGINES. 35 At the opposite end of the case is the cam which works all seven valve-tappet rods. The distributor is driven by a half-speed shaft, and the magneto by a cross-shaft and bevel gearing. The engine is mounted with its shaft vertical, as shown in Fig. 7. A bevel gearing is there- fore needed to impart motion to the horizontal propeller shaft. Cylinders, bore 110 mm., stroke 92 mm. ; power developed, 55 horse- power ; weight, about 155 lbs. No fly-wheel is used, as the explosions, occurring at regular intervals, give the crank a constant torque. The “ R.E.P.” (Robert Esnault-Pelterie), the first successful seven-cylinder engine, has all the cylinders mounted on the upper half of the crank-case, four being The “REP”- • in one plane and three in Engine. another. The crank lias two throws, operated by four and three pistons respectively, the piston rods of each group being attached to a single big-end. Extremely light pistons are used, and to save weight the bearings for the gudgeon pin of the piston rod are made part of a piece which screws into the socket in the centre of the piston head, and is secured by a screw. A peculiar feature of this engine is that one valve passage serves for both inlet and exhaust. The inlet valve is of the ordinary mushroom-headed type. The exhaust valve has the form of a cylin- drical collar surrounding the inlet valve stem, and moving up and down in a cage, the walls of which are perforated. When the collar uncovers the ports, the cylinder is put into communication with the exhaust pipe. The seven-cylinder “R.E.P.” weighs 115 lbs. and develops 30 horse-power. A ten-cylinder engine with two sets of five cylinders, mounted in four planes on top of the crank case, is made. It develops 40-50 horse-power. The cylinders of these motors are provided with external fins, and are cooled by air draught., This section may end with reference to the Adams Farwell five-cylinder revolving air- cooled engine. Like the Bayard-Clément, it runs round a vertical crank-shaft. The 36 horse-power size is remarkably light—only- 97 lbs. The 63 horse-power type weighs 4 lbs. per horse-power. Centrifugal force is used in- stead of the usual coiled springs to close the valves. EIGHT-CYLINDER ENGINES. The first extremely light aeroplane engine put on the market was the Antoinette, which * has won a high reputation for itself. The air- cooled type scales only about 21 lbs., the water-cooled about . Antoinette. 5 lbs., per horse-power. Thø cylinders, of forged steel, are grouped in two sets of four, mounted at right angles to one another on the top of an aluminium crank-case. Two pistons operate each of the four throws of the crank-shaft. The cam-shaft for work- ing the eight exhaust valves is situated inside the case over the crank-shaft. By moving this shaft slightly end-ways the engine can be reversed. The inlet valves are automatic. Where water cooling is used, a thin copper dome-topped jacket surrounds the cylinder- and the guide of the exhaust valve stem. At the bottom the jacket is soldered to an ex- ternal ring on the cylinder. Lubricating oil is forced by a small pump into a tube running along the inside of the top of the crank-case, and squirted in all direc- tions through a number of tiny holes on to the crank and cam-shafts, pistons, rods, and cylinder walls. Carburation is produced by a little petrol pump driven by the engine, which delivers petrol into eight little distributors placed near the inlet valves. The distributors store the petrol during the three non-suction strokes. When the inlet valve opens the petrol is drawn into the cylinder, being pul- verized and vaporized during the process. The supply is regulated by altering the stroke of the pump’s plunger. This system avoids