Engineering Wonders of the World
Volume III

30 ENGINEERING WONDERS OF THE WORLD. pendently of human agency, with fuel, lubri- cating oil, and electric current. The parts of an aeronautical engine are necessarily cut as fine as possible in regard to mass. The cylinder walls are reduced to the minimum thickness. Valves, How Weight p|s^onSj piston - rods, cranks, is saved. . r and gearing are made light. To avoid carrying the pound or so of water per horse-power for cooling the engine, air cooling is resorted to widely. Where water is employed, the jackets and radiators are of very thin metal. (At present it seems to be a moot point whether the weight saved by air-cooling is not more than offset by a loss in power.) To increase efficiency the cylinders are often provided with auxiliary exhaust ports, and silencers are omitted. The need for a fly-wheel of considerable mass on a four-cylinder engine has brought the five, six, seven, eight or more cylinder engine, giving a more or less constant turning effect and perfect balance into favour, as enabling fly-wheels to be dispensed with. Automatic lubrication, by means of a force pump, is a sine gud non. The aviator’s atten- tion and hands are too fully occupied in the maintenance of direction and Lubrication. . , , , -i 1,1 r balance to be available tor watching and regulating sight feeds, hand pumps, and gauges. The light mechanical oil pumps now used have been developed to a high pitch of perfection and reliability. Under the head of carburation some reduc- tion of weight has been effected by replacing the carburettor and large induction pipes by a pump delivering unatomized Carburation. J . n petrol through very small pipes direct to the cylinder. This method is, how- ever, considered to be somewhat wasteful of fuel, and to produce overheating, so that its use is decreasing in favour of the spray car- burettor. Magneto and accumulator ignition are used, either separately or in combination. The aerial motor will doubtless be much improved in the future. Sir Hiram Maxim expects that its weight will be reduced, at no distant date, to 1| lbs. to the horse-power. Even as at present developed it has shown itself capable of excellent work, despite the fact that, as compared with the car motor, it gives from twice to three times the amount of power per pound weight. It can hardly bø doubted that the inventive- ness resulting from the necessity for lightness of construction will in due course react upon the motor-car engine, and cause a great reduction in the avoirdupois housed under the “ bonnet.” One must, neverthe- less, not lose sight of the fact that a very light engine of high quality must be an expensive engine, as it requires the best of materials and the most careful manufacture, which last entails highly-skilled labour. We may now review briefly some of the many types of engines which merit notice, paying special attention to distinctive features. In most cases the weight of the engine is given. The figures are, however, hardly a fair criterion for comparison, as some makers include in their totals items which are excluded by others. FOUR-CYLINDER ENGINES. In this class the place of honour will be given to the Wright (Fig. 1) type of engine, which, however, has no very striking features. The four cylinders, arranged x , . / i , The Wright tandem m the usual motor-car Engine. fashion, have a bore of 110 mm.* and a stroke of 92 mm. The valves are situated on the top of the head ; the inlets are automatic, the exhausts operated by over- head rocking levers. Water cooling is used, water being forced through the four separate water jackets by a pump mounted on the forward end of the crank shaft. Our illus- tration shows the position of the high tension * For the edification of the reader who is unacquainted with the metric system of measurement, it should be stated that 25 millimetres (mm.) equal one inch.