ENGINE DESIGN IN 1909
I At this time of the year we used to survey design trends. Now we no longer report annual progress. Instead, we present some remarks by J. Lowrey, B.Sc., on aeroplane engine design as it was in 1909-M.—Ed.
WHILE going through some engineering books recently I came upon a slender volume bearing the inscription ” Les Moteurs d’Aviation, par G. Linnet,” and on the title page I found the date 1910. At first sight a far from inspiring discovery, yet I soon realised that I had found something far more interesting and more valuable as a source of ” new” ideas than almost any modern publication.
Based mainly on a series of tests Conducted by the Automobile Club de France in 1909, when car and aeroplane engines were still closely related, this book includes sectioned drawings and test results for a wide variety of units, as well as comments indicative of the problems then being grappled with, and it seems well worth while to give some of this matter fresh publicity. If I perpetrate any errors in translation and condensation you must blame the war, which has rendered my ever weak French even more rusty. Commencing with a chapter of discussion on general design matters, Monsieur Lumet gives an interesting sidelight on the state of progress in 1909, suggesting the desirability of dual ignition systems (now universal on serious aero engines and compulsory in most countries) and commenting favourably on the tendency to replace splash lubrication with a pressure system ; the everlasting problem of air or liquid cooling is discussed, just as it is to this day, but such artifices as the use of glycol or water under pressure are not yet discussed. Referring to possible increases in engine
torque, the desirability of using a largebore carburetter and the importance or inlet manifolds giving good distribution are fully realised, while the considerable advantages of ” overlap ” valve timing are greeted as a new and important discovery. As always, the highest possible compression ratio short of that producing ” auto-ignition ” is sought, but the importance of the fuel used is not appreciated.
Turning to possible aids to increased engine speed, it is stated that “the possibility of using aluminium pistons is at present being investigated ” ; the double advantages of lower weight and cooler running are anticipated, but possible snags were not then known.
Finally, reference is made to current attempts to increase power by the supply of oxygen in addition to or instead of the air normally fed to the carburetter. An interesting idea, forbidden on racing cars by the General Competition Rules, I believe, and one which German aircraft have been rumoured to be using. In this case it is stated that test results to date had been inconclusive, but overheating and rapid valve burning were apparently expected as the price of the considerable increase in power theoretically obtainable. The next section of the book consists largely of tables, giving the results of tests made by the A.C.F. in December, 1909, and April, 1910. The intention was that each test should comprise a three-hour all-out run on the bench, and seven engines from five different makers either survived the test, or at least put
up a reasonable performance. These seven comprised Chenu, Gyp, Aster, Lemale, and three Gnomes, while other engines tested, concerning which a discreet silence is maintained, were da Costa-de Cockborne, Vergo, Rebour, Rossel-Peugot, Fareot, and Dechartres.
On the score of fuel economy, the best performer was the largest Gnome, a 14-cylinder two-row rotary, which ran for some 28 minutes at a consumption Of 0.505 lb./b.h.p. hour before a valve failed ; presumably the carburation had been cut a bit too fine, for a repeat test of longer duration was run at a much higher consumption. In the circumstances, credit goes to the Gyp, a water-cooled four-cylinder unit, which ran for almost 21 hours at 0.52 lb./b.h.p. hour. This rather interesting engine was modelled very closely on car practice, and with a capacity of 6.8 litres it sustained 57 b.h.p. at 1,220 r.p.m., a very modest power output by present-day standards, only 8.4 b.h.p. per litre at a piston speed as low as 1,200 ft. per minute, but far better than the 4.7 b.h.p. per litre of the Gnome. In actual specific power output the best performer was a 41-litre “1′ “-head Chenu, which, despite its comparatively humdrum appearance, produced 11 b.b.p. per litre at 1,350 r.p.m. ; other engine makers claimed better figures, but not perhaps for the duration of a three-hours’ run under official observation. The final chapters of the book are devoted to the description of a wide
variety of engines, some of them of purely historic interest, but others showing design features of sufficient value to justify their re-use in the future.
First to be considered is the Aster, very obviously a relative of the present-day semi-standardised British engine, saloons, small, for the propulsion of. It is an “L “-head side-valve four-cylinder, with all the usual features of three-bearing crankshaft, siamesed inlet ports, etc., the most obviously old features being fixed cylinder heads and splash lubrication. In complete contrast to the Aster is the de Dietrich, a most potent-looking engine with a single chain-driven overhead camshaft operating fully-inclined overhead valves. In view of the recent virtual standardisation of geared aero engines it is interesting to note that in this case the airscrew is mounteAl on an extension of the camshaft, a simple
expedient which may well re-appear after the war if light aero engines of s.v. or push rod o.h.v. “V “-type are produced.
Looking through the engines produced by firms famous in the car world, it is interesting to note that Phil, E.N.V., Renault and Wolseley-Siddeley were making V8 engines, Mercedes a 60-h.p. four-cylinder, Panhard a “T “-head fourcylinder, Mors a 450 V4, Darracq 3.2-litre flat-twin, and Anzani three and six-cylinder engines of broad -arrow form. The firm well known for the remarkable Gobron-Brillie racing cars, with doublepiston engines resembling the modern Doxford marine Diesels in layout, produced an even more remarkable aero engine ; I do not know if it ran, but at least it was photographed in an almost complete state. This engine had four Gobron-Brillie blocks combined into an eight-cylinder, 16-piston “X “-type engine of 8 litres ; the general idea behind this type of opposed-piston engine is to eliminate all inertia and explosion loads on the main bearings, but this rather extreme example of the type looks to have been too much of a good thing
A remarkably interesting unit of a type quite new to me was the five-cylinder R.E.P. It is not easy to describe, but it comprises, in effect, the top half of a ten-cylinder two-row radial, three cylinders in broad-arrow form, with two cylinders behind and between them : the result is a compact fan-shaped engine, easy to mount in a chassis, a very simple and rigid two-throw crankshaft, almost perfect balance and even firing intervals in just the right order to get good distribution.