AN AMERICAN PARADOX
Joe Lowrey discusses a peculiar contradiction in the development of aircraft and motor-cars in the U.S.A. and Britain, and finds America’s light aeroplanes more absorbing than her cars
DURING the immediate pre-war years a rather remarkable paradox began to become apparent to those who interested themselves in flying as well as in motoring. America, which had developed the powerful “floating drawingroom” type of car to the exclusion of all others, was going in for light, sporting aircraft. Whereas England, home of small cars, was specialising in considerably heavier and more powerful private-owner aeroplanes.
During the first two years of this war, when the United States of America remained at peace, this development proceeded apace ; the fact that I have been able readily to obtain literature and information from firms concerned this year suggests that these concerns expect to continue expanding the light aircraft market in the future. Meanwhile, civil flying of a ” pleasure ” nature being, I believe, almost at a standstill on both sides of the Atlantic, we can study recent developments at leisure, and perhaps learn a few lessons to our advantage.
As typical of the aeroplanes in question, and for the purposes of comparison with road vehicles, I have decided to deal with machines coming below an arbitrary weight limit of 8 cwt., this being about the weight of most Morgans and other British three-wheeled cars.
In this country there are, I admit, certain aircraft in this category, but they are few in number, and in the main they are rather of the “toy ” nature and fitted with engines which are either foreign or are converted car and motor-cycle designs. In America, on the other hand, in 1941 13 firms offered 22 types of “under 8 cwt.” aircraft and more than one firm counted its annual output in thousands.
Of these various American machines the vast majority are 2-seaters, though there are individual single-seater and 3-seater types. Power outputs of the engines used range from 40 to 90 11.p., the average being about 65 h.p., while the average weight is only about 61. cwt. It is safe to say that there is no really popular British machine that is not at least 50 per cent. heavier and more powerful than these.
From the car aspect quite a lot of interest attaches to the design of these 65-b.h.p. 61-cwt. 2-seaters. Quite a considerable proportion of their weight must be represented by the wings, yet the machine as a whole must withstand the buffeting of air speeds of over 100 m.p.h. and the bumping of rough grass traversed at about 60 m.p.h., while amateur pilots probably make quite a proportion of their landings some feet above the ground.
Naturally, different manufacturers have different ideas on design, but the most popular type is a high-wing monoplane, rather reminiscent of the old British D.H. “Puss Moth” on a smaller scale ; for various reasons, closed cabin machines are definitely in the majority. Reasonably typical of their class are various Taylor-craft models, and it will be found that these machines are fabriccovered, over a mixed wood and metal structure. The wing is largely of spruce, -while the fuselage is of welded alloy-steel tube. It being a cabin machine, the fuselage is really deep and four braced longerons give the necessary strength for a remarkably low weight, the overall length being about ’22 ft. The machine is quite well equipped with instruments, wheel brakes, etc., can exceed 100 m.p.h., and when cruising at just over 90 m.p.h. it can better 20 m.p.g. Not bad on 65 b.h.p. and 700 lb
While these facts and figures are of undoubted interest and may well give a pointer to a probable line of sports car development, I must confess that I personally have been even more interested in the engines used in these machines. While the American Menasco is comparable with our Gipsy or Cirrus, and the Kinner or Ken Royce with our Pobjoy, the lower-powered engines for these lightweight machines are scarcely comparable with anything hitherto produced in this country.
For these machines the type of engine which is almost universally favoured is the air-cooled horizontally opposed fourcylinder. There are many different types, ranging from 40 to over 100 b.h.p., made by such firms as Franklin, Lycoming, Akron, and Continental, but the units fitted to the “under 8 cwt.” machines are usually of from 50 to 80 b.h.p.
Reasonably typical of the class, the “145 cubic inch” series of Lycoming engines are worthy of description. In this ease, with variations in compression ratio and operating speed, power outputs range from 50 to 75 b.h.p.
The basic construction of these engines is two main castings, each comprising two air-cooled cylinder barrels and onehalf of the central crankcase. Detachable aluminium cylinder heads are bolted to these and carry two parallel push-rod operated valves per cylinder.
The crankshaft is a short four-throw type’ carried in three steel-backed copperlead bearings ; in most cases it is a good but unremarkable affair, with hollow journals ; but in the case of a 75-h.p. engine, which uses an airscrew reduction gear, pendulum-type torsional vibration dampers are an interesting feature.
The induction system of these engines is, I think, almost unique, in that an updraught carburetter mounted under the engine feeds to a junction box cast integral with the sump, the mixture being oil heated. The effect is probably similar to that given by the now obsolete waterjacketed induction pipe (impossible on an air-cooled engine !), and while it would be ill suited to use on a car, it probably has considerable merit for the steadier operating conditions of an aero engine.
As regards general dimensions, considerations of engine width usually call for a short stroke in horizontally opposed engines, and in this case a 92-mm. bore and 89-mm. stroke are used. This gives a swept volume of 2,370 c.c., and the h.p. by the R.A.C. formula used for car tax here is 21. In the case of the intermediate (65 b.h.p.) model, the compression ratio is 6f to 1, the rated power being developed at 2,550 r.p.m. (1,490 ft. per min. piston speed) on 73 octane fuel. The weight is 155 lb. with single ignition or 165 lb. with dual magnetos.
As an indication that, while the “flat four “type of engine appears to have been adopted by different manufacturers with surprising unanimity, design has by no means stagnated, the 171 cubic in. engines of the Continental Motors Corporation are interesting.
In contrast to the Lycoming engines, 98-mm. bore and 92-mm. stroke give a swept volume of 2,780 c.c., but lower operating speeds are used and the power outputs of the different models, ranging from 50 to 80 b.h.p., are almost identical. The engines are built on quite different lines, the Continental engines having aluminium heads screwed and shrunk on to four forged steel cylinders, these being in turn bolted to a split aluminium crankcase, and the weight is perhaps 10 lb. more than that of the rival product.
One interesting detail of the Continental engines is that, as an optional extra, the carburetter may be replaced by a system of timed fuel injection into the inlet ports. I have not got any very full details of the system, but it seems to work on a very simple idea of metering the fuel according to engine speed and throttle position only. If this is the case, claims that the correct mixture is given at any altitude must be taken with a large pinch of salt, but there may be more to the system than is apparent from the manufacturers’ rather vague literature.
It is difficult indeed to foretell the future, and certainly astrology is one subject on which I am not an expert, but I think it is very probable that some time, when ” it ” is over, there will be a boom in private flying ; quite apart from utility transport, countless ” birdmen ” will want to demonstrate their prowess to the girl friend, and all the ” kiwis ” and “professional passengers” who have spent the duration making sarcastic remarks about “aerial chauffeurs ” will have to prove to themselves and others that this flying business really is child’s play.
When this boom comes the accent will almost certainly be on economy, and it is to be hoped that our aircraft and engine manufacturers will not allow the light ‘plane market to be monopolised by even our present Allies from across the Atlantic. And, maybe, one fine day we shall even be offered a road vehicle with a performance owing not a little to close study of these generously powered light aircraft.