M.Goodall, A.Tagg British Aircraft before the Great War (Schiffer)
Deleted by request of (c)Schiffer Publishing
P.Lewis British Aircraft 1809-1914 (Putnam)
Franklin Tandem Biplane
The Franklin Biplane was constructed in the Chiltern Hills during the early part of 1909 by Cambridge undergraduates H. H. Franklin. H. W. Holt, A. E. Lowy and C. M. Spielmann. Tandem biplane wings were mounted one behind the other. Twin propellers, rotating in opposite directions, were fitted behind the rear wings and were driven by a continuous chain from the 12 h.p. air-cooled twin-cylinder Buchet engine. Biplane elevators were installed in front, the rudder being at the rear between the propellers. The flying controls were operated by a pole suspended vertically. Springing of the landing-gear was effected by compressed air. Brief trials of the Franklin Biplane were carried out on the ground.
Flight, May 8, 1909.
A HOLIDAY FLYER.
BEING THE RESULT OF AN ENTERPRISING THREE WEEKS' OCCUPATION ON THE PART OF SOME CAMBRIDGE UNDERGRADUATES.
WHAT better way could there be of spending an Easter vacation - or for that matter any vacation - than by setting to work to build and experiment with a full-sized aeroplane? A more congenial task for those with energy and leisure it is indeed difficult to imagine in this year of grace 1909, when all humanity is anxiously awaiting the speedy maturity of the new era of flight. And the prospects, too, of such an undertaking! At worst, a healthy time in the open air, combined with hour after hour of absorbing interest; while at best, success in the conquest of a difficult task which very few men have as yet actually accomplished.
Thus, with variations, were the thoughts of a party of go-ahead Cambridge undergraduates, Messrs. H. H. Franklin, A. E. Lowy, C. M. Spieimann and H. W. Holt to wit, when they evolved a mutually satisfactory design during term, when they bought the engine in advance, and when they ordered material in readiness to make an immediate start once they had established themselves with their host, Mr. Franklin, in his ideal home on the Chiltern Hills. Here, with a large field ready to hand as a prospective aerodrome, constructive operations were commenced without delay, and soon four large calico planes began to spread themselves to the fickle breezes. Bamboo spars and struts, assisted by diagonal bracing of piano wire, came into use for the main framework; and overhead was erected a skeleton "hangar" of rough wood posts and hempen ropes to prevent the whole device taking a premature leap into the air, as it frequently seemed inclined to do when the wind was gusty. Everything was nearly ready just in time to allow of one or two actual trials before vacation ended; but "there's many a slip" in experimental work, and as events turn out fate denied its favour at the eleventh hour by causing one of the chassis wheels to give way, too late to allow of making good the damage. Reluctantly, therefore, the flyer had to go into retreat ere an actual flight was made with it, but even the building of it was an experience of value, as it afforded an insight into many little details otherwise apt to be totally overlooked by the enthusiastic experimenter.
There was the general design to be prepared in the first place, and the natural desire to make it original, which led to the construction of a double biplane type, that is to say, one having four main planes totalling 540 square feet in area arranged tandem-wise in biplane formation. The idea was to obtain greater stability by having two centres of aerial support, fore and aft of the pilot respectively, it being assumed that a slight increase in the angle of the rear planes would suffice to render them effective in the "wake" of the front planes. In setting out the curves Sir Hiram Maxim's book came in handy, as it did also in connection with the wooden propellers, a pair of which, most carefully made and finished, but possessed of curious concave bosses, were arranged to be driven on parallel shafts by one continuous chain from the 12-h.p. twin-cylinder air-cooled Buchet engine.
Lack of opportunity prevented the motor from acknowledging its appreciation of this implied compliment to its capacity, for it was, of course, asking rather a lot of it, bearing in mind that the flyer itself was by way of being full-sized, and that even Mr. Wilbur Wright rates his engine at 25-h.p. or thereabouts. Among the special features of the flyer was a system of control for giving stability by the use of hinged corner pieces on the extremities of each of the main planes. These corner pieces, as our illustrations show, were hinged diagonally and so arranged that their front edges dipped or tilted to vary the angle of inclination. The use of the front edge for this purpose is contrary to the general principle adopted by other experimenters who, when employing flexing systems, invariably govern the angle by the movement of the trailing edge. It would have been interesting to have been able to observe the character of the control afforded by this change of method. The articulation of the planes was designed to be operated from a central vertical pole placed directly in front of the pilot's seat, which was mounted just behind the front planes, the engine - constituting the other portion of the carried load - being situated just in front of the rear planes. This pole was connected to the corner pieces by wires arranged diagonally, and the system was such that practically any combination-could be obtained from a direct movement of the pole. In front of the forward planes was an elevator, and behind the rear planes was a rudder, these latter members being under separate control. The machine, as a whole, was mounted upon wheels carried by compressed-air cylinders in such a way as to give a pneumatic suspension.