In order to insure the completion of this house-boat by the time the aerodrome was expected to be ready for trial, it was built under contract. Immediately after its delivery in May, 1899, work was begun on the superstructure which carried the launching track. This superstructure was a considerable undertaking, involving a turn-table weighing about 15 tons, supported on a double circular track, and this track in turn was supported entirely from the side walls of the house to avoid having columns in the middle of the floor. From the photographs, Plate [38], Figs. 1, 2 and 3, it will be seen that the entire superstructure was supported by three trussed girders extending across the boat above the roof and carried by vertical posts built into the side walls of the house. The turn-table was 48 feet square and the launching track carried by it was 5 feet gauge by 80 feet long.
FIG. 1. FIG. 2. FIG. 3. PL. 38. HOUSE-BOAT AND LAUNCHING APPARATUS, 1899 [◊]
In making tests of the models, it had been the practice to carry the main body of the aerodrome up a ladder to the upper works of the boat, the wings being also carried up in the same manner. As the large aerodrome was expected to weigh at least 640 pounds, of which 350 pounds would be the steel frame with its undetachable parts, such as the engine and its appurtenances, it was seen that something more effective than a ladder would need to be provided for getting the aerodrome from the interior of the boat to the launching track [p157] above. It was therefore decided to place the upper works of the boat rather nearer the rear end than the front, thus leaving a space over the front end of the house through which a large trap-door might be cut in the roof, and it was thought that in this way the aerodrome might be passed up to the launching track by the use of suitable ropes and pulleys. The upper works were so arranged, and a sliding trap-door was provided in the roof, but more intimate knowledge of the difficulties of handling so large and heavy a frame made it certain, even before the aerodrome was ever placed upon the house-boat, that it would be impossible to transport it to the upper works by passing it through the trap-door. A different plan was then resorted to. A very large door was constructed at the rear end of the house, through which the completely assembled frame could be carried in a level position and placed upon a large raft, consisting of a lattice flooring over pontoons, moored at the rear end of the boat, as clearly seen in Plate [38]. In order to raise the aerodrome frame from the raft to the upper works, a large, but light, mast and boom, with suitable stays were provided. As the wings, when mounted in their proper position on the aerodrome, would be interfered with by such a mast, the mast and boom were so devised as to be capable of rapid erection and dismounting, only five minutes being necessary for either operation. In Plate [38] the mast and boom are seen in position in Fig. 3, while in Figs. 1 and 2 they have been dismounted.
The construction of the launching track and car was begun in November, 1899, but their completion was long delayed, as they were frequently put aside for the more immediately important parts of the work. Moreover, the arrangement of the struts and clutch of the launching car depended entirely on the form and dimensions of the frame of the aerodrome, which could not be entirely decided until a proper engine had been secured and tested in the frame to determine what modifications of it were necessary. In the spring of 1902, however, the launching car was entirely finished and a number of tests of the large engine were made in the shop with the frame mounted in position on the car.
From the description of the “overhead” launching apparatus (Part I, Chapter X [◊]) which had proved so successful in the tests of the models, both in 1896 and in the later experiments of 1899, it will be recalled that the essential features of it were a track and a light car with three hinged struts which extended below the body of the car, and against which suitable co-acting bearing points attached to the frame of the aerodrome were tightly drawn by means of a clutch which gripped a special fitting fastened to the aerodrome frame near the central point of its length. After the engine of the aerodrome had been started and got to running at full speed, the car was released and moved forward along its track by the combined force of the thrust of the propellers and the pull of the coiled launching springs. Just before the car reached the forward end of the track, a cam at this point caused the clutch to open and release [p158] the aerodrome, which immediately dropped slightly, as it had purposely not quite reached a speed sufficient to cause it to soar. This slight drop of the aerodrome, even if it were only a fraction of an inch, made it possible for the hinged struts, against which it had been held by the clutch, to be folded up by their special springs against the floor of the car, thus leaving the aerodrome free in the air without danger of entanglement.
The struts referred to above were three in number, two being placed near the rear and one at the center of the front of the car. The use of three points of support had the advantage of furnishing a rather rigid foundation against which the frame could be tightly drawn by means of the clutch-hook without risk of straining it. In designing the “underneath” launching apparatus, which was very thoroughly tested in the experiments with the models in the summer of 1899, the plan of having three struts with the aerodrome drawn tightly against them by means of a central clutch-hook was continued with most satisfactory results.
When the position of the struts on this launching apparatus had been changed so as to permit it to be used for the quarter-size model, it was found, in making shop tests of the engine with the aerodrome mounted on the launching car, that, owing to the greater vibration produced by the gasoline engine, the three points of suspension did not hold the model in a sufficiently rigid manner. It became necessary, therefore, to use four struts, the two rear ones being left as before, and the single one in front being replaced by two interconnected ones arranged similarly to those in the rear. After making this change no difficulty was found in holding the aerodrome rigidly against the struts, and this modification was therefore immediately introduced in the designs for the large launching car which was already under construction.
PL. 39. METHOD OF ATTACHING GUY-WIRES TO GUY-POSTS TO RELIEVE TORSIONAL STRAIN [◊]