158 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 27 



the aerodrome, which immediately dropped slightly, as it had purposely not 

 quite reached a speed sufficient to cause il to soar. This slighl drop of the 

 aerodrome, even if it were only a fraction of an inch, made il 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 ear, 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 lie 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 struls, and this modifi- 

 cation was therefore immediately introduced in the designs for the large launch- 

 ing car which was already under construction. 



Experience, both with models 5 and (!, and with the quarter-size model, had 

 also demonstrated the necessity of providing some means whereby the aero- 

 drome frame would he relieved of the torsional strains produced upon it by a 

 side wind striking the under surface of the wings when the aerodrome was 

 mounted on the car preparatory to a lest. The means for preventing these tor- 

 sional strains in the case of the models, when the " overhead " type of launch- 

 ing car was used, has been described in Chapter X of Part I. However, with 

 the " underneath " type of launching car, a differenl means was necessary. A plan, 

 in which outriggers projected from the body of the car and wires running from 

 these outriggers up to the main ribs of the wings, with means for releasing 

 the wires just before the car reached the end of the track, was used with the 

 " underneath " car in the tests of models 5 and 6 in the summer of L899, but the 

 outriggers were frequently deranged by the sudden stopping of the car at the 

 end <»f the run and they were replaced by a simpler arrangement. In this plan 

 the torsional strains were relieved by providing, at the forward and rear ends 



