Mi. 3 LANGLE1 MEMOIB OM MECHANICAL FLIGHT 173 



was found possible to gain practically fiftj per cenl in the strength of ilie entire 

 system of guy-wires used on the frame. 



.Many small changes were from time to time made in the various small fit- 

 tings by which the guy-wires were attached to the frame, nearly all of these fit- 

 tings having been originally made of a very mild grade of steel owing l<> the fad 

 that it was so very much easier to work. At the lime these fittings were made 

 it was constantly expected that a trial of the aerodrome would he possible very 

 soon, and it seemed necessary to expedite the work as much as possible and 

 avoid the delay involved in using grades of steel that would have been mate- 

 rially harder to work. As is always the case in work of this kind, retrospect 

 shows many instances where what was .-apposed to be a short cut to results 

 actually proved to be the longest path, but the work as a whole was remark- 

 ably free from imperfect pails which necessitated reconst ruction. 



In the construction of the frames of the models it had been customary to 

 fit the tubing accurately at the joints and to join it permanently together by 

 brazing, as this was not only the lightest form of joint that could be made, 

 but also the most expeditious method consistent with securing a strength of the 

 joint comparable with that of the tubing itself. The construction of the frame 

 by this method of brazing the joints together permanently, offered, however, 

 several serious drawbacks: among them, that when a tube got injured it was a 

 considerable task to replace it, while the brazing of the new tube in place re- 

 quired extreme care to prevent the frame from being warped when completed, 

 as the tube became longer while very hot and contracted after the joint had 

 set. Furthermore, the great heat required destroyed to a considerable degree 

 the desirable qualities due to the tube being "cold drawn," a reduction of 

 strength of something like 25 per cent being almost inevitable, even when the 

 brazing was most carefully done. It was, therefore, decided that in the con- 

 si ruction of the large machine all of the main joints should be made by a sys- 

 tem of " thimbles," and it was planned at first to make these thimbles by 

 brazing short pieces of steel tubing into the proper shapes and angles so that 

 they would accurately fit the tubes which were to he joined. The construction 

 of the thimbles in this manner, however, seemed to involve an excessive amount 

 of work; and, as it was found that very thin castings of aluminum-bronze 

 could be obtained, which would show a tensile strength very nearly as great 

 as steel, it was decided to make up patterns for the thimbles and cast them of 

 aluminum-bronze. 



The alumiuum-lu-onze castings were obtained and properly machined to fit 

 the tubes, but when il was attempted to " tin " the interior walls of the thim- 

 bles it was found that the solder could not lie made to stick to the bronze. 

 A- a considerable amount of work had been expended on the machine work of 

 these thimbles much time and effort was spent in attempting to devise " fluxes " 



