NO. 3 LANGLE1 MEMOIK ON MECHANICAL PLIGHT 1*"'!) 



The " bearing points " were not attached to the I'vame at the time these 

 photographs were taken, but are seen leaning against the scales in (lie fore 

 ground of Plate 4G. Their position on the frame will he more clearly seen in 

 later photographs, where it will be noted that they were made use of in the 

 more elaborate system of guying which was adopted. 



While, in general, the frame at this time seemed to be reasonably stiff and 

 strong, yet it was subjected to a very thorough test by supporting it at differ- 

 ent points and suspending from it weights to represent the various parts, such 

 as engine, aviator, wings, rudder and so forth, the deflections which were pro- 

 duced by these weights being carefully noted. It was further tested by subject- 

 ing it to vibratory strains, such as it would be likely to meet in actual use. After 

 this the whole frame was tested against torsional strains, such as would be 

 caused by the wind twisting one set of wings more than the other. As a result 

 of these tests it was decided that the frame should be strengthened as far as it 

 was possible to do so without greatly increasing the weight, which even now 

 was found to be rapidly increasing beyond what had been calculated as permis- 

 sible. The main guy -wires were replaced by heavier and stronger ones, and 

 while these were found to add somewhat to the stiffness of the frame, yet some- 

 thing more seemed necessary to insure safety. 



The delay in securing the engine, which had been contracted for with a 

 guarantee that it would be delivered in February, 1899, had become so serious 

 and had delayed the completion of the frame to such an extent that the ques- 

 tion of building an exact duplicate of the large machine, but of one-quarter its 

 linear dimensions was being carefully considered at this time, and it was decided 

 to make no further changes in the guying of the large frame until after the 

 small one was built. On account of its smaller size changes could be more 

 readdy and cheaply made on it, and the advantages of different methods of 

 guying could be just as well studied. Later, when this was completed, it was 

 found that, with the same system of guying that had been used in the larger 

 frame, the model was so very stiff that it did not require any further strength- 

 ening, the smaller scale, of course, accounting for the difference. What was 

 thought to be the best system to follow in strengthening the frame of the large 

 machine was, however, first tried on the smaller one, and it was found that for 

 a very slight increase in weight a very great increase in strength could be ob- 

 tained. This change in the system of guying consisted essentially of building a 

 " trestle " of tubing at a point on the upper side, midway between the pyramid 

 and the rear end of the frame. One of the former sets of guy-wires which 

 passed to the rear of the frame was then replaced by a set which started at the 

 foot of the rear tubes of the upper pyramid, passed over and was fastened to 

 the trestle, and from there passed to the rear end of the frame at the points 

 where the longer guy-wires from the pyramid had formerly been attached. The 



