NO. 3 [JANGLE'S MEMOIB ON MECHANICAL FLIGHT 171 



required at least one, and in some eases two turn buckles, the weight repre- 

 sented by this single item rapidly became so formidable as to require serious 

 attention. In the construction of the models, it had been necessary to employ 

 some special turn-buckles in connecting- the guy-wires of the wings to their guy- 

 posts in order to secure the minute adjustment of the wires necessary to pre- 

 vent the wings from being warped and distorted by unequal and improper ad- 

 justment. These turn-buckles had been made in the Institution shops, as the 

 very lightest ones which could be secured in the market were from ten to twenty 

 times as heavy as it was necessary for them to be to provide ample strength. 

 In the construction of the large aerodrome, however, the large number required, 

 and the desire to complete the machine at the earliest moment, made it advis- 

 able to procure the turn-buckles, if possible, from outside sources, and a very 

 careful search was accordingly made among the various dealers. After much 

 delay some bronze turn-buckles were secured which were very much stronger 

 for their weight than any others on the market, but upon testing them it was 

 found that while they weighed 45 grammes, their average breaking strength was 

 only 593 pounds. Previous experience had shown that turn-buckles which would 

 not break under a less load than 750 pounds could certainly be made to weigh 

 not more than 18 grammes. As even at this time it was realized that at least 

 100 turn-buckles would be necessary for the entire machine, the excess weight 

 which the heavy turn-buckles would add was felt to be absolutely prohibitory, 

 and the construction of steel turn-buckles was immediately begun in the Insti- 

 tution shops. These turn-buckles were at first made in several sizes, and while 

 some few were at first made " double ended," most of them were threaded at 

 only one end, the other end being provided with a swivel-hook, or eye. They 

 were at first made of mild steel, the swivel-hooks, in fact, being made of wire 

 nails in order to utilize the head of the nail as a shoulder without the expense 

 of machining rod steel of a size large enough to form the shoulder. It was 

 found, however, that the weak point of this type of turn-buckle was the swivel 

 end, and most of those which were then on hand were made double ended by 

 removing the hook, tapping a left-hand thread into this end of the shank, and 

 fitting a threaded eye-socket in it. The guy-wires themselves were attached to 

 the eyes of the turn-buckles and to the fittings on the frame by twisting loops 

 at the ends of the wires, and although the very greatest difference in the strength 

 of a completed guy-wire may result from the way in which the loops are twisted, 

 yet, after much training, the workmen were taught to twist these very uniformly, 

 following the plan which can be best understood by an inspection of the draw- 

 ings in Plate 55 which show the loops more clearly than they can be described. 

 After the loops had been properly twisted, soft solder was run all through the 

 twist in order to unite firmly the twists of the wire. Although special grades 

 of wire were found which showed very high tensile strength when the wire was 



