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SMITHSONIAN CONTRIBUTIONS TO KNOWL] 



vol. 27 



tested without having loops formed in its ends, yet it appeared that the twist- 

 ing of these high-grade wires so seriously affected them that in the case of guy- 

 wires with loops at the ends, better final results could be obtained by using 

 softer grades of steel. The wire which was actually found best, after much ex- 

 periment, was a good grade of Bessemer steel of a medium hardness, which had 

 been " coppered " to prevent rusting. However, even with the softer grades of 

 steel wire, LI was found that there were sometimes hard spots in the wire which 

 revealed themselves only upon test, and that when a hard spot occurred in the 

 twisted portion where the loop wa> formed, the final strength of the completed 

 guy-wire was sometimes only twenty-five per cent of what it should be. The 

 precaution was then taken to siibject each of the completed guys to a test strain 

 at least twenty-five per cent greater than it was calculated the wire would have 

 to stand in actual use, so that no accident from defective wires would be likely 

 to occur. 



Later on, however, much trouble was caused by the loops in the ends of 

 some of the guy-wires slipping, owing to the giving way of the solder which 

 had been run through the joint, the amount of slipping, while small, being suf- 

 ficient to alter completely the relative stresses on the various wires, thus caus- 

 ing distortion of the framework itself. In order to avoid this difficulty a new 

 method was devised of attaching the guy- wires to the turn-buckles and to the 

 fittings by which they were carried to the frame. This method consisted in 

 threading the ends of the guy-wires so that they could he inserted directly 

 in the threaded ends of the turn-buckles. The wires when connected in this way 

 to the turn-buckles showed absolutely no slip, and the entire system gained 

 greatly in strength thereby. The only disadvantage which was found in this 

 new method of attaching the guy-wires to their fittings, was that if the wire was 

 bent very close to the fitting, it would break in the screw thread very easily. 

 But since most of the guy-wires when once attached to the machine are always 

 tight, and in fact, under more or less strain, there was in most cases no likeli- 

 hood of the wires being endangered by being benl close to the fittings. Since 

 the screw threads, which it was necessarj to adopt in this new plan of connect- 

 ing the guy-wires, had to he very much liner than the threads which had been 

 used in the turn-buckles previously constructed, it was necessary to make new 

 turn-buckles, the others being to,, thin to permit of their being bored out, bushed 

 and re-threaded. The new turn-buckles were made of a much higher grade of 

 steel, and probably represent very nearly the maximum of strength for the min- 

 imum of weighl possible without the use of some of the very much higher grade 

 steels which have recently come on the market, hut which are exceedingly ex- 

 pensive to work. By means of this improved plan of attaching the wires, 1 it 



•The drawings Plate 55, which illustrate many of the fittings used on the frame, show the guy- 

 W l res as -, of loops twisted in their ends, these drawings having been made before 



the final plan of attaching the wires had been devised. 



