Tuning Airplane Wires 



Ever notice how a tuning fork vibrates when you strike the correspond- 

 ing note on a piano? Airplane wires are tuned on that principle now 



ONE of the most 

 common 

 troubles on all 

 airplanes has been the 

 difficulty of correctly 

 adjusting the tension 

 of the wires used for 

 bracing the wings. 

 Some of the wires may 

 be tauter than others, 

 after a few hours' fly- 

 ing. There has been 

 no ready means of 

 correcting this fault. 

 In consequence, great 

 stresses have been 

 thrown on some of the 

 \\'ires, while others suf- 

 fered hardly any ten- 

 sion at all. 



In tightening wires, 

 mechanics rely en- 

 tirely on their touch 

 and hearing. They 

 twang the wire with 

 their fingers as they 

 would the string of a 

 guitar, listen to the 

 note emitted and 

 judge the tautness accordingly. The 

 error average on the part of a skilled 

 mechanic —after his own work had been 

 tested with scientific instruments — was 

 found to be about 30 -z^,. 



It remained for an Italian 

 aviation officer, Carlo Lerici, 

 to hit upon a practical way of 

 helping the mechanic over 

 his difficulty. The accom- 

 panying illustration shows the 

 simplicity and ingenuity of 

 his device, which is really 

 nothing but a multiple tuning 

 fork. 



A block of wood holds 

 a series of metallic 

 tongues, resembling those 

 of a mouthorgan. The 

 length of these tongues 

 determines the musical 

 note which they give off 



Ui l"t. Film ,SiTv. 



Airplane wires must all be at the 

 same tension. Here a new multiple 

 tuning fork determines pitch, hence 

 tightness, and fitness for flying 



when struck, and this, 

 of course, depends up- 

 on the number of 

 times they vibrate in 

 a second. Tuning 

 forks vibrate in sym- 

 pathy with strings of 

 corresponding notes. 

 A "G" tuning fork, 

 for example, will vi- 

 brate sympathetically 

 when held close to a 

 piano on which the 

 note "G" is struck. 

 Similarly, when an 

 airplane wire is 

 twanged by a me- 

 chanic, and the Lerici 

 ''\abrometer" is held 

 close to its end, one 

 of the metallic tongues 

 on the instrument will 

 \abrate in sympathj\ 

 The mechanic has only 

 to take note of the 

 vibrating tongue and 

 read the number of 

 vibrations per second, 

 written below it on 

 He then takes the in- 



Thc multiple tuning fork 

 consists of reeds clamped in 

 a block. Each end vibrates 

 at a certain known pitch 



the wooden base, 

 strument successively to the other wires 

 and "tunes" them by tightening or loosen- 

 ing them respectively, until their \abra- 

 tion periods correspond with that of the 

 first wire tested. 



According to the inventor, the chance 

 of safety is increased 

 fully lo*^',' by making all 

 wires equally taut. A se- 

 ries of tongues with 20-40 

 vibrations per second is 

 sutticient for all the mod- 

 ern airplanes used in the 

 war. 



The same principle is 

 currently used in de- 

 termining the frequency 

 at which electric genera- 

 tors are operating. Reed- 

 meters are among the 

 simplest existing. 



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