Bronson- 



—Iransverse Vtt 



orations 



of MeuaaL l 



tyring s. 





Table IX. 



(Rubber 



cord.) 





L. 



n. 



T. 



Out L. 



InL. 



34 



12-60 







16-20 



17-6 



35 



15-18 



20 



18-74 



21-3 



36 



17*25 



40 



22-62 



27-0 



37 



18-78 



60 



28-7 



35-4 



38 



19-95 



80 



36-0 



46.0 



39 



20-98 



100 



44-9 



58-8 



40 



. 21*83 



120 



52-4 



71-8 



42 



23-23 



140 



59-0 



80-4 



44 



24-15 



160 



65-2 



85-1 



46 



24-88 



180 



70-5 



87*4 



50 



25-80 



200 



75-6 



89-1 



54 



26-35 



220- 



80-3 



90-9 



58 



26-73 



240 



84-9 



92-0 



65 



27-00 



260 



88-0 



92-9 



75 



27-28 



280 



91-0 



93-6 



85 



27-60 



300 



93-8 





95 



27-90 









105 



28-25 









115 



28-38 









71 



The similarity of the curves obtained with the rubber cord 

 and those obtained with the springs is very noticeable. This is 

 especially true for the first part of the length-tension curves in 

 figs. 7 and 9. which would seem to indicate that the rubber is 

 in a state of internal stress, even when there is no external ten- 

 sion, which was certainly true in the case of spring 7. Fig. 9 

 also shows what a very important effect the previous condition 

 of the rubber has upon the relation between the length and 

 tension. The condition of the rubber is also to a considerable 

 degree dependent upon time and temperature, which explains 

 why it is so difficult to make satisfactory measurements with it. 



Although, there are some irregularities in the curves given, 

 especially those for the rubber, and for the springs when the 

 tension was so small that the effect of the restraint of the ends 

 was considerable, yet the following conclusions seem to be 

 justified : 



1. In the study of the transverse vibrations of helical 

 springs and india-rubber cords one radical difference is noticed 

 between them and ordinary strings, namely the fact that their 

 length varies greatly with the tension instead of remaining 

 very approximately constant. 



2. While the frequency of the vibrations of the springs and 

 rubber cord is expressed by the formula usually employed in 

 the case of ordinary strings, yet the results obtained are very 

 different on account of the great variations of the length with 

 the tension. 



