G. S. Moler — Transverse Vibrations of Cords and Wires. 337 



Art. XXXVI. — An Instrument for Demonstrating the 

 Laws of Transverse Vibrations of Cords and Wires / by 

 George S. Moler, A.B., B.M.E. 



[Contributions from the Physical Laboratory of Cornell University. Communi- 

 cated by Edward L. Nichols.] 



This piece of apparatus was designed to meet a want, felt 

 in the laboratory, for an improvement over Melde's method of 

 producing transverse vibrations of cords and wires. 



It seemed desirable to produce a circular vibration which 

 would appear of the same amplitude when viewed from all 

 sides and which could be maintained for an indefinite length 

 of time ; so that the proper adjustments of length or of tension 

 could be made while the cord was in motion. It also seemed 

 desirable to maintain a constant rate of vibration when cords 

 are used which offer more or less resistance to the motion. 



The general arrangement of the apparatus is shown in figure 

 •1. To produce the circular vibrations the cord is attached to a 

 crank of small throw, which is kept at a constant but high 

 rate of speed by means of a regulator. A is the main shaft, 

 driven by a belt running over a pulley at B. Upon the crank- 

 pin at C is a small block having a hook to which the cords D 

 are attached. To prevent the tension of these cords, which 

 may sometimes amount to four or five kilograms, from exert- 

 ing a ^ull upon the shaft and thereby greatly increasing the 

 friction, a cord is carried from the box E to the block C through 

 holes in each end of the latter and back to the box E ; then to 

 a tightening pin F as shown in figure 2. This device allows 

 the block to move freely and easily under the largest loads. 



At G is a pinion which drives another shaft with a similar 

 crank and block. On this shaft is a spring which holds the 

 wheel H in line with the pinion. This wheel is fastened to a 

 slotted sleeve which, when it is not desirable to drive both 

 cranks at the same time, can be moved, by compressing the 

 spring, until it slides past a pin in the shaft. A turn of the 

 sleeve then holds the wheel in a position where it will not en- 

 gage with the pinion. 



From these cranks the cords are carried, as shown in figure 

 5, to two movable blocks which can be clamped at any desired 

 position upon the base of the instrument. These blocks carry 

 small pulleys over which the cords pass, the ends of each cord 

 being fastened to a scale pan and the proper tension secured 

 by the use of weights. 



A cord one meter long is commonly used, but the apparatus 



works quite as well with shorter or indeed with much longer 



Am. Jour. Sci.— Third Series, Yol. XXXVI, No. 215.— Nov., 1888. 

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