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Page:Popular Science Monthly Volume 90.djvu/463

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How to Make Mechanical Crystal Chimes

Tones produced by rubbing partially filled drinking glasses with revolving wheels

Bv J. S. Zerbe

��EVERY one is familiar with the musical tones produced by gently rubbing the fingers over the edge of a tumbler, the neces5ar\- preparation for producing the sound being moisture. The vibrator>' ac- tion is greatly augmented by acidulating the water, using the juice of a lemon, citric acid or vinegar.

The illustration shows a de\'ice which is easily made, wherein a dozen or more glasses can be used, the proper tone and pitch of each being determined by the amount of water which is carried in the glass. The music from such a group is exceedingly sweet and unlike that of any other instru- ment. The tones are considerably improved by mounting the mechanism on a box, which thus serves as a sounding board.

As herein shown the base is simply a board, i6 in. long, and 8 in. wide, with a post at the rear corner of each end on which is mounted a longitudinal bar, the top being 6 in. from the base. Parallel bars are placed 2 in. below the first one. These are slightly separated from each other, to receive between them the rear ends of the lower members of U-shaped key-bars.

The key-bars are made of soft steel strips, each 14 in. long, 3^ in, wide and 1/16 in. thick. These are bent to assume a U- form, the upper and the lower members being parallel with each other. The rear end of the upper member is secured to the top of the longitudinal bar by means of two screws, while the lower member rests be- tween the two parallel bars mentioned. On the forward ends of these key-bars are mounted the keys for the musical scale, the natural scale being preferable, which keys are spaced equidistant from each other. The keys representing C sharp, D sharp,

��Keys representing the natural scale are used and clear musical tones are produced from the^ glasses

��F sharp, G sharp and A sharp are placed between the keys thus indicated.

Before the key-bars are put into position two J^-in. holes are bored through each member, one hole 2Y2 in. from their rear ends, and the other 5 in. distant. These holes ser\'e as bearings for spindles, each ot which is 2 in. long. On the upper end of each spindle is a grooved pulley, and on the lower end a disk, a little less than half the diameter of the top of a glass. On this disk is strapped a thick rubber band, of the kind which is wider than the thickness of the disk, so as to form a receptacle for hold- ing water on top of the disk when it is in position. An endless belt passes along the two trains of pulleys, starting from a power pulley which is operated by a crank. An idler pulley at the op- posi te end , which is capable of being moved a limited dis- tance, ser\es as a tightener for the belt by which adjustments are made. The tumblers used are of thin white glass, and these are arranged below the spindles so that a disk is within each glass, but fully 3^ in. from the rim at the rear side of the glass. In that position a downward pressure on the key will cause the lower member of the key-bar to move to the rear, through its bearing, and thus bring the rotating rubber-tired disk against the inner edge of the glass. In mounting the glasses on the board they can be securely held by a coating of thick gum tragacanth.

Water is put into the various glasses, and more or less added until the proper musical pitches are obtained. A mark is then placed in the side of each glass so that there will be no trouble in refilling them to get the correct tones. The disks may be turned by a motor or by an assistant.

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