Savart’s Wheel

SAVART’S WHEEL

 

Savart’s Wheel is a tuned rasp. On this page it appears in two forms, and to give an idea how the instrument works, I’ll describe the version shown in the smaller photo on the right. This version consists of 30 wooden disks of graduated sizes on a motor-driven spindle. The edge of each disk is surfaced with ridges spaced about one eighth inch apart. As the spindle turns, the player holds a special plectrum against the ridged edge of one of the disks. However many ridges rotate past per second is the frequency that sounds. With disks of different diameters, the ridges-per-second numbers are different, so by holding the plectrum against different disks you get different notes. The plectrum has an attached radiating surface in the form of a styrofoam cup. The cup acts as a soundboard, projecting the sound out into the air. In the version of the instrument shown in the main photo, the graduated disks are replaced by a single cylinder, with ridges and valleys at carefully calculated spacings carved into the surface of the cylinder itself. 

Thanks to Ian Saxton for the crucial work of fabricating the cylinder, as well as programming for the fabrication process and for the motor controller. In the audio clip, Savart’s Wheel is backed by a wannabe rock band. The tune is a variant of the widely known early blues song sometimes called “Baby Please Don’t Go” or “Another Man Done Gone.” A video of this instrument can be found among the demonstrations in this youtube playlist.

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