Wind Chimes Project Information

During the first and second weeks of Spring Quarter 1999, interested Rose students will design, make parts for, and assemble a set of wind chimes.

This involves most of the activities below

• Deciding what frequencies are desired
• Using information below to cut steel conduit to length for that frequency
• Testing the sound frequency and quality (FFT program and by ear)
• Drilling holes to support the pipe
• Experimenting with 'striker' materials for quality of sound produced
• Making a top support to hang the pipes from, or some other form of mount for the pipes
• Making a 'sail' and 'striker'
• Modifying the pipes or design if not satisfactory
• Having an informal contest for 'wind chime bragging rights'

Here are some facts about frequencies in bars of circular cross-section
(conduit is hollow pipe, a special case of a cylindrically shaped bar)

• longitudinal waves (down and back) travel at the bulk wave speed (V~5105 m/s for steel conduit)
• measuring bar length and the lowest longitudinal frequency lets you calculate V.
• for wind chimes, one wants the transverse frequencies, given as follows
• k=2 Pi/wavelength, and for the lowest resonant bar frequency, k = 1.000375 3/2 Pi/Length
• frequency f = k^2 V kappa/(2 Pi) , and kappa is given by
• kappa = radius/2 for a solid bar, and is 1/2 sqrt(Ri^2+Ro^2) for a hollow pipe (Ri, Ro are radii)
• for the lowest transverse bar frequency, the nodes are 0.225 of the length from each end
• this is theoretically where one would want to support the bar so energy is not lost through the support

Here is a maple file which calculates frequency based on bar length for 3/4" steel conduit : pipes.mws

Here is a maple file which calculates frequencies on the musical scale : scales.mws

Here is a How-To wind chime web page by Jim Kirkpatrick, kindly supplied by Buckner Creel