This is potentially a very educational project. Several learning objectives are possible, depending on the subject area of interest:
- Mathematics: Solve simple equations to match pipe length to notes.
- Physics: Learn about the relationship between length and first-mode vibrational frequency.
- Music theory: Learn about the relationship between frequencies and notes.
- Shop: Learn how to measure and cut wood, join it with nails or glue, and work with metal pipe.
The basic idea with this glockenspiel is that there is a wooden frame with two rows of nails sticking out of it, and rubber bands joining neighboring nails in each row. The rubber bands hold the pipes in place while giving them a lot of freedom to vibrate. The hard work is making sure the pipes are the right length and held by the rubber bands in the right place.
The amounts of material below, and measurements mentioned later, assume our nine-note range from C6 to D7.
- About eight feet of type M 1/2" nominal copper pipe. Despite being called 1/2", this has an outside diameter of 5/8", and a thickness of about 0.03". You need the total length of your pipes (see Step 2 for pipe length calculations) plus about an inch per pipe to compensate for mistakes and to allow tuning. This is the expensive part of the project. (Our Lowes sells 10' for $12.) Note: If you combine pipe from two sources (as we did--we used some old pipe that was lying around and some pipe we bought), you will have to make separate calculations and measurements for the two pipes, in case the dimensions are not exactly the same--the tuning is very sensitive to the dimensions.
- About four feet of approximately 3/4" x 2" wood. The 3/4" is best left as is, but the 2" can be varied from about 1" to 3" with no harm. Any kind of wood will work.
- 20 to 28 nails, approximately 1.5" long and 1/16" in thickness (20 nails if the wood is joined with glue, 28 if the wood is joined with nails, in between if both are used)
- 15" of some sort of tubing that can loosely fit over the bottoms of the nails to keep the rubber bands for sliding down; we used heat-shrink tubing (but didn't shrink it); in a pinch, you can cut up drinking straws; or you can go to Lowes or Home Depot and pick up two feet of some cheap plastic tubing
- Drill and drill bit for pilot holes for the nails; a drill press can make life a bit easier
- 20 rubber bands, approximately 6" circumference
- wood for one or two hammers; we used about 8" of 5/16" dowel for the handle and about 1.5" of 7/8" dowel for the head
- a phone, tablet or computer with an app that calculates the peak frequency of sound coming in through a microphone; we used an Android mini-tablet and found that the free Fourier application was best, though some of the fine tuning was double checked with gStrings; you may find that some specific music tuning applications don't work very well for this, because your initial tuning will be quite far from an official note
- a calculator or a calculator app
- pipe cutters (we were cheap and used our hacksaw--that was a ton of work, and messy)
- flat file or other sanding/trimming tool (belt sander, disc sander, bench grinder, Dremel, etc.)
- Optional: wood glue (I used Titebond II)
- Optional: paint
Here is my nine-year-old untrained daughter playing a scale and a piece.
Step 1: Some theory
Once you buy your pipe, the only thing you can really control is the length of the pipes. The longer the pipe, the lower the main frequency. The formula is:
Once we've calculated A, we can choose the frequencies we want for the notes and solve the equation f=A/L2 to calculate the length of the pipe. The solution, of course, will be that L is the square root of A/f.
My value of A was approximately 67,600,000 mm2/s. You can use this to get an approximate idea of how long your pipes should be, if you're using type M 1/2" nominal copper pipe like I was, for planning. You can look up the frequencies for different notes here. For instance, C6 is 1046.5 Hz, so the length L will be approximately the square root of 67,600,000/1046.5, or 254mm. If that's your lowest note, like it was for me, this will be the length of your longest pipe.