Work in progress, especially some of the customizer options, but the pipes are printable, playable, and more or less in tune.
A Tabor pipe is a tin whistle with only 3 holes (thus, playable with one hand). Ordinary straight Tabor pipes are upwards of 270mm long, not really printable on my bed, but if you take the pipe and fold it.... A true Tabor has the 3rd hole on the bottom, a little SCAD work should enable you to add that option.
Ultimately, I want to be able to print two well tuned Tabors (in different keys) in mirror image and attach them to each other so they can be played simultaneously.
Nothing special going on in the print process. Overhangs are 45 degrees, except in the holes.
Print takes about 3 hours at 0.14mm layer height and 40mm/s print speed, 15% hex infill, 3 shells and 4 layers top and bottom. A soprano D consumes about 5m of 1.75 filament with the walls set at 0.64mm thick.
The larger parts are having shrinkage problems in ABS - PLA seems to still be working well up to the width of the printer bed. The "Cv1" low variant is much larger than the soprano D, it barely fits on the bed when turned diagonally and is showing a 16 hour print time, consuming 25 meters of PLA... I'm going to try to print that one next, after this hurricane passes. Drying the filament (baking at 180F for 2 hours) and a bit of hairspray on the bed seem to be helping the PLA print stay stuck.
Acetone vapor polishing
Only for ABS, it's not necessary, but can make a nicer finish.
There's a through hole near the end which I put there to facilitate "hanging" this part in a jar over heated acetone - it makes the surface much smoother, but the part will be smelly for a few days.
I heat about 3/4" of water to a boil in a pot, then pour about 1/4" of acetone (nail polish remover works) in the bottom of a glass jar, put the part on a wire hanger in the jar, put the jar in the pot (now heating to just under 100C), put a plate over the jar lid and wait for 10 minutes or so, then remove and let the part sit for a few hours to "firm up the skin" before touching it. Oh, and the water is boiled on the stove, then carried outside (to sit on the grill) to make the hot acetone vapor. I've been dumping the used acetone on a weed growing in the sidewalk, it doesn't seem to mind.
I've heard that "flame polishing" does a similar thing for PLA, but I've never tried it.
First: http://www.ggwhistles.com/howto/ is a great guide for practical whistle making... when I get this completely figured out, I plan to mail him one as a thank-you.
OpenSCAD makes parametric design very accessible, and tuning a whistle like this is all about setting up the parameters.
I'm using an app called gStrings on my phone to read the pipes' tune.
Some notes on windway design around p. 29 here http://www.fomrhi.org/uploads/bulletins/Fomrhi-113.pdf
Not sure if I'm ready to engage with this crew yet: http://forums.chiffandfipple.com/viewforum.php?f=1
For a first design, I'm working on a 268mm D pipe, which should also play E, F# and G by opening the bottom 1, 2 and all 3 holes, respectively.
The main trick I have to accomplish is figuring out the "equivalent length" of pipe bends. My first guess was to assign them their "centerline length" which resulted in a very flat tune (pipe too short). So, I moved to assigning each 90 degree corner an equivalent length of the pipe diameter. This gave me a 598Hz D (40 cents sharp), 672Hz E, 752Hz F#, and 798Hz G - all about 40 cents sharp.
For my next iteration, I tried "discounting" the final bend since it opens as a hole. This moved all the finger holes back about 12mm (it was late, I didn't think about it before starting the print and going to bed) - and the tune with the holes "open" is quite similar to the longer pipe with the shorter body. With all holes closed, the D is now about 40-50 cents flat. So, if the overall length hits the middle of trials 1 and 2, D should be getting close, but the holes need to move about 6mm closer to the end. D 572, E 675, F# 760, G 800 before polishing, and just a tiny bit flatter after polishing.
I've printed a couple of Alto G pipes now, one with 6 holes (more a tin whistle than a Tabor) - the low note is still hard to hold, I haven't tried "rigging the fipple" yet - that's next. Also, since the low note is the only one resonating completely through the lower bends, I revised that area to have a larger diameter curve, which does seem to help.
So far, I like the "tone" of ABS and thicker walls better than PLA with thin walls, but there are more variables at play than just the material type. A big variable is hole roughness, if you get a good seal on the finger holes, PLA and ABS sound very similar.
Pipe length affects resonant frequency
The printable thing is a musical pipe like a tin whistle, but more compact (and printable).
A variety of pipe diameters and lengths are available in the customizer, and the .scad code is available for tinkerers to design their own variants.
Basic resonance in a tuned pipe
With the customizer, you can print a variety of whistles to demonstrate. The sopranos print relatively quickly, easily and cheaply (~5m of filament, maybe $0.10 for $20/kg filament), students can have their own whistles to experiment with and keep.
Blowing in the mouthpiece starts a resonant wave in the pipe. The instructor can demonstrate on a variety of pipes of different lengths and diameters. Students will experiment on their own. Ear protection is recommended. Closing the finger holes makes the pipe longer and the frequency lower. Compare the length of the pipe to the speed of sound and frequency of resonance. Note how blowing harder can change the resonance from a(n approximate) quarter wavelength to a half wavelength, doubling the frequency in the same length pipe.
Playing two identical pipes with slightly different pressures will vary the resonant frequencies enough to demonstrate beat frequencies.
Holding all holes shut plays the base note of the pipe (marked near the mouthpiece). Opening the bottom hole plays one tone higher, opening the bottom two holes plays the next tone higher, and opening all three holes plays the next semi-tone higher. The tune to "Lean On Me" is pretty simple to play with this sequence.
If you customize a long first pipe, you can fit the next 3 finger holes on the middle pipe. Due to the fold direction, they are opposite of traditional recorder tuning holes, but otherwise work the same.
Breath control keeps the note constant, changing air pressure changes the octave the note plays in.
Traditional Tabor pipes move the 3rd hole to the bottom of the pipe - this should be a fairly easy change for an scad tinkerer to make. I think the relocated 3rd hole is the small part of this redesign - having the pipes folded changes the sound produced (albeit subtly through additions of higher harmonics) and also dramatically changes the way the instrument is held, carried, etc.
Students can examine and modify the SCAD code, designing their own variations of the whistle which they can see in 3D on the screen and possibly print.
- Printed pipes in a variety of sizes, hopefully at least one for each student to keep
- Cell phone with a frequency measurement/tuner application, such as gStrings
- Calculator app on the cell phone to calculate wavelengths / speed of sound
- Ear plugs (if students are permitted "free time" with the pipes for experimentation)