Tuned Waste Pipe in C

A while back I started looking into how a recorder works and came across an article on the Physics of Music Instruments which explained the maths behind the hole sizes and positions.
The more I thought about it, the more I wanted to make my own recorder from scratch to prove I could. I could have started small, but I don’t do things like that. I realised that the inside diameter of my Woodnote bass recorder head was about 40mm (40.4mm) and the waste pipe I had used for making a support to carry my monopod on my bike was also 40mm (actually about 41mm outside diameter). In theory they could be made to fit together and so avoid making a headjoint for a while.

I put the two together and with a pipe about 1.9m long, I got a low note. On investigation, using a software tuner on my computer (Auto Tuner), I found that the note was only a couple of tones lower than my bass recorder, it was obviously a harmonic and reducing the pipe to about 94cm produced the note C3. Hmm, maybe this was not going to be a bass recorder, but a great bass.

I took the formulas from the website and entered them into an Excel spreadsheet so that I could calculate my own hole positions and sizes based on the frequencies needed and once I was sure it was about right, I set about drilling holes. I drilled each hole individually and undersize and then, using the tuner for guidance,opened them out with a needle file to bring up to frequency. After a few hours, I had a waste pipe that, by covering the holes with fingers or tape, would play from C3 to A4 on pitch. I will admit the low C was difficult to achieve without the harmonics forcing it up.

It was totally unplayable, as there was no practical way to reach all the holes, however, my daughter and I could play a scale between us. The next stage was to try making some keys. I picked up some brass rod and tube from B&Q and set about fashioning my own keys. The pads were made from more of the waste pipe with a pad of foam. Springs were made by winding a paper-clip around the brass tube. Initially the brass was glued to platforms of waste pipe that were attached with Superglue to the instrument, but this didn’t prove to be long lasting. The next approach was Araldite and in the end I used brass brackets and then re-enforced areas with Araldite. Working out the key locations, I realised that I should have located the holes differently which would have made keying easier, but this was a prototype after all.

Long before I reached the end of the keying, I realised that it was not going to work. My approach to the keys had created keys that were too flexible with too much movement in them. Also, while the diameter tube was the same as my bass recorder, it didn’t work for the lower notes; the harmonics took over.

The above post was drafted back in May and since then I have explored manufacturing alternate keys, more along the lines of a clarinet key. This has been more successful and at some point I will return to my second prototype. I already have the hole positions calculated for a different pipe size that will make it more practical to key.

This entry was posted in Music and tagged , . Bookmark the permalink.

Comments are closed.