If you've ever seen those little music boxes you wind up, or crank, and they play a little tune over and over from a little metal drum of notes, but wish they did more than play the same 10-second tune over and over for eternity? If only you could change the song and write your own music for it... Now there's an idea.
After a year of design and work, I completed my Re-Programmable Music Box / Mechanical Synthesizer / Organ Grinder Thingy. It has many names, and is 100% non-electric. Just wood, metal, and good ol' people power.
I began this project as a sort of proof-of-concept, designing something from scratch without a lot to base it off of, and a whole lot of engineering problems to solve. Also, I didn't really know what I was doing. It was intended to be a learning and problem-solving experience. And it was a lot of fun.
If you like my work, please vote for it in the Woodworking Competition beginning October 3rd.
Step 1: Design and Planning
I started with the idea: a large wood cylinder will hold metal pegs. It will rotate and force the pegs to pluck metal tines, which are tuned to specific notes.
I selected 12 notes across, since it seemed like a very flexible number of notes and allowed me to fill it with a simple 8-note scale in the middle, with a few extra high and low notes. I could also tune in flats or sharps if I wanted some specifically, or get almost all of a chromatic scale in. I selected 32 notes "around" the cylinder, because that's what you need to play Pop Goes The Weasel, or any 8-bar song using quarter notes.
The cylinder is made of softwood, 8" in diameter, that I picked up from a nearby carpenter for free. I found a belt that fit snugly around it to use along with a few gears and a belt for the cranking mechanism.
The tine material was cut from the prongs of a garden rake. This works great because it is flexible but snaps right back into place. The tine holder design was sort of up in the air until the rest of the machine was done, so that I could do testing. Initial designs were too complex and tiny, but the final design (image 3 below) is about as simple as possible, I believe.
Originally I wanted to use almost all wood for this project, but it turned out wood wasn't going to offer the precision that I needed for the tines. I ended up doing it with a CNC at my college. In Step 7 I hypothesize how it could be accomplished without such expensive tools.
When designing the wooden frame, try to place the pieces to get as few exposed edges as possible. The edges you do have, try to align them so that they create borders and still look appealing to the eye.