As the title suggests, the plans for this project changed quite often. The only thing that did not change was my decision to have a purely mechanical driving force with no electricity required.
The bicycle-mounted music box plan and its demise
No bike. It turned out the old bike I wanted to use was gone. So before the workshop started I had to revise my idea of a bicycle-mounted music machine to an inverted music box in an oil barrel.
The oil barrel music box plan…
The cylinder (2 in the picture) would be inverted, that the pins turn inwards. The comb teeth (3) would then have been mounted inside of the barrel (see crude sketch)
…and its demise
It ain’t easy finding things that sound nice. On the first day of the workshop I started with the comb teeth part of the oil barrel music machine. I tried one steel bar of approx. 2 mm thickness – too stiff.
The steel bar sounded as dull as this photo is blurry.
I tried to cut up a piece of sheet steel – too loose. After lunch I decided not to pursue the idea of having a nice sounding melodic instrument anymore.
The final plan – a drum machine / sequencer
I had to act fast to have at least something to show at the end of the day. So I inverted the inverted music box and made it a a drum machine. The thing I wanted from the drum machine: it should be programmable and make 4 different sounds: bass drum, snare, hi-hat and cymbal. I started working on a cylinder that would act as the sequencer part. I found a nice steel tube with a ~20 cm diameter and cut it to a length of ~40 cm. This piece of steel tube was the one part I had to show at the end of day 1.
Day 2 – Drilling, thread cutting, welding
My plan was to be able to trigger four different “drum sounds” with a resolution of 8 steps. So I had to drill 4 times 8 holes around the circumference of the tube. Tim came up with an easy to use and quite precise measuring tool to help me with this task: a piece of paper. We cut the paper strip to the length of the tubes diameter, folded it to have 8 subdivisions, unfolded it and wrapped it around the tube.
After marking all the 32 holes, I used a hand drill with a 4.5 mm tip to drill the holes for the M6 thread. I used 4.5 mm tip because of my slightly wobbly drilling style. Before cutting the threads I “cleaned” the holes with a 5 mm tip. After cutting all the threads by hand, which happened to be a very meditative exercise, day 2 was almost over. I welded 2 small steel bars on each end of the tube so that I could mount it on day 3.
Day 3 – Finding the center of a circle and things that go bang
Applied geometry! I probably learned in school how to find the center of a circle, but when it came to drilling a hole into the steel bars I welded onto the tube in the almost exact center, I had to ask Tim to share some Pythagorean magic with me. It only took a right angle and tools to make marks. Here’s a sketch of the process:
Brilliant! After a little bit more welding, the sequencer part was almost done and fixed to a wooden board. The presentation at the end of day 3 came closer and closer and I again had the task to find things that sound nice. I wouldn’t say that I failed… But things did not turn out as I expected…
People had fun playing with it, I had fun building it and no hard feelings when I sacrificed it to the scrap metal gods after the presentation.