This winter break, I soldered together version 7.1 Magnetic Cello circuits, fixing that darn short and cleaning up wiring a bit. I’ve switched out the circuit on Magnetic Cellos #1 and #2, and #3 is patiently waiting for its turn. Once I get enough of a reprieve from class and homework, I’ll disassemble the instrument and install and tune the new circuit. And once I screw together #3, that will be it. It’s tough to keep my perfectionism in check, but there will be no more improvements worth making… on the instrument itself.
The bow, however, is a different story. I got some good feedback from my cellists over winter break, and it turned out the magnets in the instrument’s magnetic bow were too wimpy. Because of the way we were manufacturing the bow, we had a limited amount of space for the magnets. I was aware of a slight decrease in bowing power and length, but, thanks to some feedback, I realized that I had made a mistake. The instrument was almost unplayable on longer notes.
After playing around with this magnet calculator, I realized that adding magnets along the length of the bow did very little to increase pulling strength (and thus induced current in the coil). We needed wider, not longer, magnets. I ordered some magnets that were twice as wide and, not surprisingly, the Magnetic Cello sounded louder at the same volume setting, could detect bowing further from the coil, and could play notes about twice as long.
It took a little bit of kanoidering, as it always does, and a small increase in bow size, but the bigger magnets fits snuggly into the new design. We sent the files over to Ponoko yesterday. In a few weeks we’ll have new, stronger magnetic bows, made out of this nice walnut MDF. Redoing the bows gave us a chance to round off the corners, add a logo to the bottom layer, and add better cable strain relief–but that might just be my perfectionism popping up again.
Once we get the new bows come in, it should be a simple operation to solder in the switch and glue everything together. And then the Magnetic Cello will be done, and will be something I would be proud to sell.
I also spend winter break designing the Guitar Chord Card. They look great, but there a few problems to work out. I’m not quite ready to put up more details, but let me know if you want to try the current iteration (the minimum order was 200, so I have more than enough to go around). Mom: ask Grandma for a few, I gave her a bunch before going back to school.
So, the Magnetic Cello is coming together, and the Guitar Chord Card is progressing quickly. Once the cellists have a chance to try out the new bows, we’ll be ready to sell. Almost there.