This info is tremendously helpful. I am so thankful for you guys willingness to share your knowledge and the pictures.
I was able to get several assorted springs from a local woodwind repair shop. The general policy is that he doesn’t sell parts, but since I’m not trying to repair something he made an exception. He even gave me some tiny screws. Andy, thank you for the Ebay link. I kind of forget Ebay exists sometimes. That’s quite a reasonable price for the springs.
Terry, I am attempting to model my key similar to your McG#. It is putting my CAD skills to the test. I can model square boxes with rounded corners all day long, but naturally shaped and curved surfaces are forcing me to learn more about geometry. This means I don’t have a prototype printed yet, ha. I also have only had a couple hours to work on it the last few days.
I like the idea of the double springs, but for now I will plan on just one to eliminate extra moving parts and alignments. If I had a rock-solid mounting method already I would consider it, but I have a long way to go.
I am back with an update! Before you get your hopes up, I do not have a working key on a working flute, but I have made progress. Designing things that work seem to always take longer than I expect, but I enjoy the process and I’ve already learned a lot. I’ve printed two models so far, and the second one is promising.
Designing: I am no 3D design genius, and I am always happy to get helpful criticism. Before this, most of the models I’ve made could be sketched flat on a plane, and then extruded in various directions in various layers. That method isn’t useful for more complex shapes. I almost extensively used “lofts” to make this – drawing multiple flat sketches in different planes and then connecting them to each other. I tried to imitate the McG# shape as best as I could.
Prototype: The first print especially made me realize how low quality my 3d printer is. I printed with PLA in 0.08mm layers, and it was rough. I had it a little too thin, (it was flexible) and the spring screw went right through the touch. The 2nd print is a little better. I used a rough file to clean up some imperfections, but didn’t do any sanding.
I have it temporarily positioned on one of my first bad PVC flutes. No G# hole, no pad on the key yet. The printed ring has a slot that allows the spring to theoretically get past the fulcrum point, as well as keeping it from splaying to the side. The spring surprisingly worked to my satisfaction without any modification. Compared to a concert flute or clarinet key (with needle springs) it feels firm, but I think that will help seal the hole better. When I press it all the way it has less resistance than when its sitting closed! Here’s a video. 3d printed simple system flute key prototype V2
Next version with have some minor geometry changes, and I will tighten the space between the key and the “blocks” so it can’t wiggle side to side (see the first picture).
It can be fastened on a flute/whistle (25mm OD) with two M2.5 screws through the back holes.
(I would suggest you using PETG, which is stronger than PLA and have longer life.)
Here is the download link of the STL file:
And when you are making keys on a thin wall flute, it will be hard to form a counterbore for the keypad, so I would suggest you make the top of the key curved, and use thin EVA foam as keypads to get a good seal.
