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Posted: 15 Dec 2021 11:23 am
by Eric Moon
Here's a quick mockup of the kind of thing I'm thinking of...
Image

changer fingers shown in full raise position...

Posted: 15 Dec 2021 11:30 am
by Eric Moon
thanks, already great insights here. Thanks for the links. Good point about the G# string also.

I'm expecting to need a pretty strong spring to counter balance the string tension, as well as a way to adjust the spring...

pretty clear there will be a lot to experiment with. I haven't been able to find a more powerful servo yet, that can move that fast, but I'll keep looking. And maybe some clues in those links.

Thanks all!!

Posted: 15 Dec 2021 12:50 pm
by Ian Worley
Eric Moon wrote:...I'm expecting to need a pretty strong spring to counter balance the string tension, as well as a way to adjust the spring...
One big challenge to consider here is that the tension the springs are counteracting will vary as string pitch changes. On the smaller diameter strings that variability is more significant. Springs are also susceptible to changes in their mechanical properties with use and changes in temperature. I am skeptical that you'd be able to achieve a reliably stable and consistent neutral "open" position on a solid finger changer design with just springs and a lightweight servo.