Equal pull pulley system - need ideas

Question

Equal pull pulley system - need ideas

Andy Martin (Automotive)

(OP)

30 Apr 19 15:29

I have a very compact device that I'm designing. It pulls cords (fishing line) that operate the chords on a guitar for people not able to use the fret board.

Here the problem - a first class lever pulls on three cords simultaneously in response to finger pressure on the other end of the lever. I need to pull all three cords with equal force. With two it would be simple - just loop them around a single pulley and pull the axis - the pulley would turn to equalize the force. But what can I do with three cords?? Really struggling to come up with any mechanism (nearly as simple as a pulley) that would equalize the force on three cords.

https://www.thingiverse.com/thing:3531399

Any inspiration?

Andy

Compositepro (Chemical) · Answer 1 · 2019-04-30 15:39:13

https://en.wikipedia.org/wiki/Whippletree_(mechani...)

Andy Martin (Automotive) · Answer 2 · 2019-04-30 16:20:20

Hmmm, interesting. I had not heard of a whippletree before, but I recognize the mechanism. Not sure I would have the width available to accommodate the width required for the system of levers. Can you think of anything similar using pulleys?

Compositepro (Chemical) · Answer 3 · 2019-04-30 16:42:25

You do realize that pulleys are a form of lever. You will have to use your imagination to make things work for your particular application. Think shoe lacing or corset lacing with pulleys rather than eyelets.

Example 5 in this link: https://www.psychometric-success.com/aptitude-test...

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Equal pull pulley system - need ideas