e-Nable ratchet force amp pulley concept v1.1

By UltiErik

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e-Nable ratchet force amp pulley concept v1.1

By UltiErik

44
2
Free
It's free to download

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e-Nable ratchet force amp pulley concept v1.1

By UltiErik

at 2024-05-03
Concept for e-Nable prosthetic hands to have more force for weaker wrists that also have a limited bending/travel range. This is made possible with a pair of pulleys combined with a ratcheting mechanism. This would allow gradual increase of the grip of the prosthetic fingers to increase as you bend the wrist several times.This will act like two pulleys on one axle. Each pulley has a different diameter. If you put cable across both of them, each pointing in a different direction, you can pull one of them and get more strength on the one that has the smaller hub. https://www.youtube.com/watch?v=K9eESS9ZBsU The cables should fit through the holes if they're 0.4 mm, but you may want to increase its size a bit if your cables are bigger.Compared to directly pulling the cables, this will duplicate the force if you make the same amount of bending movement twice. You can also decide on a 1:3 ratio for 3 times the strength. In any case, if you can only bend a little, you can do it three times and still grip completely. The pink part would be part of the fixed part of the prosthetic the pulleys that rotate within it need a 3mm bolt as an axle to rotate on, which should also be a fixed part.A release mechanism hasn't been developed yet, but that shouldn't be too hard. Also, it needs to be tested and the spacings/sizes adjusted. Feel free to continue where I left it.Updates:V1.1 now it has animation and also the cables are rendered. You see the cables move with a ratio that corresponds with the pulleys. The force ratio is inverted (slow moving cable has amplified force)V1.2 made the part a bit bigger, made the teeth deeper and the pawls thinner and longer. Made the ratchet well a bit fatter (stronger) and the holes for the cables wider.

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SkipMeetze
SkipMeetze
over 10 years
Thanks. At present I know how to use Tinkercad only. Your STL files imported into Tinkercad just fine and I'm accustomed to editing such imported files by adding to, subtracting from and changing dimensions. I think my single pawl might have some advantages over the 3 pawls, and it provides an easy reset feature. I'll upload it soon!
UltiErik
UltiErik
over 10 years
Attribution in the description is currently the way to do it. We intend to add a 'formalized' way to do this. Thanks for thinking about this. The strength, all of the sizes and the number of pawls are configurable in this parametric model. The sizes of each of the components was meant to be tuned once we started printing them we can make them more realistic. You can also configure how deep the teeth will be (more strength but also more strength needed to lift the pawls). The dimensions I had entered right now were for printing it on my Ultimaker 2, but they should be easy to change if you load the .scad model in OpenSCAD.
SkipMeetze
SkipMeetze
over 10 years
Erik, I am very excited about this idea being useful for e-NABLE prosthetics. However, I found the V1.1 design to be too small to print successfully on MacGyvrBot. I re-designed it to be a little over 30mm, and using only one (longer) pawl. I'm planning to test one more iteration, then publish the design. I would like to attribute the idea to you and to this design, but don't see how to do that other than to bury the attribution in the description.
UltiErik
UltiErik
over 10 years
Hi Skip! Great to find you here at YouMagine! I tried to upload the video at the airport and that mostly worked, I didn't see that I still had to approve the publication. Now it should work. If you print it, you can press the "+ add" or the + button under "Printed by" to share a picture and of course I'd be interested to know what the results were (you can add them there).
SkipMeetze
SkipMeetze
over 10 years
Erik, the video seems to be private and I can not view it... A very interesting concept and I look forward to trying it. Perhaps mount the ratchet on the gauntlet, the driving string connected to the back of the palm and the finger-pulling string connects to the to the tendons with the zip-tie tensioners that I have been playing around with.

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Joined almost 12 years ago Tilburg, the Netherlands

Erik is long time 3D printing fanatic, has been an early RepRap contributor and is one of the co-founders Ultimaker BV. He created YouMagine while at Ultimaker. YouMagine is no longer an Ultimaker-owned platform, but Erik continues to develop and impr...

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