Reverse the pulley and tensioners?

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Aztravis
Posts: 4
Joined: Tue Feb 17, 2015 12:13 am

Reverse the pulley and tensioners?

Postby Aztravis » Tue Feb 17, 2015 12:24 am

I am new to E-Nable, 3d printing, and prosthetic hands/arms. That being said, I am looking for a designer/volunteer to help me reverse the way the cyborg/raptor hands function. Looking at the way manufactured prosthetic hands and arms work, they tend to have the hand/hook begin in a closed position and when the user initiates the pull, it opens. As it stands right now, the raptor/cyborg hands begin in an open position until the user initiates inward movement to close the hands. It seems that it would be more useful to have a hand that is always trying to be closed so the user would not have to always have pressure on the object being lifted or held.

Is this something that is even possible or useful?

My printer comes in tomorrow so I will be testing out anything that is submitted.

Thank you community!

AdamArabian
Posts: 32
Joined: Mon Feb 16, 2015 2:04 am

Re: Reverse the pulley and tensioners?

Postby AdamArabian » Tue Feb 17, 2015 5:49 pm

Indeed - and there has been a lot of dicussion on it and we really want to move forward on it. The challenge is that it means there is a force always trying to close the hand which must be overcome with wrist action. Thus if you want to be able to hold a five pound weight, you need to be able to extend your hand with at least that force plus weird angle plus inefficiencies, which is really hard to do.

The hands you're talking about that are industry standard use the musculature of the back to make this happen - much more powerful muscles....

That being said, it NEEDS to be done so I'm all ears!

NathanRamsey
Posts: 5
Joined: Tue Feb 17, 2015 3:05 pm
Location: Buffalo, NY

Re: Reverse the pulley and tensioners?

Postby NathanRamsey » Wed Feb 18, 2015 2:22 pm

What we're talking about is voluntary opening (VO) versus a voluntary closing (VC) terminal device (TD).

Terminal Device (TD) - The functional "hand" portion at the end of a prosthesis, which usually has movable joints. It can be a hook, claw, moving hand, non-moving "passive" hand, or a wide variety of other configurations.
Voluntary Opening (VO) - Pull opens the TD. Most upper extremity prosthetics are VO. It's generally easier to maintain hold of an object for a long time using a VO TD.
Voluntary Closing (VC) - Pull closes the TD. An example is the TRS model, which I think has some similarities in design to a reacher. It's generally easier to align the TD to grasp and release objects with a VC device.

I've personally used both, and there are advantages and disadvantages to each. I'd like to see some VO models. Thick rubber bands are often used to hold the TD into a closed position in a VO system.

Prosthetists have decades of peer-reviewed scientific research behind them, and a history that dates back thousands of years. We should approach their work with the highest amount of respect, and borrow as much from their designs as possible.
Congenital left hand amputee, long-term prosthesis user, occupational therapist, and assistive technology specialist employed by the University at Buffalo Research Foundation | npramsey@buffalo.edu

NathanRamsey
Posts: 5
Joined: Tue Feb 17, 2015 3:05 pm
Location: Buffalo, NY

Re: Reverse the pulley and tensioners?

Postby NathanRamsey » Wed Feb 18, 2015 2:27 pm

Also, the Dr. Who fan in me wishes this thread was called "Reverse the Pull-arity". :)
Congenital left hand amputee, long-term prosthesis user, occupational therapist, and assistive technology specialist employed by the University at Buffalo Research Foundation | npramsey@buffalo.edu


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