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Topic: Home-built mechanical finger prosthetic  (Read 19634 times)
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« on: September 11, 2012 06:42:13 AM »

I know... The subject line of this post is a mouthful! There just isn't any other way to reasonably describe this thing Cheesy

I've built a large number of unusual things. This is, however, the most unusual, fun and important project that I've been a part of. In December of 2011, a man by the name of Richard Van As who saw one of my Youtube videos sent me an email with these pictures in it:

He very simply asked if would consider partnering with him to build a mechanical replacement for his missing digits. I was excited to jump in and figure it out with him! The catch: he and I live 10,000 miles away from each other. What ensued was a lot of emails, pictures and drawings sent back and forth, and Skype sessions. Now, after a lot of tinkering, we have our first truly functional prototype:

<iframe width="420" height="315" src="http://www.youtube.com/embed/PkmHfT_rDf8" frameborder="0" allowfullscreen></iframe>

We aren't patenting the design; instead we're giving the knowledge away for free. I thought Craftster might be a good place to share some info on the construction of this device.

Here's a rundown of the parts of our prototype:

The hand mount (A) is made from rigid material and formed to the amputee's hand. The lever arm (D) is attached to the hand mount with an axle at position (I). The passive tension system is attached to the hand at position (F)
The artificial finger is made up of a rigid lever arm (D) to which pulleys (C), a form fitting sleeve (B), hinge (E) and Finger tip with grip pad (G) are attached. A cable runs from the finger tip (G) through the pulleys and  attaches to the hand mount at position (H)

We don't have photos of the complete process yet (mostly because we haven't perfected all the steps, lol Smiley ) but I would like to share with you, at least, the wonders of an amazing material called "thermoplastic"!!!!

To start things off, Rich sent me an exact copy of his hand so that I could have an in-person version of it when building models of our designs on my side of the globe:

It's cast from plastic and very durable (so that when I'm clumsy it doesn't break!)

Thermoplastic, I'm fairly certain, has been imbued with magical properties by some sort of ancient race of mythical creatures. It's more likely that it's just a marvel of modern chemistry.... but imagining it being created magically is more exciting.

This is the first time I've worked with it and it's indescribably useful. You cut out your pattern and then immerse the piece of plastic in boiling water for about 20 or 30 seconds. It then turns into a clear, completely flexible material that can stretch and it even adheres to itself! The amazing part, you can take it straight from boiling water, shake off the excess droplets and then handle it without it burning you. It's not even uncomfortably hot. For some reason it's a terrible conductor of heat, but I digress.

After preparing the thermoplastic, I use the model of Richard's hand to create whichever part of the mounting system I'm experimenting with. Here you can see me forming it to fit around his index finger stump. The flaps at the top are later bent together and then the thermoplastic fuses to itself.

Here I am fusing the flaps at the tip. In front of me is my electric kettle, a measuring cup to hold the boiling water, and a bowl full of ice water. After the part is formed, I immerse the part into the ice water. This cools it rapidly and turns the plastic back into its' high-strength, rigid form.

After the hand-mounts are made, then it's a matter of mounting the other hardware and components to the device & sharing what we've made with each other on our Skype brainstorming sessions. Here's a link to a story on our blog that shows both how we communicate with each other on the project as well as an exciting development! Richard's mind is starting to sort of "feel" with the prosthesis!

On 11/17/12 I will be flying over to South Africa to meet Richard in person for the first time and work to finalize our design! For those that are interested, we will be posting video updates on our progress on the fine-tuned version on the site that I linked to above. Smiley

November has come and gone, and my visit with Rich went very well! Here's a video that summarizes what we did together: http://www.youtube.com/watch?v=cyC6_LY7oq0
« Last Edit: December 16, 2012 03:41:50 PM by ChainCrafts » THIS ROCKS   Logged

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« Reply #1 on: September 11, 2012 06:52:50 AM »

What an amazing thing that you are doing for somebody that you don't even know!!!  Bravo for you.

Thermaplastic is actually fun stuff to work with.  My partner needed a brace when she shattered her wrist and they made it from thermaplastic.  I was lucky enough to be given the leftover scraps to work with.

I applaud you.


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« Reply #2 on: September 11, 2012 07:30:28 AM »

This is AWESOME!!  I'm looking forward to seeing the final product.  And what a way to get a colaboration?  Ain't the internet grand, eh?  Cheesy 

Hope you have a safe journey - on my birthday! Wink


« Reply #3 on: September 11, 2012 07:31:13 AM »

Whauw! What a great thing to do - and it is very generous af you to give the knowlegde away for free. There must be thousands of people with similar problems.

« Reply #4 on: September 11, 2012 07:48:37 AM »

That is truly amazing. Posted the video to my Facebook for others to see.

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« Reply #5 on: September 11, 2012 07:49:54 AM »

What a brilliant device and making it available like this means people who can't afford something like this could  make one for themselves or have a friend make it for them. Especially in Africa.
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« Reply #6 on: September 11, 2012 07:55:09 AM »

you are so amazing


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« Reply #7 on: September 11, 2012 08:13:14 AM »

That is awesome!  YOU are awesome both for doing it and for giving the information freely.  I applaud you with as many prosthetic hands and real hands as I can find.  So pretty much just my two hands.

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« Reply #8 on: September 11, 2012 08:37:02 AM »

This is so exciting! I just featured this project on Craftster's Facebook page. Thanks for sharing. Smiley

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« Reply #9 on: September 11, 2012 09:08:23 AM »

This is a truly amazing project! Thank you for sharing it here, you guys are both so awesome

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