The Spare Hand project: idea is to make a spare hand that can carry light grocery bags or hold a dog leash...A simple, cheap, easy to make, prosthetic for people missing a hand...It could be put on or taken off quickly, just for short errands in the winter...Only for some simple tasks, not intended to replace a full motion prosthetic...
http://www.kjmagnetics.com/proddetail.asp?prod=RX436DCSPC-BLK&cat=16 Ok, so I found a magnet that can fit a number 10 screw...My idea is to make a new index finger & thumb, like the one above, & screw the neodymium magnet on the end of the index finger & then another on the top of the thumb...The combined pull if you put the index finger magnet to the top of the thumb magnet will be about 20 lbs...This means you could carry up to a 20 lb. bag of groceries by making the index finger touch the tip of the thumb...My thought is that people missing a hand, but wanting only basic function of carrying a bag of groceries, could use this very inexpensive to make, magnetic prosthetic...You could also hold the loop of a dog leash, another useful function...Of course, the more Plasti-Dip that I put on the prosthetic, the more cushioned it will be...But that is for when I am finishing the piece...For now it is helpful to be able to see how this is made...because theoretically, people could use this idea to make their own prosthetics...Wouldn't that be more fun than paying someone else?
revised design above:
This is what I've been doing today...trying to revise the design to make it lighter, & simpler...Now I am going to wait for the neodymium magnets to arrive, then I am going to screw then onto the tip of the thumb & the tip of the index finger...At some point, a dip in Plasti-Dip will coat everything & make it hold together better...The clear pipe in a flex material is so that when the prosthetic rests against the stump of the left arm, that it will feel comfortable...
Note: Monday night at 11:48 pm... The locking nuts, because they sit on the end of the screw( instead of more in the middle where regular bolts have to sit with a washer) are tenuous in my opinion, for strength possibility...They are neat & great but I realize that any weight on them might cause them to nick off...
I don't know either whether the decision to use screws instead of custom cutting threaded rod was the right decision...Sure it is easier to use pre-cut 2 inch, 1-1/2 inch & 1 inch screws, but when I cut the rod with a bolt cutter, my weird by feel lengths feel more organic when the whole thing gets put together...
The clear rubber pipe really works well though...That was a totally new innovation that happened today at Canadian Tire (hardware store)...I was looking for tiny rubber bands, to cover the copper strapping at the bottom & create a nice rubbery bottom, but they didn't have any so the store employee suggested plumbing washers, those black rubber circles...So I stood looking at rubber washers, looking for ones big enough to encircle the 1/2 inch copper strapping...
Found two...But I needed like, well, a whole lot of them, & for 1.49 each pair it was too expensive...
I noticed some tubing...I asked for help...Someone else came & I asked if there was any tubing to fit the 1/2 inch copper strapping inside of it...So we looked...Together we decided that the 1/2 inch tube was too snug a fit, but the 3/4 inch diameter clear tube was gorgeous...She cut a foot for me...Delighted, I now had a way to cover the copper & rest the prosthetic comfortable on someone's stump where the hand should have been...
Of course, if I ever get to the point where my idea actually works, then I will have to create a strap to swing around the tube like a U, & then attach to an arm cuff...This would be the way the "hand" would attach to the person's arm...
Honestly, at this point I just want to say that art is usually what you call a real thing that fails design quotas...Ok, I am being harsh...But what I mean to say is that if this thing fails as a real prosthetic, it will be relegated to the world of art, which is far less judgemental than the real world...
I try to admit failure on some sort of regular basis...It keeps me humble & keeps my work pure...Once failure is admitted I can move on...The work often gets kept by me as I reminder of my toil & trouble...Failures often represent far more work time than successes...
Let's give this some time...prosthetics are hard...
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| Ok so here are some refinements I have come to for now... |
Tuesday: Above in the photo, my little tape measure, the pink thing, flexible & with Imperial & Metric, size 10-24 screws (10 is the diameter of the screw, the 24 means the thread count like does it have many little threads or just a few), locking nuts-these are bolts that have a little circle washer attached to them that has little tiny spikes on it-if something presses up against the little circle washer with the spikes it rotates freely, so then the bolt doesn't come loose-the only thing is locking nuts won't thread UP a rod or screw, they just sit at the end only...To the right is a bolt cutter-that is what you use to cut a 10-24 rod or screw if you need a custom size-they are easy to use surprisingly...Notice I string cord through cardboard & paper to make a sketchpad-I write this because people forget that used cardboard makes a great backing for paper...I use nylon string, it is strong...
I have come to think that if I boil down the whole prosthetic hand idea into something essentially functional to the essence of the function of a hand that it may just be the ability to carry a grocery bag or hold a dog leash that would provide a slight upgrade in functionality for someone missing a left hand without the burden of having to carry a whole prosthetic hand around...There is something about the lightness of movement that amputees or people born missing limbs like...They don't like prosthetics often because they are not accustomed to the extra weight of the limb...
My idea was to design something so simple, so inexpensive, so easy to use, that it would add a little bit of bonus to someone's life without a whole lot of problems...
When I was boiling down the essence of hand in my mind, I started thinking about the opposable thumb idea...That the opposable thumb is supposed to be this such great invention...If that opposable thumb is so darn important, then it must be grabbing that is what is key...Because with an opposable thumb you can grab...
So with that in mind, the grabbing, & after observing our friend's needs, I decided two main things would be helpful to him...One to be able to carry two grocery bags of food, one in each "hand" instead of just one...And being able to hold the loop of a dog leash in either "hand"...Seeing as he has his right hand, the device for the missing left can be a manual...Manual as in, if the grab mechanism was manual by magnet, that the grab could be executed by using the right hand as a helper hand...
I am now down to just a thumb & index finger...But even more pared down, the index finger is now just a 2 inch screw & a 1-1/2 inch screw, held together by a copper strapping joint...I am going to add bolts to those, seeing as my idea of going boltless leaves the strapping kind of too loose...
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| things I have to get...bolts & separate locking nuts that can ride up the screws to hold the copper still... |
http://www.myrdalorthopedics.com/ I am adding this link here because, well, you can buy prosthetics of course in Canada...This is one such provider...I'm not giving up, just saying that these things do exist...I just thought maybe I could bring some fresh thinking into it, that's all...
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| Ameliorated: added some bolts & washers to make it all more secure...trimmed the clear tube...Am awaiting the neodymium magnets that will screw onto the tip of each... |
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| You can see here what bolt is what & the other materials I use...In case you want to try your own... |
My next step is I think I am going to 2 part epoxy around the bottom screws...Not sure...
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| Got this great idea this evening to also cover the "fingers" with clear tube too, flexible but sharp edges won't bite you! |
Comment: Wed. Feb. 6, 2013 at 7:34 pm evening...
So, I made this Carry hand, this time, with the thumb & index finger the same length...Did alot of deep thinking about this...I decided that a longer thumb would be an extra benefit to a person...Imagine if your thumb was as long as your index finger? When picking up a bag with handles, you wouldn't have to make sure your thumb got a grab, because your thumb would be the same length as your fingers...This would give people who use the "Carry Hand" an distinct advantage over people who have hands...I think that is ok...
After I made that decision, I left it alone in my mind...Later when I went to re-evaluate the idea I thought of something even better about this! If both the thumb & the finger of the "Carry hand" are the same length, then handedness doesn't matter!!! That means that the same device will work for people missing either a right hand or a left hand...This drives price down & makes it way easier for the seller...Neato Coolo!
Ok, attachment ideas: My uncle made an off the cuff remark about taking a glove & filling it with foam...But it was smart! from there, I was thinking a custom to whatever your skin colour is, skin coloured glove of sorts, of sorts 'cause only a thumb & index finger glove, but the shaft of the glove goes up over your wrist & up your arm, not sure how to make that secure, that will come...
So theoretically you could just pull this prosthesis on like a glove, & remove it like a glove...Like just cause you are going grocery shopping & want to carry 2 bags or you want to walk your dog with the "Carry Hand" & talk on your cellphone with your hand that isn't missing...(Yes, this design began with someone in mind who was only missing one hand...But you could totally get 2!!! Use them for both hands!)
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| carry hand is inside the glove now...first 2 fingers... |
http://sarigrove.com/2013/02/11/sparrycarry-looking-for-a-name-for-a-prosthetic-hand-that-helps-you-to-carry-things-a-spare-hand/ Hi, if you want to see the further progress on the "Spare Hand" please visit this link at our other blog...
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| the glove ( a winter glove with a wrist strap that tightens) |
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| the basic design, without all the bolts & washers though...One 2 inch screw (10-24 size), one 1-1/2 inch screw (same size 10-24), 1/2 inch copper strapping(comes in a box in the plumbing section, on a roll)...clear rubber tube...3/4 inch diameter... |
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| before dipping in Plasti-Dip, I put on the copper strapping with some locking bolts and copper wire so I could dip without getting dirty...Ended up pouring instead of dipping cause my tube was too wide for the mouth of the Plasti-Dip jar... |
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| before I screwed in the neodymium magnets...washers help bolts to not slip... |
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| after pouring on plasti-dip...drying, hung from something... |
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| here are the magnets...careful they are very strong & can injure fingers by pinching...learned the hard way... |
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| magnets...neodymium...from KJ Magnets online...bolted in... |
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| here is the spare hand, with the magnetic device inside the 2nd & 3rd fingers...stuck to the fridge holding an empty grocery bag...Handy place to store the spare hand! |
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| this is how the magnets come together...inside the glove... |
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| you should know that magnets can seriously ruin a computer, iphone or ipad or ipod...so keep them AWAY! (yes, this is a design flaw...sigh...) The spare hand should probably be used for outdoor applications because of the danger to computers...Oh well...I tried... |
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| me, Sari Grove |
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