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Category: Mechanical works

Angular constraints of prosthetic grippers and functional success correlation [technical evaluation]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Angular constraints of prosthetic grippers and functional success correlation [technical evaluation]; published February 11, 2019, 04:55; URL: https://www.swisswuff.ch/tech/?p=9322.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Angular constraints of prosthetic grippers and functional success correlation [technical evaluation]}}, month = {February},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9322}}


I had evaluated, subjectively, the grip performance of various prosthetic options that I have. These have been already analysed in the context of grip taxonomy, where so far, research has largely focused on grip geometry as such, using some idiosyncratic logic that I found not too relevant.

Using a more relevant logic, I approached the question of grip mechanic from a different angle, both verbally and proverbially speaking: from a user angle, both actually geometrically and subjectively speaking.

I realized that most of my frequently used grips and grip situations fall into a far more narrow range of angle distributions than I had ever assumed.  So I sat down to add "typical object angles" to my already present grip success statistics over a list of my most frequently or typically used grips. Then I did that in theory and THEN I figured, why not go and video some. Thereby, a prosthetic hook as gripper device appears to be a lot more advanced, design wise, geometrically, in reducing device materials, bulk and design to approximate a really good overall use performance than the iLimb (which I have here also for as much testing as I like) and with that, many current commercial (or other) multi articulated hands.

In fact, prosthetic hands appear to be by far the older (and thus possibly less reflected) geometric design idea of a prosthetic arm's terminal device than the definitely more modern split hook. I may also go history hunting, but the claim that a split hook is old or outdated, and that therefore by inference a prosthetic hand is automatically new or more modern, as an idea, is wrong, particularly technically speaking. But also historically, to replace a hand with a hand is a straightforward design idea, that does not take any imagination, thus it is reportedly old, very old.

The far more elegant reduction, also of angles and controls, to fit into the limited action and option constraints of an arm amputee, is certainly that of a body powered split hook. It boils down the prosthetic needs to a successful sleek elegant reduction of a functional minimum, making it the ideal choice for anyone that wants a maximum of performance from a minimum of failure, cost, decay, bulk, futile grip attempts and total overhead. The subtle distinction is that a "body powered split hook" is an entirely different beast than a passive hook, obviously, which probably no one ever noticed, particularly not the people that assumed that a body powered split hook is best portrayed by installing a "Captain Hook" metaphor.

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Real work - Real Men Don't Eat Quiche - Real Programmers Don't Use PASCAL [reference to popular culture]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Real work - Real Men Don't Eat Quiche - Real Programmers Don't Use PASCAL [reference to popular culture]; published December 6, 2018, 08:37; URL: https://www.swisswuff.ch/tech/?p=8850.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Real work - Real Men Don't Eat Quiche - Real Programmers Don't Use PASCAL [reference to popular culture]}}, month = {December},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8850}}


When I mention real work as opposed to work one does in the role of a pansy boy, I certainly mean this both seriously and tongue in cheek.

Only if you spend your days with real work will you ever understand. You will be dripping wet from sweating. Your clothes will be so entirely smelly from external causes. Your materials will be in dire need for cleaning ever so comprehensively. You have worked for many hours. And you will go back to do it all over again. A prosthetic arm that is built to last 3 years dies within 5 seconds, 15 minutes, or 2 months - using stock commercial parts, it burns and dies like paper consumed by a slow fire, component by component.

Welcome to the world of real work.

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Artwork - DIY - Red Hand series - yellow Lean Ergonomic Grip Orthogonizer (LEGO) hand - stainless steel 3D-print, acrylic yellow spray paint [first test]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Artwork - DIY - Red Hand series - yellow Lean Ergonomic Grip Orthogonizer (LEGO) hand - stainless steel 3D-print, acrylic yellow spray paint [first test]; published February 10, 2018, 16:57; URL: https://www.swisswuff.ch/tech/?p=8283.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Artwork - DIY - Red Hand series - yellow Lean Ergonomic Grip Orthogonizer (LEGO) hand - stainless steel 3D-print, acrylic yellow spray paint [first test]}}, month = {February},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8283}}


Approximating the quintessential and ubiquitous LEGO hand, I designed one from scratch, got it manufactured in stainless steel and spray painted it with yellow acrylic color.

Here is the real LEGO hand used in advertising and action.

And here is the one that is Ready To Wear and so in its own way, my newly designed item is the first real humanly wearable and thus real LEGO hand. With that it may challenge your views on anthropomorphism, functionality, and on the Uncanny Valley.

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3D-print molded Protosil RTV 245 (durometer shore 40A) silicone covers for Toughware Equilux [proof of concept, demo of "bionic" grip]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - 3D-print molded Protosil RTV 245 (durometer shore 40A) silicone covers for Toughware Equilux [proof of concept, demo of "bionic" grip]; published February 4, 2018, 11:50; URL: https://www.swisswuff.ch/tech/?p=8248.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - 3D-print molded Protosil RTV 245 (durometer shore 40A) silicone covers for Toughware Equilux [proof of concept, demo of "bionic" grip]}}, month = {February},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8248}}


It is sometimes more fun to present the technical results before or even instead of explaining exactly why.  So in short, I 3d-designed and then printed molds to make grip covers for really serious grip performance of a Toughware Equilux device.

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Modifying Shimano Ultegra road bike setup on a Colnago C40 for left handed use - second approach [technical right below elbow amputee core focus work / bike adaptation]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Modifying Shimano Ultegra road bike setup on a Colnago C40 for left handed use - second approach [technical right below elbow amputee core focus work / bike adaptation]; published January 27, 2018, 15:30; URL: https://www.swisswuff.ch/tech/?p=8196.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Modifying Shimano Ultegra road bike setup on a Colnago C40 for left handed use - second approach [technical right below elbow amputee core focus work / bike adaptation]}}, month = {January},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8196}}


After a first approach, where also the history and idea where it came from is detailed [link], I now set up and tested a second approach to modifying my Colnago C40 carbon bike with a triple chainring Shimano Ultegra chainset.

The extensive testing of my first approach that I had performed there lead to a range of concise detailed issues and problems. There were now addressed, all, and thus a second (and significantly better) approach resulted.

As stated before, no disability sports advocate specializing in road bikes and no bicycle mechanic specializing in individualization and custom solutions over the years ever thought this was possible in this way. They all said it could not be done. And I had asked a few of them, since it had bugged me a lot. And as I had sold my Cannondale road bike after the amputation, thinking there was no way, I now got myself a road bike back and decided to go down my own path to really use it the way it is meant to be used.

Generally and as part of riding a road bike, I wanted fast and comfortable gear switching, fast and accessible and comfortable braking, and I wanted to be able to enjoy various and if possible equally comfortable sitting positions or body positions. A great road bike trip may be a lot longer than a fast mountain bike trip into the forest. Last but not the least, as amputee my stump usually would suffer from vibration induced pain after 20 minutes  particularly with hard connectors such as the Mert or Freelock adapters, so padding definitely was an issue.

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Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment [article out]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment [article out]; published January 4, 2018, 14:29; URL: https://www.swisswuff.ch/tech/?p=8066.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Case-study of a user-driven prosthetic arm design: bionic hand versus customized body-powered technology in a highly demanding work environment [article out]}}, month = {January},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=8066}}


 


This is a blog post of one of the rare focused and well based scientific journal articles that really explains how real work, body powered and myoelectric arms relate and go together for a unilateral right below elbow amputee in a physically demanding work environment.

The prior presentation of this paper [poster at Cybathlon symposium 2016], which had been more pragmatically worded (with me thinking people would know anyway), this was now written up as article and published. During that process, the reviewers clearly made great points of all kinds of aspects I never knew were not sky clear to everyone.

So maybe, writing a ~ 30 page case study with > 210 references does clarify stuff, at least potentially and for those that actually read it. But possibly, it still requires attention to even just read it.

Knowledge does not come easy, Highlander! (Nakano, in: Highlander III The Final Dimension)

 

If you are more interested in visionary posts, read about the gadget features of the prosthetic arm in Kingsmen: The Golden Circle [link]. And technically, myoelectric control did have it coming. That technology remained uncool for four decades [link].

Publication [link]

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Toughware Equilux - new VO (voluntary opening) / VC (voluntary closing) body powered device - industrial grip pads [concept, beta]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Toughware Equilux - new VO (voluntary opening) / VC (voluntary closing) body powered device - industrial grip pads [concept, beta]; published August 17, 2017, 20:15; URL: https://www.swisswuff.ch/tech/?p=7569.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Toughware Equilux - new VO (voluntary opening) / VC (voluntary closing) body powered device - industrial grip pads [concept, beta]}}, month = {August},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7569}}


Read about the Toughware Equilux here. All prosthetic hooks, prehensors or grippers lack the option of using industrial grip pads. Pads that are readily available, cheap, durable and that the user can easily switch.

And grip pads and grip gloves are a real issue. As posted before, grip pads must be soft,  possible to clean, easy and cheap to replace and convenient. These requirements are in part mutually exclusive. With the knife holding issue of the Equilux, what easier than to mount some standard bike rim brake pads and take it from there.

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Grip performance enhancement through modifying terminal device gripper surface [overview]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Grip performance enhancement through modifying terminal device gripper surface [overview]; published July 19, 2017, 16:00; URL: https://www.swisswuff.ch/tech/?p=7431.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Grip performance enhancement through modifying terminal device gripper surface [overview]}}, month = {July},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7431}}


When using a prosthetic arm with a terminal device, grip performance is a key issue.

Usually, a bare steel hook such as the Hosmer model 5 works through just about every situation. That is just because that is how it is. A closer look reveals, however, that that view may be overly simplistic. If anything, it requires explanation.

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Guitar pick holder for iLimb / Dunlop TORTEX picks [3d printed solution]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Guitar pick holder for iLimb / Dunlop TORTEX picks [3d printed solution]; published February 12, 2017, 17:23; URL: https://www.swisswuff.ch/tech/?p=7198.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Guitar pick holder for iLimb / Dunlop TORTEX picks [3d printed solution]}}, month = {February},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7198}}


As we all know, I just recently designed and rapid prototyped a guitar pick holder for my prosthetic hook.

And guess what, this guitar pick holder also perfectly fits my iLimb revolution, certainly making me the first official "Cyborg AND 3d-print" endowing prosthetic arm guitar player, like, ever ; ) That just got to be raising hell, getting all these new hyped up slogan words lined up, like, together. Plus, this is just a really first test, as in, first minutes. I put in on, and 5 minutes later, this.

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Guitar pick holder for Hosmer 5 hook /Dunlop TORTEX picks [3d printed solution]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Guitar pick holder for Hosmer 5 hook /Dunlop TORTEX picks [3d printed solution]; published February 11, 2017, 00:08; URL: https://www.swisswuff.ch/tech/?p=7189.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Guitar pick holder for Hosmer 5 hook /Dunlop TORTEX picks [3d printed solution]}}, month = {February},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7189}}


I was searching for a practical way to get back to playing guitar with a pick for quite a while. I knew what I wanted - I just had to make it happen.

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Bowden cable mount for prosthetic arm [patent, explained]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Bowden cable mount for prosthetic arm [patent, explained]; published February 3, 2017, 14:30; URL: https://www.swisswuff.ch/tech/?p=7172.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Bowden cable mount for prosthetic arm [patent, explained]}}, month = {February},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7172}}


Explaining Swiss patent CH 703 982 B1 (PDF also here).

The motivation for this patent was to avoid frequent cable tears, cable rips or cable damage when using metal cables such as the ones used for gear or brake control on bicycles.

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Hosmer Mod. 5 hook clip for cell phone cover fixation [3D printed solution]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Hosmer Mod. 5 hook clip for cell phone cover fixation [3D printed solution]; published January 21, 2017, 14:34; URL: https://www.swisswuff.ch/tech/?p=7111.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Hosmer Mod. 5 hook clip for cell phone cover fixation [3D printed solution]}}, month = {January},year = {2017}, url = {https://www.swisswuff.ch/tech/?p=7111}}


Since I like to browse on my mobile phone when lying on the back on my sofa, I figured why not make a 3D thingy to allow me to do just that.

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Trautmann hook [3D printed steel parts, assembly, first use]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Trautmann hook [3D printed steel parts, assembly, first use]; published December 28, 2016, 17:53; URL: https://www.swisswuff.ch/tech/?p=7037.

BibTeX: @MISC{schweitzer_wolf_1569142428, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Trautmann hook [3D printed steel parts, assembly, first use]}}, month = {December},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=7037}}


First, I had performed a feasibility test using a PLA model that I had printed myself to see whether I really wanted a Trautman hook. After that, I had decided that I wanted one.

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