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Category: Prosthetics

TRS Jaws [new product - first use report]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - TRS Jaws [new product - first use report]; published August 10, 2019, 10:51; URL: https://www.swisswuff.ch/tech/?p=9769.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - TRS Jaws [new product - first use report]}}, month = {August},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9769}}


3 Comments

The TRS Jaws is a voluntary opening gripper where you can set the grip strength by a lever. The grip then varies between very light, maybe under 1 kg or so, to somewhere above 5 kg. This is a first real use report, after I used it permanently since roughly around May 21, 2019, give or take a few hours.

There are just a few points to address at this stage. If you wear a body powered arm for real work [link], you may now buy one.

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Adapting mountain bike (CUBE ACID 29", 2019) for left handed use [photos]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Adapting mountain bike (CUBE ACID 29", 2019) for left handed use [photos]; published August 10, 2019, 10:17; URL: https://www.swisswuff.ch/tech/?p=9900.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Adapting mountain bike (CUBE ACID 29", 2019) for left handed use [photos]}}, month = {August},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9900}}


"Last year, South Africa's Greg Minnaar (Santa Cruz Syndicate), a three-time UCI World Champion, won a record extending 20th Downhill World Cup in Fort William, Scotland. What made these wins unique was that they were the first World Cup events to be won on a bike with 29" wheels. (..) So does this mean the debate is over, and 29" wheels have replaced 27.5" ones? Not so fast!"-- Thinking about wheels? Michal Cerveny [UCI news]

As my trusted old Cube bike died due to age (profuse hydraulic leaks, spare parts > 1 month away, while on bike holidays) it was clear I had to replace it. So I bought the useful (but not overly expensive) CUBE ACID, with 29" wheels, model year 2019, for something over 900 Euros. The dealer gave me a lower price than the indicated / recommended one.

More history is here [link] with my coolest bike mod so far being the Colnago road bike with switched Ultegra levers [link].

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BLUE LIGHT SPECIAL - defect iLimb glove poses tricky Catch-22 for Cybathlon 2020 [review]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL - defect iLimb glove poses tricky Catch-22 for Cybathlon 2020 [review]; published April 21, 2019, 14:42; URL: https://www.swisswuff.ch/tech/?p=9987.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL - defect iLimb glove poses tricky Catch-22 for Cybathlon 2020 [review]}}, month = {April},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9987}}


The Cybathlon 2020 race rules confront us with two interesting Catch-22 aspects:

-hammering (if not other dangerous) activity that is not endorsed by "bionic" hand manufacturers [link]

-use of damaged / perforated covers, not endorsed by Ossur (see here)

The iLimb user / clinician manual clearly states "do not use without an approved cover", "do not use with a damaged cover", and, "damaged covers must be replaced by a qualified Touch Bionics technician or technical partner" 1.

However, the Cybathlon Karlsruhe 2019 footage clearly exhibits a torn and perforated glove (defect over the knuckle of finger II/index finger) being used during the competition during the task that has the competitor push a card into a slot.

From view of a user that had serious issues with these "glove covers" that Touch Bionics (then) / Ossur (now) sold for a premium, and who knows a lot about replacing these with better parts despite manual regulations, this is VERY interesting: because a damaged cover unnegotiably operates far outside the acceptable use condition that appears to be insurable. And insurance seems to be a thing there.

To remind you: Touch Bionics glove covers die by themselves when left alone [link] or when used for something as minor, uninteresting and light as a 10 minute car wash [link]. I was left to myself to identify a work glove [link] and a durable cosmetic glove [link].

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BLUE LIGHT SPECIAL - Hammer use to hammer nails, with "bionic" prosthetic hand, poses tricky Catch-22 for Cybathlon 2020 [review]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL - Hammer use to hammer nails, with "bionic" prosthetic hand, poses tricky Catch-22 for Cybathlon 2020 [review]; published April 20, 2019, 10:28; URL: https://www.swisswuff.ch/tech/?p=9594.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - BLUE LIGHT SPECIAL - Hammer use to hammer nails, with "bionic" prosthetic hand, poses tricky Catch-22 for Cybathlon 2020 [review]}}, month = {April},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9594}}


The Cybathlon 2020 race rules confront us with two interesting Catch-22 aspects:

-hammering (if not other dangerous) activity that is not endorsed by "bionic" hand manufacturers

-use of damaged / perforated covers, not endorsed by Ossur [link]

A hammer, particularly a cheap or small one, even more so than a heavy dangerous "real" hammer, is an unlikely tool to use with an ~80 000 USD myoelectric "bionic" device that is specifically built to sustain only the lightest of work. And the subject of hammering, technically, as arm amputee with a prosthetic arm, has become relevant since the Cybathlon 2020 directors [link] have taken it upon themselves to make it a "discipline".

STOP - HAMMER TIME?

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Becker Hand - best grip in town [mechanism visualization]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Becker Hand - best grip in town [mechanism visualization]; published April 19, 2019, 11:57; URL: https://www.swisswuff.ch/tech/?p=9609.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Becker Hand - best grip in town [mechanism visualization]}}, month = {April},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9609}}


Visualisation of the mechanism or inner workings of one of the fastest "bionic" (i.e. it has an adaptive grip) prosthetic hands has so far been relatively elusive.

The mechanism is one of the most extremely evolved in prosthetic hand device history - the manufacturer overlooks around 70 years of continuous product evolution. As many large manufacturers today do not "listen" and are not open for suggestion or critical evaluation, they are not making most of their shorter time of product evolution, further crippling their already short market exposure. This explains why the Becker hand is one astonishing perfect product - highly functional, attractive, very robust and very affordable.

Now, we worked out how to plastically show the inner workings or mechanism of a Becker Imperial hand.

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Soldering cable connection and heat shrinking tube over connection (Extreme Cyborging Microworks)

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Soldering cable connection and heat shrinking tube over connection (Extreme Cyborging Microworks); published April 4, 2019, 06:59; URL: https://www.swisswuff.ch/tech/?p=9463.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Soldering cable connection and heat shrinking tube over connection (Extreme Cyborging Microworks)}}, month = {April},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9463}}


A full understanding what amputees do or do not in their real life has so far escaped the acumen of research and development. This explains how > 85% of us still run free, without the real restriction of having to pay massive money for technology that basically makes life more difficult.

A notable exception is my body powered split hook. As we can show how academics comprehensively fail to grasp (haha) the scope and use of prosthetic arm use, even a modest achievement such as this appears quite noteworthy and definitely reportable. After all, absolutely no (0) achievement was delivered by any R&D in the domain of myoelectric arms to this day that has made it to actual everyday use and hard work delivery, both since Cybathlon 2016 (that promised it would "push" development) and generally since >40 years of "research" into myoelectric arm control. As they all have more than a lot to learn (not advancing problematically high error rates in >40 years is a catastrophe or wouldn't you say), we are called upon to focus on the basic.

Today, how to attach the cable of a power supply to a pump.

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Prosthetic split-hooks are by far the MORE MODERN concept than prosthetic hands and they did not take long to get vilified [what you all got wrong about history]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Prosthetic split-hooks are by far the MORE MODERN concept than prosthetic hands and they did not take long to get vilified [what you all got wrong about history]; published March 3, 2019, 23:01; URL: https://www.swisswuff.ch/tech/?p=9423.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Prosthetic split-hooks are by far the MORE MODERN concept than prosthetic hands and they did not take long to get vilified [what you all got wrong about history]}}, month = {March},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9423}}


We are told by prosthetic R&D aficionados, by film makers, fiction authors, popular culture and whatnot, that a prosthetic hook (i.e., split-hook) is "old", and a prosthetic hand is "new". Also, we get told that myoelectric arms are very modern in terms of control technology, whereas some recent media and prosthetic manufacturers even called myoelectric control "brain control".

None of that is true, quite obviously, while we realize that reality is rather different. Rather strikingly different, in fact.

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Was ist mit Cybathlon@SCHOOL moeglicherweise problematisch?

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Was ist mit Cybathlon@SCHOOL moeglicherweise problematisch?; published March 2, 2019, 11:39; URL: https://www.swisswuff.ch/tech/?p=9404.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Was ist mit Cybathlon@SCHOOL moeglicherweise problematisch?}}, month = {March},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9404}}


Cybathlon@SCHOOL ist ein Programm, das Behinderte, Armamputierte auch, als "Material" bezeichnet und anpreist.

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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_1569102154, 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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Myoelectric prosthetic arms do not "really" function - so whom to sell them to? [cynical economic considerations]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Myoelectric prosthetic arms do not "really" function - so whom to sell them to? [cynical economic considerations]; published February 2, 2019, 15:11; URL: https://www.swisswuff.ch/tech/?p=9304.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Myoelectric prosthetic arms do not "really" function - so whom to sell them to? [cynical economic considerations]}}, month = {February},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9304}}


Myoelectric prosthetic arms do not "really" work, we all know that, and it has been clear for decades.These factual aspects are difficult to make that problem go away like, poof. With that the more interesting question is: whom do we sell these to?

While selling to people that are gullible [link] seems to have a lot going for it, it is risky. A more sustained approach may base on taking actual risk factors for myoelectric failure into account:

  • Sweat
  • Weight
  • General error rate

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Academically published myoelectric arm control error rates since ~1980 remain extremely high, far above any real life use requirement, and not even a slight trend to more reliable control in sight: what does this mean?

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Academically published myoelectric arm control error rates since ~1980 remain extremely high, far above any real life use requirement, and not even a slight trend to more reliable control in sight: what does this mean?; published January 29, 2019, 19:00; URL: https://www.swisswuff.ch/tech/?p=9244.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Academically published myoelectric arm control error rates since ~1980 remain extremely high, far above any real life use requirement, and not even a slight trend to more reliable control in sight: what does this mean?}}, month = {January},year = {2019}, url = {https://www.swisswuff.ch/tech/?p=9244}}


I took the liberty to review published error rates for myoelectric arm controls since ~1980. In other words: how reliable is the myoelectric arm control? How has the reliability changed over years?

This is hard data that is somewhat impossible to negotiate, and it has always been there for anyone to take. So forgive me when I anticipated some clear conclusions from such information over the last years - after all, I figured, a post such as this would not run away ; ) Even though, you must keep in mind that you read this here first as well. As far as I know, despite its ubiquitous availability, and despite a very obvious background or social reason for this (which is yet another subject), this collection of data has not been formally performed before. In fact, word of mouth had it that even decades ago, no self respecting engineer would deliberately enter the field of myoelectric or robotic prosthetic hands, simply because of all options one could do, that certainly was never a prosperous looking one.

The reason for this subject choice is, that I was interested in possibly identifying a trend, or a useful figure, for the reliability of myoelectric arm controls to consider in context of daily use. I used standard key word searches on Google Scholar and edited the resulting publications for relevance. I thus performed more systematically what I had done anecdotally a few years ago when it became obvious that one should not put too much hope into such prostheses, as their ongoing and intractable issues were somewhat obvious all along - at least from view point of a right below elbow amputee performing real work.

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CE marking or norm in relation to components for prosthetic arms

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - CE marking or norm in relation to components for prosthetic arms; published December 25, 2018, 15:20; URL: https://www.swisswuff.ch/tech/?p=7749.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - CE marking or norm in relation to components for prosthetic arms}}, month = {December},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=7749}}


CE-marking or norm

The CE-marking establishes that a particular item or product conform to European product law in relation to health, safety, and environmental protection standards [link].

As this text is not public or may be hard to get into the public eye, why not just go ahead and drag it out. I started to be interested by the backgrounds of what our prosthetic limbs and their technical documentation ideally could be already a few years ago [link].  So, a few blog posts here do have a long history, longer than others, and were assembled over quite a period of time.

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How does a Helping Hand / LN 4 hand work [test report]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - How does a Helping Hand / LN 4 hand work [test report]; published December 17, 2018, 05:44; URL: https://www.swisswuff.ch/tech/?p=9027.

BibTeX: @MISC{schweitzer_wolf_1569102154, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - How does a Helping Hand / LN 4 hand work [test report]}}, month = {December},year = {2018}, url = {https://www.swisswuff.ch/tech/?p=9027}}


I organized myself the opportunity to test a "Helping Hand" (also known as LN 4 hand) myself.

You know, the one that are being built as a feel-good exercise by business people and others, and that are given away to people that seem in need. It has its own website [link]. The Ellen Meadows Foundation specifically empowers not amputees, but non-disabled people. Verbally, they claim in their mission statement: "Inspire change in the world by empowering individuals to use their hands to support putting hands on people in need. We will not stop until anyone who needs a prosthetic hand has access to one". About the hand, they write: "Originally Ernie intended to design a functional prosthetic hand for children and adolescent land mine victims. Over time he developed a design for a low-cost, light, durable, functional prosthetic hand. He knew that this would help all who need a prosthetic hand and who could not afford the available alternatives".

That means:

  • They empower non-disabled people that have hands to use their hands. That is noble, I guess.
  • They will not stop until anyone that needs a prosthetic hand has access to one. The definition of a prosthetic hand is wide open, I guess,  but they precisely state their hand is functional and durable. That? We will see about that.

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