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Category: Hosmer Dorrance

Hosmer Model 6 Work Hook [tweak / improvement / backlock feature]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Hosmer Model 6 Work Hook [tweak / improvement / backlock feature]; published June 2, 2016, 11:47; URL: https://www.swisswuff.ch/tech/?p=6102.

BibTeX: @MISC{schweitzer_wolf_1571792100, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Hosmer Model 6 Work Hook [tweak / improvement / backlock feature]}}, month = {June},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=6102}}


The Hosmer Model 6 Work Hook is by far the most robust, powerful and useful commercially available terminal device for real work, besides the Toughware PRX V2P Prehensor and the Toughware PRX Retro. This Hosmer device is particularly useful due to the backlock feature that allows the user to reliably hold also relatively heavy machines for an extended period of time (such as hedge cutters).

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ARMCAM - prosthetic hook, kitchen activity [ADL, activities of daily living]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - ARMCAM - prosthetic hook, kitchen activity [ADL, activities of daily living]; published April 10, 2016, 19:01; URL: https://www.swisswuff.ch/tech/?p=5839.

BibTeX: @MISC{schweitzer_wolf_1571792100, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - ARMCAM - prosthetic hook, kitchen activity [ADL, activities of daily living]}}, month = {April},year = {2016}, url = {https://www.swisswuff.ch/tech/?p=5839}}


I consider kitchen clean-up, dish washer emptying and that sort of thing a typical ANPPN (activity of no particular prosthetic need). But as is, one can speed things up with the right type of prosthetic. For me, housework has to move fast forward, and I mean, fast forward. I am not interested in drawing it out to a drama. I have no time to dick around.

So seeing as if some people that are totally new to the term "manual work" come to town, time to show some relaxed easy housework ploughing forward through the duties; this video was not done with any focus on speed but as normal routine clean after we had coffees and stuff to eat one weekend morning.

Using a small Mobius action cam tied to the prosthetic socket, here is that bit of kitchen activity.

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Trimming hedges with Hosmer 6 work hook and 2,7 kg cutter in 37 deg C sunny summer [achievement / benchmark report]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Trimming hedges with Hosmer 6 work hook and 2,7 kg cutter in 37 deg C sunny summer [achievement / benchmark report]; published July 4, 2015, 23:33; URL: https://www.swisswuff.ch/tech/?p=5013.

BibTeX: @MISC{schweitzer_wolf_1571792100, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Trimming hedges with Hosmer 6 work hook and 2,7 kg cutter in 37 deg C sunny summer [achievement / benchmark report]}}, month = {July},year = {2015}, url = {https://www.swisswuff.ch/tech/?p=5013}}


Bimanual activities that require a prosthetic arm (one with industrial qualities) often times evade the prosthetist, the societal arm chair citizen, the academic researchers, the media makers that "use" amputees as stereotypes, in many aspects - one risks to overlook the simple glory, the sunshine that goes with doing it, the hardness of it, the pride. And the fact that it requires putting one's mind to something that is not just as self understood as it may appear.

What seems to be never considered is the fact that I really need a prosthetic arm for actual bimanual activities. It is for these situations where there is a need to work two-handedly, where a prosthetic arm attains a deeper relevance and importance. And it is not just me, that as a need there, actually. That is the type of stuff one generally needs a prosthetic arm for. Those activities are the ones where insurances usually tend to agree to pay for a prosthetic arm - a prosthetic arm that works through these tasks, mind you: hard work, repetitive work, two hands required, very hot, very cold, dangerous. Leaving the amputee totally intact, by the way.

Operating a hedge cutter is just not possible, safe, or easy with just one hand. In other words, we talk about real work. And no, you cannot "just put your mind to it". Sure with a small tiny clipper you can approximate the sound and feel - but with 2-3 kg and overhead work with a long powerful cutter, one-handed is a big risk, and operating the switch together with directing the blade is very hard.

That, as opposed to drinking coffee, reading news paper, just going for lunch with a food tray, cutting pizza or meat, shopping with bags or baskets, tying shoe laces, talk past a Bialetti when making remarks about "making coffee", opening a fridge, wearing correctly sized trousers, walking a dog, drinking alcohol, or such  - all of these work with a Becker hand, with a passive arm, with a hook or without prosthesis quite well, too.

Not, like, hedge cutting. This requires, like, a real prosthetic arm. It cannot be done without prosthetic arm, with a passive arm, with the "bionic" stuff (their control paradigm is just not safe for that type of work), certainly not with "3d printed" gadgetry that risks to scratch up your stump in no time. I talk about reliability, comfort, overuse, asymmetry, grip function, the stuff that hopefully, my real sustainable living future is made of.

To show what is required, or done, with a prosthetic arm in 2015, I cut the outer and inner perimeter of my hedges in the early afternoon of what turned out to be the hottest day in July in Switzerland since a long time, at over 37 deg C, using a Bosch AHS 55-16 (2,7kg) 450W electric cutter and a super tweaked body powered prosthetic arm with a Hosmer model 6 (back lock containing) work hook. The work contains overhead as well as low down feet height cutting.

 

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Body powered arms [technical design overview]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Body powered arms [technical design overview]; published November 21, 2013, 07:05; URL: https://www.swisswuff.ch/tech/?p=2371.

BibTeX: @MISC{schweitzer_wolf_1571792100, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Body powered arms [technical design overview]}}, month = {November},year = {2013}, url = {https://www.swisswuff.ch/tech/?p=2371}}


Body powered arms are not the same. Despite everyone saying they understand what these are, these arms are not the same.

My setup explained, a generic setup explained. To show similarities and differences. For those in need to learn about this, technical differences to myoelectric arms are explained.

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Cutting meat using prosthetic body powered arm with hook or hand [ADL]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Cutting meat using prosthetic body powered arm with hook or hand [ADL]; published March 21, 2011, 01:03; URL: https://www.swisswuff.ch/tech/?p=387.

BibTeX: @MISC{schweitzer_wolf_1571792100, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Cutting meat using prosthetic body powered arm with hook or hand [ADL]}}, month = {March},year = {2011}, url = {https://www.swisswuff.ch/tech/?p=387}}


It is sometimes asked how this is done. There are many ways, including getting the waiter to get the cook to prepare it pre-sliced (my favorite lazy night out option). But no problem to get it done with the prosthesis.

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Approximating the Carroll Quantitative Test for Upper Extremity Function comparing hooks [V2P, Dorrance, Otto Bock] and hands [Otto Bock, Becker Lock Grip]

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Approximating the Carroll Quantitative Test for Upper Extremity Function comparing hooks [V2P, Dorrance, Otto Bock] and hands [Otto Bock, Becker Lock Grip]; published February 8, 2010, 02:09; URL: https://www.swisswuff.ch/tech/?p=280.

BibTeX: @MISC{schweitzer_wolf_1571792100, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Approximating the Carroll Quantitative Test for Upper Extremity Function comparing hooks [V2P, Dorrance, Otto Bock] and hands [Otto Bock, Becker Lock Grip]}}, month = {February},year = {2010}, url = {https://www.swisswuff.ch/tech/?p=280}}


I am not saying that the Carroll quantitative test for upper extremity function is necessarily the test most related to my own Activities of Daily Living (ADL). It is not.

But manufacturers are going above and beyond their call of duty to build "bionic" prostheses that seem to excite their engineers, the media and that by and large miss the point of functional prosthetic support while public money for research is wasted away on similarly useful gadgetry. Can you believe it? With a BeBionic hand you can even grab an apple? How amazing! With the iLimb, you can hold a water bottle! Wild! And the Otto Bock Michelangelo hand can also grab an apple. Oh, well.

So again amputees are mostly on their own as far as the real works are concerned.

On my way trying to get an understanding of the interplay between grip angles and usefulness I am trying to work towards better defining a modern test for relevant dexterity. And for that, it helps to play with a previously established test and then discuss maybe what it does well, what it does not show, and what it can be used for.

Furthermore, current advertising for "bionic" prostheses [Michelangelo, BeBionic, iLimb] usually show activities that any prosthesis can achieve and as such do not prove a particular point.

After reading through Carroll's paper, I decided to implement the following tasks:

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Dorrance 555 aluminum hook with nitrile covers

Cite this article:
Wolf Schweitzer: Technical Below Elbow Amputee Issues - Dorrance 555 aluminum hook with nitrile covers; published February 6, 2010, 23:51; URL: https://www.swisswuff.ch/tech/?p=279.

BibTeX: @MISC{schweitzer_wolf_1571792100, author = {Wolf Schweitzer}, title = {{Technical Below Elbow Amputee Issues - Dorrance 555 aluminum hook with nitrile covers}}, month = {February},year = {2010}, url = {https://www.swisswuff.ch/tech/?p=279}}


I also use a Dorrance 555 aluminum hook with nitrile covers. It is light, and it is extremely powerful and sturdy. Compared to the Otto Bock Movohook and right after wearing a few days, I would rate it as more precise, more sturdy, lighter and more versatile.

The rubbers were a feature that some may look at as outdated - but I would not go that far. After wearing the Otto Bock Movohook 2Grip for over a year now and after working with it a lot, I have to say that it is heavy (the Dorrance 555 is light), even freshly after a service/overhaul the Otto Bock hook's tips are not precise and neither is the Otto Bock hook joint (the Dorrance hook has a ball bearing and is rather precise), the Otto Bock hook has two spring settings (but I often only use one spring tension setting and that is the strong action one; if I need two spring settings these are 'strong' and 'ridiculously strong'), the Otto Bock spring has a slightly stronger initial resistance to pull (whereas the haptics of rubber tension is - hard to describe - pleasant to my shoulder). And the Otto Bock spring accidentally falls off, as they don't seem to fix the spring too well.

First I cut myself an adapter piece (instead of buying yet another Otto Bock bolt) and placed a washer under the ball of my cable so it would fit and stay in place.

Then I increased the hook's strength by buying some castration bands [see Open Prosthetics on that issue] and now adding one. I don't have this tool they use to put on rubber bands, so I just rolled it over the claws and pulled it into position. No problem.

Very nice. I do like the vertical claw position, also I find it better for typing.

Some more about highway robbery on a great Open Prosthetics blog page: I use castration rubber bands instead of the official rubbers that sell 40 pieces for 37 US$ or so at amputeesupply.com. Alternatively they sell castration bands for 17$ a pack (without shipping) at amputeesupply.com.

Now, I got 100 pieces for 15 CHF - one for 15 cents (that includes shipping and handling; price without shipping is ~ 2.70 CHF). That's a fair price for standard rubber rings that I can live with.

Get your supplies at proper stores. Not at amputeesupply.com.

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