Janet and John

Janet and John summarize this blog post in their discussion:

Alex Roy and the Morgan Threewheeler

In one of his many videos, Alex Roy discusses style and coolness of automobiles with a TV show host.

They establish, that, clearly, a car, that transcends time in coolness, and in ultimate grunt, has these two qualities:

• the most reliable in terms of motor and drivetrain, with adequate modern materials [error, error]
• the most fitting — where necessary classical, conventional. established or optimized — shape factor [see here for ultimate skin fit tips for body powered versus skin issues for myoelectric]

From that approach, here are eight simple questions to ask if you need to know whether a particular prosthetic arm will work for everyday use in real work situations  [link]. All this is not exactly rocket science or neurosurgery though [link].

He makes his case for a modern version of the Morgan Three Wheeler, an extremely light weight car with a Mazda gearbox, a motorbike motor and a wooden chassis. While this is obviously intentionally contentious, he makes a few extremely valid points throughout unintelligible babble, expressions of sheer joy and showing an assortment of scarves.

Watching his series of technology comparisons or assessments from view of a die hard automobile lover, some of the resulting appreciations are not nearly as relevant from my view as some of the single arguments or observations that he makes about technology in general.

For someone like him, that took car driving to a high level in terms of some achievements, it is the blend of technology, what function should or should not contain, and human interaction, where also emotions clearly come in (or, if they do not come in, do not come in).

General design principles

The enjoyment that comes with very intelligently combining ancient proven principles with the most modern of implementing these, design and material wise, can be very high (the enjoyment when non-intelligently going about ancient and new proven principles and their combination, can be, as suggested elsewhere, relatively low [e.g., link]).

Recently I made such another such experience by introducing myself to a real road bike and by then even improving that first setup further. There, top Swiss road bike assembly mechanics and disability sports specialist road bike mechanics alike all had told me in my face that a left handed use modification could not be done, like, at all, and they urgently required me to get a trike or to consider an cable-less electronic gear switch system with some Bluetooth technology or whatnot. I had initially been afraid to even get close to this subject. But after playing around with my significant other’s bike brakes and gear levers for a bit I was, like, screw it, let me work this out by myself. There is definite enjoyment in getting mechanical rides so they remain (and end up being) pure and fast, light and elegant that also is lasting and sustained. The smile on the face is there to stay. For bikes as well as for a well built prosthetic arm, like mine.

Body powered arm design principles

Body powered arms provide this as well, at least in principle. To achieve their full potential I found that body-powered arms also need a few aftermarket improvements, that me and friends developed together, some of which now are patented not primarily to make millions or even just a few cents, but primarily in order to prevent large manufacturers of junk to sell our designs back to us:

• Using a shoulder anchor rather than a figure 9 harness, using flexible plastic and carbon fiber for building it, solves the plexus compression problem [link].
• Using a true Bowden mount principle solves the cable shredding and curved routing high impedance problem [link].
• Using a quick lock ball lock wrist solves the wiggle problem of the prosthetic wrist [link].

There, the maturely developed drive train of a car may be seen as analog to a proven body-powered setup.

The build cannot be left to beginners – it as to be mechanically proficient. Mechanical design wise, you want the latest, and material wise, you want the best. And the looks can well be as they happen to be: most likely, no one (really) cares. The look in the end may be “technical”, “raw”, “mechanic”. Just like a Morgan Three Wheeler has a raw, technical mechanical look that does not make it less cool a bit. The real enjoyment is slightly elsewhere.

These points are re-iterated with a video series of Alex Roy’s Polizei 144 where he comments on “Morgan Three Wheeler versus…” (…some other cars). He addresses needs and performances of cars based on real world criteria – an approach that is sorely needed for prosthetic arms.

After all, cars are to walking or running are what prostheses are to being an amputee. Cars are modern locomotion prostheses. The approach to their embodiment thus may have a few shocking similarities. Just as cars, prosthetic arms also contain governing design and build principles, underlying control and design paradigms, that may provide much of the apparently undeclared differences that modern research or component development forget. If you have zero control concept, you cannot get the details right either – and that R&D totally lost oversight over control error rates for myoelectric arms can be easily seen by looking at studies over the last ~40 years [link]. And just because I may declare something as being more junk than something else, that does not mean there is not also an underlying and extremely well thought out principle.

Maybe this all (here..?) is one big giant test to see whether you are, in fact, able to discern, recognize and understand principles of control and design while only getting offered some handles, glimpses, jokes, puns, teasers, the occasional actual explanations, and superficial or deep peeks into what really plays out. Just maybe.

One true to life aspect seems to be that “real men” (in no way meant other than tongue in cheek) [link to datamation article] providing “real work” (rather than “pansy boys wearing junk”) require adequate tough materials, no time wasted on painting or adding doodles, no material wasted on added deadweight. The joke is only so and so good though. In the end, Real Men (note the difference from “real men”) do provide some experiences and solutions that others can build on. If you can provide better mechanical solutions, then you are The Man.

Hypothetically, if a Real Man could build a website that then would be jocked full of technical insights, even the kind that no one else really cared about, and if another Real Man walked in, took these tips into closer consideration, then would put together a 30$ body-powered prosthetic arm, and would have yet another Real Man train the use of that body-powered arm for just ~40 hours, and then would see to it that that user performs well, also at a Cybathlon 2020 prosthetic arm race, and if they then would even win, outrageously though, given that the Cybathlon was specifically designed to make that type of prosthetic arm not win – what would that tell us about design principles and how Real Men go about these? You may very well also do your own research.

The myoelectric arm may compare to an after market Mustang where the body powered arm may come across as a legendary newly build Morgan Three Wheeler. How to go about assessing true nonsense or junk is quite adequately shown by Alex Roy here.

What is junk and what wins?

Along these lines:

• • Myoelectric arms are electric, they need batteries and electrodes. These periodically if not increasingly if not ‘always’ malfunction. They sure need constant attention. They appear to be even built to planned obsolescence, with gloves so thin they die even when left alone [link]. My well-built body-powered arm works for many months without complaining. It also does not fall apart in the cupboard all by itself. Therefore myoelectrics are junk and the body powered arm wins.
  • Myoelectric arms are heavy and noisy. When manufacturers are asked about the noise, they act as if it was a feature. Children however should be seen, not heard, that is the underlying principle here. Here, however, myoelectric arms, particularly “bionic” hands, demand unwarranted attention, even intentionally so, therefore they are junk and the body powered arm wins.
  • Myoelectric arms chafe up my stump both due to mechanical fit [link], and electrical burn reasons [link]. No one intentionally hurts a disabled person, as underlying principle! So they are junk and the body powered arm wins.

• With my body powered arm, independent of just how much I sweat [link] or freeze, I can reliably ride and hold my bicycle handle bar and thus ride my bike. All other arms that cannot do that are junk, and the body powered arm wins.
• Myoelectric arms are super cool to pose on Instagram. No one cares, however, about images where people are posing with junk generally, and so the body powered arm wins.
• Myoelectric arms stop working shortly after I break out in sweat. I just need to get jobs done where I sweat, even a lot. The folks in R&D could identify that as a problem and probably solve it by increasing SNR technically and  by using up a lot more batteries. But really, all that happens is that with myoelectric arms, I cannot get hard jobs done. No one cares though, stumps sweat and stink, that’s a fact, myoelectrics are all junk, and the body powered arm wins.
• Myoelectric arms and body powered arms can be theoretically compared using statistics. But, no one can do proper statistics. These statistics would have to explain to someone that does not want to understand this why myoelectric arms are junk and the body powered arm wins. Them bean counters in R&D may even think trashing some 4000 bucks worth of dishes over a year is a cool amount of money waste simply because they cannot get the real life correlate of “92% correct recognition” right [link]. But no one cares about statistics either, so myoelectric arms keep being junk, these statistics are junk, and body powered arms win.
• There is the Extreme Cyborging dimension of true hard use. Check these. The body-powered arm is the Chuck Norris of prosthetic arms. The body-powered arm wins.
• Myoelectric arms are unreliable. You cannot even plan grips. They are junk, and body powered arms win.
• Myoelectric arms cost an arm, if not a leg as well. If you cannot build a functioning myoelectric prosthetic arm that survives arctic, desert or alpine abuse, for affordable amounts of money, your myoelectric arm will be junk – and the body powered arm wins.
• Myoelectric arms will be a great financial win for the manufacturer and the technician as they get to sell them for a large percentage surplus. So alone based on that, they are junk and the body powered arm wins.
• Myoelectric “bionic” arms are made specifically to “look” good on still images. In real life, no arm amputee is rated based on their looks on still images, but how well they move and act, like, on how many furniture pieces they can carry, how well they sweep the floor, how they carry themselves when having to perform “technical surgery” on a wrist watch or such, using a very precise split-hook, and how much they can handle manually generally. Not how good they look when someone says “freeze” and takes a flash photo. Myoelectric prostheses therefore miss the target, so they are junk. Body-powered arms win.
• Myoelectric Otto Bock batteries contained ~10 USD street price batteries sold for ~700 USD or thereabouts. These people that sell these batteries must think amputees are a glutton for punishment on top of being amputees. Therefore myoelectrics are absolute junk, and the body powered arm wins.

Of course you have every right to believe there to be a different truth. A person’s wishes are their kingdom, after all.

But after giving me a run-around for the first 2-3 years with regard to stock part body powered setups and after further and more offensive runarounds with the myoelectric arm, this is not a protocol, or a superficial attempt to be blunt, but a succinct summary, based on painful experience. I could type a similar list about why myoelectric arms are junk and wearing no prosthetic arm wins, and provide examples as well. Your mileage may vary.