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.
Not too many tools are required.
Apart from a regular Dremel with an ez-lock cutting kit, I used grip tape (Aliexpress brand) and some electrical tape (Isolationsband). Also, allen keys to adapt the gripper position and a bit of old used grip tape to cover the brake.
As I have extra sensitivity regarding low frequency vibration transmitted by the bar. I am not the only one, other amputees also suffer pain when riding for over 20 minutes with a hard stump/arm-bar connector.
How to effectively pad that, check my page with the first approach where this is detailed [link].
How to install a grip tape well is shown here:
- Ultegra brake / shifter levers shortened and flipped / facing each other, for superb one-handed access
- Bike photos
- Prosthetic arm for bicycle riding
- Test ride
Ultegra brake / shifter levers shortened and flipped / facing each other, for superb one-handed access
The levers on the left side of the handle bar (seen from sitting on the bike, that is) are now facing each other.
They are super easily accessible and they all shift to the most comfortable direction.
Shifting cassette up (faster gear, higher ratio)
The lower flipped lever is the one to examine closely here.
Switching a gear or two up: superb.
Shifting cassette down (slower gear, lower ratio)
Using the down switcher works flawlessly, obviously.
Braking front brake
Even using the front brake from an upright top-down grip position works marvelously well.
Braking both brakes
I cannot tell you in words just how much a piece of cake the use of both brake levers at once now is. This is just unimaginably great.
Views of the setup
What you also see are my headlight (middle of the bar) and the camera mount (I filmed the test ride, full video below). Also the right handle bar is really padded well to reduce vibration when I grip it with the prosthesis (setup detailed below as well).
As you see, the brake and shifter levers were shortened and the bottom one is mounted in a flipped-upwards position.
This is extremely convenient.
The Colnago C40 is in the tradition of great Italian bicycles. It has a beautiful, visually loud style and so it shows pride in all details. I really love this design over the currently cool and clean designs of bicycles with nothing on them really.
Prosthetic arm for bicycle riding
I did try
- Mert hand (Mert Lawwill)
- Freelock hand (Wilfred Mijnheer)
- Becker hand
- Toughware Equilux
- TRS Prehensor
For road bike, and in short, the TRS Prehensor wins.
It has a slender opening that lets me pull out fast, faster than the others. It is voluntary closing so I have a full power lock by just making a round back, and just as fast as I lock it with an extremely hard grip, I can open it and change riding / sitting / body position. Locked body position really was the biggest problem of the fixed bar position adapters such as Freelock and Mert hand.
I can use the TRS Prehensor on a heavily padded handle bar. The vibrations then are reduced and there is no pain already after 20 minutes of riding. Using the Freelock and the Mert hand both forced me to take frequent breaks when riding, and so after 30 minutes the fixed position would cause back pain that forced me to take a break every 10 other minutes, stretch for 3 minutes, then go on. That is how I made it up to the Stelvio pass a few years ago. Instead, I now have a TRS Prehensor with the obvious permanently available dynamic cable control and I can let go and grasp the handle bar also during the ride and without stop whenever necessary. This includes the ability to stretch during rides which is not a given as arm amputee with a bike adapter.
TRS does sell also specific bicycle adapters, but my experience with fixed adapters is not good, the back aches really bad at the latest if you ride over 100 km or so. The TRS Prehensor is the best buy from here, and best to see what all you can do with it, before expanding purchases.
What has to be noted are these details:
- electrical tape (yellow) around ball lock adapter of TRS Prehensor
- long rubber lock for the cable connector (is detailed below)
Since the cable will be fixed inside a tight bike jacket or rain jacket, a considerable amount of push force is exerted there.
Cable connector lock
The cable connector my prosthetist installed on my arm is an Otto Bock cable connector. That part essentially is a metal cylinder that allows me to put the terminal device adapter cable inside and thus extend my prosthetic arm control cable to control the terminal device.
As the adapter cable usually falls out of the Otto Bock cable connector really fast, a hollow cylindrical metal clip is offered to hold the connector cable in position. That usually does not work, so I use the PVC insulation of power cables (here: orange) to slide over the cable connector.
With a very long (here: orange) locking cover, the one thing that happens always with short covers is that moving the prosthetic arm back and forth under a long sleeve, such as a tight bike jacket, won't accidentally open the lock and allow parts to fall out. This is more critical than you think.
Another small adaptation is a tiny bit of crumpled up paper that I jam into the Otto Bock cable connector. This prevents the compression nut on the adapter cable of the terminal device to slide back a few millimeters and accidentally hang on to the oblique edge the lock capsule has there, which then causes a "bang" when applying force to the cable at the moment when the compression nut jumps out of the edge again.
In addition, I used one of these camera bands they ship with pocket cameras (below image, gray band) to secure the orange cable lock to the prosthetic socket. It cannot fall down or get lost that way.
These all are provisions to tweak this prosthesis into an error-free handling under heavy real life constraints. Reversely put, if you do fine without such securing measures, you probably do not work under these constraints. You will only need them once a lot has already happened that you may not want to know.
I wear a PUPPCHEN wrist lock. Despite re-assurances of other manufacturers, theirs might be the most durable, that ain't the case. The PUPPCHEN wrist was designed and manufactured by guys that build custom locks for wagons and that build also medical implants. The idea of how it should work and all testing was delivered by me. I am not paid by them and never signed a contract there. But people have a weird concept of safety and warranty: you do not even need a warranty, safety assurance or such if the device actually works. While that is a foreign concept to a lot of commercial prosthetic items, we are a Swiss outpost, I grew up also in part in Bavaria and our mindset reflects that.
The lock is service free under a full forensic pathology work load for over 4 years under my full wreckage use, which includes regular handling of very heavy weights, riding mountain bikes also with spike tires in winter, and a lot more. It costs 1'500 CHF, and it lasts a very, very, very long time which plays out if you use it a lot. The price only pays material and manufacturing, there is no marketing or associates getting any pay out. We devised this as pure disability support project.
I am not over-insured for accidents, and I mostly do not want any device inflicted risk due to my overall situation, slowly getting older. Also I love the comfort of service-free tight and extremely functional, non-wriggling parts. Having a device that really works the part is by so very far the better business for me as a heavy user, than giving a big company money and then negotiating failure consequences, damages and so on. Building a wrist once, and doing it right, definitely also is the better preparation for the next 20 or so years. If there ever was one true insight, it was that this right hand was not going to grow back. So I might as well wear parts that really last, last well, and that are worth relying on.
Wear whatever you want : ) Your choice, your risk.
This test ride shows the use of the modified setup.
The upper brake / shifter lever controls the front brake and shifts the chain wheel. The bottom brake / shifter lever brakes the rear wheel and shifts the cassette.
Further test rides [update]
- 4. Feburary 2018 - about 3 hours, moderate ascents/descents, absolutely magnificent in very aspect - body position, only a temporary back ache that went away, absolutely perfect control of brakes and switch levers from various positions.
If for whatever reason with the above detailed setup, you are happy and successful with your bike ride I am happy to take all the credit for that. Maybe send me a picture if you have one of a glorious moment : ) But if you break or damage something, if you fall, have an accident, injure yourself or others, put someone at risk and so on, whatever bad it is, I won't take responsibility, then it must have been you or someone else. Bike riding is really not for everyone. In any doubt: don't do it, don't modify your bike, don't ride it. If your health condition and drug intake, including prescription drugs and whatever else is used, influence your thought pattern, bike modification or bike riding ability, best to consult with your doctor, or a doctor, before. If you do not know whether your bike, or modified bike, is insured, it is your responsibility to take proper steps to check that. Whatever the specifics, ultimately this all is your responsibility. Good luck and have fun.
Remember, you read this here for the first time.