My father in-law Bob MacDermott became a triple amputee long before I met him after a farming related accident. After hitting a power pole with a cultivator and stepping out of the vehicle, he was electrocuted. After being found by a farmer and brought to Kindersley hospital he was rushed to the Saskatoon Burn Unit. On the ambulance ride there, the ambulance blew a tire and rolled three or four times throwing Bob into a stubble field.
It’s really an incredible story which is captured better by Curtis Gillespie in this article…
Needless to say, Carrie and I look up to him for his resilience and as an inspiration. He never uses the cards he was dealt as an excuse and mostly he just makes me laugh and feel better about myself when I do stupid things haha.
Anyways, here’s where the mechanical design aspect comes in…
Bob has really started to enjoy cycling on his electric bike and approached Carrie and I to make a bike prosthetic for him as he had just been using a basic gripper to steer the left handle of the bike.
Bob felt that the functionality with existing models was not sufficient for his uses. His main concern was that existing models are quite expensive, they don’t provide good articulation, and they cannot be detached easily/conveniently without causing injury to the user in an emergency situation.
We wanted to help of course and it was a welcome departure from our usual focus on automation and robotics. It was more of a quick 1 day build to help out our family.
The orange and blue portion connects to Bob’s existing arm/socket prosthetic. The orange bit can slide back and forth to adjust the reach / wrist length to the user’s comfort. It’s not a ton of adjustment but it definitely could be made to be longer.
A gas spring ball-joint was used because it was the most readily available ball joint that could snap on and off the bicycle. With more time we may elect to design something more fit for purpose that would snap off easily in an emergency… Although Bob seems to prefer a more secure connection.
To be honest the clamp was a bit of a dud in terms of the design. It was more complicated to CNC mill than it needed to be. Not to mention the end cap of the bike handle had to be taken off before the clamp could be attached to the handle bar. We ended up using a set screw to attach it securely to the bike handle which wasn’t optimal.
I will be simplifying the clamp design significantly to make it cheaper to produce and to fit more bikes in the future.
Bob is going to give this model a thorough test on vacation and let us know what we need to change for the next one!