A Bicycle for Brother Steven–Part 2(of ?)

well I will describe the attempt to convert a standard exercise bike into something that can be used by someone with a spinal cord injury. Today I will discover some of the things that I discovered in this attempt and how I attempted to solve these problems.

In the last post I described how I built a system to keep my feet on the bicycle and keep my legs from flopping to the side. with that system in place I rapidly discovered a large number of other problems. The first problem was that my legs could not really handle the distance they had to move to push the pedals. After considering a number of solutions, I talked to a friend of mine who happens to be a pretty good amateur bicycle mechanic. We decided, and is later proved to be the case that the bearings for all bicycles are the same size. This meant that we could choose pedals from a different bicycle and put them on this machine expecting them to fit. We went down to the local goodwill and for a couple of dollars picked up a child's bicycle. As we expected, the pedals fit perfectly and significantly shorten the distance that my legs needed to travel in order to push them.

The next problem that we discovered was that the device was smart enough to have a ratchet allowing the pedals to slip whenever they were moving in the wrong direction. The problem with this is that we were hoping to use the momentum of the flywheel could carry the pedals along those portions of the cycle where I was too weak to push. If the pedals were allowed to slip backwards, this would not work properly. My friend pointed out that the device that was slipping also came in a nonslip version and volunteered to come back in a couple of days with a suitable, non-slipping gear.

Once these two modifications were in place, I discovered the next problem in my theory that I would be able to push a bicycle which could be pushed with the pinky finger. The problem is that legs have a significant amount of weight and as a cycle is pedaled, this weight moves up and down. In theory, the weight of the leg moving up in the weight of the leg moving down will balance each other. Reality is not right so simple and in various portions of the cycle significant weight will have to be lifted.

once the device was assembled and tested, I discovered that it tended to move to a neutral position where the pedals were horizontal and one leg was forward and one back. with the strength that I have I was able to rock the pedals back and forth but not move over the top to the other neutral position. Rocking the pedals back and forth took significant effort and the exercise involved could be considered a victory although it is not like the same thing as being able to move the bicycle. I have been considering a number of schemes to balance the weight of the legs and decrease the effort in moving the cycle to something that I can manage it this time but I have not come up with a plan which works to my satisfaction.