Wheelchair Hand Drive

  • We started out with a design that would house a free wheel mechanism taken from a bike. After completeting the design and getting it to work, we realized that we couldn't go backwards, nor could we easily find a way to power the other side of the chair. After this we decided we need to create our on mechanism, this way we could power both sides and go backwards.

    In our second design, the entire mechanism is 3D printed as opposed to just the housing. The mechanism uses a dual ratcheting and stacked gear system. One ratched would engage into the bottom or top gear, and the stacked gears would mirrored. When one ratchet is engaged, the lever would propel you forward. When one ratchet disengaged the other one will engage into the other gear. This way the lever would propel you backwards.

    After playing with this design for a while we found that only having two ratchets  would cause strength issues, so we moved onto a planetary ratchet which would displace the forces over three ratchets instead of just one. We are still working on this design, but it works with a circular detent in the middle. This detent uses springs to press the ratchets into the gear. When we rotate the detent, the ratchets will reverse and engage into the other gear.

  • We created a system that allows the user of a wheel chair to go faster. Instead of moving in the wheel chair by pushing the wheels, our mechanism allows the user to use a rowing motion that allows the person to go faster and exercise different muscles. We used the free wheel mechanism and made different attachments to the free wheel that would enable it to snap onto the wheel easily and be ready to use. 

  • We started off this studio by learning Autodesk Fusion, the software we will be using for this project. Fusion is a 3D modeling software that allows you to edit dimensions and sizes on models you make. We spent the first few days making objects in the software as exercises. I made a phone case.

    Once we were done learning the software, we brainstormed as a studio on what improvements a wheelchair needs and how we can hack it. We want to accessorize the wheelchair as opposed to redesign it. We broke up into groups and started to brainstorm ideas in-depth more.

    Our group decided on making the wheelchair faster. We live in a busy fast paced world that the wheelchair hasn’t necessarily kept up with. We want to use a ratchet mechanism, which would allow the user to wheel faster in the chair in a rowing motion as opposed to a wheeling motion, a similar motion to the arms on an elliptical machine. We are mainly focusing on the ratchet mechanism moving the wheelchair forward but hopefully if we have time we can work on brakes as well.

    We started our project with a pile of bike parts. We wanted to get the parts from the bike wheels to see if we could use them for our project. We took the wheels apart and explored, and found that we already had some mechanisms that we could recycle instead of creating our own. We started making attachments that would make the bike parts usable for our particular situation. The tricky thing is that because of the parts that we have, the wheels can only turn one way so we have to use a slightly different system for each wheelchair wheel. The left and right wheels are flipped mechanically. We spent the day designing separate parts for each.

    We continued our process of making parts and testing them out for a while. We worked on the right wheel first. We decided to put the concept of wheelchair brakes on hold, and decided to just work on the speed aspect of the project.

    Throughout the project we have kept the design pretty simple, although we did end up needing one slightly major design change. After testing our previous spider attachment design we realized that we needed to beef it up because it was breaking when we applied force on it. We also realized that the way we were connecting the 8020 bar to the mechanism wasn’t helping our design. It was giving it too much torque, and adding stress to the entire mechanism. We took out the need for a right angle with the 8020 bars and redesigned the connector to accommodate the changes.

    On the last day we had another realization. After we put one of the sides together we realized that we had made two of the same sides, but in different ways. We made two of the right sides. Although this was unplanned and would be considered a mistake it was good that we had done it. We had come up with two completely different ways to do the same thing and through doing this we found that one way was much better.

    Once we had wrapped our mind around making the left side of the system, it actually wasn’t that difficult. We had all the hard parts made, and just had to edit them a little to be able to use them for the left side.