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A project log for Hand Drive

A wheelchair attachment that allows any wheelchair to be powered in a rowing motion. It is 3D printable, open source, and available to all.

Kate ReedKate Reed 08/14/2015 at 18:200 Comments

Right Side

We realized that we had too many ratchet problems at once, so we decided to isolate each of the problems and deal with them one at a time. We started working on the individual pieces of the ratchet as opposed to the entire ratchet mechanism.

We were having a hard time getting the springs to work on the ratchets, and having them do what we wanted them to do. We realized that we needed longer springs, so that they would distribute the pressure, and have more springing power. We also realized that we needed to redesign the actual ratchet, so it would have space for the bicycle nark, which is the part that secures the end of the cables.

We made all these changes and it seems as if the right ratchet is set to go.

Force

Part of the reason we had such a hard time making the ratchets is because the angle that the ratchet locks into the gear has to be very precise. If the angle is wrong, the ratchet has rotational force, and doesn’t actually lock into a stop. It is harder to place the ratchet that is in the upright position naturally, because we have to place the holes for the ratchet as if the ratchet is down. We are doing the guess and check method.

Back Tracking

We have been working on the placement of the ratchets and the springs and getting them just right. We went through and tried every single one of our prototypes again and really analyzed each one of them. It was good to see them all together. We decided that the sides should be as symmetrical as possible for the ratchets and it would be simplest to go back to the normal springs.

The steel springs are officially too unpredictable and hard to work with. We had the concept down and how the mechanism should work theoretically, but the steel springs were simply too unpredictable and were slowing us down, so we abandoned them.

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