Bigger and Stronger

A project log for Antigravity Arm Floats

Wheelchair mounted orthoses to enable someone with very low muscle tone to move her arms without the encumbrances of gravity

mike-turveyMike Turvey 10/10/2016 at 10:560 Comments

If there's been a theme to this project, "Bigger and Stronger" has definitely be it. I was initially crazy with optimism at how strong and rigid the ABS 3D printed parts would be. One example of that is the pole mounts where the arm floats attach to the wheelchair frame.

This mount worked fairly well. Each side is 3mm thick. That means that when both sides are bolted together, it's 6mm thick. And it's printed with solid infill for maximum strength. And, as it turns out, it flexes a little bit under load. Since this is the point where all of the weight and length of the arm floats attach, any small flexion here is magnified significantly at the far end of the arm floats.

Here, you can see a side-by-side comparison of the old part (blue) and the new design (pink). The thickness is increased from 3mm to 4mm throughout the part. And ribs have been added to give the part a better grip on the pole.

Here, you can see a green version of the new design in use on the chair. So far, this new design has proven to be very solid and stable. It's surprising how much benefit came from going from 3mm to 4mm in thickness.