This is an early prototype, but I think it's underlying design segmentation shows promise: a "hub" to which the end effector attaches and a series of "petals" that can be individually modified and customized to fit each individual residual limb. The hub and petals join via an easily described interface of two screws and bolts. This will hopefully allow for a lot of compatibility across CAD tools as the salient dimensions can be sketched on a napkin.
My thoughts so far:
- This prototype seems a bit small-- will scale up for the next revision
- The bolts (even six M4s) add a bit of weight
- The nut traps are a little loose-- easy fix for the next rev
- Pipe threading on the hub may not be the most useful end effector attachment interface-- will look into cam-locking chucks for the next rev
- Three petals is probably not the best solution. I suspect four petals, two narrow, two broader, will provide a better fit in transradial cases.
- It seems that a lot of sockets incorporate features for cable attachment and guidance. Will research more and add to next rev.
- I'm not sure the second strap slot solution I implemented is the better one. Will experiment more, but am still considering the "fold-out" slot seen in rev 1 of the petal.
- I'm also working on a printable ratcheting mechanism for adjusting the circumferential compression via the strap running the perimeter of the socket. I'll probably integrate it into an individual petal that can be dropped in.
- Would it be advantageous to allow the top edges of the petals to fasten together to create a continuous lip around the top of the socket?
- Are there some standard end effector interfaces that could be printed or attached to the hub?
- What do folks think about "sealing" the interior surface of the petal so that adhesive-backed foam can be easily used without lint etc. getting stuck to the adhesive where its exposed through the expansion mesh slots? I've modeled and will test this soon.