New Elbow Joints

The Otakon deadline has come and gone, of course, and Patcon is coming up, most likely to zoom by me before I can finish this project. I’ve decided that I’m not entirely happy with the original elbow joints that I made (though I think they were nice work, and it’s great to see how simply something like that can be accomplished – I just really feel the precision on my projects ought to be better than that.) so I’m working on new ones (to be recast) using the last two 14mm hemispheres I have on hand. I have ordered more hemispheres, but with a little luck I ought to be able to get by with what I’ve got.

The big change in this effort is that I’m now using the Dremel as a way to check the alignment of the hemisphere relative to the rod, and to correct it. My first attempt with this technique involved mounting the hemisphere on the rod, then chucking it into the Dremel and sanding it down until it was centered. This reduced the diameter of the part from 14mm to 13mm, and I’m concerned about the resulting part’s uniformity as a sphere. But this part is very far along at this point – I scribed lines in it by holding a razor saw to it as it spun, and I puttied some minor mistakes and primed it to check the surface – it needs some more work but if I decide to move forward with it, it’s nearly ready.

My second (and last, until I get that order of hemisphere parts) attempt at this was done by first sandwiching 3mm worth of plastic plate, drilling a hole in it, and mounting that to the rod. Then it was chucked into the Dremel and sanded down until it fit inside one of the hemisphere parts. From there, the hemisphere part was carefully aligned on top of the shaped styrene. Alignment was checked using a pencil touched to the hemisphere while it was spinning. (If the hemisphere was off-axis, the pencil would make contact with just one side of the hemisphere. If the hemisphere was on-axis, the pencil would make a complete circle around the part, or close to it, and that circle could be checked to ensure it was parallel to the edge of the hemisphere.) Minor alignment issues were corrected by sanding the outside of the hemisphere as it was spinning. I think with a little luck this version of the part will work out nicely.

My plan is to complete this hemisphere-on-a-stick part and scribe two lines in it on the Dremel – one about 20 degrees from the planar side and one about 20 degrees from the axis – the idea being that for different projects I could fill in these lines or take advantage of them, as needed. Then the part will be recast, and the castings will be performed in different ways in order to create both the male part and the female part of the hinge from the same mold. If the first mold works out, then I’d like to alter some of the cast parts from the mold to pursue my 3-part hinge idea.