Thanks. Looking forward to it.
The problem with the ball joints is something I should have seen coming, but overlooked it. I'll find another way. I remembered, that my first ideas was to go with some kind of saddle joint anyways. Just went with the idea of ball joints on a whim. There are other options.
>What are the threaded rods at the bottom of the torso going to be for? Are they intended to let the whole spine assembly move up and down?
They are meant to hold the whole thing in place, till it's pulled in one direction but still restrained by the other stings. Which was a naive idea, I know. Wanted to try it out and thought it was easier to do so than it really was. These rods also represent the twisted string actuators I plan to put into the full scale model.
Today and yesterday night I worked on some improvements:
I gave up on the bad design of the eyes in my test face, and implemented the new approach I mentioned before, based on Bezier splines. It's still not good looking but the underlying technique is way better now, and I can change it more easily. I'm glad I found that way by just trying out something. It only works with creating the Bezier spline in a certain way, otherwise it has more than four points which need to be constrained. Though, the whole idea of the printed face might go nowhere, since printed paper faces of anime characters might look better anyways. Then again, not anyone has a color printer for dead trees or a printshop close by and there might be other benefits. It's slightly 3D for example. The old design was severely flawed, because I made the mistake of picking the wrong layer to build upon. This is something to look out for, happens sometimes to me and can be very annoying. Let's say the eyes and eyebrows weren't really attached to the face in the old design, it only looked like it from the front, but there was a gap in between. That is solved now. For the future I will need to look at some more anime faces to see if and how I can improve the new design.
Then I had to add some supports to my shoulder joint design, which I don't even know if it will go anywhere. I have a few other approaches in mind as well. However, the holes for the strings needed some support and I prefer to put such into the CAD design myself. This also proved more tricky than anticipated since it's fairly complex. I printed a sized down model of it and it looks good so far, but the test setup still isn't finished.
Then, my elbow joint also made some progress and has been (partially) printed.
The photos of my prints are on my tablet, so no photos here but nothing special to see anyways. I hope to focus on the elbow joint and motor holder next, so I can test part of my arm design with the twisted string actuator soon. Also need to cut the tubes and need to make the electronic wire setup less flimsy first, though.