In an earlier post I had made an enlarged replica of Arisu's arms so that I can use it to test joint making with.
I have since then realized that I probably should have kept the arms as simple as possible without the detailing or contouring. Just simple cylindrical and sphere shapes. This would have made it much easier to get a smooth and clean joint. Then I can add the details and possibly slight modification of the joint to make it all work together.
Here I have used the enlarged wax arms and tested out making the elbow joint. The test I made had a sphere attached to the lower arm and an elbow part extending from the upper arm. (Please ignore contours since I did just that while making the elbow. I just didn't feel like remaking a test subject for this.)
Although the angle is not a true 90 degrees, it is getting pretty close. To increase the angle of the elbow I would need to remove some of the inner arm areas that are touching and increase in slot of the ball on the lower arm.
Do you know how hard it is to hold a elastic joint apart with one hand? Well I did the best I could so you can see how the ball joint looks inside. When you increase range of motion by removing wax that is touching on the arms you also have to increase the slot length.
The ball joint is not a perfect sphere. To the contrary I made it almost like an oval so that it does not rotate in ways I don't want it to. You should be able to pull the arms together and back straight, but you should not be able to twist an arm around the socket. Just like you shouldn't be able to spin your head all around your neck. Scary.
Am I happy with this amount of flexibility? No. I think it is too limiting to just have 90 degrees. If you look at my Joint Study Elbow Drawing you can see what I am aiming for. I would like something closer to 120-145 degrees so I may be looking at doing a double joint of sorts. What I did was pretty much what I drew in the lower left side of the picture in the Joint Study Elbow Drawing. Also, you can scroll down that page to see an idea of how much you need to remove from the arms to have the angles you want. The tighter the angle, the more that is taken away from the arms. I could have tried 120 degrees if I wanted to, but I could already tell by my pictures that the amount of arm removed would not look good to me.
But if you are happy with 90 degrees or close to that, then there are still other options to think about. Do you want the elbow noticeable? Do you want it on the top arm or the bottom arm? Do you want the ball joint fixed to the top arm or the bottom arm. Will it look good if the ball joint is on the same arm as the noticeable elbow? How much better would it be if the ball joint was not attached to either side but instead is free floating?