I've finished up a set of long needed upgrades to address a joint problem: lack of a locking mechanism to retain the pin swivel joints in place. Long overdue, but I now have the tools and tech to pull it off. The main priorities were to upgrade the arms with this new tech, then the legs.
The mechanism is fairly simple, but annoying to build by hand in multiples. The principle is to use a locking ring clamp around a groove in a pin. The ring must have an opening to behave like a spring, so it widens as the pin passes through, but contracts after the groove reaches the position. The ring should then hold the pin in place but also allow for rotation. Much easier to do with plastic parts than Magic cards and paper clips.
simple excel spreadsheet to calculate diameters in terms of paper lengths and thicknesses. I had some old ones from a few years back, but re-made some new ones to help do fit checks. Probably would be easier to use drill bits since metal doesn't deform as easily as paper, but that's how we roll.
I used Magic cards rolled around the 6.35mm (1/4") diameter rod to form a sleeve with the thickness of two cards. That thickness is the minimum I found needed to allow the rings to bend outwards and also remain stiff. A strip about 45mm long is enough for the inner housing. I used another 45mm long strip to connect the two halves with the ring in between to hold the assembly together.
The new locking mechanism allows me to do another upgrade: fixing the ankles. Right now, the ankles are just a hinge joint. I opted to upgrade the feet to provide two swivel joints and a hinge joint to allow for better poseability and stability. However, the foot requires a more delicate structure due to the small envelope. Therefore, I needed to downsize the scale of the locking pin mechanism.
The new foot and ankle fixes some problems with articulation, allowing for better balance and stability. I can now reduce my reliance on obitsu stands, at least for barefoot poses.