Styrene hinge joints can be as simple as cutting a piece of thin tube into sections; glue parts alternately between each piece you're hinging, then inserting a piece of wire through as a pin.

[In] other cases you can fabricate solid pieces by layering pieces of sheet styrene, and us[ing] a length of wire through a drilled hole. Either works well.

I've also had occasions where I've used existing screw holes on figs as hinges, simply by widening the hole on the piece nearer the head of the screw. That way the screw's only 'fixing' to the far piece, and can rotate freely inside the near piece. This is how I gave elbows to my Energon Rapid Run.

I've also made tiny ball joints before, to give elbows to an Armada Terradive. I cut the arm in half, and drilled a small hole in the upper arm, gluing in a short piece of wire. To this I glued a small spherical bead. Then I used a spherical burr in my rotary tool, with a slightly smaller diameter than that of the bead, and carved a channel into the lower arm, wiggling the ball at the peak depth to create the socket.



This is my Rapid Run elbow. The screw hole was already in place, but since I was getting rid of the old arm anyway, I decided to make use of the screw hole near the upper arm rotation joint and turn it into an elbow. All I did was take a small round file and use it to widen the hole in the black component. This way the screw would pass through easily without actually screwing it in. So now it's screwed into the yellow panel, but can rotate freely within the black component. I can tighten or loosen the elbow as I please just by adjusting the screw.






Also on my Rapid Run, this is a scratch-built hinge I designed to help the head fold into the chest. The two halves of the hinge are simply cobbled together by fusing layers of styrene together with poly cement. The actual hinge part was done in a similar manner to the one above. I drilled a hole through with a diameter similar to the actual shaft of the screw I was using (not accounting for the thread), then used a slightly wider bit to widen the hole in the 'near side' piece (the one that the screw passes through to reach to further piece). Again, this means that the screw fastens into the far side part, while allowing the other piece to rotate freely around it.




Not sure how well you can see this (the left arm seems to be easier to make out), but I created ball joint elbows on this Armada Terradive. I started by cutting the arm in half, then drilling a hole into the end of the upper arm and gluing in a short piece of wire. A small round bead then formed the ball itself. I drilled a pilot hole in the lower arm to the right depth, then used a spherical burr a little smaller than the bead to drill down and then wiggled it round to make the actual socket. Then I used my scalpel to carve the slot in the elbow to allow the arm to move from being straight to bent.




These are the leg panel hinges on my WiP Universe Jazz. As I said, these are dead simple; just a case of gluing alternate lengths of tube on the two halves and inserting a length of wire to act as a pin.

Believe me, none of these are that complicated. The most tricky to get working is the ball joints, but all the others are dead simple, and pretty much amount to cutting styrene to shape, drilling a hole and fitting a pin of some sort.