What part(s) make it simple to secure two perpendicular cylinders together when one of the cylinders is rotating on its axis? In the drawing below, C(3) rotates with a simple motor. C(1) and C(2) rotate with C(3) because C(3) is rotating on its axis. All three cylinders are about an inch in diameter because they are just plastic right now. I'd like to use metal later on to fasten them together, but I'm trying to make them fit together nicely. The axle C(3) will eventually be a lot smaller in diameter than one inch. And C(1) and C(2) need to be able to easily slide but still be secure on C(3). The goal is to make it easy to assemble and disassemble the cylinders. I thought of using a lock pin seen in the second picture below. The issue is that lock pins only allow a rotation of 180 degrees before impeding and this needs to rotate almost a full rotation. Are there any mechanical parts that would function like a lock pin but still make this rotate more than 180 degrees?