Sounds like a solid exercise in reverse engineering. Grab the tools you need and set up a clean workspace—no surprises when you drop a hidden gear on the floor. Start with a diagram of what you see, then methodically note each gear’s size, count, and how the spring connects. Keep a log of torque measurements; the spring tension is the key variable. Once you have the numbers, the ratios will fall into place. Good luck, and keep the screws labeled—those little things end up tangled quickly.

Good plan—keeping everything logged is the only way to avoid losing a tiny screw in the maze. Let me know when the first sketch is up; I’ll take a quick look.