Very fun to play with, easy to print, minimal cleaning. Fun to wind up, and fun to watch spin. The 3rd idler gear spins so fast and so easily, its own momentum could unwind the spring in the opposite direction, depending on how you balance the light and heavy gears. Basically it's a printed spring, a pawl inside a drive gear for winding up, and 3 idler gears that prolong the action. The original files had some issues (some were "inside out" and didn't work with some slicers). I redid the whole thing in Solidworks and played with the tolerances until it was very easy to assemble but sturdy without glue. I also added chamfers to all bottom layers (to counteract squishing, which is especially hard to clean between 60 teeth in 4 gears....) Still - BIG BIG PROPS to the original designer, especially now that I know how sensitive the ratio of power in the spring to the weight and size of idler gears is - and here it's very fun and precise. When I tried to resize or remove some gears, the spin got too fast or too weak. Even removing "excess" material from the gears, replacing it with spurs, affects the weight, so I recommend you print one of the three idler gears "full" (without spurs), so it's heavier, and then test it in positions 2, 3 or 4... (do use "print one at a time", unless you like cleaning) Enjoy.