Zipper Model shot 2

This is the hardest build I've done, and it's far from being done. It's the classic Chance Zipper. One electric motor rotates the boom, which rotates the 8 yellow gears on the sides, which powers the belt with all 12 cars on it. This model was so troublesome, I have a gallery dedicated to it. It is now able to run continuously without major problem for over an hour

Model is completely based off Greg Nuse's K'Nex Zipper model

this shot you can sort of see inside the boom better - there is a differential setup, with one end stopped, which drives the vertical gears, which in turn, drive the belt.