I built this LEGO Great Ball Contraption module, the Rainbow Solaire, from plans by Matt Norman, available at GreatBallPit.com. It’s essentially a sweeper module which uses the big yellow banana gears from the Bucket Wheel Excavator set, driven by a Power Functions M motor via a clutched gearbox. The bottom U shape is formed with two old skateboard ramps from LEGO Sports sets. As usual, I made mine out of parts I had to hand, which meant whacky rainbow colours. The module shifts balls pretty quickly, an will hold quite a large number in its U shape to regulate the flow.