Grist Mill

Here's a simple grist mill. I redesigned this so that the trough is a separate file, which reduces the need for supports. Just glue the trough to the back top edge of the wall where the wheel would go. Glue the pin into the hole on the side of the building. Slide on the wheel and then glue the end cap onto the pin. The wheel needs to spin freely with the paddles angled upward.

You'll need a small recirculating pump that can fit in the trough behind the building. Run the outlet hose from the pump up to the connector at the back of the trough above the wheel. Depending on what type of filament you use, you might want to paint the entire structure first to make sure it's water resistant. Then fill the pond with water.