Differential turbine garden spinner

Two turbines combine their output via a differential, and the difference in motion turns the entire contraption until both turbines are rotating at the same speed. The entire contraption should automatically point into the wind.

The turbines can be adjusted to point in different directions. This allows one turbine to catch more wind than the other, allowing the mechanism to sense wind direction.

The model demonstrates the mechanical principles of the differential and the constant velocity joint.

Printing

The file Differential turbine garden spinner ALL PARTS contains every part. Other files break the model into the main assemblies.

The parts are arranged in their assembled state and need to be arranged on the print bed, so select “no” when the Prusaslicer asks asks if the file should be considered a single body with multiple parts. (Selecting “yes” is useful to see how everything should be assembled.) Make the walls thick enough in case it proves necessary to drill out axle holes as needed for the nails or wire on hand.

Assembly

Refer to the pictures to see how the model assembles. Most parts glue together, but a few have screw holes.

Additional materials:

• Glue to fasten parts together
• The turbines and gears rotate using panel pins as axles - these are fine round wire nails. Any straight wire of about 1.8mm diameter should do and can be cut to length as needed.
• The main assembly rotates on a ball bearing. There are 3D printed raceways in the model that need to filled with 6mm BBs or equivalent.
• Pair of M4 screws and nuts to secure the arms to the main body
• Pair of M3 screws and nuts for the hinges in the arms

Software used

Shapr3D was used for modelling, and https://www.stlgears.com/generators/3dprint was used to generate the bevel gears.