My son and I have been working on this model for a while now. We've finally gotten the dimensions very good for connecting with Lego® Technics parts.
They run pretty smooth by blowing in the funnel or connecting a balloon. Our ultimate goal is a balloon powered car or boat. We're not quite there with the torque yet. Suggestions for improvement are welcome!
It's an OpenSCAD model so tweak the geometry to your heart's content…
The author marked this model as their own original creation.