Not the most efficient vawt but is fully 3d printed and it works with 3d printed bearings. Use 16mm PVC tubes or with any other diameter pipe (see openscad file for full hack). Based on the paper: Increase in the Savonius rotors efficiency via a parametric investigation https://www.researchgate.net/publication/228957621_Increase_in_the_Savonius_rotors_efficiency_via_a_parametric_investigation Also check my educational vertical axis wind turbine: https://www.youmagine.com/designs/educational-vertical-axis-wind-turbine OpenSCAD files available. 1st. test de bearings tols (https://www.thingiverse.com/thing:3112100/) 2nd. print it 3rd. that's it