Variable Configuration and Pitch Propeller

grabcad

This is rock bottom.My project is the prototype of a variable geometry propeller.A non-fixed propeller can change the "pitch", meaning the angle, of its blade to change the thrust.Fundamentally in my project I added another degree of freedom that allows the propeller to change the blades' angle relative to the center of the propeller,Modifying the angle, which could be called "configuration", the blade assumes a different section relative to the angle of attack (which is the angle perpendicular to the air flow).When the configuration range is wide enough and the diameter of the rotor is suitable,the speed of the blades' tips can be lowered by changing the configuration and this can provide a higher efficiency in multiple use cases.One of the use cases of my project could be using it in environments with multiple atmospheric densities. Similarly to NASA's Dragonfly drone, a drone that will land on Titan possibly in about 14 years.I started the design process while reading 3D printing articles, it took me some time to understand the precision of a 3D printer, although I chose from the start FDM printing to develop my project.I did some concept CAD models to test the degree of freedom and to see the overall measures; while learning how to modeling, I used Autodesk Inventor.In the prototype to simplify the process I chose to use these "fit" parameters multiplied to the tolerances to address the printing imprecisions.(I haven't found any article to do this the right way, so this is what I did:)printTolerance = nozzleDiameter/2 \\Printing tolerance (rule of thumb)clearanceFit = 1.25 \\Free movement (rotation or sliding)transitionFit = 0.85 \\Held in place but easy to disassembleinterferenceFit = 0.30 \\No movement, resist forcefreeFit = 1.5 \\Free movement (looks good)If for example I need a printed part that goes into another 3D printed part, the distance between its walls will be d0 = 2 * printTolerance * [neededFit]Some design considerations I've made are:-Pitch arms that pull rather than push in contraposition to the major force to avoid deformation.- Using 45° angles to avoid supports.-All ball bearings fixed in place to sustain axial load.-The shaft is a carbon-fiber tube, to reduce weight, and squared to sustain better radial load and avoid rotation of the pitch and config shafts.-The bushing around the shaft is 3D printed and has some margin for deformation to account imprecisions (I read about IGUS filaments for 3D printed bushings but I discarded it for sake of simplicity).The range of motion of this prototype:configRange = 60° \\the range of motion of the blade that changes the geometrypitchForward = 10° \\thrust forwardpitchBackward = 10° \\thrust backwardI used Autodesk Netfabb to export the .STL files.I also used Ultimaker Cura (although any slicer would do fine) to apply some infill optimizations that I have defined with the extra bodies in green (watch the renders for references), this should add strength to the parts only where needed, while it may reduce a little the print time and the weight.(I still struggle to define the infill with .STL files just because they can only contain one 3D body and I need multiple bodies and their positions, therefore I used 3MF files)Sizes:Height = 119.45mmLength = 101.80mmWidth = 112.200mmThis is the first project of this kind that I've done,I hope you like my design as much as I enjoyed doing it.Name:Ibrahim BendebkaSchool:Secondary school Altiero Spinelli, field of study:Computer science and Telecommunication,School code:MITF008514