Parametric Multi-Blade Propellor Generator

thingiverse

This is a parametric propeller model generator which can create propellers with multiple blades. It was written in OpenSCAD 2015 and uses coding that won't work in older versions. The script makes workable propellers but not necessarily the most beautiful ones. To beautify them up, you may want to take the generated model into something like Blender and with a bit of loop bridging make some nicely merging shapes around the hub. If you would prefer a folding prop, go here: Parametric Folding Propeller Generator It (currently) has the NACA4412 airfoil as the blade profile. This produces a very thin blade which is getting into the realm of being a bit too bendy. After a bit of testing I may replace this with a thicker airfoil. If you want to use a different airfoil look for the line; Airfoil_points = [[1000,1.3],[950,14.7], .......,[950,-1.6],[1000,-1.3]]; ... and replace it with your preferred airfoil. The base scale is 1000 units, so you will need to adjust your preferred airfoil to conform with this. I got the points for this airfoil from the airfoil archive http://m-selig.ae.illinois.edu/ads/archives/coord_seligFmt.tar.gz, and used the following file: http://m-selig.ae.illinois.edu/ads/coord/naca4412.dat. I have created a Python3 based Airfoil .dat file to OpenSCAD conversion tool on my website. This will produce compatible OpenSCAD files from any *.dat* file you download from the UIUC Airfoil database. You can find it here: Airfoil .dat to OpenSCAD Conversion Tool With regard to printing, you may find the trailing edge gets too fine to print so it may be truncated a little. You can see this happening in the photos where the last 0.5 – 1mm has been lost. I have not tried this on an FDM printer but feel that some sort of support will be required. All parameters are mm unless otherwise stated. The exception is the blade diameter and pitch which you can fill out with either metric or imperial values. Refer to the diagrams and list below. Here is a rundown of the parameters used. The fundamentals • Pitch adjustment was originally introduced to de-rate the pitch angle so that my calculated pitch angles would match what I was measuring from a commercial propeller. • Leave these both set to 1.0. It is left here because it may be useful for adding washout to the propeller. • PitchAdjHub: Pitch adjustment factor at the hub end. • PitchAdjTip: Pitch adjustment factor at the tip. More Blade and Hub Parameters • BldCtr: This is the position of blade centreline about which the blade is scaled and twisted. It is expressed as a % of the distance along the blade chord measured from the leading edge. • PropShftD: Motor shaft size. • PropHubD: It is not really the hub diameter as such but more an expression of the clear area around the motor shaft. • PropHubDCutterMax: This is a bit of a dumb number. It refers to the imaginary outer diameter of a cylinder used to cut the back of the hub into a slope which will match your motor. • PropHubT: Propeller hub thickness To cater for pinned hubs that appear to be used in small multirotors, the following parameters have been introduced to give an option for pinned hubs. If either or both of these parameters are set to zero the option is disabled. Refer to the diagram included in the images for a demonstration of these parameters in action. • HubPinD: The diameter of pins • HubPinPCD: The pitch circle diameter of the pins There are a number of other parameters but they are variables for use in the code. You are welcome to put numbers in them, but they will be overwritten anyway and have no effect. They are: Poz1, Poz2, StrtAngi, EndAngi, StepLi, StrtWi, and EndWi. Good luck.