Parametric Folding Propellor Generator

thingiverse

I have an FPV Shadow RC plane from Banggood that I bought a while ago, and the standard kit includes a bunch of 6-inch diameter x 4.5-inch pitch propellers. For quite some time, I would break a propeller (and often rip the motor off) every time I landed because there was nothing to stop the propeller from motoring over or being in a vertical position when it touched down. To alleviate this problem, I added two large coreflute tails that extended below the plane a bit like twin keels on a surfboard. It looks pretty ugly but helps prevent damage to the motor mount and props that I was experiencing. However, what I really felt my FPV Shadow needed was a folding propeller. After hunting high and low for quite some time, I finally concluded that small 6x4.5 folding propellers did not exist, and so I decided to see if I could come up with a parametric folding propeller that could be 3D printed. This OpenSCAD script is the result. If you would prefer a regular non-folding propeller, go here: [Parametric Multi-Blade Propellor Generator](https://www.thingiverse.com/thing:3506692). This script was written in OpenSCAD 2015 and uses coding that will not work in older versions. I suspect the Thingiverse customiser may have problems with it so I would suggest you download the .scad file and use it directly in OpenSCAD. The model is for the blade only, but if you want to make a complete propeller, simply duplicate the entire script and mirror one of the blades around the Y-axis. You will also need to adjust the SpinHPinRad parameter accordingly. There are a number of parameters that you can adjust to suit your needs: **The Fundamentals** Pitch: Use PitchI for Imperial measurement, or PitchM for metric values. Diameter: Use DiamI for Imperial measurement, or DiamM for metric values. Blade Maximum Width (mm): MaxChdW **Calculation Factors** Statns: This is the number of stations along the blade where the size and twist is calculated. A higher number will improve the smoothness of the shape but add to the calculations. SectRes: The number of intermediate steps between stations. The higher the number, the smoother the shape is but it adds significantly to the calculation time. **Pitch Adjustment** The 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. As it turns out, I must have been measuring the commercial propeller pitch poorly and I should have just run with my unadjusted pitch angles. So, 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 end. **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. SpinHPinRad: This is the distance from the shaft centerline to the centreline of the propeller hinge pin. SpinPinD: Hinge pin diameter SpinHubD: This is difficult to describe but is the diameter of the bit of the blade base around the pin. See the diagrams for a clear guide. SpinHL: This is the width of the hinge section. SpinHubVTweak: This factor will allow you to move the hinge pivot forward or backward on the blade to suit your needs. This may have advantages when making pusher type folding props. There are a number of other parameters that you can adjust, 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! 22 March 2019 - Added a "Glitch Guide Image" to explain the method for eliminating the occasional appearance of artefacts around the hinge by tweaking the Statns parameter.