Folding propeller for pusher and tractor planes

Application

This is a high performance 6x3 propeller for RC model airplanes. The 6 means it has a size of 6 inch in diameter (roughly) and the 3 means that is has 3 inch of average pitch. 

Thanks to the straight form, without the usual L-shaped rods, it can be used both for pusher and tractor configuration planes (i.e. with the propeller in the back or in the front). 

Spinners (the middle part of the folding propeller) are included for 5mm and 6mm axis. With the 5mm spinner, it can be put directly on cheap drone motors, that usually come with a M5 threaded rod. There is one special 5mm spinner, that will avoid that the blades fall too far back while the motor if off. At any sensible rpm, the centrifugal forces will keep the blades well straight out.

I have tested this part up to 18.300rpm, which is the upper end of sensible propeller speed in my take. During all my testing, I have not seen one failure. If that propeller speed does not give enough thrust for your plane, then you should probably go for a bigger propeller, which will be much more efficient. I would be careful however to print bigger props, as they could disintegrate with the higher centrifugal forces involved. 

I have developed this propeller with lots of trying around on contour lines in Libre Office Calc and then designed it my putting the found coordinates into FreeCad. You may be able to imagine that this was a lot of work and frankly at times it was nerve wrecking. 

Now I am very happy with the final result and I hope you will be too.

Printing

A propeller blade it tricky to print, no doubt about that. But Prusa Slicer 2.6 alpha came to my rescue just in time. Thanks to the organic supports, it is now possible to print the blade on its side and remove the supports without causing noticeable damage. You can open the added .3mf file in PrusaSlicer 2.5 but it will fall back to the regular support, which will cause a mess. I recommend to try PrusaSlicer 2.6 alpha, which works like a charm already.

I have printed and tested all prototypes from well dried Prusament PETG. I have not measurement results with any other material. Do careful tests if you use PLA or others. 

Post-printing

The printed parts will require some very minor clean up, after the supports are removed. Shape the outer contour line with some sandpaper and give it a nice round tip at the end. The tip is intentionally printed slightly flat, to make it printable. 

Assembly

The only thing you need to assemble the folding propeller are two little nails with 1.44mm diameter (take what you have if it comes close). IKEA delivers exactly these kind of nails with many pieces of furniture to fix the backside. The are ideal, as they have a rough surface all around. But similar nails should do as well. You absolutely need to glue them in with a drop of glue that works for your material. DO NOT USE FILAMENT or other none-metallic pins. The forces on these pins are enormous!

For optimal performance, make sure that you use the propeller with the upper edge (during the print) as the leading edge during rotation. That means that this is the edge that is cutting through the air. The lower edge (where the supports connect) is the trailing edge during rotation. If you are unsure which is which after the sanding, look at the surface at the rod. The side with the unclean surface is the lower edge, i.e. the trailing edge.

As any propeller, this folding propeller needs to be well balanced to run well hat higher rpm. Much to my positive surprise, all prototypes came out almost perfectly balanced right from the printer. You can so some slight sanding on one blade if your propeller should be imbalanced. Do not fly with an imbalanced propeller!

Disclaimer

Propellers that run at high rpm are very dangerous!!! If the propeller disintegrates, the propeller blades can become high speed projectiles that can cause serious injuries or death or cause significant damage! Use this part and your own risk and test it at your intended use case in a safe environment first. 

Use is part completely at your own risk!

Please like it if you like it

Your satisfaction is my reward. Please like this design if you like it

Happy printing!