Spinner for folding prop on RC model aircraft

This spinner allows to connect two folding prop blades and attaches them to a cheap drone style brush-less motor, to use it for a fixed-wing plane. In my case this setup drives a homemade motor glider with 160cm wing span, producing 600g of thrust at 12.000rpm from a 7.5x4 inch folding prop. This is enough to give my plane a very nice, but still realistically looking climb rate.

These drone motors are produced at huge quantities, which is what makes them so cheap, despite their decent quality. As propeller connector, they have a simple M5 screw bolt sticking out at the top. As they are not made to drive bigger props, it is wise to limit the maximum rpm from your RC transmitter, to avoid overheating your motor. My setup could produce significantly more thrust at higher rpm, but I decided that 12.000 rpm is a good number, as the centrifugal forces increase with the square of the rpm, and the thrust was just fine for me.

A word of warning on the usage of this thing: All parts of a propeller are subject to very significant centrifugal forces. A single 3.1g lightweight blade with a center of gravity only 4.1cm from the axis, spinning at somewhat over 10.000rpm, causes a pulling force on the spinner in excess of 10kg!

That is why I have extensively testes this part. I have loaded this spinner (and even a somewhat smaller version) up to 32kg with a language scale, which was the maximum load before my test stand gave up. I was not able to tear apart this spinner during my tests. So I know that my printed part can handle these forces well. I strongly recommend to do the same if you print and use it. I will not be responsible if you propeller disintegrates, which can be seriously dangerous!

Caution must also be used when selecting the bolts that hold the propeller blades. I absolutely do NOT recommend to use pieces of filament, although it is easy, fits well and can be fixed by touching it briefly with a hot soldering tip. At my tests, the filament bolt gave in at 15kg, so this is really just for very small planes (e.g. indoor slow flyers).

My clear recommendation is to use metal pins (e.g. little steal nails) as bolts. I had some leftover nails from an IKEA kitchen back-wall kit with about 1.8mm diameter and cut them to an appropriate length. To hold them in place, I used a super glue brand which I know works extremely well with PETG (which is by far not the case for all brands).

This thing is tested in real RC flight situations and for me it does exactly what it is supposed to do. I have developed it as part of a new 3D printed RC plane that I have just in the makes and which I will publish soon here.

Print instructions

Printer Brand: Prusa

Printer: I3 MK3S

Rafts: No

Supports: No

Resolution: 0.15mm

Infill: 100%

Filament: DasFilament.de PETG Silver grey

Notes:

I strongly recommend to use PETG over PLA for this mechanically loaded part. I also recommend to print with a relatively high temperature within your suppliers specified range, to optimize the layer adhesion (printed mine at 235°C).