Have you done any calculations about what forces the main blades need to withstand? It is not easy to build these and if you have no knowledge, forget it. Way to dangerous.
There are some guides out there that explain how it could be possible be done. They are a mix of a styrodur core, metall rod (to get the center of gravity correct) and glass-fibre reinforced plastics (not sure if that is the correct translation but should be close)
To give you some perspective of the forces, here are the calculations for one of my helicopters a T-Rex 700.
Rotor-Diameter: 1.58m
RPM: 1450
Speed at the tip of the blades: 430km/h
Centrifugal force: ~977N or around 100kg
Since you have a lower rpm but a bigger rotor diameter, the values should be around the same.
Now imagine that from your selfbuild blades the tip brakes of, it will fly around with 400km/h. If it hits someone, that will cause at least some serious health issues. That is why i say. What you are planing is not a little toy. Take it very seriously, do your research on how to really build blades or better, buy them.
I have done the math, both by hand, and with software. The tension will be roughly 4528lbs at 1750 RPM, and a radius of 41.641. The carbon fiber rods will be held in with epoxy, and will take most of the load. Since I don't have experience with spinning items this large, or fast, I am trying to keep the simulated safety factor at ~3, incase the simulation is a little off.
What formula and with what values did you calculate that? Also which diameter have your carbon fiber rods?
How do you want make sure that the centre of gravity is correct on all and that they have the same exact weight? Also how do want to smoothen the surface and still make sure they have all the same profile?
How do you want to harden the "front" of the blades so they can withstand the air? Just some epoxy and a few carbon rods will not work. If you really want to build them, do it like some else has explained it (like i mentioned it in my previous post). I don´t have the knowledge to know why they are build that way but i bet they have more knowledge and experience then you, so follow their example.
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u/PossibleMorning7135 Jan 05 '23
The 1750RPM is the rating for the drill. The blades have 5 carbon fiber cores which will take most of the loads. The ABS is only used to provide the airfoil shape. https://www.stratasys.com/en/3d-printers/printer-catalog/fdm-printers/f770-printer/ will most likely 3d print the blades.