As everybody is working on ways to improve electronic response I thought it was time I did a little work to see what can be done beyond the electric motor. Coanda and Bernoullis effect put to good use.
Wind disturbance was the reason behind the side cut outs. It was fine flying in a constant high wind but it did not like flying in its own ground effect due to the pressure distribution problem. The aerodynamic effects are centered around each motor a opposed to a global effect. This FMC-3 design was about 30% more inefficient if you need an example of the wrong way to go. It has the center of aerodynamic lift above the center of mass ( as do many out there) so the pendulum effect has to be overcome by the motors working overtime whenever there is a lateral movement. In an ideal world those two points should at the same point.
The hull sits on top of the X frame, it is mounted in only four places on small evo rubbers, so the whole hull assy. is isolated from vibration. X frame is oval section and is made from hard balsa covered with a light cabon/epoxy skin. Tip vortices go up with increased pitch angle. The best efficiency comes from absorbing the available power into the largest thrust area i.e.large dia, x small pitch angle.
No vibration issues. 5 mm motor shaft, 3 bearings and 15 cm clearance on the hull. 14.4.5 props fully balanced.
Mounting the motors in this manor reduces prop overhang and thus any risk of vibration frequency oscillations.
Like I said profile drag is a square law. Put your arms under the prop wash and you incur significant drag penalty and turbulence. Because MK did it the wrong way does not mean we all have to follow!!!!
I have tried a duct system. My conclusion was that it could not produce any more lift than it's own weight. There is however another way to do this which is where the shroud is significantly large in diameter than the prop with a large bell mouth. This is called an augmenter tube. I have not tried it yet but it could work in theory.
Comments
Those are Pulso X2820/12
What Motors are you using, like the mounting.
Wind disturbance was the reason behind the side cut outs. It was fine flying in a constant high wind but it did not like flying in its own ground effect due to the pressure distribution problem. The aerodynamic effects are centered around each motor a opposed to a global effect. This FMC-3 design was about 30% more inefficient if you need an example of the wrong way to go. It has the center of aerodynamic lift above the center of mass ( as do many out there) so the pendulum effect has to be overcome by the motors working overtime whenever there is a lateral movement. In an ideal world those two points should at the same point.
have you tested this frame in wind gusts ?
i have made some test with tons of frame type and i think you will have stabilization problem when flying on the wind as i have on my tests.
No vibration issues. 5 mm motor shaft, 3 bearings and 15 cm clearance on the hull. 14.4.5 props fully balanced.
Mounting the motors in this manor reduces prop overhang and thus any risk of vibration frequency oscillations.
Like I said profile drag is a square law. Put your arms under the prop wash and you incur significant drag penalty and turbulence. Because MK did it the wrong way does not mean we all have to follow!!!!
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