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Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
And if under camber can be used.
It can if you are design the blades as aerofoil rather than drag, and a tip to airspeed ratio of 3:1 is normal optimum for aerofoil, but the angle is realeted to drag at a certain airspeed, I think around still, with drag at 10% eff and aerofoil at 39-40% eff, you can replace the airspeed to meter/second of prop and times 3 to get the TSR, then decrease the angle of attack until the thing comes out of stall or a massive jump in thrust
the pictures at the top, the topleft one, is the blade shape I would make the length based on rpm, and the angle is
Side not, the pancake motor is supposeable more eff not from the electrical side, but maybe from the angle that the magntic coils are further from the centre of the shaft, make the speed to torgue graphs more straight rather than ecillpe, or adjust more to the environment.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Patrick wrote ...
i continue with the math....
Z sub q is the circumferential velocity as the radius goes out.
im trying to figure out inhaled mass. And if under camber can be used.
I think we will end up with a NACA profile, with camber.
I'm just thinking through the 'tip speed', 'centripetal/centrifugal' thing. Working on 700feet/second tip velocity.
Overall mass of props has to be as low as possible, but strong enopugh to withstand centripetal/centrifugal forces.
I think we need to decide on CSA of prop before deciding on profile. Strength required to overcome centripetal/centrifugal forces with tip speed of 700 feet per second gives us a starting point.
Sorry about the slow response, feel like I've got pnumonia today.
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Propeller Physics and VABs Program.
