How many RPMs does it take to achieve lift?

[Neodymium50]

Hey! I'm new to science forums, and I need some help on a project of mine. I am making a electrically powered helicopter, ride-in size. I have the circuits halfway designed, but I need to know how many rotations per minute it takes to achieve certain amounts of lift, and how many volts it would take to turn a motor at certain speeds, so I can use the resistors with the right amount of Ohms. If anyone is concerned about safety issues, I'm not going to try to fly it until I learn how. If I can design a working helicopter, I might be able to get a scholarship later. I'm wanting to go to college and get a good degree on engineering. By the way, what college degrees do they have? I can never remember them all.

Plz help! -N50

Edited February 7, 2009 by swansont
turned volume down

[Mokele]

It's all going to depend upon the aerodynamics of the rotors. You need to find that out before anything else. Different rotors will have different lift and need to spin at different speeds, will have different masses (thus will be harder or easier to spin up), etc.

[Neodymium50]

Another question: Would a rotor with a larger curve on the top do better than one with a smaller one? In Bernoulli's principle, it says lift is achieved by the lowering of air density because of movement... so a bigger curve would mean more lift, wouldn't it? Or does it need to be more aerodynamic so it can move faster? And what would be the best type of metal? Would aluminum work, or is it too flimsy?

[Mr Skeptic]

A ride-in sized helicopter, and you are asking for help online building it ... may I suggest you need one of these.

 

Incidentally, are batteries powerful enough to power a helicopter? How many seconds do you think you can fly with them?

[Externet]

100.

 

You may also click on "next" here :

http://www.cybercom.net/~copters/mech/R22_panel.html

 

Good one ,skeptic ! :D:D

[NowThatWeKnow]

Another question: Would a rotor with a larger curve on the top do better than one with a smaller one? In Bernoulli's principle, it says lift is achieved by the lowering of air density because of movement... so a bigger curve would mean more lift, wouldn't it? Or does it need to be more aerodynamic so it can move faster? And what would be the best type of metal? Would aluminum work, or is it too flimsy?

 

NASA Foilsim will let you calculate lift with different angles of attack, airfoil size, camber and speed. Change the "Input" field for different options.

http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html

The lithium ion battery would give the most power for weight and is used in radio control aircraft with excellent success. It does get pricey as the size goes up.

[GDG]

You may want to pick up a good book on aeronautical engineering first.

 

Yes, the curve of your airfoil will affect the lift generated -- but also the drag, requiring more torque to spin the rotor.

 

Consider carefully the centrifugal forces on your rotor tips when you're going full speed: what happens if a rotor blade fails while spinning at 800 rpm? A: it turns into a javelin traveling at high speed, straight through the house next door, the car parked next to it, anyone standing in the way...

 

You may also want to first familiarize yourself with the federal regulations that govern the design and construction of aircraft by amateurs. The FAA recommends that you take a copy of your plans to the nearest FAA office before you buy any materials or start building. In addition to the regulations, they have a nice advisory circular to help people interested in building their own aircraft.

 

Finally, you may want to seek out your local Experimental Aircraft Association chapter.

 

Best of luck

 

Grant