Radial & Co-Axial

[XH558]

So ok I know about lift .... simply put a 9 ton SeaKing helicopter sends down 10 tons of air from its rotors and thus ergo it lifts .... I realise that';s over simplifying it and I know that really all helicopters do is beat the air into submission ... but you get my drift 

So that';s Radial ... blade pushes air down more than vehicle weight = lift

So now help an old man understand co-axial ....

So .... you then you put another motor and another prop under that original motor and prop - presumably spinning the other way - if i see it correctly - now the wind from the top one flows down through the other prop - which is only a very short distance below - and you still have one column of air going down ....

The top motor pushes air down an inch or so and that air - going very fast - hits the other prop - goes through it and continues on down having been thorough another spinning thing ...

Does that double the air going down .. if so how ... the top prop only seems to send air an inch or so before it hits the other prop??

Can';t see it       

[endure]

Isn';t lift generated by the pressure differential between the top and the bottom of the rotor blades in the same way as a fixed wing aircraft?

[XH558]

Isn';t lift generated by the pressure differential between the top and the bottom of the rotor blades in the same way as a fixed wing aircraft?

It might well be ... if I understood it ....  ::) ::)

[ChrisH]

Isn';t lift generated by the pressure differential between the top and the bottom of the rotor blades in the same way as a fixed wing aircraft?

So the airflow is a side effect of the lift generated by each blade and the downforce of any air is not the main force? I';d never really thought about the coaxial issue, interesting.

[dp106]

I imagine (and it really is only me imagining) that the second rotor is effectively sucking the air through from the rotor above assisting it with the effort of moving all that air?

I dont think the rotors act the same as a wing on a airplane, the propeller is deflecting air downwards to create the lift?  If not I better stop sanding the back of my props down to balance them

[endure]

http://www.decodedscience.com/how-do-helicopters-fly/20418

http://en.wikipedia.org/wiki/Coaxial_rotors

[XH558]

http://www.decodedscience.com/how-do-helicopters-fly/20418

http://en.wikipedia.org/wiki/Coaxial_rotors

Do you know I';ve been flying models 40 odd years - including helicopters - and that';s the first time I';ve really given any thought to the lifting potential of a rotating wing as opposed to the thrust of the ';wind'; they generate  :embarrassed :embarrassed  ... of course it';s not the wind at all it';s the lift of the wing itself so I now see that the wings rotating opposite one another produce double the lift and by contra-rotating do away with the need to have clockwise and counterclockwise props on different arms - presumably all the top props go one way and all the bottom props go the other ...

Very interesting ... now I see it 

[Crispin]

The two rotors are contra-rotating to counter the torque which is why a normal heli has a tail rotor.  The lower root would have less effect than the upper because of he now very turbulent air. Vortices firm over the blade which reduce efficiency.

It';s fine for toys as it is simpler / cheaper to do.  To yaw the heli,  a speed difference is created and the torque causes yaw.

My somewhat simplified version of it. :)

[endure]

The Russians think it';s ok for bigguns too!   

kamov KA-50

[kilby]

The Russians think it';s ok for bigguns too!   

Not just the Russians as this is probably the replacement for the Blackhawk for the special forces.

With a top speed of about 230 MPH

http://en.wikipedia.org/wiki/Sikorsky_S-97_Raider

Also very popular with naval fixed wing