h a l f b a k e r y
Veni, vidi, teenie weenie yellow polka dot bikini.
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This helicopter has two counter rotating single bladed rotors. One travels clockwise, the other anti-clockwise. Once the helicopter is moving at speed in a forwards direction, both blades slow down and stop facing forwards and now act as wings.
Old counter-rotating design
http://www.pilotfri...cques%20Breguet.htm
Early attempt [wagster, Oct 09 2004]
Sikorsky S-69
http://avia.russian...igo/sik_s-69-r.html
Latest attempt - note massive rigid blades [wagster, Oct 09 2004]
Kamov KA-115
http://www.kulikovair.com/Coaxial.htm
Another recent attempt. Flexible blades with spacing. [wagster, Oct 09 2004]
[link]
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Once the blades are stopped, what makes it go? |
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Counter-clockwise, shirley? |
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/Once the blades are stopped, what makes it go?/ |
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It would have a either a conventional propellor or maybe a jet engine to provide thrust. |
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The rotors will be positioned like two discs on top of each other when the aircraft is stationary. When the aircraft picks up speed, the anticlockwise blades will flex up on the right hand side as they now have more lift (their forward motion through the air is now combined with the speed of the aircraft). Conversely these same blades will flex down on the left as they move backwards and their airspeed and lift is reduced. Given sufficient forward speed of the aircraft, these blades can stall. The resulting rotor tilt will be reversed in the clockwise spinning blades, and the blades will eventually strike each other unless spaced quite some distance apart. |
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This has been baked, but not very successfully. I will try and find a link. |
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PS The 'stop the blades and use them as wings' trick has also been baked, a little more successfully as I recall. |
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Kinda like a hummingbird with a rotary wing? |
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[wagster] Isn't this different because there are only two blades in total? One going one way, the other going the opposite way. |
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Some random thoughts: Those blades that move forward, whose speed of rotation are combined with the relative wind of the forward motion of the craft, are called the "advancing" blades and the ones whose rotational speed is subtracted from the relative wind are called the "retreating" blades. In today's designs the swash handles the change of pitch used to even out the lift across the rotor disc with the advancing blade's pitch reduced and the retreating blade's pitch increased. Fully articulated rotor heads, like those used in the MD/Hughes 500/530s also have lead-lag hinges that allow the blades to find their own spacing, bunching up in the advance and relaxing in the retreat. While there are other reasons for lead-lag, this has an effect of slightly slowing the advancing blades and speeding up the retreating blades making for a bit more balanced lift. |
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Ah, the real engineers have turned up. [bris] - the fully articulated system you describe seems like proof that you shouldn't write off any idea as being 'too complex'. |
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Sorry, [humanzee] you're quite right, I didn't interpret this properly the first time. It's a neater idea than I thought. I think you still have two problems, not necessarily fatal. Firstly, in all other systems the lift is more or less balanced at any time, in yours there are two points every cycle where the lift comes from only one direction, presumably from the front and back alternately. This will set up a lot of strains in the shaft and vibrations in the aircraft. Secondly, how do you slow down the blades, lock them outwards and then flip the retreating blade over so that the leading edge is pointing forward, while moving forwards at a couple of hundred miles an hour? I wouldn't like to be inside at the time. |
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Jets slung under stub wings I should imagine. |
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[wagster] I think it would be better to flip one of the blades when both of them are locked, facing the tail of the aircraft. And then bring them out to the wing positions. The body of the craft would have to be able to provide lift while the wings are being set up, or maybe it could use trust vertoring (something clever and expensive anyway). I don't see how you'd get around the other problems wagster mentioned though. |
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//Counter-clockwise, shirley?
ghillie, Oct 09 2004// |
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We prefer 'Widdershins' round these parts. |
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Once each rotation, both blades will be together and their angular momentum will act to seriously destabilise the craft. Unless by 'single bladed rotors' you actually mean twin bladed rotors (ie. two vanes on each rotor) |
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