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Seriously though, a helicopter has an extremely small wing area compared to an
equivalant fixed-wing aircraft, and therefore has a tremendous wing loading The type of loading that would rip the wings off a GA airplane. The reason it works on helicopters is because of rotor speed and cintrifugal (sp?) force. A relatively high rotor speed (speed of the rotor blades through the air nearing the sound barrier) creates a great deal of lift per square foot. However, because the rotor blades are spinning, cintrifugal force puts the blades under tremendous tension. This holds the blades in a relatively level plane and keeps them from flexing upwards excesively and breaking off. While more blade area can be traded for lower rotor speeds (Hughes built one with a rotor speed of 16 RPM), you cannot ignore the necessity of cintrifugal force. A group of students from MIT tried to build a human powered helicopter a few years ago. They used a 2-blade 60" chord 100+ foot disk setup with extremely low rotor speeds. While the blades made plenty of lift, the students could not make them strong enough for the given weight to keep them from either coning upwards or breaking off. The same would be true of inflatable blades. Harry |
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Mark Hickey wrote in message . ..
(sanman) wrote: I was reading about inflatable wings: snip So you'd be riding a sort of lightweight automotive vehicle along the road, and you could switch to helicopter mode, with inflatable rotors popping out on the top of your vehicle. Your engine would then power the rotors, and you'd fly away. Once you landed again, the deflated rotors would be tucked back into whatever compartment they'd popped out from. Cmon, there are all kinds of wierd-looking lightweight concept cars out there, so why not this? What would be the main difficulties with a concept like this? Given that centrifugal force keeps the rotors from folding upwards anyway it seems a relatively small change in the principles of operation to have such a mechanism. If inflatible was no good how about folding/telescopic . . . or just ribbon/strip with a weight on the end. ## Miniature emergency parachute hat ## Since the "wing" area of a helicopter is much less than that of a parachute, and that a helicopter CAN land softly without an engine why not have a small device that:- Is an auto gyro that infates out of a bag Uses gas jets to accelerate the blades to operating speed lowering the wearer safely to the ground. Would be smaller and lighter than a conventional parachute? Maybe a pyrotechic charge could be used as a gas source? Perhaps a small hand grenade would be enough to get it going |
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"sanman" wrote in message om... So you'd be riding a sort of lightweight automotive vehicle along the road, and you could switch to helicopter mode, with inflatable rotors popping out on the top of your vehicle. Your engine would then power the rotors, and you'd fly away. Once you landed again, the deflated rotors would be tucked back into whatever compartment they'd popped out from. Cmon, there are all kinds of wierd-looking lightweight concept cars out there, so why not this? What would be the main difficulties with a concept like this? Woodpeckers. Wayne |
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Sanman
On a parallel plane to your rotor blades. The DOD (Goodyear) some years ago built a inflatable airplane (XAO-3). It folded up the size of a big suitcase. The wing and control surfaces were 'blown up' an provided lift and control surface. The unit was designed for dropping to downed pilots behind enemy lines. They would blow it up and start a little put put motor and fly to a safe area. Had a renge of over 300 miles as I recall. Think a air pump was on the little motor to provide air to inflate. Never made it into production but the test articles flew. You might want to research this to see if you can get any ideas and not have to reinvent the complete wheel G Big John On 29 Jul 2003 15:51:24 -0700, (sanman) wrote: I was reading about inflatable wings: http://www.spacedaily.com/news/plane...-wing-01a.html http://www.ilcdover.com/EngineeredInfl/inflatwing.pdf and I wondered why these couldn't be implemented as rotor configuration, for a "flying car" type of vehicle -- ie. a car that could instantly convert to helicopter flight. If you look back at those older Hiller helicopters, they had big, thick, rigid aluminum rotors: http://avia.russian.ee/vertigo/hiller_x-2-235-r.html http://avia.russian.ee/vertigo/hiller_xh-44-r.html An inflatable equivalent might be somewhat thicker and yet not be so rigid, and would not have the high mass penalty. So you'd be riding a sort of lightweight automotive vehicle along the road, and you could switch to helicopter mode, with inflatable rotors popping out on the top of your vehicle. Your engine would then power the rotors, and you'd fly away. Once you landed again, the deflated rotors would be tucked back into whatever compartment they'd popped out from. Cmon, there are all kinds of wierd-looking lightweight concept cars out there, so why not this? What would be the main difficulties with a concept like this? |
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Big John wrote:
Sanman On a parallel plane to your rotor blades. The DOD (Goodyear) some years ago built a inflatable airplane (XAO-3). It folded up the size of a big suitcase. The wing and control surfaces were 'blown up' an provided lift and control surface. The unit was designed for dropping to downed pilots behind enemy lines. They would blow it up and start a little put put motor and fly to a safe area. Had a renge of over 300 miles as I recall. Think a air pump was on the little motor to provide air to inflate. I saw this on the Wings channel. The airbag had a lot of yarn like attachments that ran from the top to bottom of the wing so that it stayed flat instead of blowing up. With enough pressure and inflated structure can be extremely hard, compressive wise, but it still doesn't have much buckling strength. Think of a long thin balloon that they make animals out of at the carnivals. Get it bent a little, and the rest goes very easily. A rotor would be a REALLY long, thin balloon. -- ----Because I can---- http://www.ernest.isa-geek.org/ ------------------------ |
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"Ernest Christley" wrote in message .com... Big John wrote: Sanman On a parallel plane to your rotor blades. The DOD (Goodyear) some years ago built a inflatable airplane (XAO-3). It folded up the size of a big suitcase. The wing and control surfaces were 'blown up' an provided lift and control surface. The unit was designed for dropping to downed pilots behind enemy lines. They would blow it up and start a little put put motor and fly to a safe area. Had a renge of over 300 miles as I recall. Think a air pump was on the little motor to provide air to inflate. I saw this on the Wings channel. The airbag had a lot of yarn like attachments that ran from the top to bottom of the wing so that it stayed flat instead of blowing up. With enough pressure and inflated structure can be extremely hard, compressive wise, but it still doesn't have much buckling strength. Think of a long thin balloon that they make animals out of at the carnivals. Get it bent a little, and the rest goes very easily. A rotor would be a REALLY long, thin balloon. -- ----Because I can---- http://www.ernest.isa-geek.org/ ------------------------ Yeah, but it doesn't _stay_ broken. Relieve the load, and it pops right back out. The problem is with air pressure. If you use high pressure, atmospheric pressure doesn't bother you, but a leak is catastrophic. If you use low pressure, leaks aren't catastrophic, but altitude changes affect the rigidity of the structure. Tim Ward |
#9
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To add a little more to the goodyear plane.
The bags had built in leaks so that they would not overinflate with altitude The motor ran an airpump to keep it full. You would have the same inflation problem with your rotor. Now that would be one piece of engineering....... "TIM WARD" wrote in message ... "Ernest Christley" wrote in message .com... Big John wrote: Sanman On a parallel plane to your rotor blades. The DOD (Goodyear) some years ago built a inflatable airplane (XAO-3). It folded up the size of a big suitcase. The wing and control surfaces were 'blown up' an provided lift and control surface. The unit was designed for dropping to downed pilots behind enemy lines. They would blow it up and start a little put put motor and fly to a safe area. Had a renge of over 300 miles as I recall. Think a air pump was on the little motor to provide air to inflate. I saw this on the Wings channel. The airbag had a lot of yarn like attachments that ran from the top to bottom of the wing so that it stayed flat instead of blowing up. With enough pressure and inflated structure can be extremely hard, compressive wise, but it still doesn't have much buckling strength. Think of a long thin balloon that they make animals out of at the carnivals. Get it bent a little, and the rest goes very easily. A rotor would be a REALLY long, thin balloon. -- ----Because I can---- http://www.ernest.isa-geek.org/ ------------------------ Yeah, but it doesn't _stay_ broken. Relieve the load, and it pops right back out. The problem is with air pressure. If you use high pressure, atmospheric pressure doesn't bother you, but a leak is catastrophic. If you use low pressure, leaks aren't catastrophic, but altitude changes affect the rigidity of the structure. Tim Ward |
#10
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Well, polymers and reinforcement fiber technology are continuing to
improve. You can even buy carbon-fiber reinforced polymers these days, with superduper tensile strength. But I would imagine that kevlar, spectra, vectran would have enough strength to do the job for a small personal transportation vehicle. They would be able to handle the high pressures. To ease the load requirements, the rotor could be 4-vaned. Each pair of opposing vanes could have a commonly inflated structure -- that way if a single vane suffered a rupture, then it and its opposing partner could be deflated/depressurized, while the remaining pair of rotor vanes would take the load while you landed. Or why not even a 6-way rotor? Someone who responded to my posting suggested weighting the rotor tips for flywheel effect. The centrifugal force from the weighted tips would help to keep the rotors rigid and reduce the possibility of buckling. Flywheel energy could also help in the event of an unpowered landing due to engine failure. |
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