Has the lightest autogyro glider possible (today) yet been built?

dcnblues

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I'm new to the forum and to autogyros, so I hope my questions aren't annoying to anyone. I'm simply curious. From a clean sheet of paper, in 2012, what's the lightest autogyro glider one could build to land a hypothetical 225 lb pilot? I've read the 'autogyro hang glider' thread from 2009, but it didn't really address my question.

Given modern materials, I'm imagining a one-piece composite carbon, 2 blade rotor, perhaps the kind of composite bearing sets which are turning up in bicycles, and probably some kind of spectra webbing harness to support the stem in some kind of foot launch harness (hang glider style). With a minimal carbon frame and tail boom for a (small as possible) directional stabilizer.

I'm imagining a specific use (balloon launch) which would require only landings, not takeoffs. *Edit: I'm also curious about keeping a foot landing design from having the rotor hit the ground in flare. I assume that the larger the rotor diameter, the higher off the ground the rotor needs to go, but that reduces what may be useful ground effect.

I guess primarily I'm wondering about blade design. With weight savings, the ideal rotor would probably be shorter in diameter than anything previously made, right? I'm aware blades gain efficiency with size, so there'd be a limit to how much smaller they would get. I also suspect that the blade design wouldn't change much in profile, but don't know. If smaller in diameter, it would spin faster, I'm also guessing.

Mostly I want to imagine a sleek toy along the lines of an expensive, top line carbon road bicycle. How light do you experts think such a rig could be made, if money weren't much of a factor? Under 40 lbs? This is a hypothetical, and again, I'm just curious.
 
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I'm imagining a specific use (balloon launch) which would require only landings, not takeoffs.
What you're describing sounds like driving nails with a wrench.
Mostly I want to imagine a sleek toy along the lines of an expensive, top line carbon road bicycle. How light do you experts think such a rig could be made, if money weren't much of a factor? Under 40 lbs? This is a hypothetical, and again, I'm just curious.
A very expensive wrench...
 
Prerotate

Prerotate

How do you plan on getting the rotor up to flight speed prior to release from the balloon? Simply dropping it will be a quick trip down.

Larry
 
One of the four rotors used here will probably be the lightest. Gamera Human-Powered Helicopter Project.
Just change the twist and add some strength. -Dave

Thanks Dave, that was friggin cool. All ground effect, but still cool. I suspect the blades were designed both for very very low gearing / speed and ground effect, so not practical for gliding. But still cool.
 
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What you're describing sounds like driving nails with a wrench.A very expensive wrench...

Please explain.

And I said it was a hypothetical, and if money weren't a factor. However, making molds and vacuum bagging carbon is getting easier (advanced techniques becoming common knowledge) and carbon fiber getting cheaper.

I'm guessing, but don't know, that a glider wouldn't have blade tip speeds that carbon coated with a hard epoxy (with UV protectant of course) couldn't handle.
 
Larry, is that an absolute, or function of altitude? If an unmoving but freewheeling rotor dropped from, say, above 10,000 agl wouldn't spin up on it's own, I didn't know that.

What's the terminology for how fast it needs to be spinning before it becomes self-sustaining? I said I was new to autogyros, didn't know that, but would like to read up on it. What do I search for? Many thanks.
 
Please explain.
What i mean is what you're describing is best accomplished by a parachute. If you want to make it from a balloon to the ground, a parachute is the right tool for the job and you can definitely catch some good thermals while you do it. On a good day, you can glide for hours!

A gyro glider on the other hand is going to by a much more expensive option and it won't do nearly as good of a job from a balloon jump. Even with great thermals, you're still going to have a pretty quick trip to the ground, although, it'll still be survivable.

*quick compared to the parachute
 
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What i mean is what you're describing is best accomplished by a parachute. If you want to make it from a balloon to the ground, a parachute is the right tool for the job and you can definitely catch some good thermals while you do it. On a good day, you can glide for hours!

A gyro glider on the other hand is going to by a much more expensive option and it won't do nearly as good of a job from a balloon jump. Even with great thermals, you're still going to have a pretty quick trip to the ground, although, it'll still be survivable.

*quick compared to the parachute

Ahh, thanks for that. But I have to disagree on some things.

Starting with the cool factor. I find autogyros, and particularly an autogyro glider basically counter-intuitive. People are used to either big wings, big canopies, or powerful engines as being necessary for safe flight. The idea that a couple of skinny little blades could save you from gravity is kind of thrilling. I like that.

The application I have in mind would be well served by a time to the ground midway between a parachute's descent rate and free fall. I'm thinking of something new, pretty much just as a thought exercise.

I still don't trust parachutes. I like free fall, but would never base jump as I want to pull at 5000 feet, and have time to use a reserve in case the primary snarls. This is debatable, but I'd consider the autogyro I have in mind safer than a chute.
 
Ahh, thanks for that. But I have to disagree on some things.

Starting with the cool factor. I find autogyros, and particularly an autogyro glider basically counter-intuitive. People are used to either big wings, big canopies, or powerful engines as being necessary for safe flight. The idea that a couple of skinny little blades could save you from gravity is kind of thrilling. I like that.

The application I have in mind would be well served by a time to the ground midway between a parachute's descent rate and free fall. I'm thinking of something new, pretty much just as a thought exercise.

I still don't trust parachutes. I like free fall, but would never base jump as I want to pull at 5000 feet, and have time to use a reserve in case the primary snarls. This is debatable, but I'd consider the autogyro I have in mind safer than a chute.
I think you have to consider the mechanics involved in acually being able to autorotate to the ground, as well. I personally, have no clue how long it will take you to spin up the blades in free fall to be able to support lift. I'm pretty sure though, your blades will have to be spinning before you jump to prevent them from just flapping (which will rule out a balloon jump, but that's neither here nor there.

But if we say it takes 10 seconds for the blades to spin up to support lift, that's more than 1000 ft of altitude you'd lose just waiting for the blades to being able to carry you. Then after that, another ~200ft of altitude to change that 0 kts airspeed into a speed fast enough to glide. That's 1200 ft right there. Even if the blades spin up as fast as 5 seconds, you'd still lose nearly 500 ft in spin up time and transitioning into a controlled glide. Probably best to stick with parachute...
 
A report on a gyro air drop system can be found here:
http://www.rotaryforum.com/forum/showthread.php?p=491737#post491737

The start up procedure is covered extensively

Excellent paper, many thanks. That's actually exactly what I had in mind, but instead of army cargo, dropped from a plane then remotely piloted to the ground, a non-pilot passenger.

Larry, thanks for telling me that to designing a rotor that can self start in freefall is not practical. This guy had a system stabilized by a drogue parachute and the design called for a spring to prerotate:

These three possible outcomes show the effect of pitch on start-up. Low and negative pitches make start-up easy, however, there is a significant performance sacrifice. High pitches do not even allow the rotor to rotate in the correct direction. Between the two lies a region where start-up is difficult but possible, and here the desired flight performance is achieved.

With a collective, gravity powered pre-rotation is not an issue:

With collective, the pitch could be adjusted to provide optimum performance during each stage of flight. Basically, the entire start-up process could be simplified. Not only would the need for a pre-rotation device be eliminated, but the initial yaw rate caused by that device would be removed as well.

I've learned a lot from that. Not the least of which is that a lighter rotor is not necessarily better.
 
Maple seeds don't fly, uhm?...;-)

An idea. The pilot can go in the pod where the seed is located.

It will make for a wild ride to the ground.
SeeingStars.gif


Dave
 
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A report on design of a self starting rotor can be found here:
http://www.rotaryforum.com/forum/showthread.php?p=491749#post491749

That's also very interesting. Thanks for the link. If you don't have a collective, you can put the blades on a delta 3 hinge, and they'll self start and change pitch as they open. Again, not sure about how much altitude required, but even if it's a few thousand feet, that sounds like it could be fun.

-Wind tunnel test results are presented for a small two-bladed autogyro rotor with high coupling between flapping and feathering such that when the rotors flap upward they feather to a negative pitch angle. This type of hinge is comnmonly termed a Delta-3 hinge. The purpose of the offset Delta-3 hinge in this application, is to allow the rotor blades to fold along a fuselage and be self-starting from a vertical free fall with a rotor angle of attack of 90 degrees.

Really though, there are two main factors which seem to make an ultralight, foot-landing autogyro glider impractical: I had been under the impression that you could get benefits from lighter materials, which would lead to smaller rotor diameter, which might mean it would be more practical to foot land / flare without touching the rotor to the ground. But the reality is that you want MORE energy in your rotor, which means MORE mass, a rotor with fewer blades (2 as opposed to 3) as this increases rpm (and therefore energy) and you want longer blades as you gain efficiency re: drag.

This is all new to me and interesting to learn. It's also possible that all the existing autogyro research has been goal oriented toward speed and glide ratio performance. Essentially, little research may have been done that would benefit the evolution of something like a hypothetical lightweight ridge-soaring autogyro like a hang glider. And a good analogy might be found there. Hang gliders have evolved with the goal of glide ratio above everything else. And the results have been very cool performers, but they're heavy (pushing the limits of foot launching), and they don't handle particularly well (those at the extreme end of performance require wingtip rudders to turn, rather ponderously and too wide for many thermals). Then, paragliders came along and with slower descent rates, and much smaller turning radii, turned out to be superior in many thermaling situations.

I'm still not sure there isn't an advanced materials, three bladed, fat cord, superlight wing with tip weights and a superlight and collective hub out there waiting to be designed. Engineers such as those in Roto Rooter's link might be able to design something that worked.

I think a major requirement would be the performance advantage of a collective. But all collective design has been in the area of powered flight, so as far as I know, no-one has tried to make one with far lighter stress requirements. And even with that, the physics and aerodynamics of rotor flight might make it impractical or not safe enough for real recreational use. The Bottom line, I'm guessing, is that no one knows.

Many thanks for all the help. I love learning this stuff. I figure the more I learn, the sooner I might get back in the air (I'm a writer too broke to build or rent any flying toys).
 
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An idea. The pilot can go in the pod where the seed is located.
It will make for a wild ride to the ground.

LoL ..... is that what they call starry eyed, Dave? Anyway your animated character gives a good impression of what awaits you if you take a seat in the seed.

If you want to give it a try you might copy this one from an intrepid Frenchman:
http://www.davidszondy.com/future/Flight/gyroptere.htm
http://modelbox.free.fr/analyses/MS2002_10P/SCRH_Papin/index.html

and it's not just a drawing or a model:
http://modelbox.free.fr/photoscopes/Papin_Phot/index.html
 
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I love learning this stuff
In that case, Ian, rotary wing aircraft are for you....;-)
I started 15 or so years ago and I feel I'm nowhere near the point where I would start to design the machine of my dreams, so much left to learn... hope your progress is much faster.
Anyway they have room in this forum for enthusiastic dreamers .... welcome and have fun!


PS:
But the reality is that you want MORE energy in your rotor.... superlight wing with tip weights
Tip weights would perhaps be the answer in the quest for a light rotor with high kinetic energy
 
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Ian don't give up so easily.


What if;
  1. 1. The lifting craft had a connection (mechanical, or electrical, etc.) to the rotorhub of the Autogyro Glider and it is used to pre-rotate the rotor.
  2. 2. The skin of the composite blades had a cloth layup that provided a Torque-Pitch elastic coupling. See; Stiffness Characteristic of Composite Rotor Blades With Elastic Couplings
  3. 3. The Autogyro glider had a very small and light onboard power storage device, which was also provided with limited energy by the connection from the lifting craft.
  4. 4. The pre-rotation by the lifting craft assures that the Autogyro’s rotor will not go into a reverse rotation windmill brake state after the drop.
  5. 5. The loss of the pre-rotation causes the torque-pitch coupling to lower the pitch of the blades to the conventional autorotation angles of attack.
  6. 6. Descent
  7. 7. At the landing flare the pilot initiates the consumption of the energy in the onboard storage device.
  8. 8. This energy is used to apply torque to the rotor blades and this causes the torque-pitch coupling to increase the pitch of the blades slightly, while this additional energy is being consumed. The intention is to provide a very soft landing. For a single-rotor craft this additional source of rotational inertia must not react with the fuselage and cause it to yaw.

Also, this may have something of interest; OTHER: Aircraft - Gyrocopter - Non-powered


Dave
 
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