View Poll Results: Why is jump so rare?

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  • Nobody wants it

    1 12.50%
  • Initial cost too high

    4 50.00%
  • Too much maintenence

    1 12.50%
  • I think it's dangerous

    2 25.00%
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Thread: Jump Rotorhead Dynamics

  1. #11
    Quote Originally Posted by James J. Judge 42935 View Post
    ........In a gyro, with the engine not powering the blades, there is no shock to the engine, and as the energy in the blades dissipates for lack of forward movement, a normal dead engine landing could be made.

    There is the possible danger if the engine failed soon after lift off and you were over an area with no open space to settle into, you would be toast.......
    Even with an open place to land, it would be difficult to land safely if there isn't sufficient forward airspeed to facilitate a 'flare' to land. The CarterCopter's demonstrator blades had enough inertia that blade rpm was maintained until the transition to normal flight speed had been made. It still required an experienced pilot to make that transition. In Dick DeGraw's machines. the rotors are constantly fed power through a transmission arrangement in the order of 10 to 15% of engine power. This means the transition should be less complex but still requires an experienced pilot. Dick's machines are complex in design but simple in the application. Just what one would expect from a genius!
    Dean Dolph
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  2. #12
    Yes, Dean, I’ve been reading everything I can get my hands on about gyros and flying theory and technique for 20 years, and it always says when your engine dies you trade altitude and forward momentum for blade energy so that you have enough energy for a flare at landing. No questions there.

    Then along comes that CarterCopter demo machine (in that video you sent with your first post).

    https://www.youtube.com/watch?v=CFNc1iY8wi0#t=25

    I’ve watched that video so many times over the last year or so, noting the relative size and positions of elements in it, the plane, the hangar, the clouds, the pavement, and it sure looks like he goes straight up, to a remarkable altitude, at least a hundred feet and maybe much more than that looking at the hangar below, hangs there a few seconds, then comes straight down and lands in the same place. He doesn’t seem to slow down just before set-down, and it’s a bit of a thump, but not real ugly.

    That's supposed to be impossible. It says he has 20 lbs of weight in the blade tips, which is a lot, but they still couldn’t possibly store that much energy, could they? What the heck are they doing? Does anybody have any idea?

    Could they possibly be using blade pitch somehow? Maybe using a higher pitch would gain more energy from the descent, or maybe it would create a drag effect to slow the descent? So no flare at the bottom?

    You can tell I find this stuff absolutely fascinating. The trick is to make sure that fascination doesn’t get me killed. So far it’s only on paper so no worries. And I have the sterling example of the Wright brothers and Igor Benson to show how to do it with best possible safety.

    Dick DeGraw certainly is a genius. He built an intermeshing helicopter before his gyrhinos, and obviously used that knowlege in the gyrhino since that rotorhead is a powered three blade heli with flap and lead-lag. And his lead-lag dampening seems to be invisible in the photos . That's interesting too. There are videos of helicopters shaking themselves to pieces from ground resonance, even though certainly those commercial machines had lead-lag dampening to protect against it. No doubt Dick has allowed for it - somehow.

    "Dick's machines are complex in design but simple in the application. Just what one would expect from a genius!" Oh yes, and I would not pretend to be in Dick’s league, wouldn’t begin to even consider trying what he has done. For me it has to be simple all the way, simple in design, simple to make, and simple to use. Gotta have all three or its a no go.

    Jim

  3. #13
    PRA Secretary JOHN ROUNTREE 41449's Avatar
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    Everything about flying and other some sports are calculated risks. Most aircraft only mitigate the risks as long as the pilot flies by the POH as well!
    The 1st Carter Copter single place mitigated the risk of engine out using a new rotor blade design with severely tip WEIGHTED blades that HELD their energy.

    However the blades were not much fun to fly from what I was told but great for a jump take off. = Trades offs, always trade off with aircraft too.

    The other solution choose a reliable engine and maintain it with regular inspections? Of course, in general, those cost more.
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  4. #14
    I believe that a jump takeoff is very dangerous unless you have a very reliable engine. It's complicated and requires more maintenance.

    I would love to see a variety of pre rotators that will pre spin our blades to a 300 rpm minimum. This would make the takeoff as short as possible.

    If I want to jump take off I'll stick to a helicopter.

  5. #15
    Quote Originally Posted by James J. Judge 42935 View Post
    I’ve watched that video so many times over the last year or so, noting the relative size and positions of elements in it, the plane, the hangar, the clouds, the pavement, and it sure looks like he goes straight up, to a remarkable altitude, at least a hundred feet and maybe much more than that looking at the hangar below, hangs there a few seconds, then comes straight down and lands in the same place. He doesn’t seem to slow down just before set-down, and it’s a bit of a thump, but not real ugly.

    That's supposed to be impossible. It says he has 20 lbs of weight in the blade tips, which is a lot, but they still couldn’t possibly store that much energy, could they? What the heck are they doing? Does anybody have any idea?

    Could they possibly be using blade pitch somehow? Maybe using a higher pitch would gain more energy from the descent, or maybe it would create a drag effect to slow the descent? So no flare at the bottom?
    Jim
    Jim,

    The Carter Copter Technology demonstrator doesn't have to flair when it lands because it uses a high tech "CAT Strut System" that was designed to absorb the impact of a vertical landing. Carter did this with a complex "smart valve in a strut system" that he isn't sharing with anyone, as he has hopes to license the technology and make money on it someday.

    The late "Larry Neal" of the Butterfly LLC, created a similar landing system using off the shelf parts with his G-Force Landing Gear. It isn't quite as capable as the Carter system, and it does have limitations, but it is still a pretty impressive landing system, and it allows vertical drops from as high as 30 ft. without any damage to the system. But coming in from 200 ft. Larry would always keep a little bit of forward momentum (15 mph minimum) to create a soft landing. That gives his Gyros a much wider safety margin for landing speeds, but you still need to keep some forward speed or limit how high you drop down from.

    Doug Barker

  6. #16
    PRA Secretary JOHN ROUNTREE 41449's Avatar
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    Good one Doug! Check out the Carter video's and the Butterfly's landing gear it works and that would mitigate most if not all the damage in an engine failure on take-off.
    I like it when people find ways to make things work instead of just saying it cannot be done.
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  7. #17
    Doug,

    Thanks for that input. It’s really amazing that Carter has a landing gear that will absorb a 150 foot autogyro mode drop with no flare. Your post prompted me to go to the CarterCopter website, which I should have done long ago, and they give a surprising amount of capability information.

    They began with a Butterfly single, apparently ultralight, and added their amazing landing gear and an even more amazing rotorhead and blades. Of course they don’t give many details about how things are actually made. On the head and blades, apparently they eliminate excess weight by having a single very flexible spar that carries the centrifugal force between the 2 blades and is flexible enough to twist to change the pitch? Some very high tech stuff way beyond the finances or capabilities of the rest of us.

    Maybe I’m crazy trying to come up with something do-able and on a shoestring budget for the rest of us, maybe it’s just impossible, but I’m havin’ fun trying anyway. The weight remains the bugaboo. If there’s no economical way to reduce the weight, is there a way to deal with it?

    In an earlier thread, I think it was Chuck Beatty who wrote "Another requirement is for the mass of the rotorhead and stuff mounted thereupon to be as small as possible. Mounting electric starter motors, batteries and the like at the rotorhead may provide a ride with less shake of the airframe but increase the periodic in-plane flexing of the blades and hub. Some attempts at utilizing crisscrossed seesaw rotors have resulting in cracks developing in the rotorblades."

    The weight I’m talking about is way way way more than a starter motor and batteries. Can it be dealt with?

    I think that "periodic in-plane flexing" is essentially lead-lag type movement? What else could it be? I would assume that additional weight would refuse to transmit the vibration and tend to force the blades to absorb most of it, causing the damage? Could this in-plane flexing be ameliorated with damped lead-lag hinges? Even if they only moved a little bit to essentially absorb vibration? And then combine this with shock absorbers on the teeter bolt to absorb two-per-rev, and with a "flexible" mast? In other words, give the vibration some place to go other than the blades.

    Is it possible to account for all of these at once on a theoretical basis? Has anybody ever tried anything like this, or any parts of this, at least for the record?

    Yes, I have a lot of questions, and I hope that if there are any experts out there who have answers, that they will indeed answer. Thanks all.

    Jim

  8. #18
    Well, it’s been about 6 weeks since any more posts to this thread, though the number of views continues to grow, higher than I ever thought it would. Which prompts more thinking, which is dangerous stuff, but hey, flying isn’t?

    It’s interesting that this thread, which I considered to be pretty much over, has continued to grow, and has accumulated about 10 times as many views as I could ever have imagined. Is it the word Jump that is responsible? Are there actually a lot of members who are interested in jump?

    The second thread has a quarter of the views, and no comments except for John’s instructions for posting. even though the initial drawings are there. But then again that one’s not titled jump, though that’s what the drawings are.

    It’s curious too, that no experts have made comments about the weight problem. Maybe I really am in uncharted territory. Maybe the answers I’m looking for just aren’t out there. Maybe, since the principle has always been lighter is better, no one has even considered that the extra weight might be worth it, maybe they are more interested in a cushy cabin enclosure than putting the extra weight in something like jump, especially since the consensus seems to be that it is impossibly complicated, expensive, and dangerous.

    I am convinced that none of those three things are necessarily true. Maybe there is no more expertise to be had. Maybe there is no weight problem. There are helicopter rotors with weights measured in tons. Maybe the only way I’m going to find out is to just go ahead and build it. Since that’s what I’ve always wanted to do anyway, looks like I should just do it - probably a couple years worth of reading, learning, experimenting, building, testing, testing, and more testing. It’ll be interesting to say the least. Far better than wasting away staring at the idiot box.

    Take care, all. Fly Safe.

    Jim

  9. #19
    PRA Secretary JOHN ROUNTREE 41449's Avatar
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    I believe all things can be overcome. If you want it I would at least try. There will be others who want one too. Only so far no one has bought the right to Dicks to manufacture and it works well. So I only question the demand.
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  10. #20
    Thanks, John - I have decided to push on because the challenge is so interesting. I suspect that Dick's design, though it obviously works very well, may be too expensive to be commercially successful. In my patent searches there were many designs to be seen, but none of them to be seen on flying machines, and they look to me to be too expensive. Can I do better? Why not. Two bicycle mechanics did better. And I have a huge wealth of published information to draw on that they did not. -- Take care.

    Jim

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