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

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  1. #1

    Question Jump Rotorhead Dynamics

    Guess I should start with an intro. My name is Jim Judge and I’m sort of an oldie-newbie. About 20 years ago took a gyro flight with Chris Burgess and got hooked, joined PRA, after a few years decided it just wasn’t happening financially and dropped my membership, but never stopped dreaming and drooling. I’m now retired, have re-joined PRA (which makes me an oldie twice over) so have some time, but still not the dough. I have just applied for a patent, in the wild hope that it could make a few bucks and I could yet fly, but that’s jumping way ahead. There are still questions that require expert experience.
    A year ago was thinking how cool it would be to jump start, yet almost nobody is doing it. Why? After much reading it looked like the rotorheads are just too complicated and expensive to buy and maintain. So decided to play with it, just for fun.
    After 5 rejected designs, Number 6 is simple in construction, and one I could build, and I think will work. Except – solving a mechanical problem is one thing, making something that will fly is quite another. Have read everything I can get my hands on, spent many hours with PRA forums, yet - well - guess I should take the unknowns one at a time since the thread might become too confusing all at once.
    First one is weight.
    Spin-up to 150% of flying rpm approximately triples centrifical force, requiring proportionately stronger and heavier parts. The entire 30 foot unit, gimbal, head and Fleck blades approaches an estimated 180 lbs. It’s huge, but is it impossible? For a 2-place?
    Have to lift about 60 lbs. more weight. Need wider wheelbase for stability on the ground. Can probably handle them. But can you throw that much weight around up there? Teetering?
    The central section that teeters with the blades comes in at about 52 lbs. Will that act like a flywheel, resisting the teetering motion? Would it matter if it did? Maybe create additional blade root stresses? Other problems?
    Thanks to all -
    Jim
    Last edited by James J. Judge 42935; 03-11-2015 at 07:14 PM. Reason: Newbie lack of knowlege of system

  2. #2
    PRA Secretary JOHN ROUNTREE 41449's Avatar
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    Hello Jim
    Actually it was hard to vote as my real choice would have been not that I don't want it but I do not have much need of a jump take-off gyroplane or I'd buy a helicopter.
    It is illegal to land at my house, office, and most of the parks in San Diego. All of my friends here may only fly their helicopters from airport to airport just like my FW so what is the point of owning a slower more costly helicopter in San Diego.

    If I had a use or need for it would be great.

    There are two jump gyroplanes flying made by dick McGraw. He and his wife bring them to Bensen Days and Mentone most years. They are described as not being dangerous but not for a novice pilot either.

    Just not sure where you could use the jump take-off capability and having it just to have it is not appealing at least to me, just more to maintain.

    But they are cool!!!!
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  3. #3

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    I have 1,000ft grass strip beside my
    h
    ome. i t
    hink it would a hot set up on monarch butterfly. make my strip seem a longer
    buy the way does anywone have any experience with the Monarch Butter Fly machine?

  4. #4
    Quote Originally Posted by James J. Judge 42935 View Post
    .....A year ago was thinking how cool it would be to jump start, yet almost nobody is doing it. Why? After much reading it looked like the rotorheads are just too complicated and expensive to buy and maintain.
    Since modern gyros are meant to be simple then adding jump capability seems to add complexity when that is something that most are trying to avoid. Dick DeGraws designs certainly work and I wouldn't think the jump mechanism weighs any where near 52 pounds. Like John has said, they are more a novelty than something useful.


    Quote Originally Posted by James J. Judge 42935 View Post
    ....... The entire 30 foot unit, gimbal, head and Fleck blades approaches an estimated 180 lbs.
    Jim, to give you an approximate comparison between your design and Dick DeGraws lets start with blade weight. Dick uses Dragon Wings blades, if I'm not mistaken and while I don't know what length blades he is using I'll tell you that the 23 foot DragonWings weigh 42 pounds with hub bar. The Fleck blades never approached the popularity of the Dragon Wings, Rotordynes or the very heavy, by comparison, SkyWheels. The SkyWheels 23 foot blades and hub bar weigh approximately 75 pounds. And all of those I have mentioned are efficient blades. I don't know how efficient the Fleck's are. The Dragon Wings are reported to be the most efficient with the SkyWheels also having a good rep. The Dragon Wings use tip weights to add some rotating inertia and the SkyWheels weight naturally makes them a high inertia blade.

    One of the most impressive jump takeoff machines I've seen was the CarterCopter demonstrator flown by Rusty Nance when it was at Mentone a few years back. It had some high weight tipped blades and Rusty said it was quite a jump experience but when asked how it handled, he reported that it didn't want to turn! In other words it couldn't be described as a nimble gyro. Here is a YouTube link that shows it being flown. https://www.youtube.com/watch?v=CFNc1iY8wi0

    Dick DeGraws machines are much more subdued in their takeoff but still impressive. Here is a YouTube link showing Dick & Karol DeGraw jumping together at Mentone several years ago. https://www.youtube.com/watch?v=9ISIlgMcb-U
    Last edited by DEAN DOLPH 8907; 03-13-2015 at 09:54 PM.
    Dean Dolph
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  5. #5
    Dean
    Thank you very much for that most informative post. Complexity was the reason for my rejecting some of my earlier designs. It’s gotta be simple, but of course can never be as simple as a standard teetering head. My goal was to make it simple enough that I could build it with my own limited shop.

    I had the Skywheels in mind when I estimated my additional weight at 60 pounds. Wouldn’t even try to compare to Dragon Wings, and it’s really interesting That Dick DeGraw is using them. He must be using some pretty hefty tip weights to get inertia for jump. And how could he gain the strength to handle the centrifugal force without significant additional weight in the head. Does anyone know what the wheelbase on the gyrhino is? That could be an indicator of compensation for weight.

    The weight problem seems insurmountable. The mechanism itself weighs very little. The increased weight is the result of the need to withstand the spin-up caused tripling of centrifugal force. Stronger parts means heavier parts, unless I could use titanium. Maybe Dick DeGraw Is?

    I had seen the videos you graciously provided, and the CarterCopter is mind boggling, but 3 or 4 times what I need. The gyrhino looks to be every bit amazing enough. The note that Rusty Nance said the CarterCopter demonstrator didn’t want to turn hit me between the eyes. Sounds rather like the flywheel effect I feared in my first post, but had not thought of in terms of control.

    It looks like the weight is just going to be there, and the question is how to work with it. Is it possible to?

    Have slept on this overnight, as usual, and a couple things occurred to me.
    1. The poll, which was added as an afterthought, seems to be just a distraction. Quite a few viewers, very few pollers. Though I would really, really like to know why Kevin O’Kane thinks jump is dangerous. Safety, after all, is absolute top priority. Could you please come back, Kevin?

    2. Thank you John Rountree for your post. Of course I didn’t like it at first, but it got me to thinking the unthinkable, what if you’re right? Maybe I’ve been hooked on jump for too long. If jump is abandoned, the tripled force and heavy parts problems go away, but the rest of the benefits remain, and they are not insignificant. Dealing with only 7,000 pounds of force instead of 22,000 is very liberating, so thank you for the gentlemanly wack on the head. I’m not likely to give up on jump altogether, but for now, perhaps it’s just too much at once. I need to learn a lot more to tackle that one.

    3. Limiting this thread to one aspect of the project was probably a mistake.

    4. This thread then has achieved it’s purpose. Though didn’t get the answers wanted, got the answers needed. So start a new thread for the new purpose and just put it all out there.…… Pitch Change Rotorhead for Homebuilders?

    Thanks to all.
    Jim
    Last edited by James J. Judge 42935; 03-14-2015 at 02:44 PM. Reason: paragraph spacing

  6. #6
    PRA Secretary JOHN ROUNTREE 41449's Avatar
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    Hello Jim

    I do not wish to discourage you only only point out that perhaps the majority have no need of jump-takeoff for where they are allowed to fly into and out of.

    However it was the carter jump-takeoff gyroplane that got me 1st interested and looking at gyroplanes at all. Latter I learned that the special weighted blades did not let it maneuver well and observed where people actually flew from and where I myself was allowed to takeoff from... I lost interest in jump-takeoff.

    The fact that you want one and have a location that you need and can use jump take-off also means that in other parts of the country there will be a small minority of our small market that have a need for it too.

    Here's Dick's design.
    Last edited by JOHN ROUNTREE 41449; 03-14-2015 at 06:41 PM.
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  7. #7
    My vote for "dangerous" ( for me). As a low hour / student pilot, I don't have the skill set to attempt a jump take off.
    K. O

  8. #8
    Thanks, Kevin. Yes, even an experienced pilot needs to approach something that new with much preparation, and practice in gradual steps. Jump starting could easily have the same problem as gyroplanes in general. Some people who think it looks so easy and jump in with both feet, with unfortunate results.
    Jim

  9. #9
    I believe with some of the unreliable engines we have s jump takeoff is very dangerous. Even a helicopter jupm like that is not recommended. Due to possible engine failure.

  10. #10
    Wow, Brent. Please don’t stop there. As a newbie I would be very much interested in which engines have developed a less than stellar reputation for reliability.
    Also, as someone who has done my own auto repair for many years, so has a little bit of engine knowledge though certainly not a professional engine guy, and who, as second nature, asks why when a problem comes up, do you have any thoughts to share as to why that movement would tend to cause an engine to fail, so that maybe preventative steps could be taken? Or have you just observed that it does happen, and if you’re not a professional engine guy either, that’s enough.

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