New rotorcraft concepts

Discussion in 'Rotorcraft' started by Birdy, Aug 19, 2008.

  1. Birdy

    Birdy Well-Known Member

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    Anyone here tinkering with an idea thats like nuthn else?
    Im keen to comm with anyone who has spent any time with different light rotorcraft typs, wether it flew or not.:)
    Im onto sumthn here, thats a x between the gyro and heli, hopefully utilising the best of both machines in one.
    Im kinda committed now, [ 45K and counting] and its never too late to change things.
    The only thing that wont change is, it WILL fly. ;)
     
  2. rtfm

    rtfm Well-Known Member

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    Birdy,
    Hope you don't mind long posts. Here goes...

    I worked for a number of years on a JTOG, and would have carried on with the project had Paul not had his accident. He was going to train me in exchange for my building and looking after his web site. So I decided to go over to the dark side and design/build a fixed wing aircraft (for which I already have a licence).

    Essentially, I wanted to build a tractor gyro with variable pitch rotors. I corresponded with the guys at CC, and had many mutually beneficial discussions with them. I believed (and still do) that the way they were going about ensuring the required rotor speed during fast flight was overly complex and an invitation to problems.

    My approach to the problem of fast forward flight was different from theirs, and consisted of a number of different (but simple) components.

    (1) First, I intended to use a hydraulic prerotator. This was not an arbitrary choice. I selected hydraulics for a very good reason. Sure, there are many ways to spin the blades up, but only one simple way to regulate rotor speed to whatever you choose - and that is with hydraulics. The power-train would go like this:

    (a) Power takeoff from the motor to drive a hydraulic pump
    (b) Pump pushes fluid through a constant flow valve - this is the important bit - because ther CFV will allow you to select any volume you wish. This volume remains constant no matter how fast/slow the engine is turning.
    (c) This (controlled flow) then drives the hydraulic motor at the rotor head
    (d) Finally, and overrun clutch at the head allows the rotor to spin faster than it is being driven, but not slower.

    This power-train is the key (in my design) to simple, easy fast forward flight.

    Basically CC have decided to manage the speed of the rotors aerodynamically. They carefully manipulate the rotor and blade AoA so that the oncoming airflow produces JUST ENOUGH driving force to keep the blades spinning at 100 RRPM (more or less). I think this is needlessly complicated and error-prone. My idea is to de-pitch the blades completely, tilt the rotor head forward to zero degrees, putting the blades into a zero-lift situation. So, as forward speed increases, the wings produce more lift. As the speed increases, the wings produces proportionately more of the required lift, and the rotor speed decays. However, you've already dialled in "100 RRPM" at your constant flow valve. As the RRPM decays to 100, the hydraulics kick in, keeping them at 100RRPM. And because the blades are producing no lift, keeping them at 100RRPM is a piece of cake, and takes almost no power at all. Meanwhile, the wings are now producing enough lift to fly the plane. You're a fixed wing aircraft, with a redundant rotor.

    Simple.

    Off you go, flying on tiny wings which only need to produce enough lift to keep you airborne at high speed. Small wings = low weight, low drag = fast flight.

    As the speed decays, you increase the rotor head AOA, while simultaneously increasing the blade AoA. Airflow spins the rotors up till you are flying on rotors and the wings are vestigial.

    So there you have it - how I was going to design my VTOG. Of course, you would need a variable pitch prop, so that you could spin up the rotors (and prop) without producing too much forward thrust. Then there would need to be some learning curve to get the takeoff sequence right. Set RRPM to 100, add rotor pitch, add prop pitch and UP and AWAY! Or something like that.

    Weighted rotor tips? Maybe, bit not necessary. I don't believe it is that difficult...

    My current fixed wing design still has a rearward-tilted firewall, so that twin masts can be attached directly to the firewall for strength, and position the rotor head where it needs to be. One of the things I have had to sacrifice in the move to the dark side, is tail height. The FW plane needs a decent tail. So I've capitulated. But the basic airframe could easily be changed to have a tail which did not interfere with the rotor.

    Well - you asked...

    Regards,
    Duncan
     
    Last edited: Aug 19, 2008
  3. Birdy

    Birdy Well-Known Member

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    Well - you asked...
    I did, and i appreciate the time you put into that post. :)
    Just one question, would the CFV setup be as efficiant as a swash plate hyd pump?
    I know your only talkn bout low rrpms/ pressure, but if your talkn bout flight rrpms, i think thered be alota wasted energy [ heat] generated by the CFV.

    We have different goals tho, so im onto sumthn different.
    My priority list;
    First is true VTO [ not jump] and land
    Second is slower min AS with better safty margine if the noise stops.
    Third [ my dream] ground effect hover.
    Speed dont interest me at the moment, but will be easy to 'add on' later. But im only talkn bout 100kts max.

    Iv got a million ideas bouncing round in my hollow head, so there will be alota trial n error.

    BTW, i was wundern where you got to.
    Hows the FW thingy comen along then.
    [ shame on you for changn sides. ;)]
     
  4. orion

    orion Well-Known Member

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    Just a side not here to rtfm's post - the fixed wing/rotor hybrid was considered for a number of years to be the ideal mix between airplane and helicopter, to the point where even our mainstream organizations started in on the concepts. Several built interesting POC vehicles but none ever made it anywhere. One of the key issues to address with the design is what do you do with the blades when you're at cruise?

    The problem with blades is that they get part of their structural characteristics from the rotation. The centripetal acceleration of the rotating mass provides the blades with a certain amount of stiffness, which allows them to produce a substantial amount of lift despite the small, very high aspect ratio area. Coupled with the rotation, the lift they produce also provides a bit of structural stability.

    When you remove a large part of the lift by depending on the wings in forward flight, you end up with essentially floppy wings (the rotor blade of course) at the top of your craft. This is especially a problem when you slow the rotor down, or even worse, stop it entirely. The cruise situation then becomes one where you have to be especially worried about flutter (a function of true airspeed) and structural divergence. The result would of course be that the blades might depart from the craft at cruise, or possibly flail it to death.

    This is why several of the mainstream concepts went to very wide chord but short span rotors. But of course at that point they became lousy helicopters, and not to mention, loud (higher rpm).
     
  5. BBerson

    BBerson Well-Known Member

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    Birdy,
    You are not the only crackpot with wild ideas in the world. I am working on a fixed wing extreme STOL (powered lift assisted takeoff and landing).

    There are dozens of ways to design the various future VTOL. The military mission has dominated the large designs. A home design should be much different, I think. Good luck with your experiments.
    BB
     
  6. Birdy

    Birdy Well-Known Member

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    I am working on a fixed wing extreme STOL (powered lift assisted takeoff and landing).
    Tell me more man. :)
     
  7. BBerson

    BBerson Well-Known Member

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    OK, here is my favored concept:
    Extreme STOL- this fixed wing aircraft would provide the ability of takeoff and landing in about 30 feet of ground roll. This requires brief powered lift but not as much lift as a helicopter needs because I have no real desire to hover for extended periods. The aircraft would be like any other airplane but with the addition of lift devices (probably lift props) to allow for slower flight but not actual hover.
    Advantages:
    1) engine failure would not be a major problem, the auxilliary lift system would only be used within about 10 feet above the ground. If the lift system failed to work on landing, the only result would be a hard landing.
    2) much less cost than helicopter
    3) more efficient than helicopter
    4) easier to fly than a helicopter

    In a nutshell, I want to land like a seagull.... the seagull can glide for hours with fixed wings, then land with a brief burst of power just before touchdown (with little or no ground run). The lift power is only needed for about 5 seconds or so for my extreme STOL aircraft.
    BB
     
    Last edited: Aug 20, 2008
  8. Birdy

    Birdy Well-Known Member

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    I want to land like a seagull....
    Mate, ever since i saw me first bird, iv wanted to be able to jump outa trees and simply spread the arms and float away.
    Iv only managed nose dives so far. :(
     
  9. Bob Kelly

    Bob Kelly Well-Known Member

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    Howdy Fellers ! good to see ya all here ! And of corse me Hero Birdy !...
    I simply plan on getting the chainsaw pre rotator to work on the gyro to make such a short take off run that I won't feel any bumps ! HEHHEHE ... thats the plan anyway, but Moveing has realy put the Gyro on the back burner for me for last year and this year... although I got the rotors almost finished now , I just do not have time to mess with it....
    but I do think the chainsaw motor will spin the rotor blades hard enough to eather lift off on its own and start chaseing its tail... (something I don't want) or make my run very short indeed... probly 10 feet or so...
    I figure landing shouldn't be a problem if I can land like Birdy does ! but that may me a few years to prefect !
    ....
    I know what Birdy is after , thats a COW Chaser that just won't give up !... now he will go under the trees instead of OVER them ! HAHAHAHHA
    ...
    I hope the "Feral" is still Serving ya well my friend , and you havn't had to walk back to the ranch yet !...<GRIN>
    ...
    Good to see you all here ! been a while !
    Best regards...
    Bob........
     
  10. Birdy

    Birdy Well-Known Member

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    Ow they hangn Bob?
    Thought you musta left the planet.
    The ferel is still ferel, got a full day at the 'office' tmorrow.

    Me VTO gyro has stoped, for now, coz i gota sell off a few moos to pay for it. ;)
     
  11. Bob Kelly

    Bob Kelly Well-Known Member

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    Nah I'm still here, just tired of the BS on the other forum so I GAVE IT UP!!!!...
    I dunno why you couldn't turn the Feral into a VTO craft by just turning the Rotor Harder....you'ed have to go way above flight speed and I don't even know if that is possable...
    you could install a small engine and prop in the VS as a anti torque fan and use throttle control on it to stear with....
    its an idea anyway....
    electric start on such small engines might be a major problem though... but I could amagon something like that working quite well... have the big main engine at idle when landing or for that matter off, and the other engines running full noise to land with....
    that means a bunch more weight though but I guess thats where ya gott'a be real creative ! HAHAHAHHA
    ...
    Keep thinkin on it Birdy You'll figure it out eventually!
    stay out'a the trees and fly safe !
    take care my friend!
    Bob........
     
  12. Don Hillberg

    Don Hillberg Active Member

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    the problem with wings and rotors in high forward flight is not power or structural / Its gust loading,vertical loads upwards lift the wings and body-The rotors flex downward and wack the pilot in the head or cut off the tail it has been done before........
     
  13. Don Hillberg

    Don Hillberg Active Member

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    A turbine exec in camarillo ca (40 miles north of L.A.)
     

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  14. tyc

    tyc Well-Known Member

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    To me, it's always seemed that rotor winged aircraft and high forward air speed, it just doesn't seem right, sort of like chocolate ice cream and peanut butter but then such things are best left up to the individual.

    It is not likely that the student helicopter pilot of today is anymore disinterested and any less thrilled than I was when I first learned to hover, to just sit there and then simply go forward and backward, all around the practice area just hovering in my own rotor downwash, which may explain the interest by so many in the VZ-1, the Williams "X-Jet" and the like. Have you ever seen the number of "hits" those videos on UTUBE still get?

    Rotor wing aircraft and high forward air speed, is it necessary? I say no, not if you're satisfied to zip along at sixty MPH or so at 300 meters or even a meter or two off the deck but then, to each his own ... just my two cents worth.

    tyc
     
  15. davh12

    davh12 Well-Known Member

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    Birdy,

    go to www.baldwintechnology.com or google mono-tiltrotor. Click on "deep dive" and watch the computer design clips. The last clip has an actual RC prototype.
     
  16. pie_row

    pie_row Well-Known Member

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    I read about a tilt wing concept in Popular... what ever. He was looking at using a hibrid design with gas and electoric. I'm thinking about a tilt wing flying wing. There is a backpack heli that is driven by a 16hp engine. It's driving twin 8 ft diametar rotors. So this is what I think I want to do. Build two rotors put them on a flying wing figure out the mixer and have at. It should be fun.
     
    Last edited by a moderator: Mar 20, 2019 at 9:21 PM
  17. Bob Kelly

    Bob Kelly Well-Known Member

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    Herr Shoffmans Back pack helicopter is indeed a Wonder and a marvelous piece of engineering...
    its Very expensive engine,along with its Made to order counter rotating props do indeed get him aloft.... but just barely!
    he went to a 2000ASL field and could not get out of ground effect... where at sea level he can.... that is how marginal a Helicopter that Back Pack helicopter really is...
    I believe his engine is a 15hp not 16hp... and turns 12000RPM
    its a very expensive Kart engine and as far as I know it has giving him very little trouble at all. there is no collective pitch control, its throttle up to assend throttle down to desend, and a tail fin controls the turning.
    ... Adding just a tiny bit of weight would cause it not to fly
    so the answer would be a larger motor, say a 250cc Kart engine!
    on the Back Pack Helicopter Forum on yahoo.uk I drew up plans that copied as close as possible Herr Shoffmans design... and out of all the designs I have made his definately looks the sanest of all... (the designs are in the file section)
    We figured 25hp to 30hp for vertical takeoff and to be able to get clear of ground effect.... however the unit HAS to be Super Light... a 300lb pilot is not going to get far on one of these!
    My own version of the back pack heli is collecting dust at the moment for lack of a decent engine... it can be done, and Has been done by more than one person....adding a delta wing so you can level out and fly fast should in my mind work fine...
    however keep up your life insurance, as these things are very dangerous!
    ...(I havn't been back to the Back pack Helicopter forum in about a year because I can't get in for some reason... I think Iforgot my password.... (and I Really dislike Yahoo!) but the guys there will help you all they can, tell them Bob Kelly said HI ! HAHAHAHAHAH!
    ...
    Bob...
     
  18. pie_row

    pie_row Well-Known Member

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  19. Dan Thomas

    Dan Thomas Well-Known Member

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  20. Bob Kelly

    Bob Kelly Well-Known Member

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    Pie-row:
    the Wankel would be the best choice... but you have to have over $5,000 to purchase even a smaller one, I don't know what the 50hp version costs though, probably $8,000 or more.
    but YES it will take that kind of power to weight ratio to get a backpack heli off the ground....O planned on using a 250cc or 350cc 2cycle dirt bike engine with the trans cut off... but starting that would be a big problem...anyway you go about it plan on a long project, I worked on mine for about 2 years, got the rotors counter rotating on a chainsaw engine but that is all that I accomplished in all that time... but I am dirt poor too
    if like Herr Schoffman you have the bucks its quite possable to buy the needed pieces and assemble one in about 6 months or so.
    but Herr Schoffman spent well over $100,000 on his unit over his lifetime from what I understand (thats about 4 BPH's though).... its not cheap !
    ....
    Dan just because you don't see it flying around all the time doesn't mean its not a exelent flying machine or idea...
    or even practical... the allmighty Dollar is realy the guide line as to see if a product is "Successfull" or not... not if it actually WORKS or not... no money to be made on it and it will die very quickly, for what ever reason, no investers, insurance problems, costs or volume of sales being low...
    in our past there is indeed a Bunch of things that you'ed think should have been successfull, but its not the unit itself... its weather it makes money or not, and that can be a much wider reason for them not being in production. Poor business desigons have sunk more good products than torpedos at ships !<grin>
    but .... you already know that LOL
    ...
    Bob....
     

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