Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 28

Thread: Building of a manned copter with a gasoline engine.

  1. #11

    Join Date
    Jul 2017
    Location
    Douglas Flat, CA
    Posts
    53
    Quote Originally Posted by Frank Giger View Post
    His idea certainly has a lot of merit and promise.
    Disagree. It combines the disadvantages of conventional helicopters with the disadvantages of multicopters, with few of the advantages of either.

    Conventional helicopter design extracts rough, unwieldy horsepower from a reciprocating engine and delivers it to one or at most two rotors using mechanisms such as shafts, gears, and belts. The mass penalty of such a system drives the convergence towards designs with short drive trains and large rotor disks, and with relatively complex control systems involving independent adjustment of the pitch of each rotor blade.

    The current trend towards multicopters is driven by increasing availability of powerful electric motors and batteries, and the availability of computer-driven controls for them. With an electric multicopter, you can have fixed-pitch rotors on each of four or more motors. You control attitude by independently adjusting the amount of power delivered to each motor. The inefficiency of the smaller rotor disks is compensated by the lighter weight of electrical power distribution and by the elimination of rotor pitch controls. Having all the motors and rotors identical yields economies of scale in production and support. System redundancy is achieved by designing so that flight is possible even with the failure of one or more motors or rotors.

    --Bob K.
    Bob Kuykendall
    HP-24 kit sailplane project

    HP-24 Project Facebook Page
    http://www.hpaircraft.com/hp-24
    EAA Technical Counselor

  2. #12

    Join Date
    Aug 2011
    Location
    Alabama
    Posts
    2,236
    Concur.

    The design he's putting forward is pretty dang complex in execution. Grab four electric car motors and find a way to generate and step up the voltage required for them.

    I also think that he's giving himself some CG problems by starting with a tandem aircraft from the start. Might as well ditch the passenger, as this thing will be loud enough to be unable to hear their screams.

    However, the notion of having a gasoline power plant (and I think he's overstating the weight of the generators needed) gets over the hurdle of limited battery capacity.

    On redundancy, forget it. If one of the rotors goes out, that's it. Period. You're done for the day and are going to land RIGHT NOW. There isn't any auto rotation or glide.

    One of the things not mentioned is just what the mission parameters of the aircraft are, or the performance goals.
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

  3. #13
    DaleB's Avatar
    Join Date
    Sep 2015
    Location
    KMLE
    Posts
    654
    Quote Originally Posted by Frank Giger View Post
    On redundancy, forget it. If one of the rotors goes out, that's it. Period. You're done for the day and are going to land RIGHT NOW. There isn't any auto rotation or glide.
    Personally, I think you have to be using a pretty broad definition of "land". I can see no way that craft could remain upright or controllable with less than all four rotors running.

    Even if there's a power combiner of some sort so that one engine can drive all four rotors, the loss of a gearbox or drive shaft looks to my non-aeronautical engineer eyes like it would cause an immediate and catastrophic loss of control, followed shortly by an impact (or "destructive landing").

    Maybe I'm wrong, though. It would certainly be easy enough to prove or disprove. How do electric powered quad-copters handle the failure of one rotor?
    Measure twice, cut once...
    scratch head, shrug, shim to fit.

    Flying an RV-12. I am building a Fisher Celebrity, slowly.

  4. #14

    Join Date
    Jul 2017
    Location
    Douglas Flat, CA
    Posts
    53
    Quote Originally Posted by DaleB View Post
    ...How do electric powered quad-copters handle the failure of one rotor?
    As I understand it, with a quad you can only retain control if two rotors are enough to support the mass and you can apply occasional upward thrust with the rotor opposite the failed one--which is to say, it probably doesn't really work. I think I've heard that, from a practical perspective, it takes six to survive the loss of any one motor, and eight to survive the loss of any two.

    --Bob K.
    Bob Kuykendall
    HP-24 kit sailplane project

    HP-24 Project Facebook Page
    http://www.hpaircraft.com/hp-24
    EAA Technical Counselor

  5. #15

    Join Date
    Aug 2011
    Location
    Alabama
    Posts
    2,236
    And we have to be very, very careful when trying to translate performance of small RC planes to full sized ones. The thrust to weight ratios are much higher in RC aircraft.

    There's a great video of an RC airplane that loses a wing and, thanks to a lot of thrust, manages to be brought back to earth with no further damage by hanging from the prop. Some wag then used some computer magic to make it look like it was an actual aircraft landing at the end, which fools a lot of non-airplane folks.
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

  6. #16
    "...And we have to be very, very careful when trying to translate performance of small RC planes to full sized ones..."

    I absolutely agree!
    And this is especially true of the "scaling" of the Copters.
    With the increase, absolutely other problems appear, which are not present on a small scale.
    I take this into account.
    That's why I'm forced to use variable pitch propellers and a gasoline engine.
    I wrote about this in detail on my website!

  7. #17
    Aviatrexx's Avatar
    Join Date
    Jan 2016
    Location
    NC
    Posts
    30
    [QUOTE=Ihor Nastashchuk;68841]We are building a manned copter with a gasoline engine and propellers with variable pitch.

    A couple of questions:
    1. Are the pilot/pax sitting in the plane of the blades? What happens when one lets go?
    2. Do the blade disks have sufficient mass to autorotate? What happens when a gearbox goes Tango-Uniform at a hundred feet?
    3. Your VPP is not "used on hundreds of thousands of radio-controlled helicopter models" because it supplies collective pitch control only. You appear to rely on differential thrust from the four blade disks for your "cyclic". Is this the only engineering misrepresentation/ignorance you are displaying?

    If you're lucky, you'll attract only half the lawsuits that Moller did.

  8. #18

    Join Date
    Oct 2011
    Posts
    184
    Ihor, if they lose power, airplanes can glide under control and helicopters can autorotate to a probably survivable landing. But if your quadcopter lost power to one or more propellers, it would flip and accelerate to the ground, tangling up the parachute if it could even be deployed. I think you ought to redesign it to survive the failure of any one component.

  9. #19
    "...misrepresentation/ignorance you are displaying..."

    I advise you to refrain from rudeness, but first learn to read carefully!

    1. It is evident in the figures and in the photo that the pilot sits above the plane of rotation of the propellers.
    2. I already answered this question - propellers with a high load on the area are NOT autorotated!
    3. I already answered and this question. For VERY DARK AND LAZY - I repeat - will be the same as with a helicopter, which broke the reducer!
    Only in difference from the helicopter (I repeatedly REPEAT) - I have a system of parachute rescue.
    Yes, instead of changing the cyclic pitch on one propeller, like a helicopter, I applied a change in the overall pitch on the four propellers.
    Why is this ignorance?

    "...If you're lucky, you'll attract only half the lawsuits that Moller did..."

    With my luck, I'll figure it out myself, without such advisers!

    "...if they lose power, airplanes can glide under control and helicopters can autorotate..."

    You're right. But only partially.

    The helicopter will be autorotated if the engine has decayed and the propeller does not get stuck. If it sticks - no autorotation.
    If the blade breaks - the same - there will be no autorotation - the helicopter will fall.

    The plane will only plan if the engine has decayed. In the event of a breakdown of something else - a wing, a stabilizer, or even a flap or aileron - the airplane is likely to fall.

    That is - the ability to plan or autorotate - depends on what a breakdown.

    But it does not bother anyone - everyone flies.

    So with my project. It depends on what will break.

    100% guarantee can be given in this life only one - WE ALL DIE, sooner or later. All the rest is just a probability!
    A parachute is a way to reduce this probability!

    Besides - why should it break?
    Look at it.

    Name:  001.jpg
Views: 417
Size:  60.0 KB

    Name:  002.jpg
Views: 416
Size:  59.0 KB

    In comparison with these propellers, mine are just a coffee grinder!
    But on helicopters this heap has been flying for decades!

  10. #20
    DaleB's Avatar
    Join Date
    Sep 2015
    Location
    KMLE
    Posts
    654
    Quote Originally Posted by Ihor Nastashchuk View Post
    3. I already answered and this question. For VERY DARK AND LAZY - I repeat - will be the same as with a helicopter, which broke the reducer!
    Only in difference from the helicopter (I repeatedly REPEAT) - I have a system of parachute rescue.
    I don't think there would be time to deploy a parachute system if one (or more) rotors fail. The high CG and un-balanced vertical thrust will flip that thing over in a heartbeat. Just my opinion. You could use accelerometers to determine when to automatically deploy -- a risky approach, but in any case I doubt a 'chute would do a lot of good outside of one or two specific failure modes.
    Quote Originally Posted by Ihor Nastashchuk View Post
    The helicopter will be autorotated if the engine has decayed and the propeller does not get stuck. If it sticks - no autorotation.
    If the blade breaks - the same - there will be no autorotation - the helicopter will fall.

    The plane will only plan if the engine has decayed. In the event of a breakdown of something else - a wing, a stabilizer, or even a flap or aileron - the airplane is likely to fall.

    That is - the ability to plan or autorotate - depends on what a breakdown.

    But it does not bother anyone - everyone flies.
    True, but that's because the failure modes you describe represent a tiny, tiny fraction of the overall total incidents. In-flight breakup, whether fixed wing or rotary, is an exceedingly rare occurrence. Engine stoppage and gearbox failure is certainly not. You cannot simply hope it never breaks because of your superior design, which I think history has shown will be nowhere near as failure-free as you imagine it might be. You really have to assume that anything that moves will break with some degree of frequency. You'll never be wrong. So... what happens, exactly, when your pilot is flying along at max thrust and the left front gearbox fails? Prop stopped or prop free-wheeling, the result is the same. In a matter of half a second or so your pilot (and his hapless passenger) will find themselves in a rapidly rotating free-fall. No control at all, and deploying a parachute will just provide shroud to contain the body parts after impact.
    Quote Originally Posted by Ihor Nastashchuk View Post
    Besides - why should it break?
    In comparison with these propellers, mine are just a coffee grinder!
    But on helicopters this heap has been flying for decades!
    You just answered your own question, I think. I don't think your system is designed and built to the same standards as Kamov. And it's not the prop hubs I would worry about, it's all the power transmission parts.

    Just do everyone a favor. When it's time for flight testing, load that sucker with sandbags instead of live bodies, and fly by remote control for the first hundred hours or so. It may be very enlightening.
    Measure twice, cut once...
    scratch head, shrug, shim to fit.

    Flying an RV-12. I am building a Fisher Celebrity, slowly.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •