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Thread: Electric powered Gyro any thoughts?

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    Electric powered Gyro any thoughts?

    Given the propensity now for quite reasonable (45mins) flight times for electric powered aircraft like the new EADS Cri Cri is there anything to be said for using this technology in the case of an Autogyro?

    The rotor energy makes for some helpfull regenerative feedback by being coupled to a generator, but is it enough to make a case for using this technology in the case of a Gyro given that the drag of a gyro rotor disk will far exceed the induced drag associated with more conventional designs like the EADS Cri Cri.

    Could a decently efficient generator double as the prerotator?

    Dave

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    Registered User Empirical's Avatar
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    Re: Electric powered Gyro any thoughts?

    Quote Originally Posted by Culleningus View Post
    Could a decently efficient generator double as the prerotator?

    Dave

    Definitely .

    But as a generator I don't see much usefulness, it would only take advantage of excessive power which might only be available in cases you choose to loose height rapidly without the help of the main motor -more rapidly when you store that energy back to the batteries (might be dangerous).

    In normal steady flight, the rotor uses the kinetic energy that in fact comes from the main motor to rotate and keep the vehicle flying so I don't see any benefit there. If you consume that energy or part of it, you'll slow down the rotor!

    In any case, if you decide to try a generator as a motor pre-rotator (or even as a powerful rotator for vertical landing), you should use one with no permanent magnets in order for the rotor to freely rotate without any braking from the magnets when the generator's output is not used for charging (and definitely a brushless one).

    BTW, this is just an estimation, I don't have experience in autogyros.
    Last edited by Empirical; November 19th, 2010 at 09:06 AM.

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    Registered User Norman's Avatar
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    Re: Electric powered Gyro any thoughts?

    Quote Originally Posted by Culleningus View Post
    The rotor energy makes for some helpfull regenerative feedback by being coupled to a generator
    Energy density, embodied energy and just plane weight arguments aside this scheme also presents the problem that the generator would apply torque to the fuselage.
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    Re: Electric powered Gyro any thoughts?

    Check out energy storage of flywheel Vs Batteries, I think you will find flywheels have always had an advantage in the density factor.
    Think of the rotor(s) as a storage medium in the same maner as a battery, then ask the simple question "does electrical energy need to go through a storage process ?".

    Consider the time between generator and motor in either direction.

    Battery power for takeoff, yes.

    As I have said before, compressed air can add as a help to the electrical power cycle of energy generated and energy used. Compressed air can be used almost as fast as electricity, thus eliminating large and heavy tanks and lines. Air is always going to be there.

    Ron

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    Re: Electric powered Gyro any thoughts?

    I don't know about anyone else, but I'd not want anything permanently attached to the rotor that has any mechanism to seize up.
    Conventional wisdom and practices yield conventional results. If that is good enough for you:
    Problem solved.

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    Re: Electric powered Gyro any thoughts?

    Quote Originally Posted by Culleningus View Post
    Given the propensity now for quite reasonable (45mins) flight times for electric powered aircraft like the new EADS Cri Cri is there anything to be said for using this technology in the case of an Autogyro?

    The rotor energy makes for some helpfull regenerative feedback by being coupled to a generator, but is it enough to make a case for using this technology in the case of a Gyro given that the drag of a gyro rotor disk will far exceed the induced drag associated with more conventional designs like the EADS Cri Cri.

    Could a decently efficient generator double as the prerotator?

    Dave
    The engergy out of the rotor has to come from somewhere. That somewhere is your propulsion engine. And, since none of the devices in the system have efficiencies that exceed 100% - the net result will be to take a gyrocoper that has, say, a 30 minute range and convert it to one with a 15 minute range (as a guess - could be less than 15).

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    Re: Electric powered Gyro any thoughts?

    An aircraft is not an automobile. Regenerative power generation makes sense for a car as it gos up and down hills, and accelerates and decelerates. The mission profile of an airplane is different; takeoff and climb to altitude, cruise there for a while, then descend and land. To generate power during descent, you'd have to fly farther under power so you could descend steeper, so it cancels out. A gyro isn't an airplane, but the same principles apply.

    About the only place I can think of where it might make sense is for an acro ship, where steep power climbs alternate with steep dives. But the power to weight ratio of a gas engine is so superior to an electric/battery system that electric is unlikely to see any significant use there either.

    -Dana

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    Re: Electric powered Gyro any thoughts?

    Quote Originally Posted by Culleningus View Post
    Given the propensity now for quite reasonable (45mins) flight times for electric powered aircraft like the new EADS Cri Cri is there anything to be said for using this technology in the case of an Autogyro?
    An autogyro is far less efficient. L/D is roughly 1/3rd to 1/4th of the electric planes. Thus, your flight endurance will be 10 minutes tops, probably a lot less.

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    Re: Electric powered Gyro any thoughts?

    Thanks again one and all!
    The point about the reaction in yaw due to the magnets (and how do we produce a motor without magnets?) I hadn't perceived.
    Yes I appreciate the Higher Induced drag from the rearward inclined rotor disk Auto. This duration is just too poor.
    The idea about using spin up from stored energy from a rotor driven generator for both landing and taking off sounds interesting.
    But as Empirical states the extra burden of the generator might make the rotor slow down too much to make the benefits even noticeable.
    Thanks, Dave

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    Re: Electric powered Gyro any thoughts?

    Judging from towed ascents of gyro gliders, behind cars it should be possible to lift off with such a gyro glider tethered to a post in the ground in a 30mph+ wind.
    Wind energy alone should provide generator energy if driven from the rotor.
    This has already been 'proposed' as a form of power generation for large gyro kites flown tethered to the ground flown high up within the jetstream.
    I have not seen anything more than research papers detailing this yet.
    If this is correct I see no reason why after a suitable period in the tethered state to charge the batteries the gyro could not break free using an electric flight system now charged up and ready for a few minutes at least of FREE (yes free) flight

    Dave
    Last edited by Culleningus; November 24th, 2010 at 11:01 AM.

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    Registered User Empirical's Avatar
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    Re: Electric powered Gyro any thoughts?

    Quote Originally Posted by Culleningus View Post
    If this is correct I see no reason why after a suitable period in the tethered state to charge the batteries the gyro could not break free using an electric flight system now charged up and ready for a few minutes at least of FREE (yes free) flight

    Dave
    I'm not sure I get the point of what you want to accomplish.
    Is it that you want to fly 100% green;

    If so, trying to fly an autogyro as a kite with you onboard until the batteries get charged, sounds like a ..risky science-fiction project!


    But let's see the facts:

    1. an autogyro is many times less efficient than a glider.

    2. a fast wind is needed, with constant direction, speed and a guaranteed duration... much faster because of #1.

    3. to be safe, you can't rely only on the wind, so you need a power-backup with immediate response from power-off to full power.


    My science-fiction solution:

    Since it's not safe to use a wind of 80+mph for any type of flying, you have to build an autogyro many times more efficient than a standard autogyro. I guess it would require a much larger rotor (which wouldn't be able to pre-rotate from the air stream of the main motor) but since it would be connected to a powerful generator you could apply power back to the rotor and be safe. But you still have to half-charge the batteries on the ground (also from the wind) as a power backup both for the propeller and the rotor. With a large rotor, it would fly slower but because of much higher drag, I'm not sure how efficient the main motor would be.

    Still, a larger rotor and a high speed wind makes a less-safe mixture!

    So, to fly 100% green AND safe, you could wait until the batteries are fully charged via the rotor exposed to a high speed wind on the ground (optionally increasing the angle of the rotor) then wait until the wind slows down and then fly without fear (for as long as batteries allow)!

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    Re: Electric powered Gyro any thoughts?

    There is a free small software app "Gyrocalc" to calculate the efficiency and performance of autogyros!
    You can change the rotor diameter, the number of blades, set the engine power etc: http://www.icon.fi/~jtki/gyrocomp.html

    On another page of the same site he is attempting to calculate the performance of a possible "Electric Autogyro?" http://www.icon.fi/~jtki/elgyro.html

    There is also another interesting page, about "Experimental Aircraft Projects", (autogyros).

    All in one personal site -that's rare.

    EDIT: Don't miss the Autogyro safety page! : Autogyro Safety

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    Re: Electric powered Gyro any thoughts?

    Thanks Emp.
    Stored energy I guess is already available in catapult glider launches, & gliders are far more efficient than an autogyro-glider. VERY GREEN.

    However:
    1) Gyros are far more roadable (being compact).
    2) They launch and land very short using pre-rotation.
    BUT
    1) They have a godforsaken L/D ratio
    1a) As a result of which they have very poor endurance, under power
    1b) As a result of which they will drift with the wind like a parachute, without power.

    In time I dare say however we might like to consider a Gyro which like you say stores energy whilst parked (via the main rotor). Particularly at sea where the wind is reasonably consistent.

    Dave

    PS Thanks for the links which show a very interesting electric gyro 'study' for a calculated 20mins duration using existing sytems.
    Last edited by Culleningus; November 25th, 2010 at 10:28 AM.

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    Re: Electric powered Gyro any thoughts?

    We need a minimum RPM to continue to autorotate using blades set flat (along their entire length) in relation to the rotor disk (autogyro blades are typically not twisted at all).

    Then we need a preferably unadulterated consistent minimum airflow 'up' through the blades.
    This latter set of affairs might as someone pointed out prove interesting if we consider the blades now as a 'sail':
    http://www.fionamsinclair.co.uk/yachts/videos/page3.htm

    Due to vaguaries of wind strength a hub generator which doubles as a motor can possibly then ensure min autorotation rpm is maintained. A small feedback loop to maintain min. rotor rpm, using LiPo cells ESC, ECU etc.

    I then pictured using this same principle but converting from windborne waterborne vehicle to airborne vehicle, using a rotorhead to mast connection that allows the rotor disk to rotate through from vertical into an to autogyro inclined back, which once charged, will take off and fly for the 20mins or so suggested in Empirical's link above for an electric powered gyro in outline. A pair of sponsons would reside in place of the boat hull shown in the video.

    Land again, recharge from windpower, and fly again once charged??

    Or a day on the water followed by a final short hop back to terra firma?

    No fuel to speak of in the process.

    Dave

    PS Does anyone have any idea how much extra energy is expended during a waterborne take-off??
    Last edited by Culleningus; November 25th, 2010 at 10:47 AM.

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    Re: Electric powered Gyro any thoughts?

    As extreme as it sounds to self-charge a parked electric autogyro from a medium-strong wind, then fly totally green, then land, recharge and repeat, IS feasible!

    The only unknown parameter (to me at least) is the efficiency of the aytogyro rotor as wind-turbine, since it is not meant to be used as such. (Is there someone good enough in aerodynamics to calculate it?)

    • According to some sources, the best wind turbines convert up to 1/3 of wind power (0.59 is the Betz Limit). Let's make a rather safe (if not optimistic) estimation that it will do 3 times worse, or convert 1/9 (11%) of wind energy. Also a rough estimation of the total conversion efficiency including the efficiency of the generator->charger->battery units 0.11*0.9*0.95*0.8 = 7.5%.

    • Assuming you incline the autogyro so that the rotor's axis points to the wind: For a 8 meter rotor and a wind of 30mph(13.3m/sec) the wind power = 0.5*(8/2)^2*pi*1.2*13.3^3 = 70953 watts (71KW!) of which 7.5% = 5.3 KW(H) that will be stored per hour to the battery.

    • An 8KWH 5C battery can provide 53HP for 3 minutes to take-off and climb at a decent height, then lower the power at 21HP (as suggested in the Jukka Tervamäki's page) and fly 20 more minutes.

    • Aero-charging of the 8KWH battery will take 90 minutes.If the efficiency of the rotor as wind-turbine proves to be better and/or a better/ligher battery will be used, the flight-time will increase accordingly and the charge time will shorten.

    BUT:

    I feel I must warn you at this point, that what is NOT feasible, is to avoid the necessary R & D (research & development) for the whole electric unit and its adaptation to the vehicle, including:
    The high power controller, the high power charger (not a cheapo home charger), the circuit which will turn the generator to motor and vice-versa, the decharge computer, the system health monitoring and the feedback console, the protective circuity, the liquid cooling of the batteries and the motor, the design of a safe battery enclosure and a mechanical suspension that will protect the extremely powerful battery pack in case of a harsh landing, the humidity protection, the choices for battery type, size and wiring, the choices for the motor and the generator, the mechanical design to mount and adapt the motor and generator properly, etc.

    Note that each choice is made on one part or just one parameter, affects everything else and a second choice on another part or parameter, depends on and affects back the first choice! And the choices are hundreds! One wrong decision and the whole system might fail! This translates to more R & D.

    In other words, you can't just pick a battery, a controller, a charger, a motor, and a generator and connect them together. This is not just a simple electric motorcycle or car which will at least move faster or slower at a shorter or longer distance.
    It's not an RC model either to which whatever happens will add to the fun! As a manned flying vehicle (of the less efficient class), it has a technology and design threshold that must be surpassed in order to even take off!

    So a custom solution (which might include some innovations) is required. Otherwise, efficiency, performance and safety, all will be so low that it might not worth it, or it simply might fail spectacularly while still on the ground!

    This development cost (to pay the right people to design it for you if you're not an expert in electronics) adds to the overall cost of the electric autogyro (assuming it will be based on an existing autogyro model, known for its safety and reliabilty).

    So ultimately, it's a matter of cost...



    BTW, there is a single reason why you should abandon any further thinking about your amphibian idea: Because you carry a powerful, high voltage source too close to a massive, conductive liquid (water & salt)! Keep away! You should not even see it's blue color when flying -so to speak!


    Take a look at this ...towed Gyro Hang glider clip:




    PS. I did some thinking and searching since I am interested in electric air-vehicles too (for development and production of some ideas in the near future -probably after my current project)

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