Hybrid Gas/Electric multi-rotor concept.

Hello everyone,
I hope I don't step on any toes here since I am a newbie to the forum.
I have searched the forums and have read a few different discussions regarding this topic so of course I know the idea is not a new one.
There was clearly some good information but it does not sound like anyone has yet succeeded in building a power plant that would work for the purpose.
I believe I have found the components that would be capable of doing the job. At least as far as a producing the raw power for the job.
My goal is to keep the generator package under 10Kg while producing 180 amps@18V continuous and a peak of more than 300 amps. All of this while carrying enough fuel to run for an hour+.

The problems I am running into are more to do with the electronics than the actual power plant.
I believe I have found the required alternator and engine combination to do the job.
But for this to actually work the gross power needs to be rectified and regulated into a form that is usable by the flight control system and the ESC's.
After that there is a motor control circuit required to actually run the generator engine to control the output in relation to load requirements. This system would have to monitor the capacity and charging status of the batteries and the amperage consumed by the drive motors allowing it to determine how much throttle to give the generator.
Finally the flight control module is going to have to know when the generator runs out of fuel to be able to use the batteries for a controlled safe landing.
The assumption is that with a generator on the rig batteries would be required but the amount of batteries required could be reduced by 50 to 75%.

The information I am missing is real world data on how much power is being consumed by a rig that can carry over 10Kg under different flight conditions. For instance I know of a 700mm class rig than can lift in excess of 15Kg running on 4 Turnigy nano-tech 5000mah 6S 65~130C Lipo Packs and 8 Turnigy G60 Brushless Outrunner 500kv motors. what I don't know is what the actual power consumption is for this rig when it is carrying a load while hovering and maneuvering.

I can run the theoretical math of what it could use as a maximum but the goal is not to provide the maximum power but instead to provide something that has a continuous power supply that can hover the rig and a peak that meets the majority of the requirements for maneuvers.

I appreciate any comments or input everyone may have.



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  • I am new to this forum, but I am working on a similar concept.  The system I am working on is less ambitious, but I hope will prove practical.  I am using a Honda 35cc four stroke engine driving a Turnigy 160Kv brushless motor.  The 3 phase output is rectified, smoothed and sent into a stripped, DC input 6s dual channel battery charger.  The charger compensates for the wandering DC voltage output and so the motor is unregulated and operates with a fixed throttle setting.  The charger provides the input to a pair of limited capacity batteries.  The entire module will be exchangeable for  the existing 4 x 10,000mAhr x 6s batteries.  I am aiming at 6 Kg for the module.

  • I think 8kw from a 5kg power plant might only be available on the Starship Enterprise

    But at 55lbs you might be able to get 8kva from a Jakadofsky JetVolt® 230/400V 8/10kVA


    Jakadofsky Jet Engines Modellbau Triebwerke, Gasturbinen, Hubschrauber Wellenleistungsturbinen
    Spezialisiert auf die Herstellung und Wartung von Wellenleistungsturbinen, Gasturbinen und Modellbautriebwerken.
  • I need an alternator for 8500 KW power and less than 5 KG weight
    would you please introduce me some, if you know any models or companies

  • I have a good idea of a workable design but of course it will take some time and effort to put it into a cad style diagram. Which I really suck at.

    I would not spend a lot of time worrying about CAD. That is mostly for presentation, production, and sales brochures. The engineers that sent men to the moon used slide rules and pencils, calculators when needed.


  • Hi,

    If you are interested in the Heavy lift quad idea, there was a kickstarter project last year that seems to have a few of your design elements already included.

    I guess the cargo capacity could be used for you alternator system


    and the main website (more updates)



    Incredible HLQ (Heavy Lift Quadcopter)
    A gas powered quadcopter capable of autonomously picking up and delivering a payload of 50 pounds.
  • HERE is the DIYD thread from long ago (internet time).


  • I do so love your enthusiasm.  Is this the general idea?

    3692943554?profile=originalI won't say it is impossible. But I am certain there are serious efficiency issues with it.

    Have you seen the Youngblood Stingray?


  • Hello again,

    Ok so it seems my initial hopes of doing a package that stays under 10Kg was a bit off. But of course since I am a bit thick in the head with determination and tenacity I have pushed forward on my calculations and research and after talking to manufacturers and doing more research I have been able to come up with a power generation solution that weighs about 15Kg and produces 400+ amps at 28V. From what I can tell with a frame, motors, batteries, electronics, etc. should come in about 8 to 10Kg leaving maybe 3 to 7Kg for camera equipment.

    Running time should be 1 to 3 hours.

    Even though there is an efficiency loss of up to 40% doing the gas/electric hybrid format I don't see a way for a direct drive gas/mechanical drive option working well.

    For starters the mechanical complication of a variable pitch rotor assembly greatly increases the probability of a mechanical failure.  

    Secondly what makes a electric multi-rotor work so well is the near instant responsiveness and almost linear torque curve of a brush-less electric motor. This is required for the maneuverability as well as the stability control systems to work effectively. Where as a gas motor has a significantly slower throttle response and narrower torque curve would become an issue.

    Finally with the efficiency trade off the possibility of increasing flight times by a factor of 5 or 10 could come in particularly handy under certain applications like search and rescue where stopping to change out batteries every 30 minutes or so can seriously decrease the long-term efficiency of the search.

    With a hybrid device that can exceed an hour of continuous flight and simply needs a refill of gas to go back up would be a significant improvement in efficiency.

    I have found a manufacturer that can produce the electronics for the application along with the alternator module. The motor being a standard RC aircraft engine is ultra light perfect for the application.

    The only real hurdle is cost. The system by no means is cheap. A custom frame with electronics, batteries, motors, props and all is not a trivial expense. The generator pack with fuel cells and motors on a one off production run is likely to cost $15000 or more. Of course in production quantities the cost could be brought down to under $7500.

    Am I crazy to think that this should be done? Of course the geek in me wants a toy that can fly for more than 15 or 20 minutes. The engineer in me loves the challenge.

    Any thoughts?


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