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Thread: Single-engine (gasoline) high-endurance hexacopter project

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    Single-engine (gasoline) high-endurance hexacopter project

    I just signed up for my senior design class at the Georgia Institute of Technology, and trying to come up with some ideas (this being one since it's not exactly common). I figured the ability to have the VTOL capabilities while having 1+ hour of endurance is a valuable asset without having to deal with the safety risk of a single-rotor helicopter.

    I wouldn't expect a whole lot of interest in the hobby community, but still forwarding this along for the sake of some market research.

    I have some ideas in mind to make this work (similar to the Curtis Youngblood Stingray/Mantaray), but would like other feedback before our team commits to the concept.

    -Chris
    Last edited by Khosravi; 30th March 2014 at 08:19 PM.

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    FPV - Fly Low airbagit13's Avatar
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    Sounds cool but why is this less complex then a single rotor heli?
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    Quote Originally Posted by airbagit13 View Post
    Sounds cool but why is this less complex then a single rotor heli?
    The absence of a swashplate, less mass rotating, etc. Setting up a single rotor helicopter (head) is mechanically much more demanding than setting up the tail of a heli. I plan to basically use 4 tail rotor assemblies.

    -Chris

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    Not really true anymore... if we were talking flybarred then yes, but setting up a flybarless head is as simple as could be and very fast. Since you will be needing a flight controller anyway to make it useful for FPV/AP then there would be absolutely zero reason to use a flybarred head.

    There are advantages to multi rotor, one of the biggest being number of flight controllers available and their abilities compared to heli equivalents, though you will be limiting yourself by the fact you would have to use a collective pitch capable controller and thus the options narrow substantially.

    It would be a fun project, but it is not less complex than a single rotor FBL heli in my honest opinion. That is a poor reason for choosing it... could be safer, though I'm not sure something like the mantaray is something I would classify as being any safer than an equivalent heli. Are you sure 4 smaller head assemblies and blades would have less rotating mass than a single rotor heli? I'm not sure it would.

    I don't mean to be negative - it'll be a fun project and I think you should go for it, but you need to think more carefully about your reasons imo, especially if it's something you have to justify as a class project.

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    Quote Originally Posted by Zeeflyboy View Post
    Not really true anymore... if we were talking flybarred then yes, but setting up a flybarless head is as simple as could be and very fast. Since you will be needing a flight controller anyway to make it useful for FPV/AP then there would be absolutely zero reason to use a flybarred head.

    There are advantages to multi rotor, one of the biggest being number of flight controllers available and their abilities compared to heli equivalents, though you will be limiting yourself by the fact you would have to use a collective pitch capable controller and thus the options narrow substantially.

    It would be a fun project, but it is not less complex than a single rotor FBL heli in my honest opinion. That is a poor reason for choosing it... could be safer, though I'm not sure something like the mantaray is something I would classify as being any safer than an equivalent heli. Are you sure 4 smaller head assemblies and blades would have less rotating mass than a single rotor heli? I'm not sure it would.

    I don't mean to be negative - it'll be a fun project and I think you should go for it, but you need to think more carefully about your reasons imo, especially if it's something you have to justify as a class project.
    The main reason behind the gasoline quadcopter is flight time over electric and ease of transport (by folding booms/arms). It should have a smaller foot-print than a traditional heli, but carry an equivalent weight. The safeness and/or complexity are really only bonuses if we are successful, and like you said, it may not be safer or less complex at all.

    Ardupilot will be used as the flight controller since I've been using them since the V1 hardware was out. I've had nothing but success with them and have teammates that are capable of modifying code to enable a VPP quadcopter.

    -Chris

    Keep the comments coming. I have to present these discussions with my advisor this week.

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    FPV Addict Scotttu's Avatar
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    What happens if you fly backwards while filming and all you see is a cloud of exhaust?


    I think 15 minutes is optimal ona battery, take a break, put another battery in.


    No gas, no fire hazard in that regard......


    It's a scientific novel idea but not practical with todays LiPo's (Speaking of fire hazard, easier to mitigate risk though)
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    Fuel is still way better than any current battery tech in terms of energy density though Scott - a gas heli will fly for (easily) double the time of an equivalent size electric... Also has the advantage that it gets lighter as you use the fuel up, whereas electric is always carrying the dead weight.

    That said, a large quad with 18" props, well chosen motors/ESCs and 6S 10,000mah will easily fly for 45-50 mins if the frame and equipment is kept light enough. It's something I've looked into doing myself. Fill up a gasser with 1.6kg of fuel however (the equivalent of the batteries) and it'll likely fly for longer.

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    FPV Addict Scotttu's Avatar
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    For fixed wing it makes sense but now you have the excess vibration, exhaust, neat experiment but not practical, IMHO...


    Electric motors don't just quit on barometric pressure or mixture levels either
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    Quote Originally Posted by Scotttu View Post
    For fixed wing it makes sense but now you have the excess vibration, exhaust, neat experiment but not practical, IMHO...


    Electric motors don't just quit on barometric pressure or mixture levels either
    Like I mentioned in my first post, I wouldn't expect much interest in the hobby sector. However, our team believes this type of vehicle will be very useful in SAR operations.

    And believe me, there will be plenty of vibration dampers in our design
    I'm used to working on gasser helis at the UAV company I work for, and the dampers we use are quite nice

    -Chris

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    New gasser motors are more reliable than you've been led to believe - you may only have to revisit your mixture settings twice a year to account for temperature. Sounds like a great project if you pitch the raison d'etre to its strengths...loiter time, payload, autonomous capability, etc. You can achieve equivalent loiter time and payload goals equally well on an electric quad, but not both together.

    Clean/dirty frame setup can eliminate vibration and you vent exhaust into the prop wash to get it away from cameras and the like.

    Vertically mount the engine to a 4-pulley, belt driven transmission and you have the makings of a relatively simple, yet durable drivetrain. Or follow a planform like the Stingray for an H-quad with the engine mounted inboard of the rear pulley. Could be some balance problems with a design like that if you didn't use a long driveshaft to relocate the engine close to the centre of lift...

    Only missing piece from a technical standpoint is the FC and you seem to have a few ideas for that. Sounds like a fun project!

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