Variable Pitch Quad Rotor - M/UAV

Variable Pitch Quad Rotor - M/UAV


DIY project ranging from a 600cc 120HP etec Ski-Doo engine, UltraSport 254 tail rotors, extruded aluminum blades from Vortech, aluminum / steel tube structural components, and a carbon fiber reinforced polymer monocoque frame.

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  • Two 3-way gearbox, CVT on center axle. See here

    I'm designing the monocoque fuselage now, but my main project is design of the blade roots and lead-lag damper plate.

    The original blades for this aircraft are only about 12" long with a 2" chord, made of Roacell foam with a carbon fiber 'C' spar and tungsten weights for inertia. The new blades are 18" long with a 3.5" chord, made from a single piece of extruded aluminum. The roots for the new blades will be about 3.5" long, for a total blade diameter of 48".

    The engine will produce 115 HP at the target RPM of 6000. Once the blades are built, I will begin testing to see what the optimum speed for lift is. The rotor with blades will be mounted to a pedestal built specifically for testing. The rotor will be mated to a 30HP 3600RPM electric motor, and lift generated will be measured by a load cell.

  • I am quite aware of how these systems work as I have a couple of them sitting in the other room, also conventional helicopter systems, having studied aviation and also worked on real choppers 

    Please note: be it a collective pitch quad or a fixed pitch quad is irrelevant They both require Flight control systems & cannot be controlled properly with direct linkages to a cyclic or RC system. 

    You are basically using the same systems as a normal chopper uses on its tail rotor but 4 of them sprouting from a 4 way gearbox in the centre.

    What stage are you currently at?

  • A regular helicopter with a fully articulated rotor system has a collective pitch AND swash plate. A variable pitch quad rotor DOES AWAY with the fully articulated rotor by eliminating the swash plate entirely. It creates dissymmetry of lift by varying pitch in a particular quadrant of the quad rotor system. So a helicopter and a VP quad rotor fly essentially the same. I can completely eliminate the electronic component of flight and replace with a collective If I intended to sit in the thing.
  • If you sit on this thing during test flights like Ritchie is saying then yes you would be a fool, Common sense tells me you will fly it as a UAV first though,  I know some guys that are going to fly a Gyrocopter as a UAV.

    Your control system/ Gyros should be able to counteract the fact that no one is sitting in it if your pilot seat is not at centre of gravity.   A quad copter is a dangerous craft for a human to sit on  they rely too heavily on gyros etc one stuck gyro and this thing will flip fast   This is not real common but can happen  conventional helicopters are capable of auto rotational landings  a fixed pitch quad is generally not   Robert yours should if you hook it up right, I cant see it being something to rely on though   I would have a fast deployable parachute or ejection seat  which would be standard with a military test vehicle.


    Even a small quad if one paremeter is out it can just flip when you try to take off  sounds like your blades are around eye level.

    Where are you located? if you get this going I would love to see it :)

  • Holy crap its not a model its your personal Scorpion gunship from Avatar :O I thought this was a large scale model not a fully enclosed and working version.

    My suggestion is now a REQUIREMENT. If you want to not die on your first test then you have no option about a model. You could be lead rotorcraft developer at Lockheed Martin but I'd say this. If you just want a cockpit build that first and use your many crashes in the model to get the rest of the airframe safe. Building a scale version would cost you $750 tops but development would probably push you to $1000 but then you would have sorted the fly by wire system and would have a better than 50:50 chance of not over powering one side and flipping directly into the ground and having one of the blade mount itself through your chest.

    The military have experimented with this and have only one type in service because its so hard to get right and you are doing without their $$$ billions and without doing the small scale testing and prototyping they do. Even the forefathers of flight used testing vehicles for their ridiculous designs what has made you think your massively complex design let alone articulation and electronics systems is going to be safe first time you use it when built with budget parts. Even basic self build helicopter is $40,000.

    You might not think you have the money to do it twice but is your life worth $1000 in test platform if so carry on.

    If your id is overpowering your ego and telling you to not listen to the people on this forum who have spent years getting a very basic quadrotor to work well with many thousands of people helping then carry on.

    If you are a developer for rotorcraft at a military contracted  aerospace manufacturer stop lying and show use the test vehicles that have given you the confidence to surge on with this.


    Boundaries should be pushed but only when lives (human or animal) are at as little risk as possible. You are worth more than $1000 and I don't know you at all.

  • I have wanted to build a quadcopter large enough to fly on for ever.  I want to use an APU from a jet to power electric motors.  same with your copter, it might be better to use 4 or 8 electric motors 1 or 2 powering each rotor.  u will have better torque managment.  



    Either read this online or buy the book. Force yourself through this bad boy three times, and you will gain unmatched knowledge in rotary wing aerodynamics. Then you guys will actually be able to make calculations to simplify your rotor blade design for these UAV projects at any scale. Completely takes the mystery out of how helicopters work.


    I highly recommend buying this book.

  • As soon as I get the blade damper, I will sketch out a new top plate for the rotor head, and try my hand at CAD. Once I have the blade grip design figured out, I'll have some made at EMS. I will attach and balance the 3.5" x 18" blades I purchased from Vortech International to one of the UltraSport 254 tail rotors I have. Then I'll mount the test rotor system to a makeshift rotor test tower. There I will spin it up to 3000 rpm and see what happens.
  • I hear ya,  there are a million things I would do if I had a million $$$ :P

    Here is a link to autoCAD training I reckon if you went through all these tuts you should pick it up.


    Other than that perhaps look at paying an engineering student some bucks to put a model together


    Good Luck!


  • I don't think I can afford to do it twice. I estimate doing it small scale with custom parts will match the cost of doing it full scale with discount parts. I guess I will test out the subsystems as I build them...


    CAD is an excellent idea though - if I knew how to use it. I hold many titles, but thats not one of them. I do need some custom parts machined though, and hopefully using eMachineShop will teach me the basics of CAD.


    Even if I never actually use it, this particular project WILL have a fully functional cockpit. Talk about a Pandora's Box.

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