A Collective Pitch Quadcopter

Quadcopters aren’t a new thing, but for all the advances in multi-rotor craft, they all still fall into the paradigm of, ‘stick a prop on a motor and repeat three more times. [Curtis Youngblood], one of the top RC heli pilots in the world, came up with a very cool drive system for a quad, requiring only one motor and granting each blade collective pitch that allows for absolutely insane acrobatic ability.

There’s only one motor inside the Stingray 500, as [Curtis] calls his new toy. It’s at the rear of this quad’s H-frame, attached to a shaft running down the spine with a pair of pulleys. All four rotors are driven by this spinning shaft.

Because [Curtis] is an acrobatic pilot, he needed a way to control his ‘copter in more than one direction. To do this, he added four servos on each arm of the quad, giving each rotor collective pitch, just like the tail rotor of a real helicopter. The result is a quadcopter that can fly upside-down with the greatest of ease, perform barrel rolls, and all the other maneuver a true 3D RC ‘copter can do.

The awesome guys at Flite Test had [Curtis] visit their hangar and had him do an awesome demo flight. You can check out that video below.

46 thoughts on “A Collective Pitch Quadcopter

    1. Have you thought about using full size RC helicopter blades and a gas or turboprop engine as a heavy lift drone? Would be really useful in Ukraine right now. As a designer is there anything that would preclude the upscale in size.

    1. What’s new about using one motor to drive four ‘things’? That’s how 4×4 cars work.

      The big disadvantage of this method is the mechanical complexity. ‘Normal’ Quadcopters just have the props sticked on the motors. That’s it. As long as the motor works, the thing flies.

      This CP Quadcopter has so many points of failure. Belt ripping, stripped gears, broken servo.

      1. “So many points of failure”
        Not really. Those belts are tough. A broken servo would kill an RC helicopter, as would stripped gears. 5 minutes of inspection before you fly (which you should be doing anyway) takes care of all that.

        1. >A broken servo would kill an RC helicopter

          thats the whole point, this is as complicated as rc heli
          quads DONT HAVE THOSE PROBLEMS, you have 4 motors and thats it, no more. You could probably even make a firmware able to land when one of four motors fails.

          RC heli is not a benchmark

      2. Watch the video. By altering the pitch via a linkage (instead of motor/rotor rpm) you have a much more rapid response as well as the ability to create inverted lift.

        That’s some crazy flying.

          1. You say that as if incorrect grammar is something to be proud of. What does it cost to take a little bit extra care and ensure that you do have correct grammar? It’s not rocket science for Christ’s sake (correct use of apostrophe there).

          2. I would say communication of ideas is more important than minor grammatical errors. We all know exactly what the intended message is stating.

            The build is absolutely amazing, so simple and for the amount of maneuverability. $800 is kind of hard to justify for a someone who isn’t “Pro” thou

          3. The contraction was “copter”, “helicopters” into “heli’s”.

            Not conventional usage but does it matter? This is a conversation, be conversational.

          4. Actually, the usage of the apostrophe is not that simple in this case. When trying to express the plural form of numbers or letters it is certainly acceptable to use an apostrophe before the s, e.g. “mind your p’s and q’s” vs “ps and qs” and “1970’s” vs “1970”. Also, many style guides state that the plural form of acronyms can either use or leave out the apostrophe, e.g. “CDs” vs “CD’s”, but the non-apostrophe case is highly preferred. However, the apostrophe is preferred when the plural form of the acronym when written out is not simply an “s” appended to the last word. So, for example, the plural of CD should be CDs because it is for “compact disks”, but the plural of RPM should be RPM’s, because it is for “rotations per minute” and not “rotation per minutes”.

      3. Yes it is slightly more complex but the gain in acro is absolute time travel compared to a normal quad. The maintenance on it would seem similar to a high end heli at first glance. The belts are actually better than gears because they can skip instead of strip. There’s only one speed controller to go bad, one motor to burn up… I dunno it seems like a really great design to me.

        Having 4 servos is the only down side in my opinion but that depends on the quality of servo required. To get the performance you see in the video I imagine you need some pretty high end, fast, strong servos I could be wrong though.

        It would be interesting to see if something similar could be done with a scratch build with lower end components.

      4. 4×4 cars work by driving four props? im pretty sure they use tires…

        There are no gears either.

        I would say its less complex since you dont have to tune the ESC’s and monitor them with a controller to know their rpm.

      5. What is new is the combination of concepts. Mainly, cuadcopter with colective pitch control for every rotor. Also, only one motor surely saves weight, even with the added complexity of the transmision system. (You will need the four servos for the colective even if you used four motors)

        All the maneouvers are performed by changing the pitch of any individual rotor, instead of changing the speed of the motors. This make posible maneouvers like inverted flying, imposible with a conventional cuadcopters.

      6. it is just inefficient.

        explain how this is slightly better than a single rotor?

        all that you gain by having multiple rotors each pointing to one direction is that you will cancel one or another… the end force vector will always be less than if it was a single rotor! always! if you don’t understand that, go have fun with your perpetual machine later :D

        not to mention that now you need 4x the complexity. 4x the stepper motors weight… etc.

        The ONLY reason this would be desirable is for a real helicopter. because then you have redundancy. I’d feel much safer flying in a machine like that one instead of one with a single rotor :)

        1. Maneuverability for one. A quadcopter doesn’t have to fight the gyroscopic force of a large (relatively) heavy single rotor, and has the advantage of controlling the direction and amount of thrust at 4 points vs a helicopter’s 1.

        2. I hunk you’re the one who doesn’t quite understand. In a conventional helicopter, you have to use some of the engines power to turn the tail rotor. This is a force perpendicular to your lift vector, so is “wasted”. A multi-rotor helicopter (Chinook, Sea Knight, K-Max, etc) use the counter rotating props to cancel the torque and can use all the available engine power for lift. The helicopter I flew actually tilted the tail rotor down several degrees to maintain a vertical lift component to make it slightly more efficient, but we still sacrificed lifting power for the anti-torque.

          And your theory on redundancy is also flawed. This design relies on all four rotors working, both for torque cancellation and for balance. Four wheels aren’t redundant in your car are they? Take off a wheel and see how well you can drive…. Engines are the redundancy in a helicopter. 2 is good… Three is better.

      7. Actually, no, this thing can autorotate like a chopper, so that even though it might be a hard one point plan landing, it isn’t a system failure as if the batteries fail on a quad or tri copter. Also after seeing this thing maneuver and perform, it completely blows away the individual motor quads. No inertial lag, complete ability to “orbit” a point (or target) for example. Very unique approach. Would likely be possible to add a parachute or parawing recovery if you don’t trust autorotation. I’d argue that kevlar belts are pretty tough, and barring combat, the copter would survived well, perhaps even better than motorized.

        Honestly, mechanical complexity is not necessarily greater, if the belts were substituted with flex shafts / cables (think tiny stainless speedometer cables) this becomes pretty scalable and much simpler to build). The real innovation is in the servo controls and variable pitch here, agreed this would lend itself to a larger gas chopper or perhaps even a human passenger model. Being able to run the single motor at constant RPM can also be more efficient than constantly varying speed.

  1. Wow, that design is absolutely awesome. Immediately I thought, I wonder if two more servos could be attached to the front and rear axles to create a VTOL design. Add a small airfoil to the sides and you have yourself a long hang time with relatively little thrust.

  2. I’m going to be “That guy” and question how this is on Hackaday. Just pointing out that it is 1) a commercial product and 2) the link doesn’t really give anything other than product information not even on hacking the Stingray…

    Yes, it’s cool… but that’s about it.

    1. 1) What’s the problem with it being a commercial product? Are you saying that HaD shouldn’t feature a product if it’s commercially available for sale? Regardless of whether it has some very cool technology behind it?

      2) Do you expect every product you buy to come complete with full instructions on “hacking” it?

    2. This is new Idea simplifying quad-copter design and makes the idea of a life size quad copters very possible it should increase battery life by quite a bit if you fly it like you would a normal quad copter (but that would be a waste of all the new maneuverability )

      And for why it is here well 90% of the people on this site will not need a step by step instructional to build one of these

      Next step fling car ;-)

    3. New Stellaris Launchpad!

      Miniature Arduino kits now available!

      Get your MSP-430 Launchpad for $4.30!

      Nixie clock kits!

      Rasperry Pi now shipping!

      Yes, it’s a commercial product being listed on a website. Unfortunately for your commentary, it is a website with a long history of posting commercial products.

      It is also a clever hack, and also a hackable hack, which was apparently designed by a hacker. The pilot/creator even goes on for a bit about his hacked controller that he has modified for his own preferences.

      That it can be purchased does not detract from the creativity expressed within.

  3. Neat tech, great stick skills, but the whole convulsing drunken monkey flying routine doesn’t do anything for me. It’s soooooooooooooo far from real flying that I just don’t get into it. YMMV.

    //used to pylon race 1/2A and Quickie500 back in the 90’s//

  4. Correction:
    Because [Curtis] is an acrobatic pilot, he needed a way to control his ‘copter in more than one direction. To do this, he added four servos on each arm of the quad, giving each rotor collective pitch, just like the tail rotor of a real helicopter.

    There is only one servo per prop. They control overall pitch of the blades.

    It essentially is a normal quadrotor, controller wise, but the blades can change their thrust extremely quickly.

  5. I don’t get how yaw works; normally half the rotors would turn slower and half faster. But in this case, they all turn at the same speed all the time. As far as I can tell, only the rotor pitch is changed, not thrust direction?

    1. That is a good question…

      The impression I had from the flight video was that the machine flies more like a plane in non-hover mode-you bank into a turn while moving forward. It’s possible to control an aircraft’s direction without a rudder flap. Most beginner RC planes don’t even have a rudder servo, just ailerons and elevator control.

    2. I take it back-watched it again, it can clearly yaw in hover.

      Look at the rotation pattern. It’s opposed left to right and front to rear, so the front left is spinning cw, front right ccw, rear left ccw and rear right cw.

      Best guess is by increasing lift on diagonally opposed rotors while reducing it on the mirror side, you’d get no net change in lift but a yaw component due to increased common rotational drag-up on front left and rear right (cw) with down on front right and rear left (ccw) would yaw to the right.

    3. 1.) Drive on the highway
      2.) Stick your hand out the window keeping it open and towards the road
      3.) Now tilt hour hand up just a bit towards the oncoming traffic

      That is basically where the lift comes from the rotter that can change its pitch much more effective than increasing the speed on a fixed rotor

  6. Umm wasn’t there another collective pitch quad featured on Hackaday a while back? Works well. It is possible to fly a ‘normal’ quad inverted with the right firmware and flat props. ie ones with no airfoil shape, Warthox does this.

  7. There is one thing I wonder, is this quad has any gyroscopes/accelerometers as classical quad ? cause on the official website it is said that they’ll implement motion sense in the future…

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.