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Voculus

Dual Rotor Helicopter - Physics, baby!

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First off, there are no engines producing any thrust! All of the lift is generated by the airfoils spinning at a sufficient speed and AoA through the air. I was absolutely amazed to see KSP work like this! Each rotor spins in opposite directions, and each blade can be rotated to change the pitch, giving me exactly the lift I need, when I want! I used RCS air jets to help maneuver, as well as two B9 reaction wheel elements. It's a bit sluggish, and a bit of a bear to fly precisely, but Old Betsy gives a good account of herself. :)

I know others have made ships like this before, so here is my humble attempt. Sorry the video is rather silent. It's just the IR parts spinning silently, and RTGs to keep the juice flowing for the SAS.

screenshot856.png?psid=1

screenshot858.png?psid=1

Edited by Voculus

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Sorry, Ionsions, I missed your post earlier. There are a number of mods you'll need to fly Old Betsy, so let's see if I do this right:

CRAFT File

Infernal Robotics

B9 Aerospace

Firespitter

KW Rocketry

Modular Multiwheels

Aviation Lights

Surface Lights

Kerbal Engineer

DMagic Orbital Science

One quick note: The video was taken before the Robotics update, and the washer speeds have changed. I now use a rotor speed of 50, and a pitch speed of 1. I also removed the airjets, since after testing, they were of little value. It likes to fly where it will, without some heavy control inputs, anyway.

Edited by Voculus

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Very interesting! The washer speeds are configurable? How do you prevent blade stall? My helicopters were always difficult to fly, too much lateral motion and I lost control. I see you had the same problem at the end of the video. That said, I had no way of controlling blade angle, since I used jet engines as a form of gas turbine, spinning the rotor axle which was essentially debris confined by crude bearings.

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Actually, the crash at the end was intentional, though it didn't blow up in spectacular fashion, as I had hoped, due to some weirdness going on when I had reverted to 0.23. With IR updated, it blows up just fine, now! As for blade stall, I've never seen it, because I can't get it traveling fast enough. I'm not much of a rotor head, so I'm not sure how blade stall would manifest itself on a dual rotor helo, or if KSP physics are sophisticated enough to allow for it. One interesting thing I did see, since KSP doesn't distinguish between leading and trailing edges, is that if I stop the blades in mid flight with the pitch neutral, it will glide rather well. :)

Edited to add, yes the speeds on all of the IR parts are configurable, which I only discovered recently. I always thought the numbers in the boxes were hotkeys and bugged. The only buggy thing was my brain. When you get a lot of mass spinning, the torque acts accordingly, so the only way to counter it on this ship was to have a second rotor.

Edited by Voculus

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I tried building a helicopter with docking washers for rotating the blades in both angle and spin, similar to yours. But when I do this, the wing pieces wobbled too much and made the craft uncontrollable.

How would I go about making the helicopter blades not wobbly?

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Hmmm, hard to say. Are the rotors spinning in the same direction? They need to spin opposite of one another, or that will definitely tear it apart. When building the craft, I placed jet engines on top of each mast, so I could line up the center of thrust with the center of mass. I don't know if the various wing pieces have different breaking/crash tolerances, or something like that. I used a particular wing from the B9 mod, and have not experimented with any others. I also strutted the fuselage sections, but not any part of the wings. Maybe the ship is flexing too much, but I'm just guessing.

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I did make one that was controllable without any reaction wheel/SAS/RCS but it didn't end up looking like a helicopter and didn't have blade pitch - just a symmetrical mess of counter-rotating fans.

Looking at your twin rotort though it just needs left/right rotor pitch, a hinge below the whole rotor to tilt it left or right. If you tilt one one way and one the other that'll give you a controllable left/right turn and both together to correct a left/right lean? Combined with adjusting front/rear blade pitch individually for front/rear pitch and together for height? It'd be fully controllable without reaction wheel/SAS magic, in theory, but probably only by a far more skilled pilot than me.

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Thanks for posting that, Darren. That vid was actually my original inspiration. :). The problem with tilting the masts, is that I can't control it with a flight stick. If I could, it would certainly make my day!

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We have the aerodynamic basis (FAR). But ... without cyclic and collective, building a functional, useful helicopter remains in the domain of the plugins.

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I tried a side mounted twin rotor design with IR mod myself about six weeks ago... but the forces ripped of the blades all the time... seems i have to get back to the drawing boards. Thanks for proving the concept :)

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My attempt

Still needs quite alot of SAS. though theoretically it shouldn't. Flyable, but very slow. Will autogyro to a safe landing from maximum altitude of ~5km.

Edited by nli2work

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