Early stages of a TiltCopter

Today everybody and their dog seem to be working on a quad project. And with my own quad having reached a relatively mature stage with stable flight some time ago, I thought it would be nice to try something different.

So inspired by the full-size Osprey tilt rotor design I just started an experimental duo/tilt copter build. Frankly I am far from sure if it will ever fly, but that is what makes it fun!

Mechanical:

My tilt design is one I used in an earlier tri-copter build. I insert a 8mm CF rods into a 750x10,5mm CF square tube and glued then together. A modified T-Rex 600 blade-holder is then inserted on the 8mm tube and fastened using glue. Finally a servo is epoxied at the side of the square tube and linked to the 600 blade-holder. Motor and ESC is a cheap TowerPro combo from HobbyKing. Cheap and easy to replace when experimenting, and the ESC has no problem handling 333mhz PWM pulses.

Hardware / software:
For control and stabilization I will use the same hardware that I used in a Quad I built earlier. A FASST R617FS receiver modified with PPM output, and the ArduIMU V2 board with custom software for stabilization and servo/ESC control.

Main body / tail:
I have yet to decide what I will do for a main body. At the very least I will need some kind of tail with a lift surface to get some balancing momentum in the pitch axis, and tail drag when in forward flight. Lots of fun experimenting to be done!

Parts:
Carbon Fiber Square Tube 750x10.5mm
Carbon Fiber Tube (hollow) 8x750mm
Align T-Rex 600 Blade holders and bearings
Turnigy S3101S Servo 17g / 2.5kg / .14sec
TowerPro BM2410-9T / 18A BEC/ 1047 Prop Combo
Futaba FASST R117FS receiver
ArduIMU+ V2 (Flat)

@Jani: At first I only plan to hover and have forward flight with motors at about 45° forward angle maximum, so I will build a minimal skeleton with just tail and no wings for that type of flight. But the next logical step would be adding wings to generate lift when moving forwards. The TR S3101S servos I use are great in that regard, since they can be moved close to 180° without any modifications by sending out of bound PWM signals.

@Jason: Sure, here is a link for the FAAST PPM modification. I am not using the DCM at the current stage. I have had some problems with stabilization performance when the airplane is not moving forward (hovering). To keep things simple I am just using the ArduIMU+ board as a 3-axis head-hold gyro and servo mixer.

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Comments

Developer

John Arne Birkeland August 1, 2010 at 8:05am

@Mike: Yes, that is pretty much how I will build it as a test platform for hovering and initial transition into forward flight. But eventually I plan to add wings so that I can convert fully into horizontal flight. If you squint you can see the Gress bicopter as a Osprey V-22 without wings.
Mike August 1, 2010 at 4:17am

Sounds like a Gress bicopter?
Developer

John Arne Birkeland July 31, 2010 at 11:02pm

When I used the ArduIMU together with GPS in a airplane I had problems with the pitch being affected by acceleration and deceleration. Also if I turned the plane against the wind hanging on it so that ground speed approached zero, the IMU would sometimes go into a oscillating feedback loop. I do not see the need for a tail gyro since I already have that gyro axis in the ArduIMU. My initial setup will most likely be a body with a fixed T tail. The elevator surface will be angeled so that forward motion will pitch up the nose to combat the forward tilted motors pulling the nose down.
Developer

Jani Hirvinen July 31, 2010 at 10:43pm

John could you explain a bit more about your problems with DCM when hovering.. What type of problems you have seen?

You plan to have small heli gyro on tail on your first body?? I think that would be good idea and then you don't need to worry so much about tail in this point :)
Developer

John Arne Birkeland July 31, 2010 at 9:36pm

@Jani: At first I only plan to hover and have forward flight with motors at about 45° forward angle maximum, so I will build a minimal skeleton with just tail and no wings for that type of flight. But the next logical step would be adding wings to generate lift when moving forwards. The TR S3101S servos I use are great in that regard, since they can be moved close to 180° without any modifications by sending out of bound PWM signals.

@Jason: Sure, here is a link for the FAAST PPM modification. I am not using the DCM at the current stage. I have had some problems with stabilization performance when the airplane is not moving forward (hovering). To keep things simple I am just using the ArduIMU+ board as a 3-axis head-hold gyro and servo mixer.
Brad Powers July 31, 2010 at 9:27pm

I don't exactly remember which pin it was (it's been two years since I hacked mine), but the FASST receivers all have full PPM output on one pin of the main MCU within it. Some probing with an Oscope should work. Good luck.
Developer

Jason Short July 31, 2010 at 8:18pm

Oh, and are you running the DCM on the imu as well?
Developer

Jason Short July 31, 2010 at 8:15pm

Could you post a link to modify the fasst receiver? This project looks really cool. Good luck.
Moderator

John Church July 31, 2010 at 7:07pm

It's been said, but yes- excellent use of a 600 blade grip!
Developer

Jani Hirvinen July 31, 2010 at 6:58pm

With those servos. People are using same idea on Tri copters to control "rudder" engine eg. tilting one of their motor. Only thing that i am concerned is that does servos have enough travel to tilt those motors about 100 degrees.. 90° is needed for take to forward flying but during takeoff/landing you need to have extra 5-10° to control body and especially yaw

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