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Tuning, Levelling, Balancing - Getting it Airborne (Tricopter)

eekay

Junior Member
#1
Good day friends,

I've completed the V2.6HV by David, and its to the point where Im trying to get it airborne. I can hover, somewhat, but so far the drift is far too crazy for me to be able to fly it properly. My most recent sessions resulted in two broken Rotor Bone motor mounts, and a lot of broken Delrin.

Adjusting my P and I gains is virtually impossible if I can't keep the thing steady long enough.

So, while I wait for new parts to arrive, I want to work on a new approach.

What further steps are necessary to ensure a Tri is going to be as stable as possible - before you even throttle up, so that when it does go up, and you focus on those PI settings?

So far I have:
- Balance Props (Done)
- Balance Motors (Ongoing)
- Finding the CoG (Ongoing, waiting for new motor mounts)
- Vibration dampening foam pads on all sensitive bits (Done)

What I'd like to know:
- Getting the craft as absolutely level as possible for sensor calibration (KK2.0). Does anyone have any hints/tips/tricks? Im thinking the use of a bubble level and shims. How does this work, and how will it affect stability/drift in the air?

Any other helpful hints anyone has on how to get a tri or any multirotor as stable in the air as possible would be great. I'd like to spend more time flying, and less time looking for broken pieces in the grass.

Thanks so much, and sorry if this has all be asked a million times. Thanks to David for the design, and the whole FliteTest crew for making this all possible.
 

Cyberdactyl

Misfit Multirotor Monkey
#2
The easiest way to get the frame level to preform the ACC calibration is to find a level surface, a kitchen counter will usually be very close. Then merely take three of the same type drinking glasses and rest your booms on them. Of course ensure you're not resting the tri on wiring or whatever.
 
#3
Center of gravity is easy to find: on the centerline left/right, and a little in front of the center point of the three motors. How far forward depends on how long your arms are and how much the tail rotor needs to angle to counter the motor torque. Expect it to be an inch or two, adjust based on how it drifts off center when not using autolevel.

If you haven't loaded new firmware on the board, you almost certainly need to. The stock firmware doesn't work well with tris. I fought mine and fought mine, it kept flipping over and generally doing anything except fly. Finally I flashed it with new firmware. After that it was smooth as can be.
 

eekay

Junior Member
#4
Thanks for the input. When the guys ship me my replacement tilt-mount I will be sure to implement it. I also need to order up a 10 pin to 6 pin adapter for the ISP cable to update the KK's firmware.

I did read and interesting quote from another forum, regarding multi-rotors. "The KK does not fly itself, you do. You will always have to give it input to keep it level, no matter what"

Puts the idea into perspective. Is it possible Im expecting a little too much out of my tricopter?
 

Cyberdactyl

Misfit Multirotor Monkey
#5
The KK2 with v1.5 or 1.6 has a pretty decent auto-level with a quad, but even when tuned "perfect" it will still drift slightly. I've had it tuned to where I got around an 'average' drift of a few cm/s. Usually however, you'll find the drift to be 10-50cm/s.

With a tri, it seems to be slightly worse. I don't blame the KK2. I believe it's the yaw and servo not re-centering perfectly. Don't get me wrong, it's not terrible, just not quite as good as a quad.
 

eekay

Junior Member
#6
By the sounds of it, my troubles are due to CoG, the one thing I didn't bother to check before maidening.

For the amount of headache Ive been having over this Tri, it seems it may be more in my interest to go Quad. Less reliance on precise movements (tilt mounts for yaw), and as a novice multirotor pilot I don't exactly need the crazy agility etc of the tri. These are things to save when the personal confidence and aptitude for multirotors are higher.

Learn by doing, and use lots of swears along the way.