I see arducopter has two possible tri-copter options; which is best? And what does it mean when the second option "doesnt need a code change"?

It's for a small 300mm foldable - the HK trifecta to be specific.

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Very nice and clean build, Euan. Way better than my RCExplorer tricopter (retired 2 years ago).

If all of your props are spinning in the same direction, your Tri will have a constant roll offset (because the tailrotor is constantly deflected to compensate for the additional torque).
Some people find this annoying. This is what happend to my tri, otherwise, it flies just fine :D.
Let us know how your maiden went.

Hi Euan, I have flown both configurations, both fly well. When using all the same direction props the tails servo just sits off to one side a touch in hover, and forward flight, to counter the torque and if your servo travel is limited you may find that you hit the stops on one side faster than the other, allowing a slightly faster yaw in one direction. You can over come this by playing with position of the tail servo.

I have to say though, the opposite rotating props on the front and straighter tail servo (in hover) just look cooler.

I usually start like this, until I run out of CCW props, then I just use all CW and twist the tail servo a bit with my hand.

And nothing flies quite like a tricopter :)

Euan - how did you go with you Trifecta? I am halfway through a build on one of these at the moment and am keen to know about your experience.

Not that great if I'm honest.

I had to decouple pitch and roll and tune them seperately. I can get a stable D rate of 0.003, which seems to be the most APM can cope with at this form factor (I have the same in a mini hex and a quad). I am still experimenting with PI rates; I can get it to "full sticks", but it's a long way from being "locked in".

Pitch seems to be the main issue; in high speed turns it wallows a lot. Straight ahead, not so bad, but throw in some roll, and it starts to oscillate on pitch.

Hi Euan,

Thanks for your update. It is a shame to hear that you have had limited success. It seems you are not the only one though, as it appears that APM powered trifectas are somewhat difficult to get right. I am not actually aware of anyone who has achieved a well tuned setup to date.

My trifecta build is now on hold unfortunately. It appears that two mini APM V3.1s I purchased a while back have manufacturing faults relating to incorrect diode selection. The problem resulting from this issue is a full 1VDC drop between my power module and reciever, which is no good at all. I am awaiting a response from the supplier at this point in time.


Having gone to some trouble fitting everything including a cut down power module into the limited internal space available in the Trifecta I am quite keen to persevere with using an APM on this frame, but may perhaps end up grabbing a Naze32 to get this cool little frame in the air.

I finally repaired the diode issue with my Mini APM V3.1s (Purchased from RTFQuads) and finished setting up my little trifecta.

To be honest I am pretty happy with the results so far.

I started with some basic tuning in the living room that provided reasonably good flight characteristics (just a little wag and wobble).  I did my first autotune flight today and got a pretty nice tune first go!  There is still a little waggle in the tail, but it otherwise feels just as solid as any of my other multis.

BTW - Perhaps your choice of prop is limiting the quality of the tune you can achieve. NOTE - I initially assembled with 7x4 HQ props but it was oscillating all over the place and quite a bit over powered with those props, so I switched to 6x3 Gemfans.  Notably, the osilations reduced dramatically when switching to the smaller and more flexible Gemfans (without any change to the PIDs - which I don't quite understand).  I will be interested to see whether the oscillation return when I switch back to the 7x4 HQs (and will report back in case you are interested).

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Can you share the PID settings that is used on APM. I havent done my maiden yet due to this. Do you have any approved PID settings for trifecta?

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