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Tricopter woes... cant get it to be stable.

stevec

Junior Member
#1
Hi Chaps,

long time lurker first time poster so go easy;)

I am a tricopter newbie I fly RC planes, and mainly single rotor helicopters. not expert but I am working on inverted piro circles in the sim and inverted circuits in real life so I'm not a newb at helis...

my first tricopter build is complete and I have the following gear on it.

HK KK board v2.1
HK red brick esc
Turnigy donkey st 3508 730 kv
10x6 props.

I flashed the kk board with the KapteinKuk tricopter firmware.

The tricopter lifts off around half throttle but it is incredibly hard to control.

super sensivitve and just plain horrible to fly.

My first attempt at a circuit ended badly.

I thought I'd have a play with the gains because it sounds like not enough gain on the controller, but when I wound the gains up I just saw loads of oscillations.

From reading about it they fly like a coaxial heli, which I must admit I don't like the feel of, but then being used to collective pitch control we all dislike the woolyness that comes with a fp heli.

how do you guys tune your kk equipped quads? unless it is supposed to fly like this but if it does then the people flying them in the videos must be RC gods!
thinking about getting another motor and esc and calling it a quad, but I like the way the tri's fly in the videos, much more helicopter like.

it could be down to me using rock bottom components in the build,
I think it may be the Red brick ESC's like a low gain on the KK board, but this takes away the stability..
but I didn't want to have to invest too much into this thing as my Helicopters cost me enough...
many thanks
Steve
 

glydr

How many letters do we ge
#3
Hi Steve,

I tend to agree with you; I think the ESCs are the issue(s) on the tri. A cheap ESC can't keep up with the signal update rate from the KK board. I discovered this with some cheap 10A ESCs on my quad (whole saga in this build thread: http://forum.flitetest.com/showthread.php?1337-HK-Super-Mini-Quadcopter_-Build-Log

The ESC problem showed itself as a high oscillation similar to what you describe! The solution was to buy (another!) four ESCs, this time TGY Plush.

Some people have managed to reflash ESCs (see here: http://www.rcgroups.com/forums/showthread.php?t=1513678) but it seems the redbrick ESCs aren't on that list.

As for KK 2.1 settings - I've got that board on my quad and found that the midpoint settings were a good start. A bit of fiddling has it more optimum but the pots aren't too far from half-way.

I've a tri that I've recently got well tuned. It's running DT750 motors, Plush 18A ESCs (possibly a bit too close to current draw for comfort) and a KK2 LCD board (which I'm happy with!). Pretty much V2.5 by Windestal (RC Explorer). This tri is for gopro duty and I think it does pretty well:

http://www.youtube.com/watch?v=Qa0DDfWn1Qs&feature=player_embedded

As a fellow CP heli flyer, the Tri is a different beast to a CP, and even (I would say) to a FP. If there is any wind or gust you really miss neutral/ neg pitch so these things are fair-weather flyers (for me at least).

I hope I've pointed you in the right direction and inspired you to keep at it.

Cheers,

G
 

stevec

Junior Member
#4
Thanks guys, I'll look into other esc's and in the meantime I'll dial in a bag full of expo...

so G, as you fly both which do you prefer for camera work? Quad or Tri?

Every time I have tried flying this thing it has been real windy as well. so maybe I'll wait for a calm day before the next flight.

Cheers
Steve
 

colorex

Rotor Riot!
Mentor
#5
so G, as you fly both which do you prefer for camera work? Quad or Tri?
The question isn't for me, but Shadow72 (Eric Monroe, FliteTest camera guy) has convinced me that having more motors means getting more stable footage (but also less flight time).

If you ask me, I don't like the whole yaw mech thing, so presented with the option I'd go with a quad.

I now wish I had built a quad instead of a tricopter...
 

stevec

Junior Member
#6
The great thing about this is I only have about £4 into the actual airframe so if I get fed up with it I can just buy 1 more esc and one motor and be good to go.

I will have a play with it but I think the ESC's I have may be better suited to a quad.

/Steve
 
#7
Did you set the throttle limit on all the ESCs (via the KK board by setting YAW to 0)? If not, do that before you try to dial in the gains.

Instructions here (about 3/4 down the page): http://rcexplorer.se/page14/kkguide/kkguide/tri.html

I am using the 30A RedBricks on mine, and it flies OK. I am going to put in some flash-able ESCs to get better stability, but as it is, I can get a pretty stable flight even with some wind (8-10mph).

The difference between crazy oscillations and completely unstable was about 1/16th of a turn on the gain pots for me. I adjusted the pitch and roll at the same rate, and left the yaw pot at 50% until I had the other two dialed in.
 
#8
I have the red brick 20amps on my quadcopter. It took some time to get the thing flying smooth. I had to reflash, and play with the gains untill I got it to where I have it now. The first time I flew mine, I felt the same as you explained. RC gods must be flying these d*** things.. but after some frustration, and almost giving up.. and tinkering more. I got it.
 
#9
Heh - I had exactly the same problem and it turned out to be the ESCs. A bit gutting really as you get it all nicely rigged only to have it fall into oscillations and drop out the sky.
 

stevec

Junior Member
#10
Did you set the throttle limit on all the ESCs (via the KK board by setting YAW to 0)? If not, do that before you try to dial in the gains.

Instructions here (about 3/4 down the page): http://rcexplorer.se/page14/kkguide/kkguide/tri.html

I am using the 30A RedBricks on mine, and it flies OK. I am going to put in some flash-able ESCs to get better stability, but as it is, I can get a pretty stable flight even with some wind (8-10mph).

The difference between crazy oscillations and completely unstable was about 1/16th of a turn on the gain pots for me. I adjusted the pitch and roll at the same rate, and left the yaw pot at 50% until I had the other two dialed in.
I used this guide to set it up. I definitely did do the throttle calibration with yaw pot turned to zero, I will hit it again just in case I didn't save it correctly.

is there any way to change these settings in a GUI? I am kind of used to flybarless controller set up through the GUI rather than tweaking pots. I will also add some expo and dual rates as I haven't done that yet... maybe it is just a case of turning down the limits but I am shocked if that is going to fix it it is like flying the worst untrimmed over responsive helicopter ever...

Glad I'm not the only one who has gone through this I was beginning to doubt the Tricopters.

Thanks again chaps.
Steve
 

glydr

How many letters do we ge
#11
so G, as you fly both which do you prefer for camera work? Quad or Tri?
My quad is a bit small for camera work - though I would like to build a camera quad. The tri is not level in hover (as I don't have CCW props) whereas a quad would be. The big win with the tri is that it really is transportable when folded (can't say the same for a quad!).

Afraid the KK board is sans GUI. For that (on a budget) you need MultiWii.