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Old Jun 10, 2012, 12:06 AM
I land in the trees
United States, OH, Bellefontaine
Joined Oct 2011
112 Posts
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Tricopter question: center of gravity

I successfully got my first tricopter up off the ground this evening. Definitely a fun moment. The flights usually only lasted about two or three seconds, and were never straight up in the air, but at least it was in the air (in between minutes of pot adjustments, trim adjustments, etc).

Tricopter - first flights (2 min 58 sec)


As you can see, it was a constant battle adjusting the pots and the trim. Besides all the tweaking between the KKboard and the radio, I think my next question involves the center of gravity. I'm sure it plays a part in getting a perfect hover, but where should it be? And if you have any additional advice on getting a proper, level, and straight hover, I'd appreciate it.

HK KKboard
FPVmanuals tricopter kit
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Old Jun 10, 2012, 12:38 AM
Registered User
Malaysia, Penang, George Town
Joined Jan 2012
66 Posts
CoG Tricopter

Hi,
The COG for a Tri should be at the center point where the 3 axis of the arms meet. Looks loke U R having fun, thats the way to go! If you are new to flying, the following might help:
Set all FC pots to 50 %
On your Tx set the following:
Throttle Curve: 0, 45, 60, 75, 90 ( really depends on your Power to Weight ratio, but that is a good start)
ALE and Elev DR: 80% Expo: 30%
Yaw DR: 100% Expo: 20%
You didnt say which firmware you are using but the above should get U hovering without being over sensitive.
Hope this help, enjoy flying.
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Old Jun 10, 2012, 06:39 AM
KK Tri Flyer
mattcro's Avatar
United Kingdom, Scotland, Glasgow
Joined Feb 2012
346 Posts
It looks like it's behaving pretty well. If you've never flown a RC heli before (don't count toy coaxial types) then it will take some practice just to get the hang of simple hovering. Keep the tail (with the servo) pointing towards you all the time to start with, otherwise you can quickly lose orientation and control.

You'll often need to give a little bit of cycle stick input just as the copter lifts off to get it flying level. Give some cyclic in the direction of the motor that lift off first, so that the tri levels out and takes off vertically.

If you've got it trimmed and balanced to the point where it will stay fairly level for a few seconds with little or no cyclic stick input then you are most of the way there - the rest is practice!
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Old Jun 10, 2012, 10:54 AM
I land in the trees
United States, OH, Bellefontaine
Joined Oct 2011
112 Posts
I'm using the 1.6 firmware on the board.

OK, just a couple questions as I slowly try to wake up this morning:
I think I can assume that the pots on the control board and the trim on my radio go hand in hand. So when it comes to flight corrections, should I just set the pots to 50% and only do my adjustments with the trim? Is one or the other more important to get a reasonably stable flight?

I will have to play around more with those D/R and expo settings that Edd gave. They look fairly similar to other folks' setups for flying tri's.

And after reading Matt's reply, I'll admit that I feel slightly foolish I didn't go ahead and compensate manually for all those uneven take-offs. I really was putting too much reliance on the tricopter balancing itself as it tried to get off the ground. Lesson definitely learned.

So, a little breakfast, and then we'll give this another shot.
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Old Jun 10, 2012, 11:16 AM
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Movie Guy's Avatar
Delta, BC, Canada
Joined Apr 2004
254 Posts
From the video, your tri looks pretty stable. I found at first if I did not get mine off the ground and out of the prop wash it would act weird and unstable. One motor would want it to begin to flip. If I give it enough to get it 3-4' in the air (that is @ 1m in metric) it will have a chance to let the gyros do their thing. Doing this in your open grassy area is the best spot at first. Does not hurt to practice on the sim either with a multi model if you have it or a CP or FP heli if you don't. Looking good, Baz!
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Old Jun 10, 2012, 11:16 AM
CD-ROM Junkie
Art Newland's Avatar
United States, WA, Bellingham
Joined Apr 2001
13,976 Posts
Looks like a cool place to fly.

It's pretty tough to know what the copter needs, trim wise, until you get up out of ground effect. 3 or 4 feet off the ground, it will be more stable. Also it's best to come off the ground quickly, I generally spool up the motors till just before liftoff, then give it a good punch of throttle to get airborne.
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Old Jun 10, 2012, 11:20 AM
I land in the trees
United States, OH, Bellefontaine
Joined Oct 2011
112 Posts
Quote:
Originally Posted by Movie Guy View Post
From the video, your tri looks pretty stable. I found at first if I did not get mine off the ground and out of the prop wash it would act weird and unstable. One motor would want it to begin to flip. If I give it enough to get it 3-4' in the air (that is @ 1m in metric) it will have a chance to let the gyros do their thing. Doing this in your open grassy area is the best spot at first. Does not hurt to practice on the sim either with a multi model if you have it or a CP or FP heli if you don't. Looking good, Baz!
Yeah, I have spent a pretty good amount of time training on the simulator in both heli and plane. When you're waiting for China to ship all your junk to you, you seem to have all the time in the world for training.
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Old Jun 10, 2012, 11:26 AM
I land in the trees
United States, OH, Bellefontaine
Joined Oct 2011
112 Posts
Quote:
Originally Posted by Art Newland View Post
Looks like a cool place to fly.

It's pretty tough to know what the copter needs, trim wise, until you get up out of ground effect. 3 or 4 feet off the ground, it will be more stable. Also it's best to come off the ground quickly, I generally spool up the motors till just before liftoff, then give it a good punch of throttle to get airborne.
This is my parent's place. I'll have 50 acres of farmland and wooded areas to play in once I get the hang of this. My house has a decent backyard, but I figured sticking with wide open places would be better.

As far as taking off, I think I better stick with slow take-offs first. Need to get my reaction times down before I just rip the throttle loose.
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Old Jun 10, 2012, 11:27 AM
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Movie Guy's Avatar
Delta, BC, Canada
Joined Apr 2004
254 Posts
I am using 1.6 on mine as well. The other thing to watch out for is wind. Try to practice in calm or almost windless conditions. The KK board does not seem to react to wind all that well as it has no accelerometers or high end electronics. Or maybe it is me that does not react all that well ; ) The simplicity and price are hard to beat though.
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Old Jun 10, 2012, 11:59 AM
Registered User
United States, MA, Swansea
Joined Oct 2009
195 Posts
I'll second that it does not like wind much. Mine like to turn when its in the wind. It's still flyable but it requires more stick control.

If you cannot trim out the rotation you will have to reposition your yaw motor on the servo, otherwise it looks like it's flying great. Practice practice practice!
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Old Jun 10, 2012, 02:01 PM
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Malaysia, Penang, George Town
Joined Jan 2012
66 Posts
Trimming for stable tri hover

@bazman,

The pot on the FC and the trim on the Tx are two different thing, on the Fc the pots are for Gyro Gain, whereas the Tx trims are for trimming out your Tx centering ( in simplier terms). Too high a gyro gain will cause the tri to oscillate, too low and the tri will be very sensitive to Tx stick movement. Two more things to lookout for:
1. Vibration - ensure proper vibration damping to the FC board, the gyros dont like vibrations at all. Balance out the props and the motors, search threat in rcgroups on how to do that.
2. Tight Tail - the mechanical setup for the tail assembly must be as sturdy as you can make it, any slop in the tail will be transfered to gyro and cause instability.
Sometimes you would need to reset the gyro : they set automatically when you arm the system, when arming, get the tri to sit as horizontally as possible, not on a sloping ground. You can force set the gyro by briefly max the throttle while the FC is disarmed.
Happy Flying
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Old Jun 10, 2012, 02:34 PM
I land in the trees
United States, OH, Bellefontaine
Joined Oct 2011
112 Posts
Well, I spent about 30 minutes with pretty good results getting it off the ground, but it's back to the workshop for a quick repair. Had a truly epic crash and broke two of the arms. Wish I had the camera running. I kept having a problem with it veering to the left once it got in the air, not to mention some oscillations (maybe with the front right motor). The last attempt had just a bit too much throttle. Got about 6 feet in the air, veered left, and crashed at an angle.
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Old Jun 11, 2012, 08:50 AM
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Malaysia, Penang, George Town
Joined Jan 2012
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Quote:
Originally Posted by bazman View Post
Well, I spent about 30 minutes with pretty good results getting it off the ground, but it's back to the workshop for a quick repair. Had a truly epic crash and broke two of the arms. Wish I had the camera running. I kept having a problem with it veering to the left once it got in the air, not to mention some oscillations (maybe with the front right motor). The last attempt had just a bit too much throttle. Got about 6 feet in the air, veered left, and crashed at an angle.
When you said veering to the left, do you mean it yaw to the left ( tail moving to the right) or roll to the left? If it yaw to the left, you might want to adjust the link from the servo to the motor to compensate the torque, if it roll to the left, sometimes because the left front motor is rotating cw, the adapter holding the prop down get loosen especially after slight nick on the prop or hard landing, check the prop tightening. In my last post I mention setting the tri horizontal when arming? The Gyro actual calibrate itself when throttle leaves zero, and you need the tri to be as level as possible. When attaching thr Fc to your tri, try to get that level too. Try and try again.
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Old Jun 11, 2012, 08:53 AM
I land in the trees
United States, OH, Bellefontaine
Joined Oct 2011
112 Posts
Quote:
Originally Posted by Eddfoo View Post
When you said veering to the left, do you mean it yaw to the left ( tail moving to the right) or roll to the left? If it yaw to the left, you might want to adjust the link from the servo to the motor to compensate the torque, if it roll to the left, sometimes because the left front motor is rotating cw, the adapter holding the prop down get loosen especially after slight nick on the prop or hard landing, check the prop tightening. In my last post I mention setting the tri horizontal when arming? The Gyro actual calibrate itself when throttle leaves zero, and you need the tri to be as level as possible. When attaching thr Fc to your tri, try to get that level too. Try and try again.
No, I discovered the problem. The gyros needed reversed. The moment I switched them, it was pretty smooth sailing. I started a new thread for my attempts here. So far so good, I think.
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