Tri HK X900 Tricopter won't fly

[Jerryz]

I'm having big problems with the rudder motor. I know that the rudder motor has to be canted a little to the right to compensate for torque. It seems that no matter which way I trim the rudder, when I throttle up, the torque rolls the motor to one side or the other. It almost seems like the servo cannot hold the motor in a given position. I was told to change the value for the rudder in the KK2 to -100. That made matters worse. Here is my checklist: 1. Motor 1 CW with CW prop. 2. motor 2 CCW with CCW prop. 3. motor 3 CW with CW prop. 4. Rudder servo plugged into motor4 port on KK2. Here is a video of what's happening.

 

[pvolcko]

I can't tell from the video, what direction is the rear prop turning?

I believe the rule is that if the motor/prop is being turned clockwise (looks like that is the direction, though it is hard to tell from the vid), it will be inducing the model to yaw left, which means you need the motor to cant in that direction to counter act the yaw. In the video it is canting right, which will act in favor of the yaw, not against it. Couple that with what looks like the gyro correction direction being to dial in even more right cant as it starts yawing left, and you get the spins.

Try a setting that cants the motor in the opposite direction for torque compensation and setting rudder/yaw gyro compensation in the opposite direction too. If you can not change either direction via settings, then try an opposite prop and change the motor direction and it should work as is (minus some gain adjustments).

And I may be totally backwards on all that. I'm very good and getting things like this reversed in my head.

If fact, you'd do well to ignore this post entirely.

 

[Jerryz]

Here is the root of my problem. First of all I watched the video from the guy at Hobby King. he had the same exact tricopter. I used his P,I,P limit and I limit settings. The KK2 board shows my rudder motor as CW with a CW prop. Well it is! Look at this video and you will see that without any input, the rudder motor rolls to the right. It does not center. If I trim to get it centered, then it rolls left. The rudder motor seems to be reacting to the torque of the motor.

 

[pvolcko]

I'd expect this tilt direction for correction on a CCW prop setup. The amount of correction shown here would only be if all of the props on the tricopter were CCW. Each prop would be inducing right yaw, so the tail would have to have a pretty steep angle to the right to counter it all. It would tilt the same right direction for an opposing pair on the front and a CCW on the back, but just a much smaller amount.

From the prior video it looked like you have opposing directions on the front and you say a CW on the back. To this correction amount should be very small and it should be in the other direction. It is possible the servo you are using is goofy footed compared to what the controller expects. In the mixer editor select the channel the *servo* is on (4), then change the "rudder" setting from +100 to -100. This should change the correction direction.

You mentioned that you did something like that already and it didn't work. In what way didn't it work? Did it piro faster/earlier in the take off? did you change the rudder setting on the ESC channel or the servo channel?

Maybe post up your mixer settings so we can see if something jumps out as wrong for this configuration?

 

[Jerryz]

Hi pvolko "Paul" thank you for your input. I have every top RC mind helping me with this including you and Hobby King. I made some changes that I did not know about. My rudder servo is digital, so I changed the rate to high. Someone told me that although the KK2 says that the rudder motor should be CW, I should change it to CCW, and I put on a CCW prop. I changed the value from +100 to -100. STILL won't fly. No matter what I do, when I throttle up, the rudder motor rolls to the right about 45 degress and spins the copter. So I trimmed it so it would cant to the left a little. Still rolls over and spins the copter. I have built three quads with no issues. I have never been this stumped before.

 

[Stambo]

I had a yaw problem on a quad with a KK2 once, no matter what I did I could not cure it.
This is what I did.
Start again, I think there is a selection for reset to default setting on KK2 then reload the tri model.
Unplug everything and restart from scratch as though it has never flown.
New model on your TX, and go through all the setup stuff again.

 

[Jerryz]

Stambo...THAT is an excellent idea. I was thinking of breaking it down and move on to something else. You are a genius and a credit to the hobby. Thanks Bud.

 

[Jerryz]

This is ridiculous. I started over as you suggested. NOW I forgot something simple like arming the board. It won't arm.

 

[Stambo]

Make sure your rudder control is not reversed. (See if it arms down left.)
Check in the receiver test screen on KK2.
Check same screen for throttle zero.
If KK2 does not see zero throttle it will not arm.
Also, you should not use trim in the radio, it will confuse the KK2.
Use subtrim to zero rudder, aileron and elevator.

Do you use autolevel on the KK2?

 

[Jerryz]

Well I haven't had the opportunity to use auto level. But I do have it mapped to my Aux channel. I guess I shouldn't have trimmed with my radio. I believe its my lack of understanding of the numeric values. I will work on your suggestions in the morning. My brain hurts from this copter. Lol.

 

[Stambo]

Here is a good vid for tri setup.

Building the Simple T Copter from www.simplecopter.com - YouTube

 

[Jerryz]

Thanks for all your help Stambo. The light bulb in my head went on, and I remembered that the KK2 won't arm unless the ACC is calibrated. I assume that's because the board has not yet established what level is. I have put way to much time in this, but I am focused on getting this SOB flying. I am working on your suggestion to start from scratch. I will keep you posted.

 

[Jerryz]

Ok...there are a lot of great people and RC'rs, Youtube people out there that gave me wonderful and sound advice. I have spent four days trouble shooting this copter. IT JUST WONT FLY. Here is a video after I made all the changes.

 

[Stambo]

is the KK2 solid or foam mounted?

How about some close up pics or video of how the servo is mounted showing linkage, arm etc.
How much slop, if any.
What happens to the servo if you yaw right and left with the tx, from behind it should lean opposite to stick.
Also, video of holding on to it with motors (slowly, keeping hands clear of props) running and what happens to servo if you rotate left or right.
I think the yaw gyro may need to be reversed but this will confirm it.

If you are anything like me, being beaten by a bunch of wires, metal and plastic is not an option.

 

[Jerryz]

Mr. Stambo..thank you for your interest. I can't help but feeling that my time could be better spent like getting a root canal without Novocaine. Somebody already suggested hold the copter in the air. Strangely enough, the motors do respond correctly to movement. The KK2 is in a plastic case sitting on foam. Why do I have a bad feeling that I either have a defective KK2 or a bad servo. Thanks to you and many other terrific RCr's, I have tried everything else. I mean It's so simple really. I mean it's rudder to rudder, elevator to elevator, positive wire to positive wire and so on. It almost can't go wrong. I built a 450 quad. Flew as pretty as you please with no trouble shooting.

- - - Updated - - -

Look at my video again. Pay careful attention to the rudder motor. As soon as I throttle up, it rolls hard right.

 

[Stambo]

I have read of KK2s doing strange things while on the ground but behaving as soon as they get in the air.
I suspect a reversed yaw gyro, thats why I suggested the hold and rotate.
When you rotate clockwise the motor should tilt right, when you rotate counter clockwise it should tilt left.

You could try plugging your servo directly into the rudder channel on your receiver, that would remove the KK2 from the yaw equation.
Obviously this would be just to see if everything else works.

I know it can be a bit frustrating when things don't go according to plan but imagine the satisfaction and knowledge you will have gained when it finally flies.

I hate to see someone give up, if you have to, just put it aside and come back to it at a later date.

When my friend set up his tri on a KK2 he had no trouble at all apart from having to dial the gains.

I think I am am going to build a Tri with my leftover KK2.
I am pretty sure I have some ESCs and motors.
I am curious to see whether I can replicate the issue you are having.