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Need Help With a Multirotor (Yaw issue, will not stop spinning)

#1
Hi,
thanks for viewing this post, hope you can help me! (first time ever making a post in a forum!)
I am new to rc flying, cant fly a plane or a heli yet decided my first build was going to be a tricopter after I found this web site and from here, davids rcexplorer.se. So now i have finished building and have crashed and rebuilt many times. I can keep the multirotor in the air now without a crash. What I can not figure out is how to stop the tricopter from rotating. I can use the yaw trim on the transmitter to get rid of most of the spin but not all of it before i reach the maximum trim setting. So when I am flying, i have to constantly counter some of the leftover rotation with the yaw stick. the tricopter is built exactly how david has done it in tricopter 2.5. From all my crashes, the booms are now slightly differnt lengths but i dont think that is an issue. (variation of no more then an inch)

So here are some possible solutions I can think of but dont know which one is correct or the best.

1. twist the motor mounts for the stationary motors to counter the rotation? doesnt sound right!

2. twist the mount for the yaw motor so at its center of pivot for the yaw mount, will counter the rotation.

3. adjust how the servo is connected to the yaw pivot mount. this seems like the most likely option.



4.maybe is something i have done wrong with the pot resitor setting on the yaw gyro? seems unlikely.

5. maybe my center of gravity needs to be moved?

once again thanks for your reply
PS, David, you rock!

Conrad
 

dezertdog

Senior Member
#3
If it's not a reversed yaw gyro due to running XX firmware (most of us run kapteinkuk v1.6), #3 is probable. With KK 1.6 use M4 for rudder.

On maiden, I had to adjust the length of my servo push rod controlling the yaw to be able to zero my rudder trim in flight. In the end I probably extended it about 6 turns to get it trimmed to zero. Just adjust it a few turns at a time with test flights in between until I got it to the point where no Tx trim is needed. As your batteries get low you might notice a yaw tendency too, but your goal should be no trim with a fresh batt.

Are your front two motors counter rotating? That will help some, but even then you've still got some torque issues from the rear and one of the front motors spinning together and so will always need some yaw trim. So bottom line, 1st trim via the the yaw control arm (extend or shorten, for my tri I needed there to be a slight clockwise bias looking down the rear boom from the back) and then if anything you should only need a couple clicks of Tx trim.
 
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