Trim changing

[furyevo]

Ok, now that I got all the other issues sorted out, I have one I'm stuck on. Evo 90, 9252 servos, Radix 710 blades, Quick UK swash. The trim will change as I fly it. I hover and trim it out, then fly for a bit. When I bring it back to a hover, the trim is really off, either left to right or front to back. I have checked the servos, they seem good, everything seems tight. What else could do this?

[mudbogger2]

are you by chance flying in the wind? I have seen people complain about this and ends up being wind direction changing in flight making it seem out of trim a little.

If thats not it
everything seems tight
Make sure nothing is too tight and causing binding like link ends being too tight.

[ErichF]

If you are sensitive to the trim of your machine, fuel burn will make a difference in pitch trim, even on an Evo.

As Jon said, wind affects the Hirobo teetering heads in such as way as to cause a rolling or pitching moment 90 degrees to the wind. It's a product of the positive, or "correcting" Delta on the Evo head, when built as instructed. While correcting Delta is desirable for 3D, it can make hovering precisely a bear in the wind.

As a result, I have modified my Evo head to uncorrecting Delta by swapping the mixing levers to the other side of the carrier (opposite the grip), and added a 20mm spacer to the pitch arm. See my gallery for detail pics. With this mod, the heli sits much better in winds, and tracks even better in fast forward flight. Keep in mind, my goal is precision, FAI style flying. While this setup will 3D well, it won't be aggressive for hard 3-D style.

Explore the possibilities built into the Evo head...you can adjust it quite a bit, if you use your head (pun intended, bad I know).


Cheers,
Erich

[Ivan]

sounds like you need ot ream your ball links to me. If they bind it will cause trim changes from the servos fighting to find center and on digitals cause excessive battery drain.

I know it is an elementry suggestion, but sometimes we miss the small stuff. :mrgreen:

Also, I had a similar challenge on my Vigor, and found the head clamping bolt, which tightens the head to the mainshaft was loose allowing the head to rock on teh shaft. This caused severe trim problems, and would bring about tracking problems as well.