hey guys , has this ever happed to you ? I have a slow pitch ossoliation front to back of about once every 2 seconds , and its fairly severe say +,- 5 degrees. it acts like a rocking chair , and I don't know whats causeing it. the behavior started after a fairly severe crash , tho I have replaces all the damaged parts I am aware of. there is no side to side ( roll ) or yaw cycles , and the heli is fairly controable other wise but its obviously far from stable . the blade tracking seems good , it may not be perfect but its close , hard to tell with the black blades . swash plate is level . and the run out on the main gear , shaft and fly bar all seem ok. my current suspects , are fly bar paddles , ( one got a bit chewed up on the crash but its not real bad , just a bit rough on the leading edge ) or perhaps the adjustable links from fly bar to blades , maybe I am a turn wrong from where they are soposed to be ? the blade pitch seems identical between the two but maybe one is a half turn from the other or somthing ?
other than that I am at a loss for what might be wrong , any ideas ? as always thanks in advance .


note to self , maybe scale would be more rewarding than 3d , I think I would break fewer parts lol

Paddles can affect the way a helicopter handles, so that isn't a bad idea. The only thing I can think of right now is the servos. Pop the links off the outer swashplate and move the right stick. I had one bad servo once and with the links on they all seemed fine, but once I took them off I could easily see one servo was bad. And that bad one made it really hard to control the helicopter. The other two servos were taking all the loads and the one servo wasn't helping. I have had the tracking off before and it never made the helicopter pitch. It just sounded bad and used a lot of energy. Good luck finding the problem.

I have been in the same boat going back from 3D to scale to 3D and so on. It seems I always go back to 3D. Mine isn't hard core 3D more of a mild one.

Nick

servo's check out fine , full range and rate of motion on all 3 , and no obvious damage to cases or workings , servo noise seems to be the same , no grinding or rough spots or delay . also , ran it up to just below take of rpm and I can see the movement even on the ground. its a fairly slow rate pulse forward then backward on the nose to tail axis . not seeing any movemnt in the servos but it must be somthing , seems too slow to be rotors or really any of the rotateing parts , but maybe its some sort of harmoic. this one has me stumped. I wonder if I might have a loose bearing or somthing some place , main shaft , or perhaps in one of the blade grips? somthing small thats translateing to a large movement eventualy? or maybe I just damaged part of the 3 in 1 or somthing. its so slow compared to the vibrations I am used to tracking down. in a way its almost creapy , its like the heli is posesed by an old lady rocking on the front porch. what is really strange is it dosen't seem to effect the hover much , I dont have to counter on the sticks to keep it in place , its like it self corrects , or rather self over corrects , just a perfect rocking motion in the air more or less in one spot with normal control inputs to keep in in a hover.

I don't have any more ideas, since I never experienced anything like that before.

Nick

Have you checked the spindle?

Take a 2X4 and put it through the skids to firmly anchor the bird to the ground. Take the canopy off. Spin it up. Look closely at the servos to see if anything is moving with out input from the transmitter. Try moving the sticks and try and observe the servos. See if the movement moves and matches and holds the stick input. I think this will narrow it down and at least eliminate the servo or transmitter/receiver possibility. May want to try this with the main blades removed as well. Just my 2 cents worth. (3D) the multiplication factor you use in determining the money you will need to replace broken parts. hAhA

well the post is long over due , but basicly it turned out to be a combination of a not perfectly centered flybar , must have miss read the ruler twice , and a slightly bent main shaft. the flybar was off by around 1/32 maybe a bit more
and I think the long arm caused most of the rocking motion
any way thanks again for all of the advice on things to check .