I'm planning on testing the over-gain theory this week - and just rebuilt the head in case I missed something last build. Unfortunately - I chipped the tail blade in the rocks a little after this video trying to get some last minute testing at night. New tail blades just came in - and I'm looking forward to finding the culprit.
Good luck on your next test. I know how frustrating these little things are to solve, but just think you'll be "pioneering" this for the rest of the rc heli youtube community. We're rooting for you. Keep on flying.
@scm6079 If the grey dampers did the job that means sudden movements got masked. I suggest you to clamp the heli to a workbench put it at hovering throttle and look carefully if there is an inexpected servo movment (please be very very careful with the blades), try the same thing without the main blades. If such a sudden movement exists maybe the problem is the receiver who sends random bursts. You can get a $7 6 channel receiver at HK a clone of the AR6110e and try it just for the trial.
I never have figured out what the source of the bob was, but here's what I've found. 1) It's NOT headspeed. I even tried over-revving the head to 3000+ -- and other than being scary fast in the bob, there was no elimination of it. 2) The tail sensitivity DOES impact it. 3) Loosening the tail shaft gearing helped reduce the bob significantly. After a couple full rebuilds and not getting it completely eliminated, I went to the grey dampers in the head, which does fully eliminate/mask it.
Hey SCM, Here is an example of real tail bob phenomenon search: "problema trex500". You can hear the headspeed drop at about 0:37. Then see the mild up/down tail movement. It's smooth. Not choppy. Don't let anyone waste your time chasing tailbobs.
Im pretty sure its the link arms that seems to be fastened on the far end of your servo, is this correct? This could give mechanical vibrations like this(the plastic is bending). You can clearly see it in the 0:24 frame. It should also not be bent like yours is, it should be straight down. However this is a long time ago, have you sorted out your problem?
I'm not sure who marked your comment as spam - probably someone who didn't read your comment on the first video. With a 6s battery at 100% I still got the bob- I can up the pinion - but I'm afraid of going too high a head speed and over-stressing parts.
Hey SCM...try different throttle % settings 95, 90, 80...etc. Or if you like to keep 100%ESC...try different pinions(pain in the neck to do). Besides the actual cause of the vibration the rpm can be controlled to avoid. Ofcourse, it's not a permanent solution. The rpm always goes down as you battery drains. I'm guessing there has to be a loose part or something.
This has little or nothing to do with a mechanical/gyro issue with the tail itself. Your "tail bob" is more likely a symptom caused by fast twitches in the cyclic, which suggests that something is wrong in the head setup, a link is hosed, or the servos are jittery.
Hey Scm, That's not your "traditional low headspeed/battery low" tailbob problem. I have a lot of experience with tailbob, because I run 5 cells and I am "powerstingy" with my Trex500. It looks more like a gyro problem(overgain) exacerbated by a vibration issue. Did you overtighten the main and tail blades? It should be "moveable" with slight hand force. Not rock tight. That's all I can think about at the moment. Here's me (search: "white trex500 inverted"). Good luck...
The more I watch your video. The more it looks less like gyro problem. Gyro is mainly side-side action. It almost looks like your swash servo's are "twitching" in the fwd/aft direction. Take a look in that area. I hope you're not using fm radio. Check the wire(esc to receiver) and receiver placement. Possibly, moving will have an effect.
