I've got the Spirit on a Goblin 420 and completed the entire setup (double-checked). Running without blades I get a random cyclic twitch, usually very tiny and all 3 servos, sometimes only 1 cyclic servo. The twitch happens very quickly and returns the cyclic to where it was. Only happens while motor is running (never just sitting still on the bench) both during and without input from the tx for cyclic control. I'm reluctant to install blades until this is figured out.

Don't have youtube so here is a link to video if someone wants to see/help.
https://www.dropbox.com/s/mgaz8vq0ej130 ... 0.MOV?dl=0

Note: the camera is not steady from me on my belly trying to one hand the phone - but I never touched the sticks. All of the random twitches are visible like tiny pitch pumps.

Tried vibration analysis and the tail can get to 90 on Z but no warning messages for vibes in the log. Of course, the cyclic doesn't twitch during analysis since the servos are locked.
Tried Pitch Up compensation of 0, 2 and 4 - no difference.
Signal Processing (extended) - checked and unchecked - no difference
Lubed the tail belt with silicone - no improvement.

Pitch range / Cyclic ring tuning - 11 degrees +- / 124 (-8)
3M taped fbl directly to main aluminum plate (not on support plastic piece)
Full rx / futaba / trims turned off

Any troubleshooting help is appreciated. I couldn't find similar symptoms in the forums.

Hello,

unfortunately this issue is very likely caused by static discharges or noise they are picking up from the ESC.
So I recommend to ground the boom and/or make sure the belt is tight enough.

Indeed the problem must be solved prior the flying, it will be happening also during flight and cause a random twitches/oscillations.

_________________
Spirit System developer

thanks for the quick reply
I'll let you know how I make out
Paul

Looks good, I tested it twice on all 3 head-speeds and I think the problem is solved.
I read up on static discharge (my first encounter in 6+ years flying) and took the all of the above approach to fixing the problem.

Removed tail boom and sanded paint/primer away in a 1" x 1" area around the break-away nylon bolt. Added conductive adhesive copper tape to sanded area.

Connected a ground wire starting at:
1 motor mount counter sunk screw
to main shaft support hex head
to top of tail pulley tension arm (used longer hex head as thru-bolt and added nut on top of pulley wheel spring arm to clamp ground wire/washer)
to aluminum main plate next to fbl unit
to aluminum tail case (long wire running under boom).

Thanks again,
Paul

Well done, thank you for all the details!

_________________
Spirit System developer