Tail wag hovering (vbar settings attached).

[bleomycin]

I had my first flight today and things went well, however i have a bad tail wag at 2300 RPM that i wasn't able to get rid of with just settings on my DX8 at the field (things are fine at 2100 RPM). I'm using the vbar governor which seems to be working after double checking with my tach. I'm not really sure where to start looking for problems, I've attached some screenshots of my settings. Thanks for nay help!

Specs:
Vbar silverline
Tail servo: bls256hv
cyclic: bls255hv
hobbywing sensor for governor
castle ice 120 esc
cc bec pro
Rail 556 Main Blades
Rail 96mm Tail Blades

[Matt Botos]

bleomycin,

Make sure your tail control system can operate freely. The wag you are speaking of is usually because the links were not sized and the servo is fighting against very tight ball links.

To check, disconnect your tail servo pivot ball link and attempt to move the rod by hand. If it is not effortless, you need to go back and size each link including the tail pitch slider links.

To size the links you will need a ball link sizer that sizes 5.5mm balls. I recommend the Boto-sizer.

700-001 Boto Sizer Ball Link Sizing Tool

Thanks,

Matt

[bleomycin]

Hi Matt,

Thank you for the help, i do have the boto sizer and sized all of the links on the cyclic side, but wasn't sure if the tail linkage and pitch slider links needed it so i had not done those. I just sized them and they move much more freely, i'll take it out tomorrow and see if the problem persists.

[bleomycin]

I went out for 2 more flights today, unfortunately the tail wag is still there (very fast wag only moving a few degrees), if i turn the tail gain way, way down the wag becomes less intense but i haven't been able to get rid of it. The vbar logs are not showing any vibration warnings. It seems perfectly fine at 2100 and 2200rpm with the settings listed in the first post, but 2300 rpm causes problems. Is anyone else with a vbar running similar head speed running the stock P and I values for tail?

[flyalan]

You might want to review this thread on Helifreak.  It is well done and covers some issues and the resolution.
http://www.helifreak.com/showthread.php?t=297657


Alan Butler
Team Synergy

[bleomycin]

Thanks flyalan, yeah i've been reading that. I'm going to take it out now with a lower P gain and see if that helps at all. Waiting for my bluetooth module to come so making changes will be easier.

[RichL]

Check to make sure your thrust bearings are not backward in the tail blade grips.

Rich

[bleomycin]

Hi RichL,

I'm mostly sure they're in the correct way, i used a digital caliper to measure them before installing, and i posted this thread/video double checking http://synergyrchelicopters.com/forum/index.php?topic=1400.0

I'm going to make some bigger vbar changes tomorrow, if the problem still persists i'll pull the tail grips apart to double check, my memory isn't so great and its always possible i made an error.

[bleomycin]

I just pulled the tail grips apart and verified i did install the bearings correctly the first time, so that can be ruled out. Would have been nice if that was the problem though, easy fix.

[Matt Botos]

- Take your main blades and tail blades off the helicopter.
- Spool the helicopter on the bench with your laptop attached to the vbar
- Look at your vbar spectrum analyzer to see if you are getting a spike at 9000-9200.

If your wag is based on RPM then its very likely you have a vibration.

The most common mistake I've seen related to the tail assembly is people using CA to glue the TT bearings into place but not getting them straight on the TT. This will cause a severe vibration.

Thanks,

Matt

[bleomycin]

I'm beginning to think my servo may be at fault. Its a BLS256HV, there is a tough section of the servo throw that i find impossible to turn smoothly through by hand (not notchy, just far more resistance), my BLS255HV's are all consistently smooth throughout their throws. I opened it up and none of the gears are stripped, but 2 of them definitely have a section that tightens up when turned by hand, putting the case back together worsens it. I don't imagine this is normal? My tail wag is not consistent at all, at times its completely gone, then slowly crepes back and worsens with time, as if it over-corrects then struggles, this is all just hovering with a few quick turns and throttle punches turn in.