Vbar help

[hanson]

Any vbar experts that could take a look at this? as this has really got me stumped.

I've recently changed to vbar on my align trex 500 dfc, the heli was flying great to start with, however I am now experiencing tail issues. The tail on occasion seems to stop responding or blow out and then come back. It's most apparent during piro wall of death style moves where the tail will hesitate then stop, also the tail seems to get a bit wippy on occasion. I've seen these sort of blow outs before on other helis and a better servo has usually fixed it.

heres what I've tried so far:

2 new tail servos (mks and futaba)
different v bar
changes to tail gain servo arm length
different tail gearbox
different torque tube
different main hub

each time I think I've sorted it, a couple of flights later it's there.

theres nothing out of the ordinary in the log except so e raised/high and extreme vibration warnings

is it possible the vibration is causing it? Has anybody seen this before?

thanks,

rich

[rich-6]

I'm a recent convert too, I've got a slow wag I'm trying to iron out.

Vibes do affect the sensors, have you spun it up without blades and checked the spektrum analyzer to make sure there's nothing out of the ordinary? I had to pull a set of tail blades off mine as they were affecting it!

Also If you're flying 3d I'd expect raised vibrations, I get raised and high just sport flying.

Another thing to check may be the thrust bearings in the tail?

[philipjdall]

Sounds to me like your I gain is too low. Try raising it incrementally.

Fyi you will need the pro software to make changes to expert parameters.

[philipjdall]

It's probably worth adding that the I gain is your AVCS (or heading hold gain). The p gain is proportional, which is used to tweak stops.

If the I gain is too low the heli will piro inconsistently (whipping) as at times its trying to hold position then at others not. This, combined with the tail letting go, are clear indicators that your I gain is the culprit. Try raising and then going into a full pitch backwards loop. Ideally it should hold right the way through

[waveydavey]

Guys it might be worth letting you know that Rich isn't a noob, he's an incredibly talented pilot that has been flying for years, doesn't post here often and thats our loss as he's got a lot to offer the forum.

Rich some good advice above, if you're still struggling pop up the club you know Mr VBar will sort it for you. Be nice to see you

[philipjdall]

I'd assumed not since he mentioned piro wall of death manoeuvres!

[hanson]

Thanks guys,

I've gone up on the gain until it was too high (violent wag) , I've also swapped out the tail box, so i know it's not thrust races.

thanks dave, I've moved the sensor to the lower mount to see if that makes a difference. It feels a bit cheeky to pop up mk to try and sort out an issue like this. I did pop up in the summer to say hello on a sunny afternoon but nobody was around.

thanks

rich

[waveydavey]

Not cheeky at all mate, come up be good to see you

[philipjdall]

I've gone up on the gain until it was too high (violent wag)

Just to check, have you raised overall tail gain or just the I-gain parameter?


tail.jpg

[Guest]

Phil's Right change the I gain, as a starting point I find set P and I to 75 works a treat (usually).

MJ

[anjki]

Hi Rich, hope your well mate.
you say the model was fine, and this has started to happen recently? My first thing to try would have been tail servo followed by checking power to servo (Bec output)
If this all checks out ok and you've got no binding etc it's time to check headspeed, this will tell us if you have enough tail authority.
ive experienced this type of inconsistency on v bar and it's normally a combination of the above, but we no you no your stuff so,if you could post your v bar parameters I may be able to point you in right direction.
Interested in Set up values to right and left,followed by all your P I gains etc.

cant prommise, but v bar tail is normally sortable.

[anjki]

Sorry maj
posted at same time :-)

[hanson]

Just to check, have you raised overall tail gain or just the I-gain parameter?


[ATTACH=CONFIG]78404[/ATTACH]

Just at overall gain so far, I will give this a try next

[hanson]

Hi Rich, hope your well mate.
you say the model was fine, and this has started to happen recently? My first thing to try would have been tail servo followed by checking power to servo (Bec output)
If this all checks out ok and you've got no binding etc it's time to check headspeed, this will tell us if you have enough tail authority.
ive experienced this type of inconsistency on v bar and it's normally a combination of the above, but we no you no your stuff so,if you could post your v bar parameters I may be able to point you in right direction.
Interested in Set up values to right and left,followed by all your P I gains etc.

cant prommise, but v bar tail is normally sortable.

hi Andy, thanks for the post. The model was flying great and was taking everything I could throw at it, then it just started to have these tail issues. I've changed the tail servo twice. I've also swapped the esc, using a koby, the second koby sounded like it gave a higher headspeed although I didn't tach it, but it still had the issue, both running a small buffer pack. I do have a crazy amount of slop from the swash and servos but cyclic wise it flys ok, so can't see it being this.

i'll post the file but won't be till later tonight,

thanks again for your help

[anjki]

Hi rich

both main tail gain and p gain look low to me, but that will depend on your left and right travel values. Post them l8er mate, but I have a feeling you may be able to reduce legnth of servo arm, giving us more available p and main gain to play with.

The thing that is still not sounding right is that it was good before, sounds as if something has changed.
Anyway, let's see them set up values first and also confirm you are getting full travel on slider at tail output shaft before we look any further.

Andy