View Full Version : V-Bar tail not holding!! Frustrating!
Rigalo
08-25-2007, 11:27 AM
I still have problems with my tail on L14.
Symptoms:
Tail creeps on bench after , and it creeps slowly around in flight.
Tried on 35 up to 70 gain just before it hunts in hover.
Servo: S9256
HS around 2100
I'm starting to think I have a defective gyro sensor. Has anybody experienced the same, have a solution, or does your's just plug and play perfect the first time?
Feedback appreciated!
Finless
08-25-2007, 11:30 AM
what gyro? I assume it is a 611 based on the servo your using? if when you move the stick and stop the tail then slowly moves to one end then it sounds like your not in HH mode?
Bob
vbar has a built in tail gyro Bob. I don't think the vbar has a rate mode either.
BobbySmith
08-25-2007, 05:29 PM
THat 9650 isnt fast enough try a 9254 and that should solve youre issues
read again bobby, 9256, faster then the 9254. even better, run a 8900G, faster than all of them!
have you trimmed the tail mechanically? if its drifting to the left, mechanically adjust to the right, and visa versa. only when its spot on, do you adjust the trim if need be on the computer, NOT on your TX.
I have my gain at 60% ish i think, seems to work well with both the 9256 i was running, and also my 8900G......well was working till i wrote it off!
Uli of Mikado has said there is no need to mechanically trim the tail as the the gyro does not have a rate mode nor does it care what "center" is.
Here's his statement on tail setup:
"The Tail setup is fairly simple. We have unlimited angle integration, so there is no really center position. Set it up to have a bit tail thrust in neutral position, then adjust the Gain like on other Gyros. Max out the Travel on both sides with the Limiters. If you discover a difference between stopping on the sides, then adjust the Symmetry to correct this.
"Since we use an precompensation for the estimated torque, the setup is much more less critical, than with an conevtional HH Gyro."
Rigalo,
What radio are you using?
- John
Finless
08-25-2007, 10:09 PM
vbar has a built in tail gyro Bob. I don't think the vbar has a rate mode either.
Ooops sorry I wasnt paying attention to the title of the post!
My Bad :(
Bob
*hits fin on the nose with a rolled up newspaper* :nanabobo
Rigalo
08-26-2007, 05:26 AM
Uli of Mikado has said there is no need to mechanically trim the tail as the the gyro does not have a rate mode nor does it care what "center" is.
Here's his statement on tail setup:
"The Tail setup is fairly simple. We have unlimited angle integration, so there is no really center position. Set it up to have a bit tail thrust in neutral position, then adjust the Gain like on other Gyros. Max out the Travel on both sides with the Limiters. If you discover a difference between stopping on the sides, then adjust the Symmetry to correct this.
"Since we use an precompensation for the estimated torque, the setup is much more less critical, than with an conevtional HH Gyro."
Rigalo,
What radio are you using?
- John
Dude (s),
I use the DX7. Now, I did exactly what you sugested here. I centred it mechanically, adjust the travel to each side on the v-stabi software around 63 both sides just before catching. So the setup seems OK. Now, this is where the problems starts. The tail creeps. I even removed the gyro from the heli, and placed it on the table, as to eleminate interference from the servo. But, it still creeps. If I look in the software on the 'Live' tab, only the tail gyro creeps, but the 2 gyro's for the cyclic is solid. To state again, I tried the gain from 35 where it does not creep, but, the tail does not hold. the moment you increase the gain, it starts to creep, but the tail holds. 'Holds' but it does creep slowly around in hover. It does a very slow piro when in hover and flying. So if I fly, I have to constantly correct the tail.
If i get home, I will post my setup, and also try to post of vid of the symptoms. From what I hear from everyone else, it looks to me as if my v-stabi has a bug, or the gyro is not working properly.
Ian, if you are around in Cambridge, I would like to bring it over for you to fly, if possible? Can you let me know, please?
Still very frustrating.
Rigalo,
Try rebinding the receiver. V-Bar learns the neutral pulse width of the cyclic and rudder channels on power up. If, for some reason, the pulse width the rx is putting out upon power up is different the output after the link is established, V-Bar would be learning the wrong neutral width. This has fixed drift issues for others.
- John
MrMel
08-26-2007, 03:28 PM
Try JKos suggestion, if it dont help, trim in the computer thats OK (not on the radio though)
I can have gain 90 with the same setup without any issue.
Double and tripple check stuff like bearings in the tail etc, if you dont have it, upgrade to thrust bearings.
BobbySmith
08-26-2007, 09:31 PM
My bad i thought you said 9650 you said 9256!!
I alwasy mechanically square my tail rods in normal mod(non heading hold) and have never had a problem
jmiceli11
08-26-2007, 09:54 PM
I had a similar problem with mine. The tail would slowly go to one extreme and stall the servo. I went under the live window of the V-bar and the bar graphs showed that the rudder was slowly moving to one extreme without any input. I sent my gyro sensor back to Mikado and was sent a new one. Never heard what the problem was. The funny thing was that the orginal gyro worked fine for many flights and no crashes and then it just went bad.
The new one was plug and play.
Make sure that there aren't any mixes that might make the tail slowly creep.
John
Rigalo
08-27-2007, 07:44 AM
Ok, this is what I did:
I rebound the tx a couple of times with various settings, to no avail. Then I disabled the 'Noise Elimination' from the 'Overview' tab. I then uped the 'Gyro Deadband' and 'RC Deadband' on the 'Exp. Rudder' tab to 18 each. That stoped the tail Gyro from creeping. It looks good so far in hover and flight as well, but the tail has a small amount of wag. Gain is 70 on the tail gyro. Not sure if it is 'wagging' or 'hunting'. Will have to play with the settings more.
The only funny thing is that if I load someone elses settings, it still creeps. I do have trust bearings on the tail, but that would not help anything when the motor is off during bench testing. The rest is pretty standard as most of you already noted. Maybe I scored a piece of non standard V-stabi!
John, my symptons are exactly the same as yours. Only difference is it did it from the start. Maybe they've send me your dodgy gyro!
Any more thoughts welcome?
> tail has a small amount of wag
Do you have to up the "Gyro deadband" to get the drift to stop? Or does "RC deadband" alone do it? I could see having "gyro deadband" causing a wag. We need Uli in on this...
- John