Nose creeps left in HH mode

[skigolfmike]

OK, this is starting to drive me nuts. (which doesn't take much) In HH mode the nose on my 550 has a slow creep to the left. I thought it was the gyro G770 3D, but I put on a 401 tonight and it did the same thing. It has to be the heli. In rate mode I can dial it in perfect. As soon as I switch to HH mode, the nose creeps left.

I have the CF frame with the upgrade motor. TR servo is a DS8900G with a Spektrum step down between the gyro and the radio. The TR servo is mounted on the tail boom.

Any thought or ideas are welcome. I'm going to pull the tail out tonight and go through the whole thing (again).

[michael88997]

have you tried adding more gain? what gain are you currently running?

[ps61785]

i have the same problem...some help your be great...and i dont think that i can get anymore gain into it...

[ukgroucho]

So this is a Spektrum DX7 or similar Tx?

You need to rebind if you have been adjusting any subtrims with the tail (gyro).


.. and yes, I can provide more details if you confirm this is a DXx.

[ps61785]

my transmitter is a DX7 yes...but i cant remember adjusting any subtrims with the rudder except for the initial setup...do i still need to rebind...?

[michael88997]

u added trim to the rudder?

if you did you need to take it out and adjust the link until in rate mode it holds still

[skigolfmike]

I have no trim or sub-trim - still does it. I rebind every time I make a change to the radio. Still does it. The Tx is a DX7 the the receiver is a AR7000.

[michael88997]

what is ur gain set at?

[skigolfmike]

75%

[ps61785]

no i have no trim set...but i had to put subtrim in when initially setting it up to get the servo horn centered...other than that nothing...

[helvetic]

you have to adjust the trim mechanically. Otherwise your subtrim will lead to a small rudder input.
As I experienced, this is the cause: The AR7000 needs a couple of seconds to bind and THEN starts to work. In the same time, the GY401 initializes, and takes the zero input signal from the receiver as the zero point.
After that, the AR7000 starts to work and sends the subtrim to the gyro. And the gyro takes this new signal as a rudder input.

Complicate? My english isn't the best, hope you may follow

good luck, Stephan.

[skigolfmike]

Would you believe I may have had the belt twisted the wrong way? At least that's what it acted like after I completely re-built the tail. I had to reverse the rudder servo and now neutral trim is close to the center of the tail shaft.

Can't say tor sure, it was very late. It just seems to me that that might have been what it was. Can't figure out any other reason.

[kkwait]

You can also reset the neutral on the GY401 by switching 3 times rapidly from Rate mode to HH...

[philiusm]

Vibration getting into the gyro causes this effect on my Swift. Wires to the gyro need to be loose, I put mine in a little loop and the gyro needs to mounted freely on its foam pad with nothing else touching the case.

I'm a little worried sometimes as I have no velcro safety straps or cable ties. I just check the gyro tape regularly.

[skydude]

I had a problem with a heli rotating inexplicably. I wouldn't say it crept, it went around just fast enough to scare the crap out of me as I was still learning to fly.

Turned out to be a bad bearing.

New bearing. Flew like a champ.

--

[ps61785]

ive tried both the subtrim and the switching between HH and rate mode and neither fixed the problem...any other ideas...

[mjdee14]

ive tried both the subtrim and the switching between HH and rate mode and neither fixed the problem...any other ideas...

Have you gotten it to hover steady in rate mode by making mechanical adjustments?


Are you saying it is OK in rate...but rotates in HH?

[ps61785]

ive never set it up in rate mode...should i be doing this...i thought that you were able to just set it up to 90 degrees servo horn to 0 degrees of pitch at that tail...im i wrong to believe this...?

[kkwait]

That is the first thing to do !!

. Set your servo horn to 90 degrees (when neutral)

. Adjust the rod so the tail blades have approximately 5 - 6 degrees positive (they need to push the tail to the left)

. Fly your heli (just a hover at at least 1 meter high) in normal mode (rate) and see how your mechanical settings are...
if the nose goes left, you have to adjust the rod to add some pitch to the tail blades and vice versa

Repeat these steps until the tail keeps straight.
When it's done, you can switch to Head Lock with no problem ! ;)

[ps61785]

thats the problem though...i cannot get my horn at 90 without subtrim...does this mean taking the servo apart to adjust gears...because that would be the only other way...

...and watching finless's videos says otherwise...and that has been my basis...i understand that there can be multiple ways to set things up...

i will try this method to see if this helps my problem though...its not unbareable...but it does drift very very very slowly...thanks again...

[skigolfmike]

ps61785: Normally, to get the servo arm on the servo at 90* you would set the gyro in rate mode and then find the arm closest to 90*. Since you didn't do that, you will have to use subtrim. Again, do this in rate mode (usually that means setting the gain below 50% (i.e. 30% is a good place to start) Make sure you have the servo going the right direction first though because the sub trim will change based switching between normal and reverse.

The way I set this up on my DX7 was to set the rudder DR switch to change gain and I put Throttle Hold on aileron DR. FWIW, Finless shows another way to do it. That works too. The way I did it you do need to check that the Rudder and Aileron dual rates match when you throw the switch. Now would be a good time to re-bind the radio too.

While the servo is centered, setup the TR linkage so the slider is in the middle of it's travel. Then check that the tail is rotating the right way. The TR rotates counter-clockwise when looking at the tail from the right side of the heli. (Main rotor spins clockwise looking from the top) If the TR is backwards, pull the tail and twist the belt the right way.

With a 401 or a 770, next you set the end point adjust on the gyro. Leave a little room for mechanical adjustment. Spin up the heli in HH mode, then at half stick I switch over to rate mode to check trim. I adjust mechanically until I get hands off hold in hover in rate mode. then flip it to HH mode and you are set. If you made big adjustments, then check the endpoint adjust on the radio. With the 401, go to rate mode and flip the switch 3 times fast between rate and HH mode to save center. With the 770 you don't have to do that.

My 550 is flying great now. I flew it a little tonight and the tail is holding great. I believe my drift problem was happening because I had the tail spinning the wrong way. Once I got that corrected my slow drift disappeared. I got in a flight tonight in cold (38*) and 20 mph winds and it flew great. This heli has gobs of power. I haven't tried idle up to do any loops, rolls or flips yet. That will happen soon though.

[mysticmead]

thats the problem though...i cannot get my horn at 90 without subtrim...

did you try flipping the horn 180 degrees?? sometimes they are a lot closer to 90 on one side than the other... or maybe try a different horn.. the less subtrim the better

[Wazzer]

or use a round servo wheel and drill exactly where you want without any subtrim at all??

[arne997]

I have the same problem. A slight drift to the left in HH. Good in rate mode.
I have done the reset by switching back and forth 3 times between HH/rate.
I have a little trim in my DX7 but since I have done the reset I suppose That is OK.

What can bee my problem?

Thanks

[mysticmead]

the trim can be and most likely is the problem.. get the tail set to have NO trim or subtrim at all, then HH mode should hold