AR7200BX getting the tail right??

[Helyfreak]

Cant get the tail to stay straight without using trim. but that's not all...


Equipment: DX8 1rst gen, oxy3 250mm plastic blades, AR7200BX, KST 215 tail servo, 1520u, 333hz. centered, 90*d all setup right as far as I can tell.

Gyro settings in Tx: pos 0= 20(led-d) pos 1=25(led- f) pos 2=30(led-g)
all three of these settings put it into normal rate mode. a zero setting puts it into HH mode which makes the tail dead and the oxy just spins counterclockwise???

scenario: every time I spool up the chopper, it needs right rudder trim(counter torque). And if I power cycle the FBL while the TX stays on, it needs even MORE right rudder maxing out my rudder trim. I know the manual says not to use the trims because it sees it as a "control input" but i'm not understanding how to fix this in the AR72.

I have the specified ~3.5* of right rudder(counter torque) dialed in per OXy3 manual.

I suppose I am confused about tail rates, HH and how im supposed to get that all set up in the TX and FBL.

I need help!!! Thank you for any input you might have!!

[bad007]

In initial setup in the TX I always set gear=gear and not gyro. Set limits to 45 and 45 to start, power up then set gyro gain so F lights up when gear switch is toggled. HH=blue led.

[Coco66]

First of all, I am just assuming that you want heading hold like 99% of the non-scale heli flyers, correct?

If the AR7200BX is in Normal mode or in Heding lock mode is shown in the color of the Status LED immediately after initialization: purple=Normal, Blue=Heading lock.

You say that your TX values of 20, 25 and 30 command Normal mode?
It should not, on a DX8 the Normal mode is achieved with negative values.
So double check the LED.

Those values sound very low, start with 40 and work you way up until your tail shakes, then lower couple points.


If I am mistaken and you really want to use Normal mode, then the precise value of the gain is not very important, a straight tail is achieved by playing on the length of the control rod.

[Helyfreak]

Ok, in the Tx. Negative gain is putting into HH(blue led) mode. I put -50% in pos 0 and the tail is locked in, albeit still using A LOT of rudder trim right. but it is working, and the higher Normal rate settings are still needing a lot of right rudder as well.

I do want both functional, I do enjoy sport flying that simulates real flight, like long sweeping FFF. Im not a 3Der yet, but working hard towards that. I

It seems despite my gain percentages, the tail needs a lot of right rudder trim. I wish I knew why, because trims not centered drives me batty lol.

Is this a matter of just changing mechanical setup? But if it is, then I would have to reset up in the AR72, which in turn, will end up right back where I started, right?.

THanks for all the help so far, got about 6 successful flights in now.

[Coco66]

Ok, if you want to solve your positive/negative mix up, which is confusing... reverse the gyro channel, and that's it. So you will have it like everybody else, where positive is HH and negative is rate.


I would not mess up with the zero value, since being the value "in between" could be malfunctioning as a default. Just forget it.


To avoid the need of trim in rate mode (which you should not use anyway) you need to setup the length of the control rod so that there is no drift in hover. That's it (thought I wrote that already). And of course you need to setup the tail limits again after that, but it will not change what you are fixing: the position of the slider when you give no input.


How is it possible that you get that drift in HH is above my knowledge, never heard that.

[bad007]

Originally Posted by Helyfreak

Ok, in the Tx. Negative gain is putting into HH(blue led) mode. I put -50% in pos 0 and the tail is locked in, albeit still using A LOT of rudder trim right. but it is working, and the higher Normal rate settings are still needing a lot of right rudder as well.

I do want both functional, I do enjoy sport flying that simulates real flight, like long sweeping FFF. Im not a 3Der yet, but working hard towards that. I

It seems despite my gain percentages, the tail needs a lot of right rudder trim. I wish I knew why, because trims not centered drives me batty lol.

Is this a matter of just changing mechanical setup? But if it is, then I would have to reset up in the AR72, which in turn, will end up right back where I started, right?.

THanks for all the help so far, got about 6 successful flights in now.

BX support will tell you setting up in RM is not needed. Install the horn as close to 90 as poss. Center the slider with the linkage at the point you do your rudder limits. If you want set a tiny bit of corrective pitch adjust the and then set your limits. Out of setup I do look at the slider position in RM for being centered or a tiny bit of right rudder.
Don't use TH during setup. Disconnect the motor. These problems seem to pop up every time TH gets used.
Model reset should have been performed prior to setup to remove any poss subtrims and trims in the TX.

[learnedthehardway]

Amain has some good BX setup videos on YouTube you might want to check out. You can have TH on during setup, I actually recommend using it in case you accidentally have the throttle/collective up when you exit the menu. That way the heli won't spool up unexpectedly. Disconnecting the motor is better but motor wires aren't always easy to access and I have done at least 20 AR7200BX setups and countless adjustments with TH on and never had a single problem. Plus when you make tuning adjustments later you probably aren't going to disconnect the motor so it's good to get in the habit of using TH when going in and out of the menus

You have to have a linear pitch curve during setup and if I remember right you shouldn't have any dual rates (d/r) set during setup either. All should read 100/INH in the d/r menu

[sutty]

Clearly it isn't the throttle itself that messes things up, and I have routinely set up my MBs using throttle hold, countless times, since they were first introduced. If it's causing an issue for people it can only be the associated pitch curves, or flight mode specific trims. However, these should never be an issue anyway, since the instructions are quite clear in this regard. New model, linear pitch curves, and no trims. If you do otherwise, then one would expect issues.

Of course trim could be used with a rate mode flight, but it would forget whatever was added when you re-initialise on the next pack, so it would be pointless, unless it was reset to 0 each time and then re-trimmed.

[bad007]

Originally Posted by sutty

Of course trim could be used with a rate mode flight, but it would forget whatever was added when you re-initialise on the next pack, so it would be pointless, unless it was reset to 0 each time and then re-trimmed.

Yup, several times in the last month this has happened and then finally discovered trim in one flight mode but not the other in the movement screen. All setup with TH and setup in RM. RM setup isn't needed and the this happens. Post #8
https://www.helifreak.com/showthread.php?t=770686

[Helyfreak]

Originally Posted by bad007

Yup, several times in the last month this has happened and then finally discovered trim in one flight mode but not the other in the movement screen. All setup with TH and setup in RM. RM setup isn't needed and the this happens. Post #8
https://www.helifreak.com/showthread.php?t=770686

That is EXACTLY what my tail was doing when trying to set the end points in setup.

[Coco66]

Why don't you just disable trim at all?

In DX8 G1 there are options for that in system menu, I assume the other radios have it too.

[bad007]

Originally Posted by Helyfreak

That is EXACTLY what my tail was doing when trying to set the end points in setup.

This happens all the time. Somewhere there is trim in one mode and not the other. Bring up the movement screen and toggle through all the flight modes. But still might not show with a small amount of trim of there, you'd have to go through the TX and double check all of them.
Since servo horns don't provide linear movement and provide a acceleration affect at there limits I just make sure,, even when not powered my servo @ horn 90 I have a tiny bit of right rudder and not worry about RM in BX at all.

[sutty]

Bad007, I'll repeat, this is nothing to do with TH, it is simply to do with not having done the set-up correctly. If you start with a new Tx model, there can be no trims, and if you disable them as suggested by Coco66 then it can't ever happen. It is specific to trim in any mode, so for example, you could have no trim in TH, and it would have been fine, but have trim in Normal mode, set-up in normal mode, motor disconnected, and still be screwed.

There is nothing inherently wrong with setting up in hold. It is what you should do.

[rhodesengr]

Originally Posted by Helyfreak

I suppose I am confused about tail rates, HH and how im supposed to get that all set up in the TX and FBL.

Well everyone has their way of doing things but here is my opinion.
First, why is your gyro channel giving you blue LED with negative numbers? Did you reverse your gyro channel? Put it back to normal. Verify on your TX screen that a positive value moves the TX monitor bar to a positive number.

Forget about rate mode. Start with HH level of around 60. If you don't get wag there, try moving slowly up towards 70.

Get all your trims in all your flight modes to zero. I think someone else mentioned that trims are set "per flight mode" unless you change that in TX Setup. I know my DX 18 you can change that feature. But in Default, a trim set in one FM won't show up in another.

You may want to just start fresh and reset your to TX model to clear out any setting you may have changed by accident.

[bad007]

Originally Posted by sutty

Bad007, I'll repeat,

Then don't, every time this happens it's the same olle thing, trims subtrm etc have been messed with and switched back and forth from TH to FMs and something hasn't got reset. Trimmed in RM, tail shafts marked etc. over and over again. The BX is go through the setup, period and fly. Not going to go back and look all the threads in the last 30 days with the same ending that where messing around with TH and setting up in RM and going back and ending up with a simple overlooked TX setting. And yes at least 2 where due to TH base settings that got missed that interfered in a FM. I'm done, I'm sure he'll figure it out even if he has to do a model reset and start over.

[Helyfreak]

Well it seems that I have fixed it, I dont know if this was right, but I just did what that guy with the 550 trex did. I just turned on the chopper got it trimmed way right, then I just shortened the linkage rod the amount needed, basically mechanically trimmed , reset end points, done. Flies straight, digital trim centered all around.

But now I worry about there not being enough throw now since the right rudder has been shortened for compensation, is this a valid concern? Or, is an end point just an end point, mechanical limits of the copter are set of course. It seems like the 3.5 degrees that lynx engineered into the tail just isn't enough to counter torque...

the chopper definitely turns waay faster in one direction that the other. This is normal right?

[bad007]

Originally Posted by Helyfreak

Well it seems that I have fixed it, I dont know if this was right, but I just did what that guy with the 550 trex did. I just turned on the chopper got it trimmed way right, then I just shortened the linkage rod the amount needed, basically mechanically trimmed , reset end points, done. Flies straight, digital trim centered all around.

But now I worry about there not being enough throw now since the right rudder has been shortened for compensation, is this a valid concern? Or, is an end point just an end point, mechanical limits of the copter are set of course. It seems like the 3.5 degrees that lynx engineered into the tail just isn't enough to counter torque...

the chopper definitely turns waay faster in one direction that the other. This is normal right?

No, should turn equally.
See 3.5 http://wiki.beastx.com/index.php/Help:FAQ_Spektrum/en
Actually tail blade pitch should be checked. BX recommends asymmetrical setup instead of setting both endpoints to max as do I. They use right 40deg and left 20deg. I just make left a few less then right max and if I switch to RM on the bench there is then a slight bit of corrective pitch and left and right rates seem the same. BX has responded to RM flights a being totally unnecessary since BX calculates center position off of the set end points. Linkage adjustment as you did is the only method outside of the tail setup as long as servo linkage travel is still good and you don't create binding. I don't have a OXY3 so I'd don't now what the max pitch is but my Outrage and D380 gives me mid 40s max and I only use 40, Align only gets mid 30s and I use the max it can give. All when the tail blades are folded the tips have 3-8mm corrective pitch no adjustment outside of just setting the tail blade pitch.

[peteski]

Originally Posted by rhodesengr

Forget about rate mode. Start with HH level of around 60. If you don't get wag there, try moving slowly up towards 70.

OXY 3 has a high mechanical tail gain so doesn't need a high tail gain - this is specifically mentioned in the user manual. On this heli with BX+ I use around 35-38% depending on head speed. That's also with a DX8 G1 scaling. That works fine for me in HH mode. 60% would be well into fast wag territory on this little heli.

As for the mechanical setup, I just went with the user manual and set the pushrod to put the bell crank at 90 deg (i.e. 3.5 deg of counter pitch), maxed out the end points and that gave a nice even yaw rate in both directions. I started with the gain around 25% and worked up from there. It actually held okay at only 25% when pottering around but needed more when pushing it a little. As above I settled on 38% for my usual head speed (3600 rpm on the OXY 3+). That holds solid in anything I can throw at it and doesn't bark.

Like suggested I always disable trims on my DX8.