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Old Oct 30, 2012, 01:24 AM
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Hey guys just wondering if anyone can help me on an issue.

I cannot get my apache tail locked. its fine in pod and boom, it stops on command, but once again now that the mechanics are fitted inside the apache, ive got a massive oversway when i input rudder left or right.

ive done everything from increasing the headspeed, taking the tail rotor blades back down to 2 blades, re-tracking the xblade and re-adding the other two blades back on to the xtail, increasing and decreasing the gyro tail gain, increased the beastx gyro head lock setting from medium to high, and back again, whilst both increasing then decreasing the amount of pot 3 on the gyro itself.

i cannot get a locked tail. its driving me nuts. its the same on my blackhawk so HAS to be a extra weight / torque / multiblade head / low headspeed / low tail authority kinda thing im guessing but dont have the know how to fix the problem.

any help would be great.
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Old Oct 30, 2012, 02:30 AM
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Hi Jay,

Is it alright when you set your giro in "normal" mode? I have had the same and it was only stable in Normal mode and waving in HH.

Then I did try the on board Giro from my HeliCommand and the problem was over???
I used before the Align 780 and as you also experience in pot and boom no problem.?

Maybe Bert has a idea he always tells that he do not like electronics but on the other hand he knows a lot how a heli reacts and how to setup this and If he can help he always will

I see now that you already have response from Bert in my own tread

Not a answer but maybe a start of it

Jan,

Ps did you got my email?
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Old Oct 30, 2012, 04:25 AM
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I am not a real expert on control loops, just have my industrial hands-on experience, and usually I can get more complicated industrial processes to respond well.

Heading hold is a pretty advanced control loop, that is getting more complicated to set-up as more factors are introduced, and settings need to be more accurate as the sheer numbers of those factors increase.

The loop is a PID, and in the industry it is very unusual to have a PID that can only be adjusted for gain and very limited on the I-factor, however on HH gyro's that is often the case.

A light (3D) helicopter is not really critical, and most heading hold gyro's have a setting for gain and a setting for delay. This makes for less than perfect adjustability, and usually the more complicated factors are factory-set to fit the general range of helicopters, say from 450 to 800.
You will find that typically, (as you have experienced yourself) that on bigger sizes scale helicopters, under circumstances heading hold will not perform all that great and if you go bigger than say, 180 cm rotors, more and more you get difficulties adjusting a heading hold.
That is a rule of thumb, there are cases known where even a standard HH gyro would perform well on a 2 metre heli, and you experience problems on a smaller machine.

When more factors, such as greater inertia, aerodynamic forces on the fuselage, different response of the tailrotor (the fin is influencing how the tail works, and that influence is even varying with relative wind direction), torsion in the tail drive, servo speed, and all those tiny factors like changing turbulence patterns around the fuselage are taken into account, it is very possible you cannot find a really good setting.

I do not know how the control loop of the HH part of a Helicommand differs from a "normal" HH gyro, but it is very likely that the factory settings have been refined, or some kind of auto-adjustment is incorporated. No idea, don't care actually. If Jan says that one works better, I believe him.

Rate mode however, is a very simple "control loop": In fact it is not even a real control loop, it is just in its function exactly the same as a shock absorber (not the spring, just the damper) on your cars suspension: it gives an additional counteracting force to the momentary movement, and that's all.

It means that it does not take any other factors into account, it just counteract the yaw, as long as there is yaw, and does nothing when there is nothing to do. The downside is you have to fly your tail manually, it just brings it down to levels where the required skill to control it are within "human range".

It also means, that it can only oscillate or dampen, but not "function not properly".
You can increase gain to the point where it starts oscillating and back it off a bit.
You can influence "holding" a bit by lever-ratio and servo speed, but don't expect too much from that. As long as the heli stays predictable, a human can control it, and that is all you need.

Brgds, Bert
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Old Oct 30, 2012, 02:54 PM
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Quote:
Originally Posted by Horseman View Post
Hi Jay,

Is it alright when you set your giro in "normal" mode? I have had the same and it was only stable in Normal mode and waving in HH.

Then I did try the on board Giro from my HeliCommand and the problem was over???
I used before the Align 780 and as you also experience in pot and boom no problem.?

Maybe Bert has a idea he always tells that he do not like electronics but on the other hand he knows a lot how a heli reacts and how to setup this and If he can help he always will

I see now that you already have response from Bert in my own tread

Not a answer but maybe a start of it

Jan,

Ps did you got my email?
Hi jan, the one about micro helis unit?

Also, in beast x, when in rate mode, the tail holds fine, but theres not much stopping power, which is the problem. it will still swing past the angle it should stop at, meaning i have to constantly over correct.

ill just have to live with it. it was the same on the 4 blade tail rotor i originally had on there. i think overall i dont have a high enough headspeed so i might change up to a 15t pinion and see if increased tail rotor speed helps with stopping power.

When the heli was flying in the weekend, the tail is locked in ff, and theres no fishtailing, but when i come to turns, mainly right hand turns, the tail will want to blow out, usually towards the right. not every time, just when too much rudder is inputted.

berts info is very helpful, thanks alot bert.
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Old Oct 30, 2012, 04:20 PM
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Rate gyro overswings. That is the nature of the beast.
If it doesn't or only little, that only means you have low top-axis inertia.

A HH gyro does its thing on the integral of rotational speed (meaning it is actually reacting to the angle of deviation, or heading) where the rate gyro does its thing on the rotational speed of yaw. It CANNOT stop "where it should" because if it is stopped, there is no correction either.

You just have to let go the tail stick a little earlier

If you have problems with the tail in only one turn, there is two factors:
1) same as the transitional lift, the tail rotor gets a little bit more effective, so in FF the trim is slightly off. That makes for the left and right turn being different.
I usually trim for FF and hoover holding a bit of rudder.

2) in turns, yu usually manipulate the pitch as well, and that works through in the Revo curve
If the tail is irregular in always the same turn, chances are, your Revo curve is off. You will be surprised how much you correct with collective in turns, and a not correctly set ReVo, will cause always the same side turn (in your case right handed) to be irregular on the tail.

Try figure out if you reduce or increase pitch when that happens, and then carefully adjust your revo accordingly.

Brgds, Bert
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Old Oct 30, 2012, 04:28 PM
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The first problem i see is the leading edge of the tailrotor not turning into the downwash from the mail blades..I always thought it was a "rule" one should keep in mind. Of course this is hard to obtain, since the apache has a left turning main rotor, and your model is right turning..
Second question; have you tried hovering without any tail gyro? I always try it, since this is the only way you can know if your linkage is setup exactly neutral. It is a possibility the gyro is already working hard just to keep the tail straight, so there is not much left to correct any external influences..

cheers,

Didier
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Old Oct 31, 2012, 12:03 AM
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Originally Posted by didier n View Post
The first problem i see is the leading edge of the tailrotor not turning into the downwash from the mail blades..I always thought it was a "rule" one should keep in mind. Of course this is hard to obtain, since the apache has a left turning main rotor, and your model is right turning..
Second question; have you tried hovering without any tail gyro? I always try it, since this is the only way you can know if your linkage is setup exactly neutral. It is a possibility the gyro is already working hard just to keep the tail straight, so there is not much left to correct any external influences..

cheers,

Didier

Hi didier, yes, to get a correct geometry for your linkage rods, you must first, on the beast x, hover in rate mode and if the heli spins during spool up, you know then whether your rods are too long or too short.

I know that an incorrect geometry will always cause the gyro to compensate, making turning and ff flight difficult, but my geomtry is fine. once spooled up. there is enough deflection to stop the heli from wanting to spin. in HH, It sits dead straight.

ill see how i go.
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Old Oct 31, 2012, 12:25 AM
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Since you saying that is fine in pod and bom I would suggest you to check the torque of the tailservo, I had this issue with mine panther and a futaba 9254, changing to a 8 kg servo solved it and it was steady as rock on the tail, since you are increasing the weight with the fuse the mass to control is bigger, just a thought since everything else seems ok,

/Jack
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Old Oct 31, 2012, 01:31 AM
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Ah... that is where your idea about more powerfull servo's holding better is coming from....
The 9254 has only something like 15 N/cm, and is way too weak for anything over a .60 trainer, and there it is allready straining noticeably.

Even an S3001 in rate mode sometimes performs better than a 9254 in HH in most "bigger" helicopters...

But that is not because stronger servo's hold better, its just because the 9254 is a very fast, but also very weak servo. Too weak to reach its adjusting speed under that load.
For a given tail rotor, the weight of the helicopter has no influence on the force needed to shift the tail slider, which for a .60 size helicopter will be roughly 10~15N.
But the fuselage has influence on how often and how much the tail has to correct, and if the servo is operating on the margin, it is likely it can do its job in a pod&boom (barely) and is overburdened in a fuselage.

Unfortunately most vendors would sell the GY401/S9254 combo as "the single solution to all tail problems, for all helicopters".
In fact, I have seen people trying to use the S9254 in Vario Benzin Trainers saying the servo and gyro were crap, and the S9254 has gotten a very undeserved bad reputation in some circles, solely because of that kind of stupidity.

Your Panther would have been flying just as good with a 30 or 50 N/cm servo of the same speed, but I guess, 80 N/cm won't do harm.

Any 600 or 700 size will not benefit from more than 30 N/cm, except for "specials" such as Fenestron or NOTAR. A fourbladed tail could use a 50 N/cm servo (but will probably work with a better 30 N/cm one too), but that is about it.

Brgds, Bert
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Old Oct 31, 2012, 07:45 AM
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Ah...i give up...bert,...why do i get a feeling that what you are saying is just .....

Belivie me,as he wrote has problem with his tail so this is a try for solution....i can tell you that 9254 works just fine but when conditions gets extreme its to week,.....bert...i think yours problem lies that you never learned to fly properly in heading hold mode when this becomed available and and now everybody
Should go yours way...nonsens....your presenting a lot fancy teories but......
Well that shouldt be in this thread and something just getted clearer now with al this talking..

/jack
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Old Oct 31, 2012, 01:51 PM
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im running the Savox SH-1290MG Digital Metal Gear Ultra Speed Servo.

Specifications:

Speed @ 6.0V: 0.04 sec/60
Torque @ 6.0V: 69 oz-in / 5 kg-cm
Weight: 56.4g
Type: Standard
Gear: Metal
Case: Aluminum Heatsink
Case Size (LxWxH): 40.3x20x37.2mm

This should be fine. im going to try changing to carbon push rods. i cant see how the main pushrod is behaving and wether or not its flexing at all, but i know the pushrod on the raised tail boom controlling the rotor could do with being a little stiffer. but as i say, it worked fine in pod and boom, and bert raised valid points about windage effect on the fuse vs stress on the pushrod/linkage/servo setup.

bascially beginning yet another process of elimination. i still think its a low headspeed & not enough tail authority being generated ballpark thing...but thats my novice theory.
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Old Oct 31, 2012, 05:21 PM
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Originally Posted by viggen65 View Post
Ah...i give up...bert,...why do i get a feeling that what you are saying is just .....

Belivie me,as he wrote has problem with his tail so this is a try for solution....i can tell you that 9254 works just fine but when conditions gets extreme its to week,.....bert...i think yours problem lies that you never learned to fly properly in heading hold mode when this becomed available and and now everybody
Should go yours way...nonsens....your presenting a lot fancy teories but......
Well that shouldt be in this thread and something just getted clearer now with al this talking..

/jack
I object to this kind of remarks.... since when does one need to LEARN flying with heading hold? The darn thing is autonomous! HH even prevents you from learning: how hard is it to learn not to touch the stick if you don't want it to turn?

I have you know, that I flew HH for a fair amount of time in all my helicopters from the moment it came availlable for my budget, I believe it was back in 2001 or 2002, and I have tried several types, as the first one, a Futaba 3D gyro (I think it was later sold as the G-400) was not the best one, even if it was "da sh*t" when it came out, and in at least one helicopter I still use heading hold to this day.
It made some of my helicopters more docile, but others (older tail drive set-ups and controlrod costructions that I could not change without visible ugly modifications) only got worse. Stronger servo's only made things even more bad. The only problem you can solve with a stronger servo, is a too weak servo, in all other cases, stronger servo's only make things worse, because the servo is not the problem so changing it doesn't help

Nobody should go my way. Rubbish. Fly what you like, the way you like it, and I am not holdig you back. But don't tell me, I do not know my stuff around helicopters: I was not the one trying a 9254 in a scale fuse, then thinking "Hey, if 8 kg works, then all tail problems MUST be related to weak servos".....

There are lots of individual tail problems that only get worse from fitting faster, stronger servo's or HH gyro's, and it seems, with several new players in the scale market, some of the problems that were solved 10~15 years ago (mostly torsion in taildrive and flexing of tailfins), come back again, as I read more and more about them.

I believe in solutions to the actual problem, not in masking a problem with plain technical overkill.
I offer solutions or ideas to try, based on experience and knowledge of what different systems do in different circumstances including heading hold, and one way of finding out what is going on, is to check what the system does when left to its own without electronic interaction from an autonomous system.
Using heading hold sure as hell robs you of all possibilities to observe what that tail is actually doing, and WHY it does what it does.

That is a big difference to the single broken record remark "fit a stronger servo" based on one too weak servo in one helicopter.

Me thinks, a 5 kilo Savox should be more than strong enough, and 0.04 sec more than fast enough. Most of my helicopters fly perfectly OK with slower and less powerfull servo's on the tail, only the two gassers have digital 8 kilo servo's on the tail, the others all analogues. THAT is the reason why I say what I say, and it is up to anybody, if he wants to take that advise or not, I have forced nobody to change from HH to rate or advised to try weaker or slower servo's.
It is a given fact that ANY tail WILL work with Rate mode, but not every tail will work acceptable with HH. So it is technically a far better approach to first tackle your problems in rate mode. If you have fixed them, there is nothing stopping anybody from trying HH.

Brgds, Bert
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Old Oct 31, 2012, 07:31 PM
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Shoot!
I'm guessing that brutus and viggen know each other from other than this thread.........

All great suggestions aside...... Jay, that damb apache looks to good to fly anyway.... LOL the thing looks amazing. I hope you figure out the tail issue.

I myself have never flown in rate mode and wish I did, as I'm sure it can only make the pilot better with all judgement of the heli response.
Quick question to Bert, so I better understand rate mode. does the tail still hold in rate mode? without tx input? I'm guessing rate mode is more for tail gyro systems and not so much fbl gyro's? I have used a gy401, a gy611, and aligns gp750. but I always set them up in HH.
I use a sk720 now and I can change rate imputes, but there is no HH or rate mode option.

Jay, this has happened to me before as well and it was also tail authority. or not enough pitch in the tail itself. if you have not already done so, I would measure the distance from the tail casing to the where the grub shaved part in the stock align tail shaft is, put the inner tail grips to match that distance and then move the outer tail grips around to match the 2 pitching together. that way you know for sure there is enough pitch for authority. but if it works outside the fuse, then that's a little out of my league to really know as I'm not too knowledgeable with scale, hence the reason I have been following you and horseman on these threads....

Happy flying everyone. These forums are for suggestions and opinions, so let's help each other!
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Old Nov 01, 2012, 03:26 AM
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Oppps...a sensitiv ...

Well...regarding the 9254.....it worked in in rate and hh for about a year without any somehow problems.....learn by doing bert....


If you taken it that somebody are saying that you dont knows yours heli...well thats up to you....i have never sayed that....but..

To say that it sometimes can be dangerous to fly in hh mode.....everything
Can be dangerous without the right equippment and thats a fact,like everything
Else the gyros in ours heli are evolving,this goes for fbl,tail,gps....everything


And....no...i dont think a stronger servo solves the worl economy but it solves very much regarding tailauthority if everything else i settet up ok.
And this goes also for the servos on the cyclic,a heli isnt stronger as the weakest point

A good measurment ( in my worl) is to compare the electronics i a 3d heli,these guys are stressing their helis in to the breking point,well if it with that kind of forces can hold up it shurly can do it in a scale where almost circles around flying around and common scalemanouvers.

Bert.gone says this once moore so its clear for you

You have very good suggestion,are giving good advices that even i that have been in the hobby almost as long as you are reading and think its interesting,but sometimes theres actually can be other solutions to problems and thats a fact,in these case you wrote"...thats were you got that a 9254..."....as i wrote,it did worked for sometime,it wasnt optinal,i swapped to a stronger servo and everything was fine....i learned by doing..that was what i wanted to share to jay.if i somehow stepped on yours ego im sorry for that,that wasnt my intention.

Buddertoast.....not really so,we just have sometimes has different thougts..
Jay...hope it solves for and yours apache,im conviced that its a simple solution,just need to find it,thats the tricky part,the good think is thats its fine in pod and bom which should make it easier to exlude some things

Cheers
Jack
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Old Nov 01, 2012, 03:32 AM
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Happy flying everyone. These forums are for suggestions and opinions, so let's help each other!



Jan,
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