Problems with the gyro gain, AR7200BX

[DMala]

Hello, I got a used 6s MiniP stretch with 6s motor last year, JRDS3500D on the tail (tail rod link on the closest hole in the arm) and JR9303 radio. When I first got it I set the tail gain to 75% as the usual starting point (on a scale from 0 to 100% for headlock), and had some nasty tail wagging right at spool up. Eventually I lowered it to 48% and got very good tail control for the 2D flying I do with the MiniP.

Recently I tried a flip and the tail got into a fast wag again. So I moved the tail rod ball link to the next outer hole of the servo arm, and with the intention to adjust the tail rotor picth, moved the servo 3-4mm forward. The tail wag got worse. So I moved the servo back to exactly the original position (which I had marked), made sure that parameter D (tail headlock gain) is very low, and now with 98% tail gain on the radio I have no wag but I can not control the tail, it blows out at liftoff!

I am obviously quite lost, any suggestion? Should I move maybe 1-2 mm forward the servo? Increase parameter D? Could it be a bad servo? At this point I have no clue. Thx

[Aryemis]

You should not be moving the servo placement randomly like that.
The servo should be fixed and at 90° to the linkage when the tail rotor is at 0°, or maybe with 5° offset to counter the torque, but not any more than that.

What is the length of the servo horn ?
Mine (MKS DS95i) works fine at with the ball at 7.5mm, and with the center being the tail rotors 0°.

Don't know anything about the BX so can't help on that though.

[DMala]

Very helpful, thanks.
I moved the servo because the original servo horn had only one position for the ball link. To move the ball link out I bought a longer servo horn and I was under impression that it did not fit at exactly the same angle of the original one, but maybe I over-compensated when I moved the servo. The original distance of the ball link was like yours, but I have now positioned it at 11mm. I have more than 5 degrees pitch of the tail rotor and I will now adjust to zero or just a few degrees.

[dr dremel]

The fast wag you had was probably from too much gain. This can be either electronic (gyro gain via tx) or mechanical gain (servo arm). By lengthening the servo arm you increased the mechanical gain. I´d go back to the original ball distance. I´ve the same setup as Aryemis, 7,5mm out and 0 deg on the tail blades when the servo arm is 90 deg to the tail rod. I´d do a new BX tail setup, especially endpoints (forgot which point in the setup menu it was).

[DMala]

You are right Dr. Dremel I misunderstood the effect on the mechanical gain of moving the ball link out. And so it did the JR tech support person with whom I "checked" my plan before of ordering a new servo horn. Will go back to the first position.

In any case if I go back to the original setup the only variable to play left is setting the tail rotor to zero pitch, hopefully that will suffice. I was also thinking if maybe I should lower the headspeed, currently 3360 rpm (measured with optical tachometer).

[Russell Harding]

The mini needs the servo horn ball distance very short (7.5mm, as stated in the manual). Some servo horns need a new hole drilled to get this close. Make sure your tail endpoints are set correctly, especially if you have been changing the tail link geometry in any way.

[DMala]

OK I am all ready to try again tomorrow. I moved the link to the inside hole of the servo horn, moved the tail servo to get 0 pitch on the tail blades, and checked the slider travel on the AR7200BX. I set the heading lock gain to 40% (G on the AR7200BX) and I may drop the headspeed a bit on the throttle curve. We will see.

[para5063]

....

[DMala]

...???

All good at least for 2d flight, I did not change the headspeed in order not to add another variable, 40% headlock gain and 0 deg. tail blade pitch, tail rod link on the 7 mm position of the servo horn. Thanks for all those who helped, eventually I will try again flipping it.

[DCflyer]

This should help you. WARNING - long post ahead. This is a full tuning guide I have put together from various reps, pro's, and stickies in the Beastx forum.







BeastX V3 Tuning

First things first!! I've had far better results with using either the 3M Gray 4011 double sided tape or the 3M 4010 Clear mounting tape. There is a bit of concern that too firm of mounting on nitro models could potentially cause long term damage to the electronics within the BeastX unit but so far no one has been able to confirm this. I currently run a single layer of either one on electric models and two layers on nitro models. I will continue testing thicker mounting options for nitro applications and post results once I have them. I have yet to run into a situation where the heli flew better with the stock tape but unfortunately have seen dozens of situations where cyclic drifts, rolling on lift off, bad wobbles under load, etc. have all been corrected by replacing the stock tape. It's very easy to transfer vibration through the multiple wires coming in to the BeastX so if you're going to try the stock tape I suggest being very careful with not securing the wires too closely to the unit and strapping the unit down very tightly with velcro.


Tail Setup/Tuning:

1. Dial #3 in middle position and Parameter D (Heading Lock) to Red.

2. I personally start with rudder ATV's at 100. Drop to 85 if you're a beginner.

3. Parameter B (Control Behavior) to Transmitter mode

4. Rudder expo to 20% (personal choice)

5. Parameter F (Tail RevoMix) to OFF, Purple

6. Fly and immediately check pirouette rate and adjust via ATV's or Dual Rates if needed. Keep in mind to not get into the "high speed piro" mode until after your done tuning the tail so try to keep it under 105 ATV for now. Don't worry about your expo just quite yet as long as it's comfortable enough to fly for you. Fly and find maximum tail gyro gain (adjusted in TX). Perform fast backwards flight if possible. Hurricanes and funnels work the best. Giving to much rudder and sliding the tail through a hard bank turn will help if you can't do backwards flight. Adjust right to the point of slight oscillation then back off 3% in the transmitter. Note: You can NOT accurately adjust this parameter in a hover.

7. Flip into Rate mode (approx 30% Rate mode gain works fine) and adjust your tail rod length to remove drifting in a hover.

8. Reset your tail endpoints in Setup Menu E.

9. With the gyro gain you found in step 6 perform fast forward flight and do full stick throw pirouettes. Piros should be smooth and at a consistent rate with no sling-shotting or whipping. If they're not consistent then raise Parameter D and try again. If you don't get any sling-shotting then perform a 360* piro and immediately go into a 360* piro the other direction. What you're looking for is how the tail acts during a quick reversal in direction. If Parameter D is too high the tail will stop, hesitate, then quickly jump back into rotation. You will actually hear this stutter or hesitation in the sound of the tail blades. Once you have raised Parameter D high enough to hear this then go back down one light. The best tail performance will be at the highest setting possible without getting these inconsistencies during reversing directions.

10. Recheck the main tail gyro gain then set your expo per personal preference.

11. Finally, adjust the tail stop characteristics by using Dial #3. Perform fast piros while hovering and quickly release rudder. Observe how the tail stops. If it continues to slide to a stop after you let go then increase Dial #3. If it bounces back then decrease Dial #3. When it gets close listen to the tail blades when you stop. If you can hear them "bark" when the tail stops your just a tad too high on Dial #3 and back it down just a hair.



Tail tuning notes:

I know the lack of RevoMix is a shock to some but what I found was that activating the RevoMix was actually causing a lot more problems than it was fixing. By de-activating it I was able to raise my tail gain, and run Parameter D at a higher setting. This resulted in a perfectly consistent piro rate and stops in both directions. Hard piro/collective maneuvers didn't have any negative tendencies and yet magically I had absolutely zero tail kick. This was something that I found the manual was not very clear on and only in talking with Stefan did I uncover that VERY RARELY is RevoMix needed.

Watch your governor gains on electric models. A governor gain that is too high can definitely cause a tail-kick that can be very hard, if not impossible, to overcome. Tune your tail with your governor gains lower than normal and work up to the highest possible gain that doesn't produce and negative tail effects.

I've found Parameter D to be very important on electric models to tail performance. Due to the largely overpowered systems we use now it's critical that this gain be ran as high as possible without causing "whipping" in pirouettes. This setting greatly depends on tail blade size and tail ratio so time spent on this step will greatly pay off if you want all that's possible for tail performance.

Any inconsistencies in tail stops from left to right piros are usually caused from the heli not being setup for a neutral tail in a hover or having RevoMix activated.

For all you old-school guys coming from the rate mode gyro days do NOT get the BeastX's wording of RevoMix confused with the revo-mix you know from the past. It's a completely different thing and is merely a language difference in terms.

CONTINUED:

Important:
Tail setup has to be done in order. Don't try to dial in the tweak the tail stopping behaviour with dial 3 or play with the gyro gain before dialing in the sensitivity. It is fundamentally more important to find the maximum sensitivity for any given heli first.

1. Dial 3 in middle position. Set parameter menu item [D] (HeadingLock) to purple.

2. Determine the maximum gyro gain (aux channel). Increase the gyro gain unto the tail starts oscillating during wide turns in fast forward flight. Then reduce the gyro gain by about 1 LED on the Microbeast display. Those who are able can also set the gyro gain doing fast backwards circuits.

3. With that gyro gain, do fast forward flights again and start piro-ing slowly. The piros should turn smoothly without getting slower into the wind and faster against the wind. If there is a strong, steady wind at the field you can also try this in a hover. Is the piro speed not constant, increase parameter [D] in the parameter menu and try again. Those who are able to do tailslides can also use tailslides from greater height with increasingly faster piros to test this. After this you may have to re-adjust the gyro gain (step 2).

4. Finally, the tail-stopping behaviour is adjusted using dial 3. To do this, perform fast piros while hovering and then stop the piro abruptly. The tail should stop cleanly without turning further and without swinging back. If the tail continues to turn after the stop or feels "soft" when stopping, increase the gain on dial 3. If the tail swings back when stopping, decrease the gain using dial 3. When tuned properly, the tail should not make much noise when stopping. If you can hear the tail when stopping, you're probably past the optimum setting.












Head/Cyclic Tuning:

1. Control Behavior should be in Transmitter mode already

2. Start with ATV's or Dual Rates at 100/100 for AIL/ELEV if you're an experienced pilot and about 85% if you're a beginner. I usually start about 20% expo. It's really a personal preference though.

3. Both Dial #1 and Dial #2 in middle position.

4. Parameter menu E (Stick Response) on Red flashing LED.

5. Parameter menu C (Pitching up Behavior) to Red LED.

6. Bring heli into a hover for about 5 seconds. Any oscillation, shudder, or wobling in the head then lower Dial #1 in small increments until it's gone. Note: If your tail is bobbing up and down then make sure you're running enough headspeed for your head dampers. Increase if needed.

7. Fly heli and set your Flip/Roll rates via ATV's or Dual Rates in the transmitter. Watch for any large bobbles or coasting when letting off the cyclic. If it bobbles reduce Dial #1. If it coasts or slides to a stop when you let go of the cyclic increase Dial #1.

8. Fly in fast forward flight and give moderate sized positive and negative pitch pumps with NO cyclic input. Watch the heli and look for a "dolphin" type movement. If it pitches up and down as you pump the collective (it will literally look like a dolphin swimming) increase Parameter C (Pitching Up Compensation) one increment at a time until it goes away. Note: In most instances you won't need to increase this parameter from the default setting so if it flies fine at the default setting then just leave it there.

9. Dial #2 can be a little tricky to adjust below a certain skill level so as long as you get done with the tuning and don't have any negative tendencies on the cyclic then don't be too worried about it. What I do to adjust it is tic-tocs on either axis. When you switch directions quickly the cyclic should have a nice smooth transition. If Dial #2 is too high then the heli will accelerate quickly on the cyclic after a quick commanded movement, hesitate for a second, then start moving again. It makes for a very glitchy feeling. The initial movement after a direction change will be overly aggressive but will "pull back" that speed after a split second then continue with the correct rotational speed. If Dial #2 is too low then the cyclic will have a very disconnected feeling and be very laggy. This dial is very dependent on the size and weight of the heli, servos, and blades so if you switch to a different set of blades don’t be surprised if you need to make small adjustments to it.

10. Cyclic Response (Parameter G) is basically like that "paddle" feel that many talk about. Increasing this will make the model very responsive to your commands and give a very "connected" feeling. If you get to the point where the heli just doesn't feel as responsive as you'd like around center stick but you can't reduce your expo any more (or... you've reduced your expo to the point where you're seeing your small corrections that you usually don't see) then increase Cyclic Response. If you feel like you need more expo but you're starting to surpass 30% then decrease it. Cyclic response will not affect your flip and roll rates and it is NOT the same thing as expo but to a lesser experienced pilot can feel somewhat similar so don't get them confused or you'll be chasing your tail. Myself, from general flying experience, I know that I'm about a 20% cyclic expo guy in general. I like a pretty fast flip/roll rate but like to dull it down just a tad around center for the precision. So, I know that if I get down to around 15% and it still feels a little slow around center then I just go right back to 20% expo and increase the Cyclic Response.

11. Dial #1 is more how "tight" or locked in the cyclic feels. While you can definitely get too high or too low on Dial #1 and cause some negative tendencies generally speaking it's more of an adjustment that will depend on how you like your cyclic to feel. Some people prefer a much more rigid and locked in cyclic so running this gain as high as possible without negative tendencies (elevator bobbles during tic-tocs, etc.) is what you'll want to strive for. If you like a "looser" cyclic (more like a flybar heli) then try decreasing Dial #1. If you get to the point where the heli isn't tracking well, feels slightly unstable in FFF, or you get that weird feeling like it's just not stable in a hover then you're too low. There's quite a bit of variation in how you can make the heli feel when you combine multiple adjustments of Dial #1 and Parameter G so feel free to experiment.





Head Tuning Notes:

600 and 700 class helis tend to be very forgiving on the adjustments and it's not uncommon to be able to get quite high up in the adjustment ranges before you notice anything bad. Smaller helis tend to be much more sensitive so when you make adjustments do them in small increments.

If you can't get your pitching up compensation (Parameter C) to dial out any dolphin action then you're looking at either a mounting tape, blade, or servo issue. Stock tape can cause this. I've seen a couple situations where the cheapo blades or even some flybar blades not dial in well. Servos that are too weak for your application can cause this too.

Get as much cyclic pitch as possible in your setup menu L especially if you're flying hard 3D.

If piroflips feel very robotic and don't flow well then decrease Dial #1 a couple notches.



Tracking is required whether you are FBL or not. You may not have had to do it before because when step G is performed correctly, and you check the blades for zero pitch, you check both, and if both are accurately zero then the tracking will likely be right too, especially if you have done step G accurately.

In step G you are meant to get the servos horns at 90 degrees, the swash level, and the blades at zero degrees.

Your description of the swash moving when you leave step G, may be indicative of the step having been performed incorrectly. Not for definite, but it's possible as all the physical adjustments to the links should be performed whilst there is a light on. If you leave G with the light off it will jump from the none corrected reference position to the corrected position, where everything should be level, and if it isn't, then you did it wrong. If you leave G with a light on, nothing will move, at all.

Go into step G and the servo selection light off, which is in the reference position, where the MB is providing the signal to the servos at exactly the mid pulse value, 1520us. At this point you should set your horns on your servos physically to 90 degrees*, or as near as is possible within the limits of your servo splines. Do not attempt to get the swash level at this stage, or it will result in an error. Your only task, with the light off, is to get the arms as near to 90 degrees as is possible, on the splines. Swapping horns around can often help you get all three very close at this point, as all the splines are not the same. *On all helis it isn't always 90 degrees, but you are aiming for the mid point in the travel, depending on the geometry arrangement, so that you don't get differential throws. Often this is 90 degrees though, so from now on I'll just say 90 degrees.

You then need to adjust these to be perfectly 90 degrees, and all matching, by cycling through each servo in turn with the rudder and adjusting with the elevator. This is now forming the electronically adjusted new centres, or MB trimmed positions. These positions are used for the rest of set-up, and for flight, not the position at the reference point, when the light is off, which is just dead centre of the servos travel, whilst no adjustment has been performed.

When any one of the lights is on, representing the servo to be adjusted, the other two will be at their adjusted centres too, as long as you have already adjusted them. This means that you can, and should, when you have finished the three adjustments, use this step to level and centre the swash. There is no time limit on this step, so you can take your time over the physical set-up of the swash. All you have to do is make sure that one of the servos is selected, a light is on, so that you definitely have all three servos at the MB stored, electronically adjusted, new centres.

To do this adjust your servo to swash links to now put your swash roughly in the middle of the available travel on the shaft. Roughly in the middle is usually good enough, but if you have any binding issues at one end or the other, you can tweak it up or down at this point too. When you are roughly in the middle of the shaft you can now go on to tweak these link lengths to get the swash nice and level using a swash tool if you have one, or fashion one from a cable tie, or eyeball it if you have a good eye, but do not forget you must have a light on, to ensure that the servos are at their electronically adjusted centres, perfectly 90 degrees, which you have just gone to so much trouble to set-up.

Having positioned and levelled the swash, then you continue up the head and set the blades to 0 degrees, by adjusting the length of your long links, so that you now have three things, precisely square arms, a level swash, and 0 degrees on the blades. These are pre-requisites for moving on here and must be completed correctly.

If you now leave step G with a light on, you will see that the swash does not move at all, and forms the exact servo position for steps H, I and J, and if you successfully completed the levelling in step G then it must be level when you leave it too. If you leave step G with the light off, you will see that the servos jump from the slightly off centre reference position, or starting position, to the corrected stored centres, that you input at G.

So if yours have always moved from level to off level, this means you had it level in G when the light was off, and as a consequence it became unlevel when the light was on, which is wrong.

This now confirms why the tracking is normally correct, in that when you have the servos perfectly set-up in the middle, at 90 degrees, you get proportional movement on each blade. If both blades set off from an equal and precisely measured 0, then they must have the same number of degrees at any point in their range, which, unless the blades are different, or faulty, must mean that the tracking will be correct.

There are some good and very simple ways, not involving a pitch gauge, as it is unecessary at this point, for checking both blades for perfect 0 degrees, which if you get that will mean that your tracking will almost certainly be perfect.

[DMala]

Great, thanks, will print it on the work printer tomorrow