Pirouette out of control, V120D02S

[gabeoravitz]

Ok so this one I can't figure out. When I try to spin the heli in place, it doesn't stay level and by the time it completes the 360 turn it's leaning one way or another and wants to go flying into the [wall, tree, ground, etc]. I'm not giving it any more input other than rudder. Is this normal? Am I supposed to be correcting for a heavy lean when doing a piro? It hovers very solidly in place otherwise.

[dbennettya]

Everything needs to be spot on and setup correctly to get pretty clean slow piros. However, usually very small inputs are required to keep the heli in the same place while rotating. Things to check:

CG
RX mounted perfectly level
swash level in adjust mode

Try disconnecting the motor. Then put collective at hover position with heli on skids on a flat level table. Now slowy rotate the heli like you want it to do in the air. Does the swash stay fixed or move around. That is what you are or aren't fighting.

Also note that the heli tilts a little during hover due to the torque and offset of the tail rotor. To get better piros maybe try mounting the RX so it is level when the heli is hovering. You'll probably need to make a custom adjustable RX mount to get it adjusted the best. First test this theory by putting say a 1/8" or so under one skid (depends on your tail setup). Then do the rotation test above and see what happens. Tweeking for lowest swash movement would yield the best piros. I haven't actually tried this just brain storming.

Good Luck, Don

[gabeoravitz]

Your wealth of knowledge on these forums is greatly appreciated, Don! Thanks!

What I'm wondering though, is that I see lots of videos of people doing piros and it doesn't appear that they're manually correcting. I just can't believe that everyone would have mounted their RX at a slight angle :-/

[ChitownMatt]

Like Don said, take a look at the RX and make sure it isn't sitting funny or touching anything... even a wire.

Triple check your transmitter and make sure you don't have any kind of control mixing turned on.

Also, a bent feathering shaft can make a heli act funny on pirouettes.

What do you have your Rudder DR/Expo set at? I keep mine at 100% rate and Negative 30 expo., just so when I kick the tail around I don't inadvertently bump the the collective.

You will always need some sort of cyclic corrections, but what you are describing sounds a bit more than expected.

[gabeoravitz]

I installed this RX myself and it's positioned perfectly, I believe. Nothing is touching it. Though I don't have it leaning, as suggested by Don.

I'm thinking a lot of the problem comes back to my crappy transmitter (WK-2602). I just can't afford a 2801 pro right now. Those things are spendy :-(

Mixing is only available for the throttle. It's adjusted using the "Rudmix Gyro" setting. When I apply throttle, the tx also applies rudder mixing. Though if I turn it off, the bird's gyro can still keep the tail straight. I'll disable it and see how it piros.

I just checked the feathering shaft the other day and it's straight as an arrow.

Dual rates on my tx are not configureable. It's 100 percent for full, and 50 percent for the lower rate. It also is for cyclic AND rudder. I believe that servo expo covers rudder and cyclic together as we'll, because when I adjusted my cyclic servo expo, I could see a change in the rudder. I don't think servo expo applies to collective servo movement. The documentation doesn't state so, at least. I'll physically check when I get home.I can't really give you the expo in terms that relate to how your tx measures them (unless it's just a matter of using negatives instead of staying above 0). My expo setting is between 0 and 100. The tx documentation states,

"To rotate V2 aiming at the central point (50%) is a linear relationship."

It then shows diagrams showing the expo curve and how it relates to the direction of knob rotation. Turning it lower makes the sticks less sensitive at first. So, I put mine at 15% to keep it from being sensitive.

MOST of the time I can recover after the piro, but it just seems like slightly more than it should be.

[gabeoravitz]

UPDATE: As of today, I can piro and it stays perfectly level. In the last few days, I've fine tuned the expos and curves, so maybe that did it? Don't know otherwise!

[jonbailie]

These helis won't stay perfectly level while piro-ing. You will need to make small corrections to keep them stable and level. This is normal behavior for these machines.

Piro routines are a great way to practice orientations because of this

[gabeoravitz]

Well it stays almost level now. Before it would seriously go out of control when I tried. After fine tuning everything, it seems to work great.

[Heli-opolis]

First off, thanks very much Don for the idea to play with RX position to see what affect it has.

Although not my 02S, which has the same 'problem', I'm experimenting with my Mini as I don't have to worry about crashing it as much. One added benefit of trying it with the Mini is that I can easily adjust the angle of the RX simply by removing two of the three mounting screws and rotating it to match the angle of the bird.

I plan on trying that this evening so I'll post back with my results, which hopefully won't be a bird in pieces.

Originally Posted by gabeoravitz

I've fine tuned the expos and curves, so maybe that did it?

Or, you instantly got good enough so that you could automagically correct for it's poor flight characteristics without knowing it. Or, maybe not.

I wouldn't think the expo's would have much to do with it other than compensating for over correction although that could be a contributing factor as well I would guess.

On the other hand, your adjusting the curves sounds interesting! Can you describe what you adjusted and in which direction and how much relative to a 'stock' setup?

[EDIT] Oops, my bad, if one of the expo's you adjusted was the rudder and added a good percentage of negative expo, that would certainly have an affect although for me, it just means I get into trouble faster.

[gabeoravitz]

Honestly, I'm not sure which aspect of my fine tuning did it, but SOMETHING made a difference. It wanted to sail when I would spin it before.

As for fine tuning it, I just made sure that at 50% throttle in stunt mode that the swash was in the center of the main shaft, and that the servo arms were as level as can be, and that I had 0 pitch. Then I adjusted travel of collective and cyclic to make sure that there was no binding when I was a full positive or full negative collective.

I did all this because I felt like I was getting bogging when going full negative or positive. Now, I got a lot less bogging and it's more crisp. However, I now am realizing that my lipos have been crapping out all along, I'm pretty sure. I ordered a replacement from Hobby King that has good reviews for our bird. I'm thinking I'll need to re-setup the pitch curves again once I actually have full power back, because once I get full torque and head speed, the optimal angle for the blades to have the most thrust without bogging, will change.

[Heli-opolis]

I took Don's advice and removed two of the three screws in my Mini and not only was able to perform a complete piro, as before it would lurch off to visit the wizard before making it even half way around but got up to three piro's in a row hands-off on the aileron/elevator stick!

The problem was though, with only one screw holding it and it being threaded into plastic at that, vibrations and the canopy pressing against it seemed to want to make it return to its original position but at least it proved to me that the position of the RX can have a BIG affect.

I've got a lot more playing around with it to do before I try something similar on my 02S but being able to piro a complete revolution hands off, to say nothing about 3 in a row, gives me hope!!

[hjns]

Hi guys,

As these small helis always tilt a bit to the right, due to the tail rotors pushing the heli to the left under the plane of the main rotors, you will always have to correct a little bit during piros. Go hover the thing in front of you from all orientations, and you will see what I mean.

If your 120 size heli does a piro handsoff, you really need to congratulate the 3-axis gyro for thinking with you here, and keep the darn thing level.

[Heli-opolis]

Originally Posted by hjns

If your 120 size heli does a piro handsoff, you really need to congratulate the 3-axis gyro for thinking with you here, and keep the darn thing level.

Also, thank Don (dbennetya) if his advice was followed to adjust the position of the RX to be inline with the natural tendency to tilt to one side.

It's amazing the difference it makes!

[gabeoravitz]

Originally Posted by Heli-opolis

Also, thank Don (dbennetya) if his advice was followed to adjust the position of the RX to be inline with the natural tendency to tilt to one side.

It's amazing the difference it makes!

You did this and noticed a big improvement? Was it an overall improvement or just with piros?

[Heli-opolis]

Originally Posted by gabeoravitz

You did this and noticed a big improvement? Was it an overall improvement or just with piros?

Hovering was unchanged, piro's greatly improved, beyond that, I don't know.

[gabeoravitz]

WOW!! Piros are night and day with my RX positioned as suggested by Don!! SO AWESOME! Thanks Don!! So simple yet makes the world of difference.

Now, I can piro my D02S almost endlessly IN MY LIVINGROOM.

[Heli-opolis]

Amazing, isn't it!

Are you able to piro in either direction equally well?

I find that piro'ing in the direction my Mini wants to rotate naturally due to torque piro's more smoothly than the opposite direction but even in the opposite direction, I can usually pull off a few piro's whereas previously, I couldn't even get it to do more than a quarter turn without it wanting to go off to visit the wizard.

I don't know what this will do to its 3D ability but at this point, I don't care because just being able to practice orientation with less worry of losing it just getting into various orientations makes it MUCH easier to practice.

Just out of curiosity, how much did you have to shim one side of the RX to get it to where you needed?

With the Mini, it is trivial to do, you just remove two of the three RX mounting screws and rotate it on the remaining center one as far as it will go, which isn't really all that far.

[gabeoravitz]

Piro in either direction works great. My own skills limit me though. I still have a tendency to apply throttle accidentally when I try to go in the Heli's natural spinning direction. If I concentrate, I can do that direction fine though haha.

All I did was take a sliver of 3M double sided stuff and put it under the one side of the RX.

[Heli-opolis]

How thick is the 3M double sided stuff?

On a different but related note, how is the left to right balance/CoG of your 02S? Is it perfectly balanced left to right?

[gabeoravitz]

I don't have a measuring tool on hand right now, but i'd guess around 1.5mm.

CoG/Balance doesn't seem to change when doing this.