Wobbly Piro's

[HeliHamish]

Hello all

Had about 6 flights today on my newly built compass 7HV, with the newly installed Spirit Pro.

I've still got a lot of tuning to go, but there's one thing I can't seem to fix. When I do a piro, in a hover or FF, the rotor disk does not stay flat and wobbles. I've checked the piro Comp and it's definitely the correct way, the swash stays facing the same direction when I rotate the heli body. My spirit is installed with the supplied M3 tape and is on a flat level surface

Also, the highest I can get my Cyclic gain without a quick osalation is 40, and is 35 or below for no wobble when I pitch up to go into a loop etc. This seems quite low, is it not?
Also my tail gain in my TX is only about 20-25 for no quick Wag (this example is at approx 2100 rpm). The tail manipulation is at 1.25.

My cyclic servos are BK7001HV, my tail servo is a BK7006HV.

Thanks for your help!
Hamish

[ZeXx86]

Hello,

unfortunately it looks rather as a servo issue. Many pilots with these servos are describing oscillations and issues like this, because BK/RJX and TGY clones are suffering from electrical noise - many of these have half-cutted cables by aluminium enclosure. So there is a short between enclosure and one of these cables. It is not visible by eye without dismounting as it is under rubber grommet.
So in the flight servos are oscillating randomly. Some servos are jittering right when the motor is started even on the ground, because it is picking all the noise. Some are jittering even when you touch it by finger.

Problem is in many cases improved by decreasing power supply voltage under 6.6V.

So what I recommend is to try to measure shorts between cases and find which servo is making a problem.

[HeliHamish]

Damn, that is not what I wanted to hear! Haha

Can't really go down to 6.6v as I'm using a 2s lipo to power electronics
And I haven't got anything to measure shorts.
So is there no way I can take the case of the servo off then try isolate them with insulation tape or something? Put it around the wires or inside of the case?

These servos are brand new

[HeliHamish]

Issue solved, redid setup and piros are now flat

[ZeXx86]

I know it is bad, I can be wrong, but at least you know what can be the issue.
Because of these oscillations servos can be too hot and damage.

You can try to verify the problem so that you spoolup the motor without blades and verify which servo is making troubles. With motor started issue can occur more likely.

By finger you can push to the servo arm in a different servo positions - you could observe strange behavior and this behavior is happening also in the flight.

Oscillations normally shouldn't occur even with 60% gain, but even that it is not indication that your servos or something else is faulty.
If servo settings is somehow inprecise it can also cause such problems.

[HeliHamish]

Okay piros are not flat, it was hard to tell when the sun was going down but I test flew again and the piros are the same, wobbly

One thing I have noticed...

Is that the swash is leaning back after initilization, when it sets "level", the swash is not level.So when I first plug in the power, the swash is perfectly level. After it has initalyzed, and the servos twitch and jump etc, the swash has set "level" but the swash is leaning back. My elevator servo arm does not go to 90* at mid stick like how I set it, instead it's down further causing the swash to not be level

It's like the subtrim hasn't been set properly but I got it perfect this morning, set save, went for a fly and noticed the piros are wobbly and my swash was not level when I landed.

I have a very quick video I will try to post.
Is this still likely to be a servo shorting issue?

Thanks,
Hamish

[HeliHamish]

Edit- can't post the video for some reason.
But here's a pic showing the unlevel swash after initalyzation

[HeliHamish]

This video of startup should work...
http://youtu.be/g-1PYnAdJ40

[HeliHamish]

Again another discovery, just trying to give people as much info as possible... This is very weird

So the swash was always leaning back. So what I did is go back into the software and adjust subtrim again to get the swash PERFECTLY level at midstick, and to stop the swash from leaning back.
So that was all good, pressed save, quit software, unplugged spirit and unplugged my lipo.
Plugged the lipo back in, waited for the spirit to boot up and servos twitched, bam my swash plate is now leaning forward after initalyzation

It's as if the subtrim is tricking me in the software, and when not connected it's different

Now, to add more to the puzzle... To make sure it's NOT the servo, I swapped the ELE servo port with the AIL servo port on the spirit...

After initalyzation the swash STILL leans foward, but ALSO slightly to the left. When I swap them back it only leans foward. (This was done without my TX connected by the way)

This is very very puzzling

[ZeXx86]

You should set and verify subtrims only with Subtrim (tuning) enabled.
If it is disabled, there are algorithms that can change the level.