Hi can anyone offer any help/advise i have recently completed a Goblin 380 Spirit build and im struggling to get the modal flying nice.

While in the hover the modal has a front to back wobble that you would normally associate with low head speed or stiff damping.

After spending some time adjusting things but with no luck a friend at my club who is very experienced (but not with Spirit) suggested that i try taking the P gain down a little and the I gain up a little.

Trouble is i cannot see P or I gain adjustments in the software.

Hi,

oscillations during hover are mostly really caused by problems in head. In 95% problem is in the mechanics but it can be fixed easily.
For example too tight blades may cause this.

Our algorithms are implemented in the way that these gains are configured semi-automatically so tuning regulation is not necessary to any helicopter. These gains are configured from for example Geometry 6° parameter too.

What is your Elevator Filter? Is the unit mounted hard on the frame so it can't flex in any way?

If you wish, then changing Cylic Gain will change Proportional gain to some extent. Elevator Pitchup Compensation will increase Integral gain.

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Spirit System developer

Reference to my previous post P & I Gain, i have spent all day at the field today trying to get rid of nose to tail back and forth wobble and a slow side to side tail moment on my Goblin 380.

I have checked all linkages for smooth running, i have tried soft/mid/hard head damming, i have changed the blades been through the heli time and time again, i have increased and slowed down head speed.

I have tried changing all setting in the Spirit System higher and lower values you name it i had done it, i have some very knowledgeable friends at my club but none who is familiar with the Spirit System.

I have attached my current set up but not sure how you will open it to view it.

Can anyone think of anything i have missed, servo's are MKS 92A+ cycilc and tail is Savox SH-1257MG.

This is a new modal so no crashes, flight log shows nothing and vibration level is good.

Thank you for the report.

After viewing your settings, I recommend to decrease Cyclic Servo frequency to 200Hz.
Some servos are not behaving very well with this high frequency, altough MKS servos are very good and I know 92A+ very well.

This behavior is very strange, because it normally does not happen with Spirit if all is mechanically correct. It should be good out of the box without any tuning, always.

Because of it I guess there is probably something we are missing.
Fortunately there are more pilots with Goblin 380, without this problem.

So I believe it can be fixed easily.

Are you sure that Axial bearings are oriented correctly? If no, whole rotor mechanics will be under high stress (but only when rotor is spinning), then even with opposite direction it can be very smooth.

In our forum you can view uploaded profiles directly by clicking the magnifier icon.

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Spirit System developer

Thank you for your reply, i have tonight stripped the head down again and can confirm everything is fitted correct.

I have changed cyclic servo’s to 200Hz as you have suggested.

I have also moved the ball link in one hole on the tail servo to see if it improves the tail although my tail travel limits are now up to 160.

I will be at the field again tomorrow so will see if its any better.

Thanks again.

OK, great.

You can also verify if main shaft is really stright, some parts are bent even they are new. This is also often reason for wobbling like you have described.

I am little bit confused, but do you have problem with the tail too?

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Spirit System developer

Hi yes tail has a slow wag as well, this is a new modal so new set up and just cannot get it right.

I have 3 other spirits on 3 different modals and they pretty much worked out of of box but I'm struggling with this Goblin.

Thanks

Another day at the field today trying to sort out my Goblin 380.

Still no luck, myself abd friends have totally stripped down the heli and gone through it checking for anything like bent/stiff linkages ect, we found nothing at all wrong.

I have tried head damping soft/meduim and hard, head speed in the video was tacked by a friend at 3050rpm.

I have posted a video in the hope someone has had this and can help.

Sorry the video is the wrong way up i have no idea how to turn it but you can still see you problem.

Regards Alan

This is the video sorry its sort, this seems to be the max file size the site will allow.

Rgards Alan

Thanks for the video.

It is really very strange.

Did you tried to enable Extended signal processing, just for test?
Also did you checked if cyclic is without any movement on the ground when motor is running? (without blades)

I know that bigger Goblins have little bit problems with rotor heads in some cases and it was nearly impossible to fix the problem. It is caused by imbalance that is created when rotor is spinning. Oscillations on the video are very same as when something is not balanced.
Can you check if there is any play in the mainshaft?

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Spirit System developer