Phasing issue - tail goes down with right ailerion input - HeliFreak
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Old 06-22-2017, 11:31 AM   #1 (permalink)
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Default Phasing issue - tail goes down with right ailerion input

Hi.

I try to setup my Soxos 700 with SK720BE and have some problems. It seems that I have a phasing issue. On left aileron input the tail goes down and on right it goes up. Should I change phasing in SK720, what do you think? In the meanwhile I will mount the SK720 again. But the mounting looks perfect.

Cheers,
Nils

Last edited by augur; 06-22-2017 at 03:53 PM..
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Old 06-22-2017, 05:55 PM   #2 (permalink)
 
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Nils, what type swashplate have you selected? phasing is radial not pitch,,,,,, post a log to be sure,,,
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Old 06-23-2017, 03:16 AM   #3 (permalink)
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Hi.

Pitch is not the problem, it is 100% stable on it. Ail and Elev input are not fine. Also there is a wobble which I cannot compensate with main gain, bell gain or hiller.

Attached a screenshot, have vibrationlogs available only.

Cheers,
Nils
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Old 06-23-2017, 08:53 AM   #4 (permalink)
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Shoot a pic of your heli. A top view looking down on the head with the swashplate below would work. Get the 720 in the pic as well. Maybe a few pics if one with everything is too far away to see detail.
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Old 06-23-2017, 08:59 AM   #5 (permalink)
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Default Phasing issue - tail goes down with right ailerion input



Swashplate is 120 degrees
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Old 06-23-2017, 11:11 AM   #6 (permalink)
 
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I'm not talking about collective pitch? Pitch = nose up/down axis.

Looking at your figures, the servo arm lengths are wrong, swash mix is way too high, you should be aiming for a 60/60% mix using 100% SK servo travels,,,,,
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Old 06-24-2017, 08:58 AM   #7 (permalink)
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Everything in your pic looks good. You do not need to adjust the phasing in the 720.
You have a different problem and need to figure that out. Georgi is a good guy to have helping you out, way more experience and can interpret the logs like nobody can. You'll get it figured out.
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Old 06-24-2017, 11:09 AM   #8 (permalink)
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Quote:
Originally Posted by georgi UK View Post
I'm not talking about collective pitch? Pitch = nose up/down axis.

Looking at your figures, the servo arm lengths are wrong, swash mix is way too high, you should be aiming for a 60/60% mix using 100% SK servo travels,,,,,


Hi.

The Soxos does not allow to change the Servo arm length. So I cannot change it.

Cheers
Nils
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Old 06-24-2017, 05:11 PM   #9 (permalink)
 
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Crap design then, you need to be around 19mm on the servo ball. Not only will any compromise here affect how your stick feel is, but also how the gyro can't work with it either,,,,,

Does this heli specify a particular gyro use?? Obviously not a SK or V-Bar is suitable,,,
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Old 06-24-2017, 06:03 PM   #10 (permalink)
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Default Phasing issue - tail goes down with right ailerion input

I owns a Logo 600 and it matches the standard setup of them. Had the same geometry there. But on Logos it is possible to change the Servo ball to 19mm which I done there. This is not possible with my Soxos. But there is no specific FBL recommended.
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Old 06-25-2017, 03:38 AM   #11 (permalink)
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Ok, done some tweaking and now I am 65 cyclic and 46 collective. Also mounted the SK720 again with ports to left instead and hard mounted.

Still same behaviour. Like to try with negativ phasing setting. What do you think about this?

Cheers,
Nils
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Old 06-25-2017, 02:58 PM   #12 (permalink)
 
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Nils, you are going nowhere fast, to identify phasing is done by inverting the heli to a hover. If the tail has moved but then returns to it's original heading when upright again then the phasing is out,,,,

If you don't post a log then I can't support you,,,,
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Old 06-30-2017, 03:31 PM   #13 (permalink)
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Why can you not eliminate the Soxos servo hub assy. and just mount up some decent arms with 19mm spacing? Looks pretty simple to me? The linkage does not need to be truly vertical for this to work! All we need is a flat swash from neg to full positive and level at the middle with the right Fbl ratios. All this can be done with the servo settings and the right arms in place.

Trying to tune a good gyro by altering its setup to bandaid a crap linkage geometry is nuts. You will find little success here by doing so. I have modded quite a few models to eliminate these problems in the past. My current 600Esp is a good example. All its horrid stock linkage system is long gone. Now direct servo to swash. And no the links are not vertical at all. Doesn't matter anymore with good fbl systems in place. In the old flybar days things were quite different. Not anymore. I have also flown with about a dozen different swashes and heads in other brands not meant for the heli.
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Old 07-01-2017, 08:35 PM   #14 (permalink)
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Some thoughts. Check to see that the forward servo is plugged into the "SW-C" position and that the left side is in the one marked "SW-L" with the last one into "SW-R". It's not that you haven't wired a helicopter before but mistakes can be made. Also make sure that you choose the correct orientation of the bus. No two blade head I have owned has ever needed phase correction even when the swash plate driver was independent of the head hub and I have put a number of helicopters together from two to five blade configurations. Hope this might help.

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Old 07-11-2017, 01:04 PM   #15 (permalink)
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Quote:
Originally Posted by dcope17 View Post
Everything in your pic looks good. You do not need to adjust the phasing in the 720.
You have a different problem and need to figure that out. Georgi is a good guy to have helping you out, way more experience and can interpret the logs like nobody can. You'll get it figured out.
the picture can't tell anything regarding the phasing of a heli. the only thing we can tell is it "looks" straight but the thing is not all helies have 90 degrees phasing!! and when that happens, and there is no mechanical phase trimmer (like the older logo 600) than the phasing has to be set in the gyro.

Nils - specifically for your problem we have to see a log or a setup file to understand your mechanics. a mechanical problem can cause this, especially if you get values like 75 for swash mixing.

From the picture it look like you have very small level on the main blade grips which should call for longer servo arms than usual...
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