Logo 550sx motor fluctuations and tail wag

Hi,

This is a brand new Logo 550sx build with following components
Stock Scorpion motor
YGE90LV v3 Mikado edition ESC
Savox servos for swash(1257TG) and tail (1290MG).
Silverline Vbar unit.

I'm running the Vbar governor mode.

You can see in the following video that the motor is making some fluctuation sounds as if it is intermittently loosing power and then catching up. This seems to translate into the tail wag. Please put on earphones to hear the motor sound better.
https://www.youtube.com/watch?v=o4dfpYOwoHQ

Any clues what is going on? I've re-done the YGE ESC programming via radio sticks. I don't have a YGE progcard.
I've re-built the head, drive-train and the tail but no luck still.

Without the main blades, on the bench I do not see this effect so it seems to happen only while loaded. With the main blades on and the heli on the ground with zero blade pitch I do see the tail kicking at random intervals after spool up.

Vbar setup file and picture attached.

Please give me some ideas to check. Thanks.

regards,
Roger.



Edited 1 time(s). Last edit at 05/16/2017 11:15PM by stark.

I think what you hear is the tail noise and not the motor.

To check this - just disconnect the RPM cable, the ESC will now run on our throttle curve only. If it is still there - it is a tail issue.

let me know.

regards (EN) / Gruss (DE)

Rainer Vetter

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I didn't yet try with RPM cable removed but I tried the following things on stock 14T pinion.

1) Switched to Castle ICE ESC with internal governor @ 2000RPM. Very smooth motor sound and no tail wag.
2) Switched to YGE90LV with internal governor (mode 2). I don't know the exact RPM but it was probably less than 2000. Also smooth motor sound and no tail wag.
3) Switched back to VBAR governor with YGE90LV (mode 1). @2000 RPM it is mostly very smooth and there is sometimes that motor fluctuating noise. At 2100RPM I see more of the noise like you heard in the video.

Is 14T insufficient for 2100RPM? Or is the problem somewhere else?



Edited 1 time(s). Last edit at 05/19/2017 09:23PM by stark.

I have a 550SE and calculated a 14t as "on the edge" for 2000 1/min. - So 2100 may be too much for a 14t and the 1100 kv motor.

regards (EN) / Gruss (DE)

Rainer Vetter

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Posting and answering - please use a PC and a standard keyboard. Answer all questions fully, take the needed time, don't forget probably requested attachments.

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Another theory could be that at 2100+ Tail is causing problems.

If I remove RPM cable as you suggested, what RPM will the rotor run at fully charged pack?

We have a throttle curve "behind" determined by basic throttle and collective add - see graph here:

http://www.vstabi.info/en/node/2031

2nd image from top ;-)

regards (EN) / Gruss (DE)

Rainer Vetter

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Posting and answering - please use a PC and a standard keyboard. Answer all questions fully, take the needed time, don't forget probably requested attachments.

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With RPM sensor cable removed I was getting quite low Rotor RPM. The motor noise was not there though. But this doesn't prove anything.

I changed to 15T pinion and internal governor mode 2. I don't see the problem there but the governor gain is not high enough. I don't have YGE progcard to make changes there. Anyway my target is to get VBAR governor perfect.

Back to vbar governor mode @2100 RPM, the motor noise and tail wag seem to have gone at the start of the pack but start to creep in later in flight.

I've run out of ideas what to try next. Things have got a lot better than when I started so I'm happy. It has got to the point that it doesn't bother me much in my flying routine. But it'd be nice to know the root cause and iron it out completely. Maybe everything (lipo, mechanics) just need some more running in .

One more thing I haven't played with is the VBAR governor gain. It has always been the default 30. Should I be increasing or decreasing the gain to improve the situation?

OK - now lets make it perfect:

First, lets dial in the static values (basic throttle and collective ad) w/o gov.
Please use a half full battery for this.
This procedure should be done by bankswitch for each rpm.
Disconnect RPM
Lower tail gain 20%

Turn on the heli at zero collective, dial in the basic throttle unless the requested HS is approximately there.
Go in a medium climb and dial in the collective ad unless it sounds not overspeeding or slowing down.
If the tail can't keep straight now - ad more collective torque precompensation at the tail.
Note: a little bit slowing down at hard attacks is accepted otherwise the tail will be into trouble too ;-(
Dial cyclic ad from 1/3 of collective ad.

After this - dial tail gain back to old value
Connect RPM
Start gov with 10% gain - it might be not that much needed now.

regards (EN) / Gruss (DE)

Rainer Vetter

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Posting and answering - please use a PC and a standard keyboard. Answer all questions fully, take the needed time, don't forget probably requested attachments.

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"Go in a medium climb and dial in the collective ad unless it sounds not overspeeding or slowing down. "

How do I do this? Please note that I'm on v5.x pro. Is the below procedure correct?

- In governor tab 1, I select "Banked Expert" and type "on, fixed headspeed"
- In Throttle input channel from receiver I select "internal"
- For Preset channel from receiver I select "CH3 | ESC | Preset"

Now in main screen I do see a "V" Throttle curve. So basic throttle would be to change the center point (50). To change collective add I just tweak the V curve at both ends.

Is this correct?

Yes it is correct!

But - seeing a V curve you are not in e-gov mode (which i thought), it may be nitro combined or expert mode ...

regards (EN) / Gruss (DE)

Rainer Vetter

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Posting and answering - please use a PC and a standard keyboard. Answer all questions fully, take the needed time, don't forget probably requested attachments.

Für Posts und Antworten bitte einen PC und eine richtige Taststaur benutzen sowie alle Fragen vollständig abarbeiten. Nehmt Euch Zeit, beantwortet Rückfragen in Ruhe und vollständig.
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I can see the V curve in main panel only if I choose "Internal" for throttle input channel. There is no collective add field in Governor parameters window.

If I select some receiver channel for throttle input then I don't see the V curve and no collective add option either. In this case how do I dial in basic throttle and collective add? Should I be doing this in the radio's throttle curve?

Sorry for confusion - i was on V6 ...

V5 has some limits - but can be cheated ;-)

I would do it this way:

set up for e-gov completely including TX channel for Headspeed control, use one bank for each headspeed for best result

You can access the throttle curve by toggling the gov in setup to "nitro combined" - but do NOT press reset. Toggle back to electric before flying again!

First, lets dial in the static values (basic throttle and collective ad) w/o gov.
Please use a half full battery for this.
This procedure should be done by bankswitch for each rpm.
Disconnect RPM
Lower tail gain 20%

Turn on the heli at zero collective, dial in the basic throttle unless the requested HS is approximately there.
Go in a medium climb and dial in the collective ad unless it sounds not overspeeding or slowing down.
If the tail can't keep straight now - ad more collective torque precompensation at the tail.
Note: a little bit slowing down at hard attacks is accepted otherwise the tail will be into trouble too ;-(
Dial cyclic ad from 1/3 of collective ad.

After this - dial tail gain back to old value
Connect RPM
Start gov with 10% gain - it might be not that much needed now.

regards (EN) / Gruss (DE)

Rainer Vetter

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Posting and answering - please use a PC and a standard keyboard. Answer all questions fully, take the needed time, don't forget probably requested attachments.

Für Posts und Antworten bitte einen PC und eine richtige Taststaur benutzen sowie alle Fragen vollständig abarbeiten. Nehmt Euch Zeit, beantwortet Rückfragen in Ruhe und vollständig.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Für Einzelkommunikation bitte ausschließlich Email verwenden! - PN, Messenger, Chat usw. werden nicht bearbeitet.
For single user communication please send a email only! PM, Messenger, Chat etc. won't be read.

Rainer,

I followed your governor static throttle tuning steps but it didn't help with the issue. So problem is elsewhere.

I replaced the YGE90LVv3 and the Standard Vbar with a YGE90LVv2 and mini-vbar-V5pro from my Atom but the exact issue was still there. This time using just Electric governor option with not static throttle tuning. Looks like mini-vbar has no option to do static throttle for governor.

However, if I increase the governor gain from 30 to 35 the issue seems to be much less.

So I think the issue has got to do mostly around governor to tail interaction.

regards,
Roger.