Tail wag issue - light in the tunnel?

[Jack2010]

I have decided to separate my loooong thread and focus here on the tail wag problem I have. You can read the begging here: https://www.helifreak.com/showthread...=235586&page=6


OK, I know I have said this several times but this one is for real (hope so :o). I believe I know the source of the problem. Finally. However I don’t know what to do next…

So, first things first. I don’t really know why I have not started with this in the very beginning. I have decided to detach everything and see if the tail wag will be still there.



To make a long story short - the only thing that is left are the motor with the pinion and the front gearing (the gearing from the main shaft has been removed). All electronics is operating.

I start the motor and… I can see that the tail servo arm (tail push rod detached) is moving left-right so the servo is getting the signal from the gyro.

The intensively of that move depends on the rpm's. There are some ranges generating more vibs/servo movement and some less. If I take the gyro in my hand while motor on and pull it up quite strongly it looks like I isolate it from the frame and the servo stops moving (meaning the tail wag is gone). If is push it down quite hard, the wag is limited but still there. Gyro gain at 67,5% (range from 50-100% = 35% if your HH mode gyro gain range is from 0-100%).

With that said the key questions are:
a/ should I focus on the source of the vibrations (motor, gearing, one way bearing, etc.)
b/ or I should rater focus on isolating better the gyro from the frame (I know, I know - I can always relace the gyro for the Spartan/Quark )
c/ both

Now, I have some ideas on few ways of gyro isolation by playing with different foams and metal plates, but I have no idea on what to do in order to eliminate vibs as such. Any ideas? Please...

Perhaps I could remove the motor pinion and see if the vibes are the same - that would tell me weather that the motor itself is generating the problem, or it is somewhere in-between the front gearing/ motor pinion…

If it is the motor itself - are there any solutions??? Or need to replace it...

BTW - I was a bit disappointed while building the heli that the gyro plate was really loose in the frame. As far as I sow it in other helis it is not the case. So, decided to change it making it sitting in the frame quite firmly. Remove this mod today… and the wag got smaller immediately (but not eliminated 100%).

[Mikej]

Jack,

Good news that you are zero-ing in on the problem - I would say that you need to address both areas - as I mentioned in your other thread the GP750s seem to be very succeptible to vibes and messing about with different tapes / foams can help. Do you have any other gyros that you can try on the 425 ??. I have used the foam / metal / foam sandwich often with good results - I often use a coin as the metal as they are quite heavy and (hopefully) damp out a lot of the vibes.

As regards the vibes I would start by finding out where it is coming from - remove motor + mount and see how badly it vibrates - if that shakes then see if you can find the problem (check UKGroucho's thread re his motor), if the motor is smooth on it's own then try with primary gear and OWB shaft and see if it comes in the, check all bearings to make sure that they are smooth and free - no notchiness.

Good luck mate - you deserves some

[Jack2010]

@Mike - thx for the support and I'm not going to give it up - HAVE to overcome those issues and become another happy Gaui user . One way or the other but will fix it

Will play with foams/tapes/plates/coins and see the results. I have Gaui GU-210 and Spartan DS760 on the way, so will test them as well, but... I would really like to eliminate/ minimize the vibes first (if possible at all). The last thing I would like to see is to mount the new gyro and get the same problem. On the other hand I know many freaks flying GP750 on their helis with no issues so it must be achievable, right? At the end of the day it is not the worst gyro on this planet...

@UKG - read your thread (https://www.helifreak.com/showthread.php?t=228211) and your Gaui motor experience/ gearing issue. However I'm not 100% sure if I understood it well enough. With that said - is it possible to photo-document your case (especially the motor thing) and describe the issue one more time, please. I hope that visual + written explanation would clarify this to me. Thanks in advance if doable.

[spootman]

Another thing to check is how the wire for the gyro is mounted, if there is too much tension on the wire it can transfer vibes to the gyro bypassing the the foam tape. Not sure where but I remember seeing a thread where people were having gyro issues and they solved them by rotating there gyro 90 degrees and remounting. Hope you figure your problem out.

[fox74]

Jack,
I was wondering have you figured out were the vibration come from, is it the blades ? or main shaft is not straight ? I would take the blades off, then rev up the motor to see vibration stops or still there, this might narrow it down.

[Jack2010]

Originally Posted by fox74

I would take the blades off, then rev up the motor to see vibration stops or still there, this might narrow it down.

This is what I did - not to many things left as you can see from my post...

[Jack2010]

Originally Posted by spootman

Another thing to check is how the wire for the gyro is mounted, if there is too much tension on the wire it can transfer vibes to the gyro bypassing the the foam tape.

I am aware of this and I believe there is no tension there.

Originally Posted by spootman

Not sure where but I remember seeing a thread where people were having gyro issues and they solved them by rotating there gyro 90 degrees and remounting.

Will try this, thx for the hint.

[Jack2010]

Investigation continues... kinda like it...

So, I’m still searching the cause of my issue with the tail wag and it looks like the motor is the main suspect now. I would like to work it out before will play with gyros/foam tricks.

I have visited the local Gaui RC store and saw two other identical motors (Gaui GM-502 1500W, 1100KV). I have immediately spotted the difference vs. the one I have. When spinning by hand those motors in the shop it was very easy and quite smooth. I mean, I had to use very little force to spin the part that is normally spinning while keeping in my hand the part that is attached to the frame/mount. Also the tik-tik (click-click - you name it ) was barely recognizable.

On contrary if I do the same with mine I have to use a bit more force but the tik-tik is so much more noticeable. I can’t say it is not working at all but the diff is very obvious.

Now, as I am not an expert the immediate question is: is this important or not? Can it vary motor to motor and mine is just a bit different but still within the „normal” behavior range or such observation tells me something is wrong?

Any experience/ideas/suggestions?

[Mikej]

Jack,

I've had that with motors before but they both work fine - I'm not sure that it really means anything I'm afraid. Hope I'm wrong.

Mike.

[Jack2010]

The tests I've done today:

1. Removed the motor with the alu mount and run it - no particular issues observed. Keeping it in the hand you can feel it is working, but would not call it vibrations. Just v.tiny. Unfortunately I do not have any other motor to compare... Very quite I must say.

2. Removed the pinion and put the motor with the mount without screwing it to the frame. Some minor (very) vibes generating almost no servo movement and in some rpm ranges (rather high) no wag at all. Now you can hear it.

3. As above but tighten the screws to the frame firmly. Visible servo move/wag and a bit of the drift sometimes. Some rpm’s worse, some better but the wag is there. No question about it. You can feel vibrations on the whole heli no matter where you touch and they are waveing so to speak with constant rpm in some specific rpm ranges.


Can it be that somehow the frame itself is strengthening the vibes like when you have two waves with the certain frequency that can either reinforce or weaken themselves?

At the moment I have now no doubts that the motor is the mother of all my problems with the tail wag. Everything else seems to be working just fine.

If it was like in #2 I would only focus on better gyro isolation been positive I can be successful, but with vibes like I see in #3 I would say this needs to be improved first.

Any suggestions on how to do this other than new motor install?

[atkinson]

Try using a piece of zeal tape. Its this green silicone like gel tape that was designed for 1/5 scale servo tape. I was having tail problems untill I stuck some of it on. Check the "see your heli pics on top of this forum" and I spoke of it there. May be worth a shot if you can't track down the problem.

[Jack2010]

OK, I owe you an update...

So, went to my local Gaui RC shop to show them my problem with the vibrations coming IMHO from the motor. We agreed that this is wrong. The guy had two other motors like mine. I asked if we can test those two and he agreed.

#1 - vibrations were smaller, but still there generating a bit of the wag but promising.
#2 - vibes so low, that the gyro was almost not reacting to it - bingo

Immediately said (like a baby ) - I want this one.
He was bit surprised, but after a while he agreed to it so I left the shop with the new motor. How cool it was!!!

So, went back home to do some more advanced testing. I have to say that vibes are still there but limited so much that the gyro is almost not reacting to it. Almost. With that said decided to put all things together (as I have disassembly half of the heli including the rotor head ) and tried how it is now... and it is much, much better.


Can’t say fixed 100%, but right now I have a believe that mechanical vibrations are limited to the extend that I can move forward again and focus on gyro isolation as well as see the diff between Spartan ds760 and Gaui GU-201 finding the best setup.


Have to say that was so afraid of this test hovering and feel so relived after it. If that did not help (motor change) I guess I would abandon it.


My HH gain is 65%-70% (on the scale 51-100%) with almost no tail wag, but has small clockwise drift. In rate mode with 45% gain (scale 0-50%) the wag is gone, but there is a small drift opposite direction.

Basically I need to tune it a bit and in the first place will work on Align gyro isolation. I have some local vendor mounting tape that is suppose to be doing miracles. Will see and will let you know the outcome.

I have to say that I am so glad I came to this Gaui forum... many thanks for the support, especially to Mike and UKG

PS. I have to say that such big diff between 3 Gaui motors was a bit of a disappointment when thinking about their quality and reliability.
PPS. Came to a conclusion that maybe plastic frame is much more vibes absorbing that people with such setup do not have issues and that is why there are no reports like mine.

[spootman]

Glad your starting to get it sorted out. I just took my XF frame out for a test hover yesterday and have some vibe work to do myself. They weren't bad enough to mess with gyro but enough to make the vertical fin blurry. I will say with this frame and my batteries the COG is spot on.

[Mikej]

Good news Jack - glad to hear that you are making progress, just int ime for the snow

[Jack2010]

Mr. Sponge Bob did the job

In HH mode I have 63% (65% is suggested to start with) and there is no drift and the wag is almost not there. Can't say it is absolutely rock solid, but acceptable for sure. I'm 97% happy with what I have achieved and can fly it now with no issues. The 3% is for the winter and assuming Spartan DS760 is better than Align gyro I'm considering case closed.

Can finally move on to the phase "B" - installing the flymentor... uhhh, that was rough I can tell you...

[Mikej]

Just fuggin fly it man


Glad you are getting there

[ukgroucho]

Just stick the Spartan on.... glad you are getting it sorted.

Sorry I did not respond to your reques for more info on my Gaui motor issue - was on vacation and not checking into the forum.
My Gaui 504 was incorrectly assembled in the factory... it ended up damaging itself so that even after I spotted the issue and reassembled it correctly it was generating lots of vibes. The vibes caused my BeastX FBL controller to have problems.

It was a good motor when it was working correctly....

[joe1l]

Originally Posted by Jack2010

Mr. Sponge Bob did the job

In HH mode I have 63% (65% is suggested to start with) and there is no drift and the wag is almost not there. Can't say it is absolutely rock solid, but acceptable for sure. I'm 97% happy with what I have achieved and can fly it now with no issues. The 3% is for the winter and assuming Spartan DS760 is better than Align gyro I'm considering case closed.

Can finally move on to the phase "B" - installing the flymentor... uhhh, that was rough I can tell you...

It looks like you are having the same issue I am having. But I can tell you that changing to a quark may not solve your problem. I am running a quark with the Zeal tape and I too have it where its 95% good but that is NOT good enought and its not the gyro...its something else. My motor seems smooth glass, the heli is quiter than my 450!!
But the tail is not right yet. Now I do notice that we both have Gaui CF frames!!! which might be the problem. But what is it!

[Jack2010]

Remember me???

Freaks, I am the biggest jerk on this planet. Have been fighting with the tail wag for weeks. Spent so much time and energy. More importantly lost the joy of having newly built heli. And have to say that reach the point that I was close to abandon this particular one...

And you know what - I was searching for everything else than the most obvious thing... bloody Align GP750.

I have reached the point that I could finally fly it, but was not 100% happy... And one day I said to myself - men, change the gyro. So I have switched to the Gaui GU-210 as a first shot... NO tail wag at 100% gyro gain. However after some time of flying I was getting small tail drift. Very small. I think it is about temperature fragility of piezo (it is very clod here already), but no wag!!! I have not even worried about mounting it properly. Just one layer of the foam.

Today I have tested Spartan DS760. Look how I have mounted it... it should not work - right? (just straped with some very thin tape on top of the GU-210 )



Surprise, surprise... At 75% gyro gain no wag. F..ing unbelievable. Rock solid. Of course I will mount it properly and I hope will forget about bed times of Align nightmare soon and finally enjoy the Gaui...

The only good thing about the whole case is that I have learned the heli pretty well, eliminated some minor glitches and tested dozen of different ways of isolating the gyro (different tapes, coins, plates, zeal - you name it).

I don’t know weather my Align GP 750 was just not working properly, or those particular vibes I had were disturbing it, or I had a unit that was oversensitive, or lese... I really don’t know. I have the same on my T450 Sport and it is superb I have to say...

[ukgroucho]

Glad you got it sorted finally!

But I have to say "we told you so" (just fit the Spartan ).

Have fun!