Extreme wobbles in tic-toc

[TommyS]

I have a fury extreme with 3X9252, GY601 TJ PRO/9254 YS91 and MPII. 90 flighs/1 year old

The heli is acting a little strange in tic toc. When you stop the heli at either side, it looks like one side is faster than the other side. It looks like the right side make the stop faster. The left side is about 0,1 sec slower to stop and start moving the other way. It looks like a little wobble or a shake. I don't se this behavior in other manouvre, but it clearly shows in the tic-toc. Here the other day it got a lot worse. But then I noticed that the o-rings had wore out. I replaced them(it used to be the orginal o-rings) with a 70 durometer o-ring inside and 90 durometer o-ring on the outside. Checked for slop on the control-system. I changed some links and tryed again.

It was back to what it used to be(the right side was a little quicker).

I have set the mashine up with MA's tool to make the CCPM interaction be minimal. I have tryed to reconstruct the behavior on the bench, but I don't see anything at slow or fast speed even if I use my hand to push the swashplate up and down. The swashplate is leve at all pitch-settings. I do not feel any slop in the servo's and I have not replaced any gears in them.

The only thing a can se, is that the servoes(3X9252) was not purchased at the same time. One of them has 100 flights on a raptor50 pitch, and the other two has 20 flighs on the cyclic of the same raptor. After that all three has done 90 flighs on the Extreme. It is only in the last 50 flights that I have trained on doing tic-tocs, and I noticed the flaw from the first tic-toc. It could have been this since the heli was new.

So do you have any idea of what I can do to make this go away?


/Tommy

[islandheliguy]

Hmmm that's pretty strange sounding. If you're not getting any interaction when you're moving the swash on the bench, it should be ok when you fly it. I don't fully understand what you mean by one side stopping faster than the other. Would it be possible for you to shoot some video of it when you're doing tic-tocs so that I can see what it's doing?

[TommyS]

I'll try to explain: I'll do a tic-toc with the tail down and skids away from me. I have full positic pitch and the heli is going towards me. When it is at 45 degree, I put in negative pitch and some cyclic. When I do that, the heli shakes a little bit. Like the right side stops faster and the heli rolls a lite to the right. 0,1sec (aprox) after the left side is catching up with the right side, and the heli is moving straight back. It happends so fast, that it looks like the heli is shaking a bit. It looks like there is some slop at the left side, but I dont feel any difference at the bech either on the links nor the servo.

The other thing I was thinking about, was that the left servo is more worn, and is slower when it has load on it. But I don't want to buy 3 new servos, if that isn't the case.

On the bench, I see no difference on the servos fast and slow without load on them. I have tryed to look for difference with some load, but it is dificult to put a load on the servos at the same time as they are moving at full speed.

Can I worn out servo act like this?

/Tommy

[ErichF]

I would agree with you that one of your servos is slowing down under load. Swap the servos around, and see if this issue migrates with the servo. Rather than doing the test with a Tic-Toc, try just doing max pitch, level climbs, and see if the disk rolls or pitches from level in a particular direction.

You may be able to get away with just replacing that older servo.

Good luck,

Erich

[TommyS]

A friend of mine was shooting a video of my tic-toc the other day, but you can't see it on the video even though I saw it when I flew. So it is not a big issue, but it bothers me.

I will try to swap the servo's and see if this issue migrates.

Is it normal to replace a 9252 after 200 flights of 3D?

/Tommy

[blakka_1]

Is it normal to replace a 9252 after 200 flights of 3D?


The servo wouldn't need replacing, but the gears inside the servo would. A set of new gears will have your 9252 feeling and performing like new. However depending on how the servo has been cared for will determine if it needs to replaced. The servo may need replacing if it has had some binding adventures thorughout it's lifetime. :)

[TommyS]

A set of new gears will have your 9252 feeling and performing like new.


I can see that if the servo has develop a slop, a set of new gears would help. But if a servo is weaker under load, isn't that the motor that is showing wear? I don't see that if I replace the gear-set, the motor is getting stronger again. But I'm not an engineer.

I don't feel any slop on my servos, when I move them with my fingers after turning the RX on.

/Tommy

[KenChoo]

Just a thought, if you're going to be replacing the servo's (some people have mentioned that 9252's wear at inconsistent rates so a set won't stay matched in a CCPM application very long), why not try the new 9255's which are supposed to be excellent in keeping their performance over time? That way you can let us all know if this is true as well : )

Thinking of going to 9255's at the end of the year when I swap out my 9252's.

Cheers,
Ken

[TommyS]

If I'm going to swap my servoes out, I think I will buy a faster servo, not a slower one. The 9252 is 0,14 and the 9255 is 0,17. It has a little more torque though.

Is there a general opinion, that the 9255 is replacing the 9252?

/Tommy

[EricLarson]

Hi tommy, there could be ton's of possibilities. Does the heli rotate at all when you do hard tic tocs? If one servo where weak, it should rotate some as the swash is driven 120 degrees so one servo being weak will cause it to rotate some.

I have some 9252's approaching 1000 flights and they still are trucking along fine. They have been threw quite a few gear set changes due to various reasons. The 9255 is an option, but most 3D guys still use the good old 9252. The 9255 has a metal gear train, so time will tell how much slop it develops over its life.

Bearing issues in the head such as radial bearings and thrust bearings can also cause issues.

All you can really do is try to change one thing at a time until you fine the item that fixes what you are seeing. I wish it was easier, but it sounds like it may be something small that is not very common.

later,

[TommyS]

I have tryed to move the servos around, and i'm not sure that the issue changed. But I had a friend look at it, and he think that the "wooble" is equal left/right, not more at the left side or the right side.

So now I'm into checking for play in the head again. I fly much alone and with some beginners, so I do not have the chance to look at others setup and find out what is to much play and what is accepable play with my gears.

So I have made a little video-clip when I push the servos and swash-plate on the bench. Can you look at it and tell me if this is to much play? Remember that the camera is on a tri-pod and the heli is flexing a little on the table when I push it.

http://62.92.89.196/tommy-web/servo-play.wmv aprox. 15MB


/Tommy

[Pete Niotis]

I'll do a tic-toc with the tail down and skids away from me. I have full positic pitch and the heli is going towards me. When it is at 45 degree, I put in negative pitch and some cyclic. When I do that, the heli shakes a little bit.



Tommy...I believe you might be using excessive amounts of pitch and possibly stalling the blades.