*Fixed* Logo 500 tail wag/vibration video

[Cameron_S]

I have been tracking down a vibration that is causing my tail to act funny. I bought the helicopter used so I do not have a real history of the heli. I know its not in the tail as I have replaced all the components with new and the vibration is still present. I just took the head apart and noticed that two of the thrust bearings on one of the grips have a larger diameter while the other side has the correct larger and smaller diameter. Would this cause a vibration in the heli?

[Big Fil]

That would surely do it.

[TheBum]

Are the thrust bearings inner and outer ends supposed to be of different IDs? The last time I took the head apart on my FBL L500, which uses the same thrust bearings as the flybar version, I noticed that there was no difference in the amount of wobble of any of the four thrust bearing ends on the spindle. I thought it odd at the time, but since it was the same on both sides, I just dismissed it as an intentional design.

[Cameron_S]

The manual denotes one with a larger id and one with a smaller, the larger on the inside smaller on the outside.

[billyd]

Yes they are supposed to be different diameters. That the first thing to fix. It may not be the problem (although it certainly could be) but you definitely don't want to leave it like that. Also be careful some of the older Mikado manuals have the inner and outer portions of the thrust bearings reversed in the pictures, so be sure to download the latest manual to be sure to get the right info.

[Long Nguyen]

They must have different IDs, small ID goes OUT and larger ID goes IN, to function as a BEARING.

[Cameron_S]

Well I rebuilt the helicopter last night. Lots of new parts. New tail shaft, main shaft, spindle, bearings in the tail and head, and new main gear. I still have a vibration and its still causes the helicopter to wag in weird maneuvers and it will not stop until I switch to a different head speed. I am running 2100 and 2300. It happens at both speeds. I have found no real pattern as to when it happens. I checked the motor bearings tonight and one is a *little* rough. Would this cause weird problems and vibrations? Any other suggestions as to what I can change? I am really considering just selling the helicopter and building a new one.

I will try to post a video to show what it looks like when it happens.

[Long Nguyen]

Should have mentioned this before, a bad motor bearing or bent motor shaft can cause very BAD vibration. I found out that this kind of vibration affects the gyro seriously.

You should start taking off main blades, tail blades, the head, the tail and different combination. Spin the motor and HOLD the heli by hand to feel the vibration. A bad motor shaft/bearing is highly suspicious.

[TheBum]

Rough bearings absolutely can cause strange vibrations. A buddy of mine, and a regular poster on HF, was having fits trying to get the VBar on his T-Rex 500 to behave. He changed out everything he could think of and he finally swapped out motor bearings. Problem solved.

[Cameron_S]

I ordered some bearings. Hopefully that will fix it.

[Cameron_S]

Here is a video to show what its doing.

[jvthert]

Sounds like a setup problem to me. Mechanically all seems smooth and it sounds fine.
My guess is that you need more gain but due to your p gain being a bit high that's not possible. So try lowering your p gain in the advanced tab of the tail section and try to get your overall gain in the 90+ region.

It's just a guess so perhaps you can post your settings for the gurus to look at!

[Cameron_S]

Here is my file.

https://www.helifreak.com/attachment...6&d=1266262448

[Cameron_S]

Put my quick uk tail on and for whatever reason the problem is solved. I previously tried a brand new mikado tail grip set and shaft, and had the same problem. Why does this heli need an upgrade to work right.

[OICU812]

That's strange honestly the 500 is the one tail I have never touched and left stock with no issue. On my 600s I opted for a UK tail but only cause I run 105mm tails on it.

[jvthert]

The mikado tail and Quick uk tail have their bolts at diferent lengths from the tail shaft. So changing your tail systems gives you a different mechanical gain om the tail control loop. I am not convinced you fixed anything that was broken. Instead you changed mechanical parameters in such a way they fit your Vstabi configuration a little better. I have had similar problems and was also thinking my tail was broken after a very small encounter with planet earth. It turned out to be a setup issue. But your heli sounded way too smooth to have vibration issues.

[Cameron_S]

What kind of changes would I have to make with the stock tail. At the time I had it installed I tried to turn the P gain down by 5 points but did not notice a difference. Do you have a suggestion for the stock tail?

[Cameron_S]

I couldn't take it so I put the stock tail back on and started to make adjustments. I ended up dropping the p gain to 65 and the overall gain to 80. Now the stock tail works great. I just flew two packs to get it right but now its awesome!

Here is my new vbar file.

[jvthert]

Congratulations mate!

[dahld]

I was looking at you file, and I'm curious...what tail rotor blades are you using, what servo, is the ball link on the servo horn the recommended 14mm's, and what is your head speed (all these questions revolve around how much "power" or how "sensitive" your tail set-up is, and I can't know this by looking at your file)?

(-: Dave

Never mind on the tail servo question...I saw on your signature that it's the 8900G.