Oxy 3 Slow Tail Wag (I have tried a great deal!)

[lukazy]

Hello,

I have an Oxy 3 285 stretch, since I built it it has a slow but steady tail wag. I have read many many threads describing the same problem on this heli as well as others, generally said to be mechanical. The wag increases speed as I increase the gyro on the tx. At 25 (on a bx7200) it is very slow at 65 very fast and 75 goes into spasm mode. at 45 the tail stops blowing out. it has never been crashed.

I have:
checked belt tension/tail rotor blade tension
checked bearings in tail rotor
replaced pitch slider
replaced tail blades
replaced entire tail rotor assembly
removed tail rode guide
tried both 47mm and 50mm tail blades
moved servo ball closer in and further out on servo horn
rebuilt and adjusted head
made sure main gear runs true
made sure one way bearing is smooth

none of this has had any effect.

i am using a brand new kst 215mg set to 1250us and 333hrtz

I am at a lose.

any help would be much appreciated.

Thanks!

[gimbleguy]

Since no one has replied or tried to help you, I will try.

Does your gyro have vibration analysis? That's what I use(vbar) to determine where on the helicopter the vibes are coming from, which helps most times.

Otherwise since you have checked almost everything, all I can suggest is to check the motor for balance. I always do this before building the heli. I mount the motor on my custom made mount and place it on my tablet, and check via the tablet vibe app, and also the gyro is connected to the mount to measure the vibes.


Also make sure governor is turned off, if you're using governor


hope this helps

[Livan75]

Originally Posted by lukazy

Hello,

I have an Oxy 3 285 stretch, since I built it it has a slow but steady tail wag. I have read many many threads describing the same problem on this heli as well as others, generally said to be mechanical. The wag increases speed as I increase the gyro on the tx. At 25 (on a bx7200) it is very slow at 65 very fast and 75 goes into spasm mode. at 45 the tail stops blowing out. it has never been crashed.

I have:
checked belt tension/tail rotor blade tension
checked bearings in tail rotor
replaced pitch slider
replaced tail blades
replaced entire tail rotor assembly
removed tail rode guide
tried both 47mm and 50mm tail blades
moved servo ball closer in and further out on servo horn
rebuilt and adjusted head
made sure main gear runs true
made sure one way bearing is smooth

none of this has had any effect.

i am using a brand new kst 215mg set to 1250us and 333hrtz

I am at a lose.

any help would be much appreciated.

Thanks!

A very quick test is to remove the guide for the tail push rod, I removed mine when I got a lazy wag after rebuild (flew great before)...

It might pop of if you crash, have not had any issues in flight and I have a few on it...

[jrman83]

The KST 215 servo is a 1520us servo. Why are you running so low? I would run at 200hz for cyclics and 333 for tail, but leave the other setting stock.

Have you broken down the tail grips completely? I mean removing radial and thrust bearings, confirmed the thrust bearings are oriented correctly, removed any compound from the radial bearings, re-greased the thrust?

[krm97]

One important thing to remember, the KST 215's are a high voltage servo and to get the best performance in ms and torque, you need to run them at 7.4V. Typical esc's like small Castle ESC's (25amp) only have 5.0V to the BEC, this will be a problem for you. Get a HobbyWing 25amp with adjustable BEC voltage, it will help.

[Wargamer]

You might have better luck posting in the Oxy forum.

There are so many possible causes of tail wag, it can be hard to diagnose. When you have increased the gain as much as you can to minimize the slow wag, but before you start getting a fast wag:
1. Is the wag only in a hover, or do you notice it in forward flight as well?
2. How big is the wag, e.g. a few degrees each way?

Mine has a slight wag in a hover that I have never bothered to tune/debug. It has no effect on my orientation flying so I just ignore it. At some point I may work on it, but for now I would rather fly.

The KST servos will be fine at whatever BEC voltage you are running. That's not what's causing your wag.