Still having tail issue.

[gointoheli]

I know there are a million posts on tail issues and I've read through many of them but haven't figured this out yet. Before my first crash, but right after my first hard landing the tail becam erratic and wouldn't hold. I found that the screw that holds the ball onto the pitch slider was stripped. I tightened it as best I could and put some CA in there (per advice of LHS) and that seemed to solve the problem.

After crashing and rebuilding, the problem is back. The tail makes a strange whirring (sorry, can't think of a better way to put it) sound when you get up to speed and rudder inputs amplify the sound. When I lift off, sometimes it will immediately want to spin and sometime it will hover ok for a bit and then all of a sudden the tail takes off.

I've ordered a new pitch slider assembly to see if that is the problem but it just doesn't seem like it would be.

I'm running the 401/9650 combo. What sould the gain be set at on the 401? I think I have it at 0

[HeliSmith]

Unhook the rod from the servo and hand spin it as you work the slider in and out. Binding? Bearings? Bent tail shaft?

I am using a DX7 and I have 72% in the gyro sense menu for gain, or right around that. I fly HH mode always.

[wespen]

I discovered my shaft was just slightly bent when doing the tail mod.
One side has a hair clearance and another one was just rubing.

Was looking ok on spool up.

Wesp

[gointoheli]

I replaced the tail shaft after the crash but didn't really check the bearings. I guess that's a possibility although like I mentioned it was doing it before the crash. I guess it could have happened during the hard landing. I wish I could better describe the sound I'm hearing when it spools up. I know that when I hear that sound I'm gonna have problems.

I'm not using the gyro sensing on the Dx7. I have the gyro set to the gear channel using end points of +60 and -100 and have the gain on the gyro set to 0

I'm also using the stock metal control rod (but not using the supports) as I intended to get a carbon tube and haven't found one yet. I'm sure that is part of the problem with the tail being a little sloppy but doesn't explain the noise and why it wants to all of a sudden take off on me.

[jaywhy]

Originally Posted by kickit23

and why it wants to all of a sudden take off on me.

What does that mean exactly? Twitches to one side? Spins uncontrollably? If it's the latter, is it the tail pinion starting to slip? (Hmmm, that wouldn't *seem* to cause a noise though... )

[gointoheli]

A little bit of a twitch and kind of erratic but I think some of that may be due to running the tail rod with no supports. Then it will Just let go and start to spin counter clockwise.

[gointoheli]

It sound almost like the tail is not coming up to the same speed as the main rotor or it's lagging behind. You can hear the mains spinning up and then It's like as you increase throttle, the tail starts trying to catch up and you hear two distictly different pitches.

[Super_Si]

What condition is the belt in? It could be a bit loose, or maybe there's a couple of teeth missing.

Sorry if you've already checked, but it hadn't been mensioned so far.

[Lzfalcon]

kickit23
Just a thought, is the gyro ok and or the servo may have lost it's centering cababilities? I had that happen on a hitec 6965 servo with a csm 560 gyro. The tail would make a whizzing sound like it was straining to hold center and would go crazy a few moments after. I went through some of what you went through and got frustrated until someone at our field suggeted the servo. The servo would work ok on the bench. I swaped out the servo and my problem went away. That's my experience.
good luck tracking down the issue.

[Skiddz]

Hold the mains still and try to rotate the TR. It should take quite a bit of force to get the belt to skip a tooth. (Don't go crazy TRYING to get the belt to skip a tooth as you might damage the belt) If you can move the TR without the belt skipping a tooth or the mains moving, you've probably got a slipping pulley or the hub is slipping on the TR shaft.

[carlo_the_wonder_frog]

I assume by 0 gain you are referring to the gyro gain menu being at 0? With the gear channel EPA's set to +60 and -100 it looks as though you have gain in HH mode of 60 and -100 in rate mode is this correct?

I would definitely check the bearings and also the 1 way bearing between the main and tail gears. A bad 1 way would make the noise you are describing and also if it is loosing its grip then it is unloading the tail and you will get a rapid spinning heli at random times. You might be able to just clean out the 1 way also and see if things improve, if they do then you know what the culprit is. My vote is on a slipping 1 way bearing.

[vetterick]

I just had a twitching problem on mine, turns out the 401 is sensitive to noise from the ESC, had to move the ESC from where it had been for 100 or so flights with a Telebee, to under the frame to make a 401 happy.

If your ESC is anywhere near the 401, try moving it!!

[gointoheli]

Thanks for the help everyone.

I figured it out. While replacing the pitch slider I noticed that the tail shaft was spinning but the gear wasn't. When I had my crash, I bent the tail shaft and LHS only had the one with the plastic gear. I figured it would get me by until the metal one arrived.

When I took the tail apart, I found that the right side of the gear was seperated and the gear was stripped and just spinning on the shaft. Not sure why that happened but replaced it and problem solved.

Thanks again!

[gointoheli]

Originally Posted by carlo_the_wonder_frog

I assume by 0 gain you are referring to the gyro gain menu being at 0? With the gear channel EPA's set to +60 and -100 it looks as though you have gain in HH mode of 60 and -100 in rate mode is this correct?

I would definitely check the bearings and also the 1 way bearing between the main and tail gears. A bad 1 way would make the noise you are describing and also if it is loosing its grip then it is unloading the tail and you will get a rapid spinning heli at random times. You might be able to just clean out the 1 way also and see if things improve, if they do then you know what the culprit is. My vote is on a slipping 1 way bearing.

Carlo, Thanks for the advice. My bad on the 0 gain on the Gyro as I meant to say delay was set to 0. You are correct on the EPA's