Tail Vibration Resolution

[JimLerch]

If your tail vibrates even after replacing the tail rotor shaft and blade hub, replace the bolts holding the bearing blade grips in place. Apparently they can be bent even if they don't appear so.

I have no idea how fast that tail is spinning, but apparently even the least bit of distortion back there causes a pretty ugly vibration (especially at high head speeds).

[sokal]

the left side of my horizontal fin vibs is this what your talking about

[JimLerch]

Yup, most likely. To tell for certain,


remove main blades
secure heli to table
power up tx and heli
slowly add power to increase head speed.
listen to tail, as power increases if the sound changes to that of a wood working router sound accompanied by the tail surface vibrating, yup something is out of whack.When everything is perfect, the tail will never change sound (just pitch) and the tail surfaces will remain calm. Once you reach this level of nirvana, I notice my battery packs last a heck of a lot longer :)

I'm absolutely amazed at just how sensitive the tail is to "something out of whack" A good nick in a blade will produce the same problem.

I chased the latest problem around after a good inverted crash. I replaced the tail rotor shaft, hub, blade grips, and blades and still had a vibration. Finally I decided to replace the stupid blade grip bearing bolt and everything went back to being quite again!

[sokal]

will try that thanks
i just thought it was normal

[Zman39]

I had the same vibration, replaced shaft, bearings, still there. I finally just took a wild guess (nothing else left) and replaced pitch slider, vibration gone and never came back. go figure?

Z

[JimLerch]

I had the same vibration, replaced shaft, bearings, still there. I finally just took a wild guess (nothing else left) and replaced pitch slider, vibration gone and never came back. go figure?

That doesn't surprise me either! When I was chasing mine about, I did a few tests with the pitch slider removed.

For fun, put a small piece of balance tape on one of the tail blades. That will demonstrate how sensitive the tail is to issues! I once tried balancing my tail blades using the trial and error approach. End result was high levels of frustration and time loss as moving the balance tape a 1/16 of an inch up or down the blade length would radically change the vibration levels

Does anyone know if the Trex-450 or similar heli is as sensitive to tail vibrations as the B-400?

Has anyone compared the tail boom diameter or wall thickness with a Trex-450 or similar?

[sokal]

this i pic of a post i found its a tail assy from a trex on a 400



http://www.helifreak.com/attachment.php?attachmentid=36308&d=1200983179
http://www.helifreak.com/attachment.php?attachmentid=36307&d=1200983179

[sokal]

well that sucked
i guess the builder at the factory did a great job with my tail grips
he striped the screws so i have to get a new assy so i may just go for the rex tailassy
or may be just the grip set
i did find an interesting thing wial all is spinning acuate the tail and u will find it no longer has full travel i found the victom itst the slider arm it acualy twists under force wich doesnt alow full travel while blades are spinning
does anyone else see what iv found

[rmillerawacs]

I have noticed this same issue with. I have flown it 10 + times now and on the last flight I noticed the tail vibration??? I did not notice it before. No crashes no hard landings?? Is this a issue from the factory? I am going to take a good look at everything and rebalance the baldes? Hope this works!!

[JimLerch]

Also watch out for MAIN blade tracking causing tail vibrations. If the tracking is "almost" perfect, it can get the tail to wiggle vertically.

You can tell the two apart, as the tail won't vibrate with main blades removed.

[visuvius]

Hi guys, I'm new to this forum (and pretty much helicopters in general). First of all I apologize ahead of time if I say something retarded or that doesn't make sense. I'm learnin' here!

I'm having some tail vibration issues and I think I found the right thread. As I power up the chopper, it seems like the tail blades aren't tracking properly; they are just slightly off and I think this is what is causing the vibration. I had a very minor accident after a piro where the main rotor blades and tail blades skimmed the ground. The film came off both sides of the main rotor blades and the tail blades where a bit scuffed. After replacing the main blades and a minor adjustment, they seem to be tracking okay.

"If your tail vibrates even after replacing the tail rotor shaft and blade hub, replace the bolts holding the bearing blade grips in place. Apparently they can be bent even if they don't appear so."

I'm going to start by examining/replacing the parts JimLerch mentioned here. I've identified the tail rotor shaft and aluminum tail rotor hub on the exploded view page but I can't seem to find the "bolts holding the bearing blade grips". Could someone be so kind as to tell me which part numbers I should be looking at on the Blade 400 Explode view? At a glance, everything seems to be okay and in one piece and I don't really know where else to start with diagnosing this weird tracking issue. The tail blades are definitely not spinning on the same axis. Dunno if that makes sense.

Thanks for any tips!

[JimLerch]

The bolts will come with a new aluminum tail hub.

The whole tail on the blade is very sensitive to "things out of whack" even a little gouge or skuff mark on the tail blades can get a nasty vibration started.

When in hover, watch the tail fin surfaces, are the "Blurry" and vibrating rapidly? Do you hear them? (once you know what they sound like as they vibrate, you can tell tail problems from YouTube videos :YeaBaby:)

Also, depending on how hard you hit, you may need blade grips.

I also replaced the vertical tail fin with a carbon fiber fin, and that helped, but I think it masked the problem more than corrected for it.

[newhelliguy]

Hey Jim
I was looking around this morning and ran across these videos on setting up a heli. I watched the one on balancing a fan (I guess for fuel heli.). Anyway he balanced the fan on two pieces of ice from freezing water in small cups. I think this would be a great way to balance the tail blades. Watch the short video on balancing a fan and see what you think. I am going to do this later. Also I did the chinese mod and could not believe how much easier the rudder arm was to move. It went from taking over a pound to move it to very easy to move. Anyway check out this video.

http://www.moretraction.com/helis/setup%20videos.htm

[Menace]

I have a tail vibration issue that I cant track down also. Could you be a little more specific about what you found the problem to be?

[sokal]

even the slightest bend in the tail shaft will cause vibration
also if the tail slider bearings are loose and the tail blades being un balanced
even the tail grips not evenly weighted will do it to

also make sure its the tail remove blades and run it up and see if vib goes away

if so its one of the shafts main or spindal
so many things

but i would replace the tail shaft first and check the tail supports

[Menace]

What sucks is I cant say exactly which crash and what broke when this issue started. All i know is that it seems to vibrate now and I didnt notice it before and I fly this thing a few times everyday. Ive replaced the main shaft, tail shaft, tail blades, balanced main blades. Dont know what else to check.

EDIT: OK I think I know what the original poster was talking about. You need to take off your tail blades and look inside the grip. There are screws in there but no shaft. It connects to the metal hub that goes on the shaft. I checked mine and even though the screws were straight and really tight, there did seem to be some play in the grip. Any ideas? Do I need to replace the grip? Should I try to find some thin washer? I only notice the slight vibration now in flight. On the ground with high head speed, it doesnt seem to do it.

[sokal]

i added a washer with a hole the size of the screw and tool all the play out
and still operates the same

[LockMD]

is there a feather shaft back there like on the main rotor?

Take both tail blades off, use an allen on one side and turn it see if you see any wobble, if so that feather shaft is bent and needs replaced.

edit: check eflh1469 with same method as above

[Menace]

is there a feather shaft back there like on the main rotor?

Take both tail blades off, use an allen on one side and turn it see if you see any woble, if so that feather shaft is bent and needs replaced.

No, there is no feather shaft. The screws go directly to the hub and there is a bearing in the grip. You would have to take it apart to understand I guess. Anyways, its only the very tip of the tail. I only see the wing vibrating slightly, its not the whole body like it was when the main blades werent balanced.

[LockMD]

I only see the wing vibrating slightly, its not the whole body like it was when the main blades werent balanced.


Are you talking of the horizontal fin is vibrating?

Mine does too....I chipped a small piece off in a wreck but that should have no flight affects other than visual appearance. It still flies fine.

[Menace]

Are you talking of the horizontal fin is vibrating?

Mine does too....I chipped a small piece off in a wreck but that should have no flight affects other than visual appearance. It still flies fine.

Yes, Im talking about the horizontal fin. It vibrates a little. I dont see any difference in flight so I guess its not a big deal. I do have another horizontal fin I could try but I dont see how some minor damage will make it vibrate.

[Wolfpackin]

Did you check the small tabs on the main frame where the tailboom supports attach?
I broke those off once in a bad crash.
I glued them back on and they held in my most recent crash.

[LockMD]

Yes, Im talking about the horizontal fin. It vibrates a little. I dont see any difference in flight so I guess its not a big deal. I do have another horizontal fin I could try but I dont see how some minor damage will make it vibrate.


you had me going, yup no big deal. my left side chipped the litt flange off in a wreck now that side vibrates - my crappy cam cant see it anyhow LOL