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T-REX 450 › T-Rex 470l bad Tail vibrations
09-29-2017 05:48 PM  10 months agoPost 1
Rotorandi

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Germany

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Hi,

my 470LM (belt version) has really bad vibrations on the tail when i fly over 70% throttle. it makes the typical vibration sound then too.
when i fly under 70% there are no vibrations.
i´ve checked everything. tailshaft is new, bearings are new, everything is fixed.
same problem with a loose or a tight belt, same problem with loose or tight tail blades.
main rotor is without vibrations. it defenely comes from the tail. i testet it at home without main blades. until 70% throttle everything is ok. over that point the tail rotor comes in a bad, bad resonance. its so strong that you can not hold the tailboom with your hand anymore because of the vibrations!
so whats the reason for that resonance?

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09-29-2017 10:16 PM  10 months agoPost 2
870heli

rrVeteran

Monson Ma. USA

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Turn down the gyro gain and set the end points lower. Two much throw and or to much gain will make the tail go crazy. Worth a try.

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09-29-2017 10:35 PM  10 months agoPost 3
Flyin for Jesus

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Troy, IL. 62294

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Does it vibrate with tail blades removed?
If so, keep removing 1 part at a time and recheck. You'll eventually remove the bad part and vibrations will stop. Only way to find out what is causing it.

EDIT: removing 1 part at a time means remove both blades, then both blade grips... do not remove just 1

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09-29-2017 10:58 PM  10 months agoPost 4
Rotorandi

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Germany

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with tail blades removed it vibrates not. only with blades!

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09-30-2017 03:34 AM  10 months agoPost 5
Flyin for Jesus

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Troy, IL. 62294

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Buy some new blades from a quality manufacturer and you should be set.

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09-30-2017 05:01 AM  10 months agoPost 6
knightofcarnage

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chicago

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Can you post a picture of your tail blades. I like to if the tips mushroom up.

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09-30-2017 09:21 AM  10 months agoPost 7
Rotorandi

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Germany

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the tail blades are new Align 74. i´ve tryed other and smaller blades too but the same..

now i even changed the thrust bearings in the blade grips.. they were totally damaget! i thougt maybe that was the problem. but the problem is still there!

oh and it vibrates not everytime! sometimes there are no vibrations, even with 100% throttle and the next moment the vibrations are here again..

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10-01-2017 10:26 PM  10 months agoPost 8
Flyin for Jesus

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Troy, IL. 62294

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You might want to get a video of it and post it up here. I'm out of ideas based on just your description.

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10-02-2017 02:38 PM  10 months agoPost 9
Richardmid1

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Leeds, England

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Could be a bent tail shaft it it does it with any tail blades but not without?

60% of the time, it works every time!

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10-03-2017 06:33 AM  10 months agoPost 10
knightofcarnage

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chicago

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I still like to see a picture of the tips of the tail blades. Most common issue I run into is the mushroom effect. Which causes imbalance and turbulence . also is the belt at the right tension ?

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10-05-2017 03:22 PM  10 months agoPost 11
Rotorandi

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Germany

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i can flex my tail shaft very easy.. you can see it in the video in the link.

Watch at YouTube

that could be the reason for the vibrations/resonance or? could it be possible that i picked a bunch with weak tail shafts? its actually the only possibility that left. i changed everything..

tail case
tail shaft
belt
pitch slider
tail blades
bearings
tail grips
tail hub

everything is smooth and without play...

nothing left except i can bent the tail shaft so easy like that!

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10-06-2017 01:15 AM  10 months agoPost 12
knightofcarnage

rrElite Veteran

chicago

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That is only a 3mm shaft, it will be easy to bend, with that leverage. But if you want to test out the metal tail shaft upgade (H47T021XXW ) see if you it helps.
http://shop.align.com.tw/product_in...roducts_id=6019

What would help is a video of the problem.

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10-06-2017 11:57 AM  10 months agoPost 13
Rotorandi

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Germany

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i tried the upgrade shafts too.. they got also 3mm and all of them were bent out of the box!
really.. not only one of them was straight!

i will try to get a video of the resonance problem. its not easy to film..

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10-06-2017 04:22 PM  10 months agoPost 14
knightofcarnage

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chicago

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That hard to believe that all the shaft you are getting are bad. Make a video.

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10-18-2017 06:46 PM  10 months agoPost 15
Rotorandi

rrNovice

Germany

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I just want let you guys know that i solved the problem.
One tail blade grip had too much play because the screw in the pitch arm was not fixed right so one blade was out of track sometimes.
I thank you all for your help.

Greetings

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10-19-2017 12:22 AM  10 months agoPost 16
knightofcarnage

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chicago

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glad you solved.

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10-19-2017 02:29 PM  10 months agoPost 17
870heli

rrVeteran

Monson Ma. USA

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Always good to start a the basics. Problem's can sometimes be magnetized by the simple things. Good you found it.

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