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HomeAircraftHelicopterHelicopter Main Discussion › Anyone got THE answer?? before I give up for good!
04-20-2009 08:35 PM  9 years agoPost 1
jgheli

rrNovice

united kingdom

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I have an issue with my trex 600 nsp. Just built. I live in the sticks with no local club or help.
As I bring the RPM up i get a tail shudder. Not rhythmic like with a tail wag ( I have seen wag caused by gyro issues on my raptor.
This is different. Every 2-3 seconds i get a shudder through the tail.
Engine is running sweet. Shudder is a left to right sort of harsh wag.
Is running smooth in between then every 2-3 seconds a juddering wag
Have managed to get airbourne half a dozen times but this shake makes me want to land! Yesterday I ran the heli through some circuits which was ok (everything on heli seems fine) but the shudder still there.
After getting previous replies on this forum I did the following;
-Replaced blades (although no damage).
-replaced flybar (although seemed perfectly straight).
-replaced feathering shaft (not bent).
-This doesnt appear to be a servo or gyro issue as its not a twitch but a shudder.
-I have the gyro cables and stepdown regulator separated.
-checked for no binding in tail servo rod
-shaft drive is in correct place - all located as it should. Locating screw is in place.
Any ideas would be gratefully received.....

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04-20-2009 08:45 PM  9 years agoPost 2
BarracudaHockey

rrMaster

Jacksonville FL

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Check the mounting tape for the gyro sensor.

Andy
AMA 77227
http://www.jaxrc.com

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04-20-2009 08:46 PM  9 years agoPost 3
jgheli

rrNovice

united kingdom

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interesting...why?

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04-20-2009 08:50 PM  9 years agoPost 4
rotormonkey

rrKey Veteran

Ottawa, ON - Canada

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Sounds very much like a gyro / servo problem. Couple things to check:

Gyro mounting too stiff? Are you using Gyro tape? Do you have a ziptie or elastic holding the gyro on?

Is movement of the tail servo nice and clean? If you turn off the gyro or plug the servo in directly, and apply a little pressure with your finger, then move the rudder stick around slowly, do you feel it skipping or doing anything out of the ordinary?

I know you've checked for binding.. What about excessive slop?

How about setscrews in the torque tube? Anything slipping in there? If you turn the head while putting some pressure on the tail to keep the head from turning, is everything nice and smooth?

If all that turns up nothing, which gyro/servo are you using? Have you tried swapping them out with alternatives ( I realize this may not be viable ).

You have to understand diagnosing something like this over a forum won't be easy. I'll be happy to throw ideas out though. fwiw a video is worth a million words.

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04-20-2009 08:51 PM  9 years agoPost 5
rotormonkey

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Ottawa, ON - Canada

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BH has a good idea.

The mounting tape needs to be thick gyro tape. If it's not, when the gyro picks up vibes you'll see random tail kicks. That's the very first thing I thought of too.

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04-20-2009 08:55 PM  9 years agoPost 6
joec

rrKey Veteran

VA

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Check the tail rotor hub, bearings, etc. I had the same problem (sounds like the same anyway) and I replaced all of that and it fixed the problem.

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04-20-2009 08:59 PM  9 years agoPost 7
floop

rrVeteran

Southern, NJ

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I had the same issue:
1. Check your tail hub make sure it is smooth! If not file down the arms until they are silky smooth.
2. Remount your gyro
3. Lean your engine out more. You'll find in the end your engine was too rich.

IT's what I do.

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04-20-2009 09:03 PM  9 years agoPost 8
sharam

rrElite Veteran

Northern California - Fly at Morgan Hill Field

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My guess is your engine - even though you say it is running sweet.

Try leaning it a few clicks at a time and see if it gets any better.

Verba volant, scripta manet

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04-20-2009 09:04 PM  9 years agoPost 9
Bart B

rrKey Veteran

chicago illinois

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Tailblade direction also.

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04-20-2009 09:05 PM  9 years agoPost 10
jgheli

rrNovice

united kingdom

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cheers guys,
You have given me some ideas to try tomorrow. Its all worth trying. I will come back to you!!
Ps rotormonkey; its a 401 and 9254 using gyro tape but I will try a different kind.

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04-20-2009 09:10 PM  9 years agoPost 11
Blade_Master1

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Canada

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Had the same problem on a trex 450 turns out the motor was the cause

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04-20-2009 09:30 PM  9 years agoPost 12
EVO76

rrApprentice

New York , U.S.A.

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while your checking, give the wires coming out of the tail servo a LIGHT tug. My buddy found an issue with his 9254, doing the exact same thing. when he wiggled the wires, it would KICK. he tightened up the servo case, and problem has gone away.

Just my 2 cents!!

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04-20-2009 09:36 PM  9 years agoPost 13
Sam2b

rrElite Veteran

Tacoma, WA

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As I bring the RPM up i get a tail shudder
I'm curious if the tail on this heli ever did perform correctly? If yes, what hardware has changed since then?

If all else fails, try this:
If you are lowering the gyro gain and it doesn't seem to help without going into the single digits in gain values, or if lowering within abnormal gyro gain levels, then try moving the tail servo linkage ball in one hole closer to the center on the servo horn. This helps with the mechanical gain and increases the resolution of the gain values adjusted.

If you haven't tried moving the linkage ball in one or two holes, try it next.

In my experience, this has fixed several new heli configurations.

_Sam B_

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04-20-2009 09:51 PM  9 years agoPost 14
30636086

rrKey Veteran

Tacoma, WA

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where is mounted? My had issues while mounted above the servos; moved back and problem solved; did you bench test it? check the connections and look at the tail rod when you turned on the power, see if twitches electronics can be a pain is the a$$. A configuration and set up that works perfect on one heli wont work in another even if they are identical.
Sam2b
If all else fails, try this:
If you are lowering the gyro gain and it doesn't seem to help without going into the single digits in gain values, or if lowering within abnormal gyro gain levels, then try moving the tail servo linkage ball in one hole closer to the center on the servo horn.
+1

I dont suffer from mental iIlness, I actually enjoy mine!

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04-20-2009 10:11 PM  9 years agoPost 15
rotormonkey

rrKey Veteran

Ottawa, ON - Canada

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Yeah, something else is try to keep the gyro wires away from others if possible. Especially wires for a Reg if you're using one.

And if you're already using new gyro tape, I sincerely doubt tearing the gyro off and putting it back on will do any good. Just saying if the tape you're using isn't gyro tape you'd have problems. You need vibration dampening for the gyro, so using zipties and elastics, etc, which lots of newbies do (because they don't trust the tape or whatever) causes problems.

If you aren't doing any of those things, and you're using actual gyro tape, then don't bother changing it. You're just wasting your time.

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04-20-2009 10:17 PM  9 years agoPost 16
VooDooX

rrElite Veteran

San Francisco Bay Area CA, US (San Mateo)

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a few pictures of your setup in detail will help us point out trouble spots liek they say a pictures worth a thousand words a video is worth a billion

Velocity 50 "99.9999999999999% of an atom is empty space." also 01001000 01001001

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04-20-2009 10:19 PM  9 years agoPost 17
drummer5140

rrNovice

Vancouver, canada

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Gain to high??

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04-20-2009 10:24 PM  9 years agoPost 18
smj

rrApprentice

cambridgeshire uk

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+1 on the engine.
Had a same problem on my 600 with 601 gyro. Changed the hyper which was getting tired,and problem gone away.

"All people have the right to stupidity but some abuse the privilege."

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04-20-2009 10:26 PM  9 years agoPost 19
A. Bundy

rrElite Veteran

Aurora,IL. 30W/SW of Chicago

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You can have the motor running right on the edge of coming on the pipe at hover.

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04-20-2009 10:47 PM  9 years agoPost 20
JetFire

rrKey Veteran

The Golden STATE

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I had a 401 on my 600N for a long time before I outgrew it and moved on with a Spartan. I never had a mounting issue that affected performance. Its not as tempermental as my Spartan and I've mounted it w/just regular mounting tape and even strapped it down on top of my servos with Velcro straps. Maybe I just got lucky but nothing seem to faze it. I only had a violent inconsistant tail wag at one time and later found out it was a combination of my engine running too Lean and slight binding with tail slider. However, I had a very similar experience as you describe with my Spartan in which turned out to be a tail servo going bad. Anyway, you can be chasing this problem for a while and sometimes you just have to try everything. If you have a spare gyro or one your friend can loan you.. I would try that and even go as far as swapping tail servo. Just My2Cents


Trex700N Pro
DX8-2.4
Spartan/BL9088

-The ONLY way you fail is when you quit.-

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