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Other › Tail becomes soft when increasing headspeed - Now with video - SOLUTION FOUND!
04-03-2005 03:02 PM  13 years agoPost 1
MFIS

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The Netherlands

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I think this is a mechanical type of issue more than it is specific to certain hardware but im running hs56 on tail with csm560 gyro. Ive recently gone to a mega 3 turn and im noticing that the higher i increase head speed the tail gets very sloppy. Gain is it 60% with no wag and at when i first fly at 80% throttle the tail wants to drift around a bit and act very soft but as the battery dies or i decreas throttle it will hold very solid.

Anyone can explain why more rpm on the either the tail or the main rotors would cause something like this?

Cheers,
Anni


<--edit-->
the solution for this problem in my case was a faulty tail rotor head. Swapping it out fixed the soft tail at high head speeds. Furthur inspection showed that it was the tiny bearings in the grips that had failed on one side. Thanks to Heliup for also pointing this out as a possible solution.
<--edit-->

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04-03-2005 03:32 PM  13 years agoPost 2
Gary Hoorn

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Annapolis Maryland USA

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Tail Drifting
Anni,
Vibration maybe upsetting the Gyro?
Gary

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04-03-2005 03:46 PM  13 years agoPost 3
takota

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San Diego, CA

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This maybe a different problem but I've experienced similar one on Shogun when the tail pitch slider had a mechanical problem which was causing extra friction. The problem was solved by slightly loosening a pair of screws to the ball link holder arms on the slider. This made the slider move smoothly.

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04-03-2005 09:24 PM  13 years agoPost 4
MrMel

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Gotland

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I had problems with that the gyro "drifted" a little, my problem was that mechanically setup wasnt good enough. Switch to rate mode and make it hold the tail with no adjustment on the radio, then you switch over to HH, and you can maybe even up the gain.

Dont know the CSM gyro, but if you can trim the delay that can be a factor, noticed that when I switched servo..

Today my gy401 hold even firmer the higher headspeed I have.

- Fredrik

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04-03-2005 11:19 PM  13 years agoPost 5
MFIS

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The Netherlands

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Its trimmed mechanically for rate and HH mode. Tail holds rock solid in both modes but when upping head speeds it becomes very soft with a tendency to drift in both directions randomly. Gain is at 60% with no wag as i stated above. Even if i could go higher i wouldnt want to. Its simply not needed and will shorten the life of the tail servo.

No this is something odd and not a typical problem. Im thinking to look into the vibration issue that Gary mentioned. I do get a loud buzzing sound like a weed whacker that kicks in only when you hit a certain point of the throttle and above. My other trex does make the same noise. Bearings are brand new precision upgrades. The fact that the tail only acts this way when the heli is above a certain speed and making that "weed whacker" sound would seem to align with gary's opinion that it could be vibration but ive got a new main shaft (rolled to check for straightness), a new feathering spindle, new bearings, and a new flybar. Cant think of what it could be. The heli doesnt really shake or wobble or vibrate that much. There is some vibration noticable on the vertical tail fin at full speed but i think this is pretty normal when you are running the thing at 2300 rpm and its sitting on the ground. Its going to interact regardless of what you do i think.

I dont know. Im a bit frustrated at the moment with both birds simply because neither one is flying right anymore. The other one is all erratic and sloppy after a crash and i did a quick repair on it hoping that things would be all right but it looks like its gonna need a complete look over cuz it flies like **** now.

The weather has been absolutely wonderful the last 4 days and i got nothing to fly. boohoo

Ahwell... its the nature of the hobby.

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04-03-2005 11:58 PM  13 years agoPost 6
dnts

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Israel

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Check the tail belt. It sometimes kick into oscillations. Try to loosen or tighten it a little.
Nir

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04-04-2005 12:49 AM  13 years agoPost 7
Coolpowered

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Youngstown, ohio

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Sounds like a loose tail belt to me,tighten it up a hair.

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04-04-2005 11:17 AM  13 years agoPost 8
MFIS

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The Netherlands

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Ok i tightened up the belt as it was pretty loose but that didnt take care of the problem. Im almost certain its an excessive vibration issue now.

I made a video of what its doing. Pay special attention to the noise it makes as the throttle increases beyond a certain point and then look at how the vibration makes the wires at the back of it creep up and the tail boom struts oscillate.

What is this? It already has a New main shaft, spindle, flybar, and precision bearings. Any ideas?

Video here:

http://www.annihilat.net/album/Heli...M/vibration.wmv

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04-04-2005 11:36 AM  13 years agoPost 9
MFIS

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The Netherlands

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Yes tracking stays dead on thru full pitch range. Ive made the head stiffer with 4 orings and 2 brass bushings from a set of older woodies. The blades are SAB 320 mm and in order to get tracking right i put one piece of tape on the leading blade (a full turn on the linkages was too much).

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04-04-2005 11:44 AM  13 years agoPost 10
MrMel

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Gotland

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Have you tried it without the blades on?

- Fredrik

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04-04-2005 11:47 AM  13 years agoPost 11
MFIS

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The Netherlands

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Im going to go try that now. Gonna remove all blades front and back and see what i get. I have to figure this out. Its driving me nuts. Its been flying great even WITH that horrible sound until the tail went soft. So i dont know if the two are related but i spose its time to find out and try to get rid of both problems.

The flybar is new.

Keep the ideas coming if you have them. Ill keep checking back here and ill let you know if/when i get it figured out.

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04-04-2005 11:57 AM  13 years agoPost 12
MFIS

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The Netherlands

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The main gear appears slightly warped. Would this cause such a problem?

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04-04-2005 12:02 PM  13 years agoPost 13
MFIS

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The Netherlands

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on second look its not warped there is just a bit of a wobble to it. very small amount tho

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04-04-2005 12:17 PM  13 years agoPost 14
TheDudeVT

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Burlington VT

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How about the tail spindle? How's that look?

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04-04-2005 12:17 PM  13 years agoPost 15
MFIS

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The Netherlands

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Ok blades all off and the same vibration is there. It is of course amplified when the blades are on but the same point in the throttle there is a noticable kick in where the vibration becomes quite strong. It's felt thru the whole frame. Im going to try a new main shaft and gear.

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04-04-2005 12:19 PM  13 years agoPost 16
MFIS

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The Netherlands

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How about the tail spindle? How's that look?
Im quite sure its not in the tail that is causing all this vibration. It seems to be coming from the main frame area. The tail issue may be something unrelated but im gonna sort the vibration first as this may fix the tail issue. I think thats a secondary issue at this point. The vibes im getting arent normal.

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04-04-2005 12:54 PM  13 years agoPost 17
MMarshall

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Herndon, VA

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Looks like you are running the carbon tail boom, this was a huge vibration problem for me.

I chased a vibration for 2 days only to find when I changed the tail boom to the extended gold one that it went away.

It appears that some people have problems with the carbon boom and vibrations, I believe there are possible cracks that are unseen that will allow any vibration to be amplified.

Mike

Gravity is a harsh mistress

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04-04-2005 01:11 PM  13 years agoPost 18
MFIS

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The Netherlands

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Ok here is the newest update.

I changed the main shaft just for the hell of it and when i spool up WITHOUT tail rotor blades on, the weed whacker sound is gone as is most of the vibration. When i put the tail rotors on there is a HUGE amount of vibration and noise. Im going to try a new tail rotor shaft now.

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04-04-2005 01:33 PM  13 years agoPost 19
WRXRonald

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Auburn, OH

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...
yes after my crash i have near exact problem over here...

a funny buzzing sound clearly representing some strange vibe... causing my tail to get all crazy and wag too....

i'm hating it, its got to boil down to one of the shafts, (although i checked main shaft, don't believe its bent, but spindle and tail need to be checked more closely. and i also firmed the head with an extra washer per side, probably a mistake, since the firmer you go the more you will excerbate a vibe-issue. i'm going eCCPM as soon as my Rotorworkz frame arrives... i'm going to do another rebuild and replace the shafts... and going with precision bearings as my main bearings now are looking/feeling pretty worn and notchy. hoping this fixes the prob....

report back in a week. but yeah, the weather is too nice here too, i hate to be missing these flight days (so i'm getting a XRB sky robo for some indoors fun while the trexy is down, that should at least tide me over a wee-bit, every heliman's gotta have a spare )

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04-04-2005 01:48 PM  13 years agoPost 20
ZZ3Astro

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Panama City, Fl

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This looks/sounds exactly like the tail oscillation problem I posted about last week. It is smooth as glass until a specific rpm, then the vibration starts up and gets worse for a few hundred head rpm... then it seems to smooth out with ultra high headspeed. No blades, only requires the tail hub on the tail shaft. When flying, if the heli is loaded down to this rpm range (during tictocs for example) the tail starts to drift in the direction torque is pushing it.

You can spool the heli up with no blades and watch the tail hub (no blades here either)... watch the center of the hub where the shaft sticks through. I'll bet you a pair of TRex paddles you will see the whole thing vibrating at this location when you hit the rpm where the shake begins in the heli.

steve

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