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HelicopterMain Discussion › Whats causing vibration noise
10-23-2004 05:32 PM  13 years agoPost 1
bluefronted

rrVeteran

Pretoria, South​Africa

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I recently repaired a voyager 50 after a crash.

I replaced :

main shaft
tail rotor shaft
blade grip spindle
boom
left frame
tank
blades
flybar
2 links

After the repairs on a few test flights , i'm getting some sort of vibration noise , similar to the noise when tracking tape gets loose on the blades.

The noise is high near the ground , when i am a metre or two from the ground the noise reduces , but when i increase the rpms the noise also gets louder , what should i look at ?? I've been through the heli up and down almost a dozen times , looking for something out of the ordinary.

I have even swopped the tail fins and rotor blades with my other voyager , but the noise is still there.

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10-23-2004 07:55 PM  13 years agoPost 2
GBNT

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uk

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Could it be coming from the exhaust manifold?

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10-23-2004 10:28 PM  13 years agoPost 3
G-DAVE

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Tyne and Wear ,​England

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You said it was recently repaired after a crash - couldn't
be a bearing broken up in the crash say on the main mast or tail rotor output bearings -
Dave D

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10-24-2004 12:44 AM  13 years agoPost 4
JFields

rrApprentice

Tuscaloosa, Al

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I know that the JR machines use those little plastic pieces for the tail control rod guides. If one of them becomes enlarged slightly then it will buzz a little from the metal rod tapping against the inside.

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10-24-2004 05:58 AM  13 years agoPost 5
bluefronted

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Pretoria, South​Africa

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The tail rod guides check out fine , but i must probably check the bearings.

Just to add , the tracking of the made blades are 100%

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10-24-2004 11:34 AM  13 years agoPost 6
bluefronted

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Pretoria, South​Africa

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I've just come back from the field , and found that the horizontal fin is causing the noise , at certain rpms it vibrates up and down and causes the noise ( similar to cardboard on bicycle spokes) , and at certain rpms it is ok ! @

Now i wonder what is the root cause of this problem ?????

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10-25-2004 06:56 AM  13 years agoPost 7
Ringomtb

rrNovice

Austin

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Blue....


since you say that the horizontal fin is vibrating up and down , how is the tension on the boom brace.
The main thing here is to find out if the vibration is coming from the body section or from the tail rotor area.

Also check the balancing of the rotor blades

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10-25-2004 07:04 AM  13 years agoPost 8
DOKEY

rrProfessor

Northamptonshire UK

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I'm guessing but it sounds like a high frequency vibe, so possible from the engine ??

How is the engine alignment ?

Fan balanced, dialed in ?

Could even come from the engine being out of tune maybe ?

Ryan.

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10-25-2004 09:33 AM  13 years agoPost 9
Fish Eagle

rrNovice

Cape Town, South​Africa

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bluefronted,

Here is what I think. As far as I know, the horisontal fin on the Voyager is fitted to the tail next to the vertical fin. I gues that this vibration you are seeing could be caused by a bent shaft on the tail rotor pulley (have u checked the new tail rotor shaft to see that it runs true by rolling it on a plate of glass or similar), or one of the small bearings in which the shaft runs could be bad. Also, check the tail pitch slider for wear on the bronse bushing.

On the other hand the vibration could be transmitted through the belt from the main drivegear which I somehow doubt since the belt might dampen it, depending on the tension you have on the belt.

Cheers boet.

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10-25-2004 11:47 AM  13 years agoPost 10
bluefronted

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Pretoria, South​Africa

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Fish ,

I did repalce the tail rotor shaft , but i must admit i did not check if it is running smooth , i will strip the tail rotor section tonight and check out the bearings and the brass/bronze bush

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10-25-2004 12:18 PM  13 years agoPost 11
wolfdad

rrKey Veteran

Southern Maryland

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On a Voyager 50, a horizontal tail fin buzz is going to be engine, clutch or associated bearing related. Since you said you replaced the side frame, I would suspect engine to clutch/clutch bell alignment. Also, I would recommend you go back and check you clutch and fan run-out. Additionally, check your engine to clutch/starter shaft alignment as well. One other item I have only seen once, is your one-way start bearing. Use a small flashlight and look down into the bearing itself and see if one or possibly more of the roller bearings is gone. This should have evidenced itself when you started your machine, however, you might have missed it. This will prevent correct clutch to clutch bell alignment. One other strong possibility is, depending on how badly you whacked-out your main rotor shaft, you may well have taken one of the bearings in either the top or bottom bearing block with it.

To be on the safe side, if you had an impact hard enough to bend both the blade spindle and main rotor shafts, I would recommend to go back and, after checking the above items, do a complete realignment on your drive train, i.e., loosen all the mounting bolts and, using a known flat surface, realign your side frames and drive train per the instructions, then tighten everything down.

wolfdad sends....

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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10-25-2004 02:42 PM  13 years agoPost 12
bluefronted

rrVeteran

Pretoria, South​Africa

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Wolf ,


The one way bearing is this the one on the main gear , know as the auto rotation bearing ??

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10-27-2004 06:31 AM  13 years agoPost 13
bluefronted

rrVeteran

Pretoria, South​Africa

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As suggested , I stripped the heli partially and found that the upper bearing of the main shaft is pretty cooked. I don't know how i over looked this.

Si i'm assuming this is the problem , will replace the bearing and try out over the weekend.

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11-01-2004 09:09 AM  13 years agoPost 14
bluefronted

rrVeteran

Pretoria, South​Africa

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Over the weekend i replaced both the bearings on the main shaft and the one on the clutch bell.The 2 bearings on the tail belt check out fine,

Tested the heli and the vibration is still there , so i guess i will have to strip the tail rotor section , as i believe that there's 4 bearings in that area alone !

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HelicopterMain Discussion › Whats causing vibration noise
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