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HelicopterEngines Plugs Mufflers Fuel › OS 50 crank mod.
10-24-2004 05:23 AM  13 years agoPost 1
George Matthews

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N.W. Ohio

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Well I did the crank mod last night flew and it today can say that I can't see a difference.
Still has high freq vibration at idle.
Runnout is less than .002 and everything is in balance.
I was hoping the crank mod would solve this.
Oh well will try something else.

George Matthews

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10-24-2004 06:36 AM  13 years agoPost 2
Brian Bennett

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Dugway/Tooele UT, ​USA

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George,
Did you check the rear bearing by chance. If its loud at idle, that is probably your problem. Describe the vibration with a bit more detail.

Brian

Team MRC-Hirobo and Model Avionics Rep

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10-24-2004 02:33 PM  13 years agoPost 3
George Matthews

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N.W. Ohio

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Brian,


The rear bearing is good, the vibration makes the tail rotor control rod buzz in the keepers. Also I see the bottom of the vertical fin vibrate at high freq.

George Matthews

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10-24-2004 03:09 PM  13 years agoPost 4
Darksider

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Derby United Kingdom

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vibration at idle is pretty normal, i've always thought it's something to do with the fact that the balance of the crank is set for a rough rpm range so while idling it is off balance and vibrates a little, does it vibrate when it's up too hovering rpm's?? if not forget it.

Gareth

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10-24-2004 03:15 PM  13 years agoPost 5
George Matthews

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N.W. Ohio

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Yeah I do see some high freq vibration at hover. Tail fin and the top rear portion of the canopy.

George Matthews

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10-24-2004 05:19 PM  13 years agoPost 6
Darksider

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Derby United Kingdom

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in that case if your run-out is as you say, your fan has to be out of balance, are you running the standard fan, if so what heli is this?? i have seen for instance before, the bottom of the start shaft on the raptor bent by the tiniest amount after a crash and not replaced cause high frequency vibration like this, though you can usually hear the one way bearing in the clutch making an odd noise in that case, and it will wear the pinion bearing to the point of creating RF noise very quickly, and begin to create rough spots on your main gear aswell, run the main gear round by hand and see if it feels smooth and consistent all the way through a full turn, if it doesn't drop the engine and get the start shaft out and check it with your dti, also might just be the simple option, try leaning the engine by a couple of clicks, a rich os 50 is usually very rough that way.

Gareth

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