Vibration problem
08-26-2004, 01:04 AM
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Vibration problem
Hello,
I have a vibration problem on my 4-star 40 (magnum 46) when my throttle is 1/3-1/2 throttle. It occurs both in the air and ground. I have held onto all of my control surfaces to see if it was some sort of flutter and it is not. It is noticeably loud, and I can see the muffler vibrating (it visually gets fuzzy).
What are the possibilities, and how should I test for them?
I have a vibration problem on my 4-star 40 (magnum 46) when my throttle is 1/3-1/2 throttle. It occurs both in the air and ground. I have held onto all of my control surfaces to see if it was some sort of flutter and it is not. It is noticeably loud, and I can see the muffler vibrating (it visually gets fuzzy).
What are the possibilities, and how should I test for them?
08-26-2004, 01:45 AM
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RE: Vibration problem
What prop ? Usually an 11" prop won't be that far out unless it's black composite. Did you replace the prop with a TF PowerPoint or APC ?
All screws to firewall and holding engine tight ?
Has engine suffered a sever one point landing ? A bent prop shaft would also vibrate at full throttle though.
All screws to firewall and holding engine tight ?
Has engine suffered a sever one point landing ? A bent prop shaft would also vibrate at full throttle though.
08-26-2004, 09:50 AM
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RE: Vibration problem
It's an APC prop (10x6), and tru-turn chrome spinner. The engine is tight to the airframe. I've also had the suggestion that a bearing is going out in the engine, and I should service it. It has had one crash on it that effected the nose, however, that was a long while ago.
The engine is running very rich, although there was a day a year ago that it ran very lean because of a carb screw that vibrated out.
Here is my hypothesis...
The bearing is starting to go out. At low speeds, the engine is not drawing enough fuel to work with a bad bearing, so it vibrates. At high speeds, the engine is pulling more fuel, more oil, and is able to build up enough to handle the problem.
BTW, does anyone know Magnum's website address? I googled them and cannot seem to come up with the proper address.
The engine is running very rich, although there was a day a year ago that it ran very lean because of a carb screw that vibrated out.
Here is my hypothesis...
The bearing is starting to go out. At low speeds, the engine is not drawing enough fuel to work with a bad bearing, so it vibrates. At high speeds, the engine is pulling more fuel, more oil, and is able to build up enough to handle the problem.
BTW, does anyone know Magnum's website address? I googled them and cannot seem to come up with the proper address.
08-26-2004, 10:03 AM
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RE: Vibration problem
I agree with Barto,
Check the prop for balance it can cause no end of problems. The spinner should also be suspect, if these two items prove to be good then you have a very real problem in the engine and you'll probably be better off to buy a new engine.
Good Luck!
Check the prop for balance it can cause no end of problems. The spinner should also be suspect, if these two items prove to be good then you have a very real problem in the engine and you'll probably be better off to buy a new engine.
Good Luck!
08-26-2004, 10:15 AM
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RE: Vibration problem
I think you're on the right track with the suspect bearings. The three I bought were bushing models.
On the 46, you'd have better power with an 11x6 ... most 40's use the 10x6.
Sorry I can't help you with Magnum web site.
On the 46, you'd have better power with an 11x6 ... most 40's use the 10x6.
Sorry I can't help you with Magnum web site.
08-26-2004, 11:11 AM
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RE: Vibration problem
Hi,
A 10X6 is definatly not the right prop for the engine. I have a 46xls and fly it with an APC 11X6. Others at my club use 12X6 or 11X5 or even 11X7.
About the bad bearing. I had a completely rusted bearing on my 40 FX (os) and never had any vibration when flying. The chrome came of from the bearing balls and made scratches in the cylinder. That causes the chrome to come off in the cylinder itself. Since I had that rusted bearing the engine is loosing power gradually.
I still think the vibration is caused by an unbalanced prop or spinner. I would check that out before changing bearings, that way you might save a lot of money.
About balancing props with spinners. First balance the backplate, than the spinner with the backplate, than the prop, and than the whole assembly. (That's the way I learned to do it)
Do a search here on RCU using the keywords: 'balancing + prop'. I'm sure you'll find all the info you need about it.
Hope this helps,
Bart
A 10X6 is definatly not the right prop for the engine. I have a 46xls and fly it with an APC 11X6. Others at my club use 12X6 or 11X5 or even 11X7.
About the bad bearing. I had a completely rusted bearing on my 40 FX (os) and never had any vibration when flying. The chrome came of from the bearing balls and made scratches in the cylinder. That causes the chrome to come off in the cylinder itself. Since I had that rusted bearing the engine is loosing power gradually.
I still think the vibration is caused by an unbalanced prop or spinner. I would check that out before changing bearings, that way you might save a lot of money.
About balancing props with spinners. First balance the backplate, than the spinner with the backplate, than the prop, and than the whole assembly. (That's the way I learned to do it)
Do a search here on RCU using the keywords: 'balancing + prop'. I'm sure you'll find all the info you need about it.
Hope this helps,
Bart
08-26-2004, 11:20 AM
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RE: Vibration problem
Hi again,
I just did a search on [link=http://www.mamma.com]mamma[/link] and found this adress. You find phone numbers there for the customer service as well as manuals etc. [link=http://globalservices.globalhobby.com/]This[/link] is the webite.
[link=http://utopia.rcuniverse.com/rcarchive/145/2003/08/3/215411]Here's[/link] the url where I found the website.
Bart
I just did a search on [link=http://www.mamma.com]mamma[/link] and found this adress. You find phone numbers there for the customer service as well as manuals etc. [link=http://globalservices.globalhobby.com/]This[/link] is the webite.
[link=http://utopia.rcuniverse.com/rcarchive/145/2003/08/3/215411]Here's[/link] the url where I found the website.
Bart
08-26-2004, 11:26 AM
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RE: Vibration problem
Hi!
A 10x6 is too small prop for a .46 engine.
You should use a 11x6 (preferable APC, Graupner Cam-prop, Bolly,Top-Flite or RAM):Never ever use a Master Airscrew prop; Those are worst props on the market regarding performance and noice!
Have you balanced your prop and spinner?
Does the spinner backplate fit the axlel on your engine? It should be a snug fit on the axle!
You said you have crasched the engine earlier....might have bent the crank?!
Also check the motormount ...is it tightly secured to the firewall...and is the firewall firmly glued to the fuselage??!
A bad front bearing usually does not cause wobbling and vibration.
Regards!
Jan K
Sweden
Re
A 10x6 is too small prop for a .46 engine.
You should use a 11x6 (preferable APC, Graupner Cam-prop, Bolly,Top-Flite or RAM):Never ever use a Master Airscrew prop; Those are worst props on the market regarding performance and noice!
Have you balanced your prop and spinner?
Does the spinner backplate fit the axlel on your engine? It should be a snug fit on the axle!
You said you have crasched the engine earlier....might have bent the crank?!
Also check the motormount ...is it tightly secured to the firewall...and is the firewall firmly glued to the fuselage??!
A bad front bearing usually does not cause wobbling and vibration.
Regards!
Jan K
Sweden
Re
08-26-2004, 12:22 PM
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RE: Vibration problem
One time I had a prop that the hole was drilled just a hair off center from the factory. It would balance fine but when on the engine, it would vibrate like crazy. I took the prop off and was able to see that the hole was not right. Put a new balanced prop on and all vibrations went away. I don't remember what brand of prop it was, but it was either a MA black, or APC.
08-26-2004, 12:38 PM
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RE: Vibration problem
ORIGINAL: davidmor
One time I had a prop that the hole was drilled just a hair off center from the factory. It would balance fine but when on the engine, it would vibrate like crazy. I took the prop off and was able to see that the hole was not right. Put a new balanced prop on and all vibrations went away. I don't remember what brand of prop it was, but it was either a MA black, or APC.
One time I had a prop that the hole was drilled just a hair off center from the factory. It would balance fine but when on the engine, it would vibrate like crazy. I took the prop off and was able to see that the hole was not right. Put a new balanced prop on and all vibrations went away. I don't remember what brand of prop it was, but it was either a MA black, or APC.
You're right, that could be the problem too.
Bart
