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Thread: K3 Vibration issues

  1. #1

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    Default K3 Vibration issues

    Still having vibration issues on my 582 B-box with GSC prop. I noticed one blade is a 1/16" shorter than the other two. This is a factory new prop. Is this normal or maybe how they would balance the prop? I'm fixin to pull the prop and weight each blade. I also have a question on the old style motor lord mounts(flat plate). Do you tighten the bolts up to the inner sleeve or do they get torqued to some spec. Couldn't fine anything in my book.

  2. #2

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    Default Re: K3 Vibration issues

    I'm having some small issues with a GSC prop also, it has just over 100 hours on it. I've been on the phone with GSC for 3 days now. The prop is pitched 19 degrees on a 3:1 gearbox to hold 6,200RPM static. It's suppose to be at 12-14 degrees to achieve the proper static.

    I also cannot idle below 3,000 RPM's without a bad vibration. Runs smooth as could be above 3,100 though. Seems to be a balance issue. I didn't think about measuring each blade though.

  3. #3
    Super Moderator Av8r3400's Avatar
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    Default Re: K3 Vibration issues

    Like in the other thread, the very first thing to check is the tach.

    Do not trust an analog tach, regardless of the brand, on a 582. A Tiny Tach can be had for less than $50 from most motorcycle/ATV shops as well as a million different places on the internet.
    Av8r3400
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  4. #4

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    Default Re: K3 Vibration issues

    Let me clarify before i throw GSC under the bus. My prop is brand new out of the box but made 20 yrs. ago, so I don't want to say GSC is a bad prop. Not being a prop expert, i'm trying to figure out why one blade is 1/8 shorter than the other two. Tracking is less than 1/8". I'm almost sure the vibration is coming from the prop and it could be a accumulation of moisture and I also understand I should not be running a 20 year old prop. Just finishing building this bird and wanted to see it run before I spend more money. Heck, after ground run for 20 minutes I had to pick up screws and washers it shook out of the plane. Don't think its quite ready to fly yet. Say, this could be a new way for an annual inspection. Bolt on an out of balance prop, run for 20 minutes, if nothing falls off, your good to go for another year! LOL

  5. #5
    Senior Member
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    Default Re: K3 Vibration issues

    I would suggest taking the prop off, run the right size shaft through the hub, (1" I believe) set the shaft on two level knife edges and see if you have a heavy blade. It's suprising how accurate this is. Jim Chuk

  6. #6

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    Default Re: K3 Vibration issues

    Quote Originally Posted by Av8r3400 View Post
    Like in the other thread, the very first thing to check is the tach.

    Do not trust an analog tach, regardless of the brand, on a 582. A Tiny Tach can be had for less than $50 from most motorcycle/ATV shops as well as a million different places on the internet.
    The Tiny Tach and the Rotax Tach match up within 50 RPM's. As soon as I hit 3,000 RPM's on the Tiny Tach the engine starts shaking hard, so I do not let it drop any lower then 3,100 when taxiing. Others do not seem to have this issue

  7. #7

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    Default Re: K3 Vibration issues

    Quote Originally Posted by avidflyer View Post
    I would suggest taking the prop off, run the right size shaft through the hub, (1" I believe) set the shaft on two level knife edges and see if you have a heavy blade. It's suprising how accurate this is. Jim Chuk
    Sounds like a good method, simple but accurate.

  8. #8

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    Default Re: K3 Vibration issues

    Quote Originally Posted by bbryan View Post
    Let me clarify before i throw GSC under the bus. My prop is brand new out of the box but made 20 yrs. ago, so I don't want to say GSC is a bad prop. Not being a prop expert, i'm trying to figure out why one blade is 1/8 shorter than the other two. Tracking is less than 1/8". I'm almost sure the vibration is coming from the prop and it could be a accumulation of moisture and I also understand I should not be running a 20 year old prop. Just finishing building this bird and wanted to see it run before I spend more money. Heck, after ground run for 20 minutes I had to pick up screws and washers it shook out of the plane. Don't think its quite ready to fly yet. Say, this could be a new way for an annual inspection. Bolt on an out of balance prop, run for 20 minutes, if nothing falls off, your good to go for another year! LOL
    GSC has a 5 year limit on their blades, after 5 years of sitting or 500 hours of flying they recommend you send them in because of moisture and cracking. I just got off the phone with GSC and this is what Rick told me. We thought my prop was old but looking through the propeller logbook it is only about 2 years old, 1 year since installed and I'm still having some issues. He told me to send it in immediately because I should not have to pitch 19 degrees to hold 6,200 RPMS

  9. #9

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    Default Re: K3 Vibration issues

    Quote Originally Posted by Rmendler View Post
    GSC has a 5 year limit on their blades, after 5 years of sitting or 500 hours of flying they recommend you send them in because of moisture and cracking. I just got off the phone with GSC and this is what Rick told me. We thought my prop was old but looking through the propeller logbook it is only about 2 years old, 1 year since installed and I'm still having some issues. He told me to send it in immediately because I should not have to pitch 19 degrees to hold 6,200 RPMS

    Did you tell Rick that you heard crushing noises as you tightened the prop?
    ANd the alum blocks are near touching?

    something odd here........

  10. #10

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    Default Re: K3 Vibration issues

    Quote Originally Posted by bbryan View Post
    Let me clarify before i throw GSC under the bus. My prop is brand new out of the box but made 20 yrs. ago, so I don't want to say GSC is a bad prop. Not being a prop expert, i'm trying to figure out why one blade is 1/8 shorter than the other two. Tracking is less than 1/8". I'm almost sure the vibration is coming from the prop and it could be a accumulation of moisture and I also understand I should not be running a 20 year old prop. Just finishing building this bird and wanted to see it run before I spend more money. Heck, after ground run for 20 minutes I had to pick up screws and washers it shook out of the plane. Don't think its quite ready to fly yet. Say, this could be a new way for an annual inspection. Bolt on an out of balance prop, run for 20 minutes, if nothing falls off, your good to go for another year! LOL
    This must shake pretty bad to have screws come out..........
    borrow a prop from someone in your area to test..........
    Likely the 20 year old prop might be ok but might be not.
    I would turf it -- get 3 new blades or at least send to GSC for evaluation.
    I never seen one that bad before..... but it does not take much to get a vibration.

    The older Kitfox satd on alum plate and they gave more vibration throught the airframe than the side mounted Kitfox 4 engien mount, But stil quite ok .

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