K3 Vibration issues

[bbryan]

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.

[Rmendler]

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.

[Av8r3400]

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.

[bbryan]

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

[avidflyer]

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

[Rmendler]

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

[Rmendler]

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.

[Rmendler]

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

[Dave F]

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........

[Dave F]

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 .

[Dave F]

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


Like I told you the other day -- 19 dgrees is just wrong unless you got about 80 to 90 HP or a gear box ratio higher thant 3 to 1...... have you counted the revolutions?

[Dave F]

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.

I think that is just the nature of the beas for this type of mount.

That being said -- it is quite serviceable and you might have other issues

[Rmendler]

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

something odd here........

yes and apparently it is just the urethane on the blade roots compressing.

I also had a local A&P take a look while he was in the hanger, he thought the noise it was making was normal and he got 19 degrees of pitch when he used the protractor so I must be using it right.

The engine is still holding at 6,200 RPM's static. I guess there is the possibility someone has opened up my 582 in the past and done some work? I do notice the compression seems a little high compared to some other Rotax's here on the field.

And yes we pulled the prop through a few revolutions with a mark on the gearbox gear and it was 3:1 on the money.

[Dave F]

yes and apparently it is just the urethane on the blade roots compressing.

I also had a local A&P take a look while he was in the hanger, he thought the noise it was making was normal and he got 19 degrees of pitch when he used the protractor so I must be using it right.

The engine is still holding at 6,200 RPM's static. I guess there is the possibility someone has opened up my 582 in the past and done some work? I do notice the compression seems a little high compared to some other Rotax's here on the field.

And yes we pulled the prop through a few revolutions with a mark on the gearbox gear and it was 3:1 on the money.


Ok 3 to 1 -- we on the same page then.
582 power is somewhat limited due to port size and timing. The Rtoax exhaust is what alos caps the power on the 582 to give max torque around 6000 rpm or so...... static set it for 6000 to 6200 rpm with your prop pitch. Get all blades the same pitch AND CHECK TRACKING,,,,1/16 to 1/8" blade to blade is accetable.
ALso Kitfox shortened the stock 582 exhaust a bit on the Y pipe and the elbow to make a sidemount muffler work and it does work well. This is one reason the 582s seem to go a long distance on Kitfox's. don't worrry about this not a huge deal really. I have done a fair bit of experimenting on them and you can get more power but the space insode the stock cowl is an issue.

light brown on plus should be ok but EGT on the ground don't mean much....check in air....... EGT gauge is not a calibrated devie per say but a guide ot let you know what is going on inside the engine... plug colour is the true indicator over all.

as far as higher compression -- doubt it but who knows whadt some have done to engines......

[JimS]

Had a GSC on my Model 4 (c-box)for years that ran as smooth as a sewing machine. That being said, I worked with a friend on his Model 3 with a B box that shook like you are experiencing. Guages would actually blur at reduced throttle. One thing we did was loosen up the bolts going through the rubber motor mounts so the engine could shake but not as much was transfered to the rest of the airframe. Those bolts should not be tightened down. You should be able to move your spinner easily 1/4 inch by pushing on it a bit. (The model 4 mount was a big improvement.)
Next, are you measuring the prop pitch with the tail of the plane on the ground or with the plane in level atitude? Or are you factoring in the angle of attack during your pitch check?
Lastly, another friend damaged his GSC prop but had one good blade. He gave it to me and comparing it to my GSC it was apparent that I could never use that blade if I damaged one of mine as there was considerable more mass to his blade than the blades I had on my plane. Point being that lighter blades will run smoother. My prop was 1994 vintage, his was a few years older.
Good luck

JimS

[bbryan]

Just got back online, been working double shift for 2 weeks. Wow, thanks for all the responses. I just pulled the prop and put it on a 1 inch shaft, It seems the heavy blade is the short blade. Totally blew my idea of sanding the tips on the long blade to balance. I don't have a scales good enough to weigh each blade, but about a half of popsicle stick on the tips of the other two blades gets it close. I don't have enough experience with this to know if that is off balance a lot or not. How would I add weight to the two lighter blades. I thought about several coats of clearcoat to add weight. I don't want to cut more off the short blade. My load motor mounts are tight so I will also look into that. I really appreciate the feedback and got the pleasure of talking to Dave on the phone, what a storehouse of knowledge.