Prop balancing questions?

RotorAndWing said:
I thought I was discussing the prop on Ben's airplane. I wasn't aware the maintenance manual on his prop wouldn't allow indexing. :rolleyes2:

Maybe Ben could answer that.
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If that's the case yer probably OK, but if it is a production built aircraft you can't always simply move the prop.

Ben could simply pull the prop shaft and re-machine it to stop the wobble.
 
RotorAndWing said:
Again, depends as this does not apply to all. :rolleyes2:
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True, but I wouldn't be advising the page to move a prop a bolt hole.

Some Fed doing a ramp check sees a prop stop at the wrong angle, would really get their attention.
 
Tom-D said:
If that's the case yer probably OK, but if it is a production built aircraft you can't always simply move the prop.

Ben could simply pull the prop shaft and re-machine it to stop the wobble.
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Wobble is the wrong word... I machine every part to .0001 thousands and mic all parts before they come off the mill or lathe to comfirm parallelism..

The point I was making is the Ivo might shift slightly in the "clocking" direction, altho I have no signs of fretting on the blade clamping face surface. As for tracking. I dial indicate each blade a few times a year during my 25 hour inspections. The tracking is RIGHT on every time. it is just that the blades are so flexible that on each revolution one tip could be out of track with the other 2 in flight... One of the drawbacks of thin tipped composite props..... Unless you guys have been around carbon fiber props you cannot appreciate to unique quirks they have,,, Dan has seen it and understands..

And for the guys sitting their thinking ( why is this idiot inspecting his plane every 25 hours),:dunno::dunno: I realize my plane is a one of a kind and completely overpowered so for safety sake I check and recheck the plane for potential failures all the time.. That is the price I am willing to pay to be on the cutting edge of auto engine conversions...:yes:
 
N801BH said:
. The tracking is RIGHT on every time. it is just that the blades are so flexible that on each revolution one tip could be out of track with the other 2 in flight... One of the drawbacks of thin tipped composite props..... Unless you guys have been around carbon fiber props you cannot appreciate to unique quirks they have,,, Dan has seen it and understands..
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Same principles as helicopter blade tracking. Sounds like you have one blade going slightly out of track while running. Helicopter blades are "matched" by weight and blade twist, and various models have trim tabs to compensate.

Not sure how your blade manufacturer does his blades, if they are weight tested and balance tested against a master.


What you may want to try is the old method we use to track blades with, the stick with a piece of chalk on the end. Stand behind the prop while the plane is running and slowly extend the stick to the back side of the prop disk until you feel the chalk touching, then remove it. Shut off the engine and see which blades have chalk marks. If 2 blades have chalk and one doesn't, replace that blade and repeat. If one blade has chalk and the other two don't, replace that blade.
 
RotorAndWing said:
Same principles as helicopter blade tracking. Sounds like you have one blade going slightly out of track while running. Helicopter blades are "matched" by weight and blade twist, and various models have trim tabs to compensate.

Not sure how your blade manufacturer does his blades, if they are weight tested and balance tested against a master.


What you may want to try is the old method we use to track blades with, the stick with a piece of chalk on the end. Stand behind the prop while the plane is running and slowly extend the stick to the back side of the prop disk until you feel the chalk touching, then remove it. Shut off the engine and see which blades have chalk marks. If 2 blades have chalk and one doesn't, replace that blade and repeat. If one blade has chalk and the other two don't, replace that blade.
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The chalk idea is a good one...
 
N801BH said:
The chalk idea is a good one...
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It's a little odd the first time you do it on a helicopter. The pilot runs up the engine and rotor to operating RPM while the mechanic stands under the rotor disk with a stick with the chalk on the end. He slowly raises it up till it contacts and pulls back. Shut down, see which blade(s) contacted and adjust the pitch links and try again.

Old tech but it works. :yes:
 
RotorAndWing said:
What you may want to try is the old method we use to track blades with, the stick with a piece of chalk on the end. Stand behind the prop while the plane is running and slowly extend the stick to the back side of the prop disk until you feel the chalk touching, then remove it. Shut off the engine and see which blades have chalk marks. If 2 blades have chalk and one doesn't, replace that blade and repeat. If one blade has chalk and the other two don't, replace that blade.
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Pull the tops plugs, place a bench (something solid) in front and near the prop. Take a pointer of some kind and attack it to the bench to just touch the prop blade. Rotate the prop (MAGS OFF) so that the next blade come in the same position. Adjust the pointer to the blade that comes closest to the pointer, measure the distant between the 2. Shouldn't be more than 1/8" or .125.

Your method works, but gives you no measurement, and I'm just not a fan of playing with moving props. :eek: There is a tolerance in blade tracking, this way it can be measured.
 
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Geico266 said:
Pull the tops plugs, place a bench (something solid) in front and near the prop. Take a pointer of some kind and attack it to the bench to just touch the prop blade. Rotate the prop so that the next blade come in the same position. Adjust the pointer to the blade that comes closest to the pointer, measure the distant between the 2. Shouldn't be more than 1/8" or .125.

Your method works, but gives you no measurement, and I'm just not a fan of playing with moving props. :eek: There is a tolerance in blade tracking.
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Your method works for a static track, but Ben's problem sounds like a blade is bending more than the others while running which is dynamic, which pulls the blades out of track and induces vibration. If all 3 blades are "matched" the problem wouldn't exist, but it doesn't appear to be that way.
 
RotorAndWing said:
Your method works for a static track, but Ben's problem sounds like a blade is bending more than the others while running which is dynamic, which pulls the blades out of track and induces vibration. If all 3 blades are "matched" the problem wouldn't exist, but it doesn't appear to be that way.
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This is true, and you are correct.

Ben needs a new prop. :D
 
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Geico266 said:
This is true, and you are correct.
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I have checked the prop statically and it is within .040..

R&W is on the right track I think, if for some reason one blade is slightly more flexible then it will pull forward faster then the other 2 and tracking gets out of kilter....
 
N801BH said:
I have checked the prop statically and it is within .040..

R&W is on the right track I think, if for some reason one blade is slightly more flexible then it will pull forward faster then the other 2 and tracking gets out of kilter....
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Use a fish scale and a dial indicator and check it by pulling X pounds on the scale, and see how the blades compare in movement.
 
Tom-D said:
Use a fish scale and a dial indicator and check it by pulling X pounds on the scale, and see how the blades compare in movement.
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Thats a good idea too.. I will try that when the conditional inspection comes up next month.

Thanks....
 
Tom-D said:
Use a fish scale and a dial indicator and check it by pulling X pounds on the scale, and see how the blades compare in movement.
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That is a good idea. :yes:

Use the static bench method to quantify the results.
 
You may be able to see the dynamic prop tracking by sighting exactly from the side with the open door to a dark hangar as a background. You may find it interesting to see how much the blades flex in and out of plane as the engine is goosed at different rpms.

On re-indexing a prop - I know it is specified in many installations, important for 4 cyl engines, and have direct experience with the radical changes it makes in how smoothly an engine runs. Now if someone could just explain why to me...........
 
Alexb2000 said:
Prop balance was $280. I had to pay a mechanic to run the motor since I couldn't be there so total out the door was $407.
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If it went from .3 to .02 then you got your moneys worth in spades..:yes:
 
Ted DuPuis said:
Ask the maintenance minimalists? :confused:
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Where are they? I thought someone would show up and say what a waste of money it is and how I have more money than sense, this is like a parallel universe.

I hope the vacation was good and not too "arctic" for you guys.
 
Alexb2000 said:
Where are they? I thought someone would show up and say what a waste of money it is and how I have more money than sense, this is like a parallel universe.
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I was wondering the same thing.

I hope the vacation was good and not too "arctic" for you guys.
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We're still up north. Currently 1/2 SM -SN BLSN OVC005, but it's supposed to improve to OVC003. ;)

Probably taking off after lunch. Tops are only around 6k.
 
Just for the record, I've seen occasions where dynamic balancing did not do any good.

but I've never seen any occasion where it did any harm.

When the crank weights on the 0-300 are worn out, balancing the prop won't cure the problem.
 
Alexb2000 said:
Sounds lovely.
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After climbing through an icing layer (about 5 minutes in it got us around 1/4-1/2" ice on the boots), it was a gorgeous flight the rest of the way with about a 5 kt tailwind heading westbound. Can't beat that.
 
Tom-D said:
Just for the record, I've seen occasions where dynamic balancing did not do any good.

but I've never seen any occasion where it did any harm.

When the crank weights on the 0-300 are worn out, balancing the prop won't cure the problem.
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Good point Tom. Dynamically balancing an engine will not make up or cover up mechanical problems. Best to have the engine tuned up before also.
 
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