Prop Balancers

[Kyle Communications]

easy

 

make up a hub..static balance doesnt do the pitch it does blade weight

 

 

[Kyle Communications]

here is a couple of pics of one Danny made. It sits on a std bearing . He just turned up a small hub to fit inside the prop hub and fitted a bearing in it so the prop turns smoothly then you can static balance

 

 

 

 

[dlegg]

OK, so I need a hub with a hole in the centre. Will see what I can come up with...

 

 

[dlegg]

I have a 2 blade that has a cartridge in the center, no way to put a hole through it

 

 

[Kyle Communications]

make a flange fto mount the prop on just like it is on the engine and just put a nice bearing in it..its so you can rotate the prop freely and adjust each blade weight so it stops anywhere.. If there is a heavy side it will always end up at the bottom

 

 

[facthunter]

Hang it on a centrally placed string and check level of tips. You need to have no wind about either. Nev

 

 

[Head in the clouds]

Hang it on a centrally placed string and check level of tips. You need to have no wind about either. Nev

Yes I agree, that is the simplest of all reasonably accurate methods. Much as I have the very greatest respect for Mr Kyle, I've not found those horizontal-shaft balancers to work at all sensitively enough.

 

Similar to the 'suspended by a string method' - to achieve much greater sensitivity it is best to machine up a mandrel which inserts into the central hub hole, or better still, inter-reacts with the bolting circle. The mandrel should have a central drilling with an internal conical termination which accepts a spike mounted on a pedestal of some kind. Ideally the termination/balancing point should be quite low, creating a fairly unstable balance whereby the whole assembly wants to readily tip one way or the other unless the tip/tip weighting is very close. That will give the best end result for static balancing.

 

It's also worth keeping in mind that more inboard weight on one blade will statically balance more outboard weight on another blade, so all may appear wonderful, when in fact it might not be perfect. Those who have balanced con-rods end-for-end will appreciate the notion ...

 

 

[scsirob]

I consider dynamic balancing as icing on the cake after a lot of other stuff has been addressed.

 

- Static balance is important.

 

- Identical setting of the blade angle on adjustable props. One blade half a degree in or out can make a big difference.

 

- Proper tip tracking. If the tip of one blade follows a different path (>2mm or so), you'll have more vibration.

 

- Even compression on the cylinders. One weak cylinder can cause a lot of vibration that you won't be able to balance out.

 

- On Rotax engines, poorly balanced carbs will mess up an otherwise smooth engine too.

 

Once all those are taken care of, a dynamic balance can squeeze out the last bit of comfort.

 

On my plane I have marked relative position for all parts of the prop, spinner and backplate so I can pull the prop, reassemble and still have perfect balance.

 

 

[facthunter]

The consideration is not whether static or dynamic is used. It's which item individually or section is balanced.in it's own right or as an assembly. If something is done as an assembly it only balances IF reassembled in exactly the same relationship with each part as it was originally balanced as. Items which have considerable length MUST be dynamically balanced as a static balance on some axis is invalid in that instance. as it could have a large offset (couple) when rotating .. Any assembly of parts individually balanced by the correct process will end up being a very reliable job.if each part is done within close parameters with no great error being possible. Internal loads are not greatly affected without altering balance masses through the engine which in many aero engines is not done due the requirement of being the lightest engine possible. Also heavier balance weighted cranks have critical torsional vibration problems being experienced at lower RPMs and more severly than when not weighted.. Balancing a running engine is not something that should be taken totally as all plus or fix -all as there's a lot of things going on there.. Even things like engine mount flexibility and critical frequencies. Torsional vibrations can be damped actively and that's common and desirable as they can be destructive but YOU can't feel those until too late. Nev

 

 

[Bruce Tuncks]

Sorry to be skeptical since I would just love to be wrong, but after trying hard I still don't see how the balancemaster works. Yep it might well be just me that's the problem.

 

There have been people here who have tried slime in their tyres but discarded it after finding that the imbalance became terrible, and why? because the slime moved towards the outermost bit of tyre. This was already the heavy point, which is why centrifugal force made it further from the axis to begin with. This point is effectively downhill for the rest of the slime in the tyre so that is where it goes.

 

If slime migrated to the opposite side, it would be a wonderful wheel-balancing thing. Alas it is not.

 

( for those who don't know about slime, it is a green thick liquid containing fibers which block up punctures from the inside. You put it inside the tube. Of course when the wheel is not moving it all flows to the bottom, and in this way it differs from the balancemaster where the mercury is in a torus.)

 

 

[Kyle Communications]

I think you will find that is why they use mercury in the ring. It is heavier than the parent it is trying to balance. then any rotating object wants to reach equilibrium so the heavy metal goes to the light side to bring it to balance. Guy Small fitted his yesterday and noticed a big difference to his Rotax. His is fitted behind the prop like mine is

 

I cant attest to the theory..all I can say is with practical experience it works...and works well

 

 

[jetjr]

Tyre slime and balance beads work pretty well to balance BUT in aircraft tyres they go from stopped to full speed too fast for it to work as its …….slimey

 

Mercury should move fast and the balancing action does work in constantly rotating things

 

 

[Brett]

Well Unfortunately I cant fit the balance master into.my cowling without major modifications and that will make it look stupid also... well, back to the drawing board. Static balancing and throw in a dynamic one after that.

 

 

[Old Koreelah]

Tyre slime and balance beads work pretty well to balance BUT in aircraft tyres they go from stopped to full speed too fast for it to work as its …….slimey...

I'd never thought of that, Jetjr. I put preseal in my tyres as it proved itself on several of my motorcycles.

No leaks, but sometimes a noticeable vibration for a few seconds after liftoff- presumably because, as you say, the slime hasn't had a chance to distribute itself properly.

 

 

[skippydiesel]

Well Unfortunately I cant fit the balance master into.my cowling without major modifications and that will make it look stupid also... well, back to the drawing board. Static balancing and throw in a dynamic one after that.

My ATEC Zephyr, Rotax 912 ULS, is very closely cowled an yet I had no difficulty in fitting the recommended BM - On my engine/prop there are about 6 potential fitting positions (the BM is "dished/offset" so each in/out fitting is two positions) after close measuring only one position suited my application.

 

 

[Brett]

Sonex cowls dont leave much play room.

 

 

[skippydiesel]

First photo shows final location - blue & yellow extended spinner/back plate screws are dynamic balance weights (washers covered with shrink tube). These two assemblies prevented the BM from being "flipped" 180 degrees to reside up against the spinner back plate.

 

Second photo (bit dark) shows BM in side view.

 

Last photo gives an idea of how well BM fits with cowling in place

 

 

 

[Blueadventures]

I think you will find that is why they use mercury in the ring. It is heavier than the parent it is trying to balance. then any rotating object wants to reach equilibrium so the heavy metal goes to the light side to bring it to balance. Guy Small fitted his yesterday and noticed a big difference to his Rotax. His is fitted behind the prop like mine isI cant attest to the theory..all I can say is with practical experience it works...and works well

Fitted in a good run with the Nynja today and BM feels good. I'll set up my gopro on the dash again and compare the vibration of the windscreen, should show difference. Ran at just under 5600 rpm WOT s&l. Do better images next time by taking better care.

 

 

 

 

 

[Bruce Tuncks]

Blue, the second and third pics are nice and sharp..are they the after pics?

 

 

[Blueadventures]

Blue, the second and third pics are nice and sharp..are they the after pics?

No just the poor operation of the camera by me. I will re do them another day. cheers

 

 

[skippydiesel]

Question: Does the BM require a significant time to work to "magic" ??

 

I ask because I have experienced low frequency vibration on 2-3 occasions, during climb out (5200 rpm). The vibration dissipates after a few moments but is quite marked.

 

 

[Kyle Communications]

If you accelerate the engine fast then you can feel it a little bit but its probably about 1 sec thats all. If you have that and on climb out it certainly wouldnt be the BM it would have settled long before you lifted off

 

 

[Bruce Tuncks]

skippy, are you sure the vibration is not the wheels still spinning? That happens with Jabirus.

 

In an early plane, they thought they were getting elevator flutter at 100 knots. It turned out that at 100 knots the wheels were starting to spin from the slipstream.

 

 

[Kyle Communications]

Yes maybe its so smooth now your feeling the wheels turning :)

 

 

[skippydiesel]

skippy, are you sure the vibration is not the wheels still spinning? That happens with Jabirus.In an early plane, they thought they were getting elevator flutter at 100 knots. It turned out that at 100 knots the wheels were starting to spin from the slipstream.

Thanks Bruce - Defiantly not the mains (I lock my brakes on lightly after TOff to prevent this) - never known the nose wheel to rotate but always a possibility (now I will have to figure out a way of checking this out - any suggestions??)