Really Nice Prop Balancer -

[AndyKunz]

Yep, IF you assume that the bling-bling-balancer uses a
"simply cut-off wire" instead a balanced shaft.

I was referring to the stock wire that comes with the TF balancer. It really is just a piece of music wire that appears to be hand-sharpened on a bench grinder.

Sorry for my english, I'm from Holland.

It's better than some Americans' around here. My brother-in-law is from Holland.

Andy

[detox]

Guys, I gotta laugh at all the hand wringing I see over minute differences in blade balance. If you do the math it becomes clear that the amount of vibration caused by minor blade mass differences is nothing compared to that caused by the blades slapping the water two or three times per revolution, or by the cable whipping around as it spins in a tube with a relatively large annular space. This is a dynamic system and that is what matters, not static balance. Minor blade imbalance is invisible when the actual dynamics of the system are considered. Worry more about blade sharpening and surface finish than about a level of weight precision that you probably can't attain anyway.



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You are probably correct, but atleast I will know my prop is well balanced.

I will rough balance using the Topflight then fine tune using the Kintech

[Steven Vaccaro]

Jay is 150% correct. I would have never believed it until I witnessed Brian B take a pair of pliers to a prop and bend the hell out of it. He never rebalanced and the boat was faster. Now there was no way that prop would have balanced on any balancer!

I have a Zro G and love it. But at $35.00 this balancer is one hell of a deal.

[Flying Scotsman]

[QUOTE=Fluid;68463] Worry more about blade sharpening and surface finish than about a level of weight precision that you probably can't attain anyway.

Jay, what is your opinion on surface finish. I prefer to leave mine with a 400 or 600 wet sand. As, I perceive I get more bite?

Douggie

[Gerwin Brommer]

Steven.

Bending a blade of a prop doesn't affect the WEIGHT of that blade.
I assume Brian changed all the blades, roughly in the same way ?
You only change the shape/pitch.
That's why it can become a faster prop.

[detox]

Thats an idea...bend your props then balance. Wouldn't that be better than an unbalanced bent prop?

[Steven Vaccaro]

Steven.

Bend a blade of a prop doesn't affect the WEIGHT of that blade.
You only change the shape/pitch.
That's why it can become a faster prop.

Gerwin with the Zro G or probably this balancer, if you leave a finger print on the prop it shows as out of balance. I have played with couping props and they show as out of balance, not sure why.

[Gerwin Brommer]

Now i'm getting a hard time, trying to explain what I mean, in English :

Imagine : any given prop, 2 or 3 or 4 blades, doesn't matter.

Example : a 3 blade prop. Every single blade has a "part" in the total prop.
Each single blade is positioned in 1/3 th op the prop.
If you change all 3 blades ( cupping, spooning, texas cut etc etc etc), BUT the changes on the blades are NOT 100 % the same, the weight of a blade in a part of it's "own section" , compared to the weight in the same parts in the 2 other sections can be different. So it's imbalanced.
I hope you understand what I mean.

[egneg]

I saw this balancer for the first time when RiverRat posted the development of it. I checked the web site but there was not a buy now button yet. After following this post the last couple of days I had to get one! I have just placed an order for the balancer with the 3/16 shaft and a 1/8 shaft as well. Hopefully I will have it by the weekend and I have a few props that need to be done. Folks might say that close is good enough and that very well may be true ... but being in a machining/manufacturing atmosphere for the past 25 years I have learned that the closer you get to perfection the better things work.

On a side note I don't see how changing the shape of the prop will change the static balance as long as material is not added or taken away. The thrust balance can change but to what degree will depend on rpm and how close the blades are matched.

[Flying Scotsman]

Now i'm getting a hard time, trying to explain what I mean, in English :

Imagine : any given prop, 2 or 3 or 4 blades, doesn't matter.

Example : a 3 blade prop. Every single blade has a "part" in the total prop.
Each single blade is positioned in 1/3 th op the prop.
If you change all 3 blades ( cupping, spooning, texas cut etc etc etc), BUT the changes on the blades are NOT 100 % the same, the weight of a blade in a part of it's "own section" , compared to the weight in the same parts in the 2 other sections can be different. So it's imbalanced.
I hope you understand what I mean.

Gerwin, I understand and your command of the English language is superb!!

Douggie

[Chop]

On a side note I don't see how changing the shape of the prop will change the static balance as long as material is not added or taken away. The thrust balance can change but to what degree will depend on rpm and how close the blades are matched.

I believe that you are changing the C.G. of that particular blade, thus throwing it off balance relative to the other blade(s), however insignificant that might be.

[Dr. Jet]

I After following this post the last couple of days I had to get one! I have just placed an order for the balancer with the 3/16 shaft and a 1/8 shaft as well.

Me too! I already have a TopFlight and a Zero-G, but this one looks good as well.

You can never have too many tools, just too small of a shop.

[Gerwin Brommer]

Egneg :

You're answering your own question :-)

"how close the blades are matched" , there's your clue !
If 1 blade of a prop is shaped different than the other(s), you're moving weight towards another blade, and away from the blade that's on the other side of the "different blade" (in case of a 3bladed-prop)

Another thing : a blade which is different from the others, will provide water to the next blade in a different way , compared to the other blades. So the OVERALL efficiency of the prop decreases.( assuming the other blades do have a correct shape)

[AndyKunz]

There is a limit to how much balancing is necessary. There's a concept of "diminishing returns" meaning that you can 8 pour hours into a perfect blade, but anything done after the first hour makes no difference on the water. There are more important things to cover than the balancing of a prop within a fraction of a fraction of a millimeter.

For instance, connectors.

Andy

[Fluid]

Why is a balanced/unbalanced prop at , for example, 30.000 revs NOT dynamic ?The "unbalance" in the flex/wire of the driveline SHOULD be "made even" by thestrut/trimm.

Gerwin, please read my post more carefully. Nowhere did I ever say not to balance a prop. What I clearly stated was that worrying about a tiny bit of unbalance is not important at all in our dynamic environment. The tiny amout of vibration caused by a blade that is slightly out of balance doesn't matter - its magnitude is completely hidden in our dynamic drive system by the vibration of the blades hitting the water and the flex cable whip.

How can you say that random, undampened cable whip is somehow "made even" by moving the strut around? Have you ever seen an rpm readout from a datalogger used in an FE boat? The rpm is almost never the same even when the boat is running straight ahead, it varies wildly. The constantly changing rpm causes wild vibrations in the drive system, the tiny amount caused by minor prop imbalance is totally meaningless. It's kinda like sneezing in a hurricane....

A prop which is not in balance will wear out the bushings/ballbearings in the strut/trim. And THEN the unbalance in the flex/wire will have influence on the prop.

No, it will not if it is only slightly out of balance. What wears out strut bushings is the slap-slap-slap of the prop blades hitting the water with enough force to move a boat at 50+ mph.

Readers are free to ignore engineering fact if they choose. I'm just trying to advance the technical end of the hobby. BTW, the designer of more R/C boat props than any one else living or dead happens to agree with me.

Also, I never said that the very cool balancer is question is not a beautiful piece of work. Owning one could be considered reward enough by itself, no matter how well it works.


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