Dynamic Prop Balancing

[skippydiesel]

Who's for it & why?

 

Who's against it & why?

 

Give me all your glowing success stories and dirty little failures.

 

I have painstakingly static balanced my prop.

 

Made multiple pitch adjustments & test flights, to arrive at an acceptable (to me) propeller performance for my take off / landing environment.

 

In my obsessive pursuit of perfection I am now wonder about dynamic balancing as the next level of worthwhile/dodgy investment.

 

Anybody care to recommend a NSW dynamic prop balancing service provider?

 

Just thought I would throw this little hand grenade into the discussion pit & see what jumps out.

 

 

[M61A1]

Who's for it & why?Who's against it & why?

Give me all your glowing success stories and dirty little failures.

 

I have painstakingly static balanced my prop.

 

Made multiple pitch adjustments & test flights, to arrive at an acceptable (to me) propeller performance for my take off / landing environment.

 

In my obsessive pursuit of perfection I am now wonder about dynamic balancing as the next level of worthwhile/dodgy investment.

 

Anybody care to recommend a NSW dynamic prop balancing service provider?

 

Just thought I would throw this little hand grenade into the discussion pit & see what jumps out.

I borrowed a dynamic balancer from Mark, of Kyle Communications on this forum. I then spent hours balancing and rebalancing my prop. I then researched prop balancers. Found two of interest, Vibrotech (Australian) sell balancer for around $1500 AUD, the other thing I found was a little thing called a "Balance Master". I was sceptical, but after having a bit of a think about it, I realised that it worked on the same principle as the bifilar weights on a Blackhawk rotor head, and purchased one from the US to try. Have to say, I was very pleasantly surprised with just how well it works. Cost me a couple of $100, but it works, and it works well. I told Bob Keen of Avid Aviation in Dalby about it, he bought a couple to try, now he's the Australian distributor for them.

They are made for Rotax 2 and 4 strokes, lycomings and much more.

 

I can put you in touch with Bob if that interests you.

 

HOME

 

 

[waraton]

Have spoken to Bob about a Jabiru/Camit variant of this and he will be in touch. Lifetime warranty on the product and according to Bob "highly effective".

 

 

[M61A1]

Have spoken to Bob about a Jabiru/Camit variant of this and he will be in touch. Lifetime warranty on the product and according to Bob "highly effective".

I will second that for "highly effective".

 

 

[Kyle Communications]

Do you notice the difference in the different rev ranges?. Does it remain smooth through out the whole range. Dynamic of course is only good for the speed you balance at thats why we use the dynavibe at 5000 rpm for cruise. But you can feel some vibration at the lower rev ranges when coming in for landing etc.

 

 

[M61A1]

Do you notice the difference in the different rev ranges?. Does it remain smooth through out the whole range. Dynamic of course is only good for the speed you balance at thats why we use the dynavibe at 5000 rpm for cruise. But you can feel some vibration at the lower rev ranges when coming in for landing etc.

If you go to that link on the 2nd post labelled "HOME', click on watch video, then select the top left one with beardy guy in the blue t-shirt. that actually shows you how it works. It constantly dynamically balances on the go.

 

 

[M61A1]

Do you notice the difference in the different rev ranges?. Does it remain smooth through out the whole range. Dynamic of course is only good for the speed you balance at thats why we use the dynavibe at 5000 rpm for cruise. But you can feel some vibration at the lower rev ranges when coming in for landing etc.

I wasn't knocking your Dynavibe in any way Mark, I really appreciated the use of it, and it did a good job., but as you are aware it takes some effort and usually is best at one rpm range. I had low expectations of the Balancemaster, and I was very pleasantly surprised at it's effectiveness.

 

 

[IBob]

I wasn't knocking your Dynavibe in any way Mark, I really appreciated the use of it, and it did a good job., but as you are aware it takes some effort and usually is best at one rpm range. I had low expectations of the Balancemaster, and I was very pleasantly surprised at it's effectiveness.

Interesting...and now I'm trying to visualise how that would work: you would think that if you had a gallery round something with mercury in it, that the mercury would make it's way round to the 'high point' of any eccentricity caused by rotary vibration, so aggravating the problem. But clearly that's not the case. Anyone????

 

 

[Kyle Communications]

I know you werent Mick...I just like to find the best solution. I watched the video and it makes perfect sense with what he is doing. I know well the limitations of dynamic balancing as I have that balancer that we use to service and balance the model jet turbines and it cost a motsa but when you have some engines spinning at 240,000 rpm you need to make sure the balance is pretty good. On that balancer we balance the rotors at under 1 mg per mm but it is capable to balance to 0.2gm per mm with a lot of fine tuning effort. On the turbines the balance is easier with the different rev ranges but on a IC engine there are far more different load directions at different RPM so you balance the prop for the most used position which is usually cruise of course. But even though my engine is smooth at cruise I notice the vibrations at the lower rpm when landing or just flying and maintaining 50knots on long approaches. The balance master would take most of that out by the look of it.

 

So you can "feel " the difference at different rpm settings on yours now with it on?

 

 

[Old Koreelah]

A couple of years back I got my prop dynamically balanced by a LAME called Steve at Rutherford. It's due for another session shortly, after I remount the prop in the correct spot. (I was recently told why it wouldn't stay level: I have it mounted at the wrong angle and the ignition magnets won't let it rest horizontally.)

 

 

[M61A1]

I know you werent Mick...I just like to find the best solution. I watched the video and it makes perfect sense with what he is doing. I know well the limitations of dynamic balancing as I have that balancer that we use to service and balance the model jet turbines and it cost a motsa but when you have some engines spinning at 240,000 rpm you need to make sure the balance is pretty good. On that balancer we balance the rotors at under 1 mg per mm but it is capable to balance to 0.2gm per mm with a lot of fine tuning effort. On the turbines the balance is easier with the different rev ranges but on a IC engine there are far more different load directions at different RPM so you balance the prop for the most used position which is usually cruise of course. But even though my engine is smooth at cruise I notice the vibrations at the lower rpm when landing or just flying and maintaining 50knots on long approaches. The balance master would take most of that out by the look of it.So you can "feel " the difference at different rpm settings on yours now with it on?

I have found it to be much smoother throughout the full range. I have left the weights on from using the balancer though, I figure the less it has to work, the better it might be.

 

Interesting...and now I'm trying to visualise how that would work: you would think that if you had a gallery round something with mercury in it, that the mercury would make it's way round to the 'high point' of any eccentricity caused by rotary vibration, so aggravating the problem. But clearly that's not the case. Anyone????

The video makes it clear, but Newtons 3rd law is what he quotes (the equal and opposite reaction one). As the heavy side attempts to go outward, the mercury is thrown to the opposite side, resulting in an equal but opposite force.

 

 

[IBob]

I'm not looking for an argument, I am genuinely interested in how this thing works.

 

For me, the video doesn't make it clear at all: it basically says if you do this it works.

 

Quoting laws of physics without saying how they apply in this case doesn't explain it.

 

Nor does saying the mercury is thrown to the opposite side. What throws it?

 

 

[M61A1]

I'm not much of a teacher, but I will try....

 

The mercury is fluid in a ring around the plate.

 

If there is no imbalance the mercury will be evenly distributed around the ring as it rotates.

 

If you introduce an imbalance, the heavy side will try to move outward, as it moves outward, the mercury wants to stay where it is, so ends up opposite to the heavy side, like moving a glass of water suddenly in one direction the water wants to stay where it is and is pushed up against the side of the glass.

 

After reviewing Newtons laws, I think maybe Newtons 1st law is more appropriate than his idea that it is an equal and opposite force, I think it has more to do with inertia.

 

 

[Subsonic]

I don't understand how this thing works either. If you have a torroid partially fluid filled, and rotate it eccentrically, the fluid will move to the area furthest from the axis. It has to, the same governor weights move outwards against the spring as they are spun, and fluid flows downhill.

 

Sounds like Snake oil to me, but if people say they have measured an improvement to validate it, obviously I'm missing something. Perhaps there is a dampening effect due to the viscosity of the mercury in the tube? If that's the case, when the unbalance is rectified by the movement of the mercury to the light side, what keeps it there now that the assembly is spinning concentrically?

 

 

[IBob]

I don't understand how this thing works either. If you have a torroid partially fluid filled, and rotate it eccentrically, the fluid will move to the area furthest from the axis. It has to, the same governor weights move outwards against the spring as they are spun, and fluid flows downhill.Sounds like Snake oil to me, but if people say they have measured an improvement to validate it, obviously I'm missing something. Perhaps there is a dampening effect due to the viscosity of the mercury in the tube? If that's the case, when the unbalance is rectified by the movement of the mercury to the light side, what keeps it there now that the assembly is spinning concentrically?

Me too. I can only think that what's happening is a bit more subtle than the first take.

 

I'm avoiding using the word 'complex' here, as lots of things labelled complex just have a number of parts, which is a different thing altogether; also it's a very popular word with politicians, where it actually means 'we'd rather not say, so we're pretending you couldn't possibly understand' or 'we don't do numbers, so how could you?' And I don't like that.

 

On the plus side, you'd have to think that the obvious action you describe (which is also what I imagine) would make any imbalance a helluva lot worse, and nobody would be fitting these things.

 

On the negative side, if it was that good, it'd be on everything...wouldn't it?

 

So right now I'm somewhere between the 'copper bracelet, but hey where's the harm' and the 'maybe this thing does have some specific applications' camps.

 

 

[facthunter]

I'm generally happy with balancing each item to it's proper limits and then you can change props without doing anything extra. Some balancing reduces bearing and engine mount loads, other makes the thing feel better regardless. Your dynamic prop balancer is reacting to forces other than those coming from the prop. Nev

 

 

[Kyle Communications]

It would be interesting to try one on a totally unbalanced prop first to see how it feels. With my dynavibe I should be able to test this. Setup the dynavibe on the prop and run it and take the measurement at a few different rpm settins this is easy. Then fit the balancemaster and run again the same test and measure any difference with the dynavibe. That would be conclusive proof that it works. I am sure these guys would have done this at balancemaster to confirm it works. Then I would balance the prop at cruise without the balancemaster to best I could get then fit the balancemaster and then use the dynavibe to confirm that the result was better again. Would be an interesting test. Anyone know of a balancemaster around that is for a 912ULS that would be free for this trial?. I am willing to give it a go. If it makes a improvement it has to be a good solution

 

Mark

 

 

[cscotthendry]

I'm very interested in the Balance Masters, concept, but the prospect of having a large quantity of mercury on my plane worries me.

 

Here's a couple of things that I think need to be considered;

 

1) How robust is the containment system in the Balance Masters?

 

2) Would it withstand a crash scenario?

 

3) If it failed in a crash or just in normal usage, it would spray liquid mercury in all directions. Who would be responsible for the clean up?

 

4) How well do they work at lower temperatures (ie what is the freezing point of mercury)?

 

5) What is the Aus government's rules on these types of devices? They are banned in New York State already and there are moves to further ban or restrict them in the US and other places.

 

I believe after doing some reading that they actually do work, but I'm a bit concerned about the practicalities / legalities. I might contact the guy in Dalby and investigate more about this.

 

 

[Kyle Communications]

I dont think there is too much mercury in them. it is quite heavy basically liquid lead and there is not a lot of weight required when balancing a prop as you will see how much weight is fitted to the spinner or propnuts. Looking at how they are made it the mercury is in a fully sealed tube and that is inside a rolled inside a metal housing that is joined together so the likelyhood of any sort of rupture or spill would be nearly impossible unless you took an axe to it

 

 

[IBob]

I'm very interested in the Balance Masters, concept, but the prospect of having a large quantity of mercury on my plane worries me.Here's a couple of things that I think need to be considered;

1) How robust is the containment system in the Balance Masters?

 

2) Would it withstand a crash scenario?

 

3) If it failed in a crash or just in normal usage, it would spray liquid mercury in all directions. Who would be responsible for the clean up?

 

4) How well do they work at lower temperatures (ie what is the freezing point of mercury)?

 

5) What is the Aus government's rules on these types of devices? They are banned in New York State already and there are moves to further ban or restrict them in the US and other places.

 

I believe after doing some reading that they actually do work, but I'm a bit concerned about the practicalities / legalities. I might contact the guy in Dalby and investigate more about this.

I guess that's why they keep bangin' on about Quicksilver: it's not so much Wisdom of the Ancients, as nobody wants to use the M word right now. Mind you, the rate we're replace the food chain with supermarket plastic bags, you'll soon be able to spray the stuff wherever you want......

 

 

[IBob]

It would be interesting to try one on a totally unbalanced prop first to see how it feels. With my dynavibe I should be able to test this. Setup the dynavibe on the prop and run it and take the measurement at a few different rpm settins this is easy. Then fit the balancemaster and run again the same test and measure any difference with the dynavibe. That would be conclusive proof that it works. I am sure these guys would have done this at balancemaster to confirm it works. Then I would balance the prop at cruise without the balancemaster to best I could get then fit the balancemaster and then use the dynavibe to confirm that the result was better again. Would be an interesting test. Anyone know of a balancemaster around that is for a 912ULS that would be free for this trial?. I am willing to give it a go. If it makes a improvement it has to be a good solutionMark

That seems to me a good and logical suggestion/offer.

 

Given that these things are recommended for trucks, buses, hogs 'n planes, it's a bit odd that nowhere on the site can I find anything that looks like a scientific test? Mind you, my ever lovin' will confirm that my eyes are in fact painted on...

 

 

[Bruce Tuncks]

Here's an interesting bit of physics.. If the airflow approaching the prop is not exactly aligned with the axis of rotation, then one blade will be getting a different angle of attack to the other. With only 2 blades, you will get a fluctuating force on the prop drive.

 

And this non-aligned airflow is usually the case, what with changing speed and engine side-thrust. And the force can be considerable.

 

Now this doesn't negate what has been said here, personally I believe that good dynamic balance is worth pursuing, but the payoff with a single-prop system will be less than with a turbine. In fact you might not notice much, I didn't after a professional dynamic balance. But then, vibration is very subjective which is why I'm wondering about a simple meter on the panel to measure it.

 

 

[Kyle Communications]

I noticed a big difference when I first balanced my 3 blade Bolly Optima 72 inch. The issue with getting a perfect balance is getting your carb balance really good as well. Not really a issue at cruise RPM but trying to get a average balance when the engine is at lower rpm is affected by the enough running slightly rough if the carb balance is not good. Some sort of accelerometer would be able to tell what you want Bruce. I sent some info about piezo stuff but using a MEMS device would be much better.

 

I was making a similar unit for model jet turbines to see how your engine was going and when it would need a balance again. But I then had just built and flown my Sav and havent really done any jet flying since so never finished the project. Now I have too many other projects on the go to get back to it. I have all the accell modules etc they are cheap now as well .

 

Mark

 

 

[M61A1]

It would be interesting to try one on a totally unbalanced prop first to see how it feels. With my dynavibe I should be able to test this. Setup the dynavibe on the prop and run it and take the measurement at a few different rpm settins this is easy. Then fit the balancemaster and run again the same test and measure any difference with the dynavibe. That would be conclusive proof that it works. I am sure these guys would have done this at balancemaster to confirm it works. Then I would balance the prop at cruise without the balancemaster to best I could get then fit the balancemaster and then use the dynavibe to confirm that the result was better again. Would be an interesting test. Anyone know of a balancemaster around that is for a 912ULS that would be free for this trial?. I am willing to give it a go. If it makes a improvement it has to be a good solutionMark

Give Bob Keen a call in Dalby. He may come to that party.

 

 

[M61A1]

That seems to me a good and logical suggestion/offer.Given that these things are recommended for trucks, buses, hogs 'n planes, it's a bit odd that nowhere on the site can I find anything that looks like a scientific test? Mind you, my ever lovin' will confirm that my eyes are in fact painted on...

Did you see the bit where he demonstrates on a test rig that uses ball bearings as a Mercury substitute on an out of balance wheel and a strobe to light it up?