BalanceMaster testing

[facthunter]

My First model aero engine was a FROG and it was smooth enough as it was.   Nev

[Moneybox]

1 hour ago, facthunter said:

My First model aero engine was a FROG and it was smooth enough as it was.   Nev

French?

[Blueadventures]

3 hours ago, skippydiesel said:

You obviously did not read my earlier comments -Yes! I fitted a Balance Master - made no (personally) discernible change/difference . I did not remove it, making an emotional rationalisation of expenditure - may help, if prop damaged, to reduce destructive vibration, for a safe emergency landing.

 

Seems a tad odd that you would recomend a device, that you don't use yourself, that does not appear to have scientific evidence to support its efficacy.

 

I have no intention of installing a Balance Master, without empirical evidence as to its efficacy, however am intersted in the concept, should such evidence be forthcoming - hense my questions on the matter.😈

 

Skip please reread my post and correct your statement as in my second parragraph I said I had a balance master fitted and very happy with it.

 

I saw the balance master on your old Zephyr and assumed you where still happy to fly with it, and you have confirmed your reason and its perceived benefit.

 

For site users information I was very happy with the reduction of vibration by the balance master and would fit one again in the absence of performing dynamic balances.  My experience was during 77 flights during 2018 and 2020.  AS I now use a Dynavibe to perform dynamic balances I do not refit the balance master (Balance master can not be on the prop during the dynamic balance procedure.)

 

Skip how many flights have you made with the balance master fitted for comparasion?

[facthunter]

No . Not French. Still made apparently.  Nev

[onetrack]

Balance master devices have been around since WW2. My first experience with them was around the early 1970's, with them being used attached to truck rims, to dynamically balance the wheel and tyre assembly.

Naturally, the company gave glowing recommendations and testimonials from users - but strangely enough, they never really "took off" as far as general use and acceptance went.

There are multiple reasons for that, but I won't go into detail about those reasons right now, because truck wheel applications are different to aircraft applications.

 

The Balance Masters fitted to truck rims contained mercury and steel balls. The principle marketed, was that the steel balls gravitated to the area that needed weighting, and the mercury added a little more weight, but also slowed down unnecessary rapid and constant re-positioning of the steel balls.

 

Then came versions using silicone fluid, or just mercury alone, and applications covered everything from motorcycle flywheels to propellers. They were always marketed as the ducks guts to solve balance problems - but many users were not satisfied with their performance.

The bottom line is, balancing is a black art, and a field all to itself. You can have imbalance coming from torsional whip in shafts, or imbalance simply coming from large rotating masses that have excess weight in one position.

 

My best mate spent 30 years balancing tailshafts and that was really eye-opening, as to where imbalance could come from, and often, how little it took to cause vibration, and how little it took in correction to get near-perfect balance.

RPM ranges can also produce harmonics that increase vibration - witness the RPM range of some aircraft piston engines that engines must not run at for extended periods. due to damaging inherent harmonic forces.

 

 A lot of people fail to understand that Balance Masters don't actually put rotating masses into precise balance. They operate by DISRUPTING the harmonic imbalance, by moving the imbalance around. 

The interesting part is the force amplitude of the imbalance with the Balance Masters fitted, is actually larger than when the Balance Master is not fitted. But because the variations in force amplitude change randomly, the amplitudes generated, don't affect any other components that might have some imbalance. 

[facthunter]

Damping and  Balance are  different things also. Balance is for 2 purposes. Reduce internal loads on parts and reduce the thing Shaking. You can do the second to some extent without doing the first at all. That would give you an Illusion that things are right when they are not. Most balancing is a compromise if reciprocating parts are involved. Nev . 

[aro]

There are a couple of videos on Youtube demonstrating how they work. Seems reasonably convincing. Arguably not as good as dynamic balancing, but it looks like the material should redistribute to reduce rotational vibration whatever the cause - maybe even blade pitch and tracking etc. They will always start out of balance due to gravity, until the vibration distributes the balance material.

 

They will not do anything for power pulses through the gearbox, so won't allow lower idle RPM on a Rotax.

 

 

 

 

[rhtrudder]

Has anyone fitted one to the flywheel end, looks easy enough, do you think it would make a difference, my plane has a noticeable vibration under 5000 feel it through the cabin support, I realize the engines run like a thrashing machine up at cruise, you only have to take you headsets off, so it may be just what it is, 

[Area-51]

1 hour ago, rhtrudder said:

Has anyone fitted one to the flywheel end, looks easy enough, do you think it would make a difference, my plane has a noticeable vibration under 5000 feel it through the cabin support, I realize the engines run like a thrashing machine up at cruise, you only have to take you headsets off, so it may be just what it is, 

You are clutching at straws; i will explain why... when a crankshaft is balanced it is done so with all ancillary components attached, flywheel, pulleys, gears, retaining bolts; the clutch plate is left out as its position is not fixed. The crank assembly is then dynamically balanced; flywheels and crankshafts are generally pre balanced separately first. I am assuming rotax balance the 912 crank with conrods attached; i could be way wrong. Adding a balance master to the rear without adding also to the front will serve no benefit.

[rhtrudder]

Okay if my problem is from the prop would it be noticeable below 5000 but smooth out above or would it be through the whole rev range

[Blueadventures]

42 minutes ago, rhtrudder said:

Okay if my problem is from the prop would it be noticeable below 5000 but smooth out above or would it be through the whole rev range

Could be carby balance or the carb opening system.  Could try redoing a mechanical balance.  If you were to do a mechanical balance make a note of the turns to get the gap that is measured with a feeler gauge and also the turns on the idle jet.  That way if they are out of speck you can adjust to speck or reset them where they were.

 

If you want I'm happy to loan you my balance master for one month if you pay the postage.  But consider the mechanical balance first.  Even a pneumatic balance if you have ethe gear.

 

42 minutes ago, rhtrudder said:

Okay if my problem is from the prop would it be noticeable below 5000 but smooth out above or would it be through the whole rev range

 

Edited yesterday at 09:44 AM by Blueadventures

[Moneybox]

1 hour ago, rhtrudder said:

Okay if my problem is from the prop would it be noticeable below 5000 but smooth out above or would it be through the whole rev range

 

If your wheel balance is anything to go by you'll notice an out of balance wheel will only wobble at certain speeds. I would say it the gyroscope effect that keeps it spinning straight at higher revs.

[skippydiesel]

I would like to see a test of the BM, using a propeller, operating from idle to say 3000 rpm (to accommodate Jabs). 😈

[facthunter]

FLAT fours are the worst motors for  uneven flywheel effects of the reciprocating parts and are notable for being prone to crankshaft breakages in cars. Nev