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Dynamic prop balancing weights

Freemasm

Well Known Member
Know the theory and basics of dynamic balancing. My question is weight application. Watched the Dynavibe videos. Understand the weight application though they probably should have mentioned longer fastener application to ensure engagement of fastener locking feature and allowance/addition of the new fastener weight. Maybe I missed it. That said, great video. Now the question.

Does EAB world keep the externally added weights installed or is there a "cleaner" method in use?

Let me know. Thanks.
 
We put all of ours on the flywheel radial 1/4" holes that are 30 degrees apart.
An AN4 bolt, stack of thick/thin/wide washers as required to hit the trim weight. You can also split the weight between the holes if the radial position allows.
After the first correction, if the new angle is 90degrees to the first, then you are working on the second harmonic and that is good!
We did use a couple washers under the spinner screws on one plane to get that last little bit, but a couple bugs on your prop is about the same!
Remember, you are balancing the whole system.
 
I do the same. Use the 12 holes on the flywheel for Lycomings. Usually, a really great balance will have weights in 2 holes, and sometimes an extra washer underneath one of the spinner screws, or even just adding a longer spinner screw has the same effect. I usually manage to get all of them below .03 IPS. Some hit .00 or .01 IPS, but a bug on the next flight will probably change that. :)

Vic
 
Balance weights should always be permanent installations, which means no washers or longer screws on spinner
(guaranteed to get mixed up on first spinner removal).
Expectations: The DynaVib is a decent unit, but I guarantee that '0' on their box won't be '0' on my Microvib II, so set your expectations accordingly.
 
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I just drill a hole in the aft spinner bulkhead at the radial location and add bolt/nut/washer. I tape them on during the test and do the drilling once the final locations have been determined.

Larry
 
@Walt. Interesting. I assume you are saying your device is better. The algorithms are probably right on top of each other as they're interpreting the same physics and using the same equations. Relative quality of the respective accelerometers is the difference?

BTW, Thanks to everyone for the input
 
@Walt. Interesting. I assume you are saying your device is better. The algorithms are probably right on top of each other as they're interpreting the same physics and using the same equations. Relative quality of the respective accelerometers is the difference?

BTW, Thanks to everyone for the input

Don't want to say 'mine is better' but MVib is an industry standard and certified for use on every model helicopter and turboprop. The MVib unit goes out to 3 decimal places for increased resolution. If cost means anything, my vibration pickup alone costs more than the whole DV classic system.
 
@Walt. Interesting. I assume you are saying your device is better. The algorithms are probably right on top of each other as they're interpreting the same physics and using the same equations. Relative quality of the respective accelerometers is the difference?

BTW, Thanks to everyone for the input

There's actually quite a bit of "options" when doing the frequency domain transform inside the box. Windowing, sample size, averaging, etc. all have an effect on the result. I've not use the microvib, but my last company had a similar level vibe analyzer that allowed you to change all those. Those options are preconfigured in the cheaper boxes and they don't even tell you what they are.

For the most part, you're paying for a lot of options that most people will never use. The nicer units can use any accelerometer, velocity sensor, or displacement sensor. I think the dynavib can use a small selection of accels, and the entry level Aces unit must use the accel that came with it. The cheap boxes are normally limited to a single input which means you can only do single plane(axis) balancing. The more expensive ones will come with up to 4 inputs for simultaneous multirotor, multiplane balancing. The nicer boxes will also print out automated reports for condition monitoring, and track vibe levels by serial number so you can see monitor vive changes over time. The microvib also comes with a strobe light option for doing optical blade tracking.

For a simple prop balance though, the cheap units are completely adequate. I looked into a microvibe a few months ago, and I could only find a used one starting around $4500. The brand-new dynavib and Aces units are 2k.
 
Yes Sir. processing power is cheap so options are abundant. For the intended application, I'd expect the default/applocable Microvib settings/options versus the Dynavib capabilities to closely mirror each other; hence, my accel quality comment. We're talking technician capabilities versus those needed by a balance engineer.

Great info though. Thanks.
 
After participating in a balancing session this past weekend with FL-Mike, my completely biased yet non-expert/non-scientific opinion is the DynaVibe system is more than adequate for us shadetree mechanics working on our RVs vice an A&P who does this kind thing as part of their portfolio on all kinds of aircraft. Could we have gotten the planes we did dialed in even better with the microvib, more than likely, but I'm not convinced the juice would have been worth the squeeze. Sometimes perfection is the enemy of good enough. All I know is I could feel the difference when we were done. YMMV....
 
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I have used my dynavibe on about 12 planes ranging from Skyhawks and Cherokees to my 4 blade mustang and a friends RV8. It is more the adequate but does take some understanding. If you are close to Georgia hi5 me up and we can do it together
 
@Chipper G

I appreciate that. Got a long way to go/hoping I can stay alive long enough to finish this project. Busted some ribs so instead of working in the hangar, I'm geeking up on stuff and getting pretty ahead of reality. Much thanks.
 
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