Dynamic prop balancing

FORANE

FORANE

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FORANE
I bought a Dynavibe and balanced my prop today. Wow what a difference! Highly recommend to all. If you haven't had the opportunity to see and feel the before and after, you should look into it.
 
I have read that this makes quite a difference. It's pretty spendy and if there's an opportunity for a few owners to chip in to buy one, i think that would work well. It's not something I would imagine would need to be done often.
 
Isn't there an app for that? o_O
 
rtk11 said:
I have read that this makes quite a difference. It's pretty spendy and if there's an opportunity for a few owners to chip in to buy one, i think that would work well. It's not something I would imagine would need to be done often.
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This place rents one:
https://www.vikingaircraftengines.com/new-products/dynavibe-classic-prop-balancer
alternatively you might find someone local who owns one or a club with one you can rent for a modest fee. Even for a first time user it's simple and made a huge difference for me.
 
rtk11 said:
It's not something I would imagine would need to be done often.
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Depends. If an owner wants to maintain a certain vib level or treat it as a preventative measure then they can perform a prop vib check at each annual. Some mechanics would pro-rate that yearly check so you wouldn't pay for a full balance each year unless it required correction. Another option, if the equipment is available, is to have a complete vibration spectrum analysis performed. When you combine the prop balance with correcting other vibration sources it can make a very noticeable difference in the cockpit and in some cases make it quieter.
 
Bell206 said:
When you combine the prop balance with correcting other vibration sources it can make a very noticeable difference in the cockpit and in some cases make it quieter.
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What are the other vibration sources you commonly see? Accessory items I’m guessing.
 
Jdm said:
What are the other vibration sources you commonly see? Accessory items I’m guessing.
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Outside the prop/spinner… engine vibration isolators (mounts), alternators, pulleys, misc loose items, and if the ½ per vib is elevated something amiss with a cylinder. It really depends on the specific aircraft and vib frequency vs a generic common list.
 
Are any necessary adjustments considered pilot authorized maintenance? How do you make adjustments?
 
Anyone know of an AP that can do this for me in the Hudson Valley/south east NY/NE PA/CT/western MA?
 
Just checked it out.
That GX3 which appears to be the latest and greatest model is $4k. The one on Aircraft Spruce appears to be an older model for sale for about $1600.
Watched a video too on how its done. I was VERY surprised (in that I simply didn't know) that the weights added to the prop were just everyday washers placed on the OUTSIDE of the spinner under the screws that held the spinner in place. Sure didn't see that coming.
 
rtk11 said:
Well, you do have to maintain balance, so you have to tape your wife's iPhone to the other blade.
:p
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Thanks for the clarification. I think Mr. Phillips was giving me a bit of misleading information as the iPhone on one blade did help the balance a little at very low RPMs but anything above starter rotation speed was much worse. Taping the wife's phone to the other side helped tremendously. FWIW ... you will need a lot of Gorilla Tape and this method can be very hard on a iPhone so using phones other than your own is highly recommended. :fingerwag:
 
guzziguy said:
That GX3 which appears to be the latest and greatest model is $4k. The one on Aircraft Spruce appears to be an older model for sale for about $1600.
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If I recall the $1600 model is the Classic and only does prop balance. The GX does more like spectrums, helicopter work, etc.
guzziguy said:
that the weights added to the prop were just everyday washers placed on the OUTSIDE of the spinner under the screws that held the spinner in place.
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Dont know which vid you watch but on TC'd aircraft the balance hdw needs to be aircraft grade like AN or MS spec. And the putting the washers on the outside of the spinner is only for the balance process. The permanent balance hdw is installed on the spinner backplate, flywheel, etc as shown for that particular prop/aircraft. E/AB aircraft might be different.
 
Ah, thanks for the clarification (non-A/P here). I watched their video on YT. Just plug Dynavibe into YT and it comes up.
 
There are other companies which offer balancers as well. I used AN-4 bolts on the flywheel of my experimental.
 
Not sure which bolt I got, but the end result is this

aa9e392b3421f48186ddde334d52ae76.jpg


There is one more bolt without the washer that you can’t see in the pic. Below is the pic of being setup for calibration.

feec4ff42327a27330dd0b080ca9b762.jpg
 
Looks like the an4 bolt with an
AN365-428A MS21044N4 ELASTIC STOP NUT
 
WannFly said:
Not sure which bolt I got, but the end result is this

aa9e392b3421f48186ddde334d52ae76.jpg
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This is how all three of my Lycomings are done as well - washers bolted to the starter rings.
 
On an important note here. Once you have the prop dynamically balanced it needs to be indexed.

This way if the spinner and backplate is removed it will go back on exactly the way it came off. I used to put a small decal on the spinner to state this was an balanced assembly.
 
Matthew Rogers said:
Anyone know of an AP that can do this for me in the Hudson Valley/south east NY/NE PA/CT/western MA?
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Matthew, I had it done by a prop shop and wasn’t pleased at all with the results. It came down to this person’s ‘technique.’ So three weeks later I took it to Kari at Tally-Ho in Danbury (KDXR). He charged about half of the original and does a phenomenal job. He takes the time to get it done right. I wouldn’t go anywhere else if you live in the area.
 
Kent Wien said:
Matthew, I had it done by a prop shop and wasn’t pleased at all with the results. It came down to this person’s ‘technique.’ So three weeks later I took it to Kari at Tally-Ho in Danbury (KDXR). He charged about half of the original and does a phenomenal job. He takes the time to get it done right. I wouldn’t go anywhere else if you live in the area.
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Great. I’ll call them and it is not too far. Hopefully it is a fly-in and fly out sort of deal and I can do it this year.
 
That’s exactly it. Call him and set up a day and then you’ll be in and out in a few hours.
 
My A&P charges $300 for a prop balance with dynavibe, I’m on waiting list last few weeks until he clears a few planes in the shop in front of me. I have never had one done, and a recent flight started noticing decent amount of vibration in my panel in cruise that changes with rpm adjustments. Above 2200 doesn’t appear noticeable in climbout, only in cruise and mostly above 2200 rpm. It definitely changes with rpm in cruise though. Vibration can be many things I know, but can only hope it is only the prop or something cheap and simple. Cheap and simple don’t seem to happen very often with me though:rolleyes:
 
I get how this works at whatever fixed rpm it's done at, but is it likely to be the same for various cruise rpms and both rich or lean of peak?

I know my mechanic is not a fan of doing this, but I've not had him explain exactly why.
 
I’m guessing but think if dynamically balanced at say normal cruise rpm it should be close at other reasonable rpms, and lop or ROP. But I’m guessing someone else would know better. There is static balancing of props and components too.
 
SSR said:
but is it likely to be the same for various cruise rpms and both rich or lean of peak?
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FYI: In general terms, vibration analysis is not a factor of RPM but of frequency. While RPM can affect the force (amplitude) of the vibration the frequency will normally remain the same, i.e., 1 unbalance event per rotation (1 per), 2 events, etc. At what frequency (1 per, 2 per, 1/2 per, etc) that vibration occurs usually determines where that vibration originates. For example, most 1 per vibs are prop related and most 1/2 per vibs are related to cylinder/combustion events in a normal situation. So once you determine that vib freq you can usually narrow down the cause and correct it.
 
Barry said:
I’m guessing but think if dynamically balanced at say normal cruise rpm it should be close at other reasonable rpms, and lop or ROP. But I’m guessing someone else would know better. There is static balancing of props and components too.
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Props are statically balanced, but not the spinner and back plate. When assembled is where the imbalance can take place.

Start with the prop. Installed and bolts torqued, the tips of the prop must be checked to be in the same tip path. In some instances this can vary, and if the tip path is more than say a quarter inch out, the blade can be re-positioned on the flange to correct tip path error.

Once all of the spinner hardware is installed now it must be balanced as a unit. This will require a few runs and a solution to be established. On lycoming the weights can be placed on the starter ring, on continental it will require weight to be added to a spinner backplate.

Once complete, the assembly needs to be marked for indexing, and I would suggest a sticker attached to state this is a balanced assembly.
 
SSR said:
I know my mechanic is not a fan of doing this, but I've not had him explain exactly why.
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If I were a mechanic (for a living and not just on my own stuff) I likely wouldn't be a fan either. The equipment is expensive, and it requires an annual calibration which is more cost. Setting up and performing the balancing takes some time with multiple runs, test weight, recheck and try more weight, repeat; in the end it consumes time. Balancing is not mandatory, so you might find those who don't wish to spend the money to have it done. At the same time, you need to find a steady stream of customers just to break even.
 
SSR said:
but is it likely to be the same for various cruise rpms and both rich or lean of peak?
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Dynamic balance can fix mass imbalance. Rich/lean won't change the mass balance - but may introduce vibrations at firing frequencies due to mixture imbalance - you aren't going to fix that by adding weights to the prop / spinner.
Spectral analysis can help find some of those things.
Example:
 
Capt. Geoffrey Thorpe said:
Dynamic balance can fix mass imbalance. Rich/lean won't change the mass balance - but may introduce vibrations at firing frequencies due to mixture imbalance - you aren't going to fix that by adding weights to the prop / spinner.
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This makes sense.
 
Are there any quality shops in Cali that can do a good job with the dynamic balance?
 
I had mine done a few years ago... dropped my Cherokee 180 off for a few hours.. I came back and he said mine was perfect and didn’t need balanced. They still collected my money. I don’t think they did anything but could be wrong! I was hoping for some amazing results too!


Sent from my iPhone using Tapatalk
 
Bell206 said:
Curious as to what was the prop balance data (IPS/Clock) the shop entered in their logbook entry.
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None! That’s they thing they said none was needed and I argued with them.. I asked them how they were supposed to add bolts to balance my ring gear and they said they could do it.. I have no idea how!
ddb673a0c6544eee678e6995fe68fdc3.jpg



Sent from my iPhone using Tapatalk
 
Bell206 said:
Curious as to what was the prop balance data (IPS/Clock) the shop entered in their logbook entry.
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If they did not actually change anything, they may not have had to enter anything into the logbook. If no bolts were turned, no screws removed and reinstalled, was there any maintenance, and therefore the need for an entry?

Not that it makes it any better for the owner, who is wondering if the shop actually did anything for the money.

I am sure they got their transmission fluid "flushed" and their power steering fluid was certainly "cooked".
 
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