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  #1  
Old 06-20-2007, 06:56 PM
MSFT-1's Avatar
MSFT-1 MSFT-1 is offline
 
Join Date: Feb 2006
Posts: 276
Default The value of dynamic propeller balancing

A couple weeks ago I did a write-up on my trip to Hartzell Propeller in Piqua, OH. After Hartzell did the necessary repair, they asked if I wanted the propeller dynamically balanced. The cost was about $250 and the mechanic that worked on my plane said it was well worth the money.

I had them do it.

Basically they use a piece of test equipment and a set of sensors to figure out where on the spinner bulkhead to add weight. Before balancing they did a run-up test for about 1 minute and determined that my prop was at 1.7 IPS (whatever that means). They added a small weight in the proper location and redid the test and then proclaimed that I was now at .45 IPS. They seemed very pleased with this.

The whole process took about an hour.

I wondered if I would even notice the difference.

It is AMAZING how much smoother the airplane feels. I could tell the difference immediately. Without a doubt, this was money very well spent. I guess it makes sense that it would be a big difference since there is a big hunk of metal out there turning at 2300 RPMs. Feeling (flying) is believing.

Bruce
N297NW
RV-8
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  #2  
Old 06-21-2007, 05:04 AM
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tc1234c tc1234c is offline
 
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Default

I had mine done a week ago at Ohio University airport (UNI). On my log book it says the propellers is balanced to .14 IPPS (should it be IPS?) using Chadwick Helmuth Balancer. The AP who did it told me the initial reading was 5. They charge $150 for the service.

Ted
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  #3  
Old 06-21-2007, 09:03 AM
Indigo Indigo is offline
 
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Default

The Chadwick manual " The Smooth Propeller " calls out for a balance to be at .2 or better to be considered balanced, if the propeller started at 1.7 that is really high, when i do balances on reciprocating engine they normally start at the .5 to .8 range and i can always acheive at least a .2 and most times i can get .1. The good thing about balancing is that even if you do not feel it the rest of the airplane can, baffling and other items that crack due to wear from vibrations have a longer life after balancing.
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  #4  
Old 06-21-2007, 09:20 AM
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randylervold randylervold is offline
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Location: Mill Creek, WA
Posts: 617
Default Worth it!

Prop balancing is indeed worthwhile just as balancing your engine or any reciprocating assembly is. In fact when you do a dynamic prop balance you're really balancing the engine/prop assembly.

Our EAA chapter has a state-of-the-art computer prop balancer program that has been a huge success. Check our web site for info, but especially interesting is the log of jobs we done found on a link toward the bottom of the page, or by clicking here. I encourage any of you who are active with your local chapters or builders groups to consider it and would be happy to speak with you on the details. The DSS MicroVib II system was around $6,000, but I think you could make it work by charging members $100 and have it paid for with 60 jobs. We paid for it when we merged the Home Wing treasury into our local chapter so we only charge a $20 fee for consumable parts (bolts & tape) and repair reserve.

Lastly, if you are considering paying someone to do a balance job make sure they have decent equipment and capable operators. For many years Chadwick Helmuth made the only balancer around and frankly the results achievable with it were questionable. Seems Honeywell bought CH and they now make computerized equipment, but if you see an old balancer with needles instead of a digital readout walk away. I know we have balanced at least a half dozen props that were already balanced by a shop with the older CH gear (and even some newer gear) and the error we measured was not good. In all cases we have been able to improve the error by at least 50% (half the error) and usually considerably more.
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  #5  
Old 06-21-2007, 12:16 PM
the_other_dougreeves the_other_dougreeves is offline
 
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Location: Dallas, TX (ADS)
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Default

Quote:
Originally Posted by randylervold
...but especially interesting is the log of jobs we done found on a link toward the bottom of the page, or by clicking here.
A quick look at the data suggests that all of the five most popular RV prop makes (not model specific!) can be balanced well. Of the 60 props balanced, 59 of them were able to get below 0.1 IPS (the only one over was a Champ with a FP Sensenich). This also suggests that there is no large difference with respect to props before balancing, with the possible exception of the WW.

Prop Before After
Sensenich 0.238 0.031
Hartzell 0.228 0.015
Catto 0.200 0.017
MT 0.251 0.022
WW 0.530 0.020
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Last edited by randylervold : 06-22-2007 at 08:21 AM.
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  #6  
Old 06-21-2007, 08:46 PM
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MSFT-1 MSFT-1 is offline
 
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Default Errors in my original post

When I wrote the original post, I was quoting my numbers from memory (obviously a flawed memory). I pulled out my paperwork from Hartzell and here are the numbers they recorded:

Pre balancing: 0.173
First run: 0.084
Second run: 0.045

These numbers seem much more inline with what other people have reported here.

Bruce
N297NW
RV-8
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  #7  
Old 06-21-2007, 09:20 PM
Bob Axsom Bob Axsom is offline
 
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Posts: 5,685
Default Did it go any faster at 2700 RPM?

Smoother means very little to me if it is smooth enough to start with.

Bob Axsom
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  #8  
Old 06-23-2007, 07:32 AM
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AltonD AltonD is offline
 
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Default

Quote:
Originally Posted by MSFT-1
. . . determined that my prop was at 1.7 IPS (whatever that means). . . .
IPS= Inches per second
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  #9  
Old 06-23-2007, 02:15 PM
raddatz
 
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Default

I balance props here in Northwest AL. and the worst one so far was a Yak at 1.5 ips. which sets off an alert on my system and I got that one down to .04. I believe that a balanced prop keeps parts from vibrating off your airplane and also relieves stress on your prop hub, engine mounts and airframe. With a balance you can also look at spectrum and waveform analysis and see what shape yor alternator bearings are in and look at your power pulses to see how balanced your cylinders are. Get your prop balanced your plane will love you for it.
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  #10  
Old 06-25-2007, 06:01 PM
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Mike F Mike F is offline
 
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Location: T67 Hicks Airfield, Fort Worth, TX
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Default

Quote:
Originally Posted by raddatz
With a balance you can also look at spectrum and waveform analysis and see what shape yor alternator bearings are in and look at your power pulses to see how balanced your cylinders are. Get your prop balanced your plane will love you for it.
Interesting, I also have prop balancing equipment (ACES 2015) but I am curious how you detect alternator bearing problems. Can you elaborate (with graphs, etc.)?
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