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  #1  
Old 04-11-2019, 02:05 PM
kritsher kritsher is offline
 
Join Date: Feb 2007
Location: Stow MA
Posts: 166
Default Prop balance - weight location

I'm having my prop dynamically balanced. The initial feedback from the person doing the job is that he'd have to drill the spinner bulkhead to install weights. Is this what others have done? Can anyone share pics of how their weights are mounted?

thanks!
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RV-12 #359
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  #2  
Old 04-11-2019, 02:10 PM
alexe alexe is offline
 
Join Date: May 2013
Location: Temecula, CA
Posts: 262
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Yes, the weights are normally mounted to the spinner bulkhead.
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  #3  
Old 04-11-2019, 02:14 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,622
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Not telling you what to do, but I just use longer screws on the backplate perimeter. An oversize nut is a convenient shim/weight to clear the nutplate, and then nut/washer(s) as needed.

A lot of guys put the weight on the holes in the ring gear (flywheel), but that's a bit of an offset from the imbalance.

edit: Never paid attention to a -12 spinner; don't know if the techniques will work there. Obviously the ring gear is out...

Charlie
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  #4  
Old 04-11-2019, 05:31 PM
Handclutch Handclutch is offline
 
Join Date: Feb 2015
Location: Bendigo, Australia
Posts: 75
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My mechanic just put stick on wheel balance weights on the backing plate flange. Havenít moved in 300 hrs.

Jack
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  #5  
Old 04-11-2019, 06:40 PM
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Walt Walt is online now
 
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Location: Dallas/Ft Worth, TX
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Quote:
Originally Posted by Handclutch View Post
My mechanic just put stick on wheel balance weights on the backing plate flange. Havenít moved in 300 hrs.

Jack
That's a very risky, un-approved way to balance and I would never do it, drill the backplate and install weights using standard hardware is standard practice. On a Lyc you can mount them on the flywheel but the 12 obviously has no such thing.
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  #6  
Old 04-11-2019, 06:52 PM
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Tony_T Tony_T is offline
 
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Location: Lacey, WA
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Quote:
Originally Posted by kritsher View Post
I'm having my prop dynamically balanced. The initial feedback from the person doing the job is that he'd have to drill the spinner bulkhead to install weights. Is this what others have done? Can anyone share pics of how their weights are mounted?

thanks!
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RV-12 #202 -- Flying
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  #7  
Old 04-11-2019, 09:06 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
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My A&P drilled a hole and installed a small machine screw for the weight.
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  #8  
Old 04-12-2019, 05:15 AM
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Skunkworks Skunkworks is offline
 
Join Date: Jun 2012
Location: Douglassville, PA
Posts: 65
Cool My A&P drills holes into spinner bulkhead too

Just had this done for a second time due to having hub half being replaced and experiencing vibrations. Recommend everyone get this done. This time around Dave got it to .1 and boy is it smooth running. Jane now has 948hrs and gearbox inspection is coming up at 1000 hrs will see the results on the gears.
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  #9  
Old 04-13-2019, 10:45 AM
rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
Posts: 405
Default Do it often

I agree, most folks would be surprised at how much smoother the whole unit is after a balance. You should dynamically balance whenever there has been a change in the rotating assembly, which would include anything from a simple prop pitch change or replacing the spinner to overhauling the engine or gearbox.

Most manufacturers limit vibration to 0.25 IPS, but it only takes about 0.07 inches per second to be noticeable by the average person. When I did my first balance check on my RV12 last year, it was at 0.68 IPS. Reindexing the prop and spinner brought it down to 0.47, but that's still a destructive amount of vibration over time. I now have it at 0.01 IPS.

My hangar neighbor has a C150 with an O-200 and he said it has run smooth that way for years. I offered to do a check for him and found 0.32 IPS, which shocked him. We've now got his down to 0.02 IPS and he says it's like a new airplane. So, even if you think it's smooth, I highly recommend getting at least a balance check - you might be surprised what the meter shows.
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Last edited by rongawer : 04-14-2019 at 08:27 AM. Reason: typo
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  #10  
Old 04-13-2019, 12:50 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by Skunkworks View Post
Just had this done for a second time due to having hub half being replaced and experiencing vibrations. Recommend everyone get this done. This time around Dave got it to .1 and boy is it smooth running. Jane now has 948hrs and gearbox inspection is coming up at 1000 hrs will see the results on the gears.
Hopefully you mean .01
.1 is not horribly bad but when paying a professional do it, they should be able to get it very close to .01.


BTW, the acceleration value that is considered noticeable is .07 or higher (not .7)
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