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  #11  
Old 08-25-2017, 06:47 PM
Pmoran's Avatar
Pmoran Pmoran is offline
 
Join Date: Apr 2015
Location: Onalaska, Wisconsin
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I might need to take you up on that offer. Flying from La Crosse, WI would be a quick trip and it sounds like it could be done in a day.
Thanks,
Pat
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  #12  
Old 08-25-2017, 09:03 PM
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bret bret is offline
 
Join Date: Feb 2010
Location: Gardnerville Nv.
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Quote:
Originally Posted by ChiefPilot View Post
I do RVs and similar experimentals for $100.
So......are you coming out for the Reno air races-prop balancing? ill even throw in lunch!
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  #13  
Old 08-25-2017, 09:37 PM
SHIPCHIEF SHIPCHIEF is offline
 
Join Date: Mar 2008
Location: Seattle
Posts: 1,412
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I lucked out, my son bought a DynaVibe. My Yak-55 does not have a spinner, so it took me 3 days to balance the prop (after a day to build a frame to mount the sensors to the M-14P engine). Balancing a 2 blade without a spinner is done by sanding off or adding paint to the blades.
OK, I'm slow and methodical. I'd be charged $1000 for that kind of service.
Get your prop balanced, it's worth $250 or more!
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Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)
2019
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  #14  
Old 08-25-2017, 10:46 PM
dtw_rv6 dtw_rv6 is offline
 
Join Date: May 2008
Location: Martinsville, IN
Posts: 454
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Can anyone attest to repeatability of the dynavibe? Spent several hours with a buddy who has one and kept trying to improve on 0.16 ips. Gave up after we backed up to a previous weight configuration and the readings didn't come remotely close to the first trial. We removed everything and ran once more and had .6 ips when the original run was 0.42.

Sent the unit back to dynavibe and they found nothing wrong with the unit.

I'm sure glad I wasn't filing on my prop
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  #15  
Old 08-26-2017, 11:34 AM
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ChiefPilot ChiefPilot is offline
 
Join Date: Jan 2005
Location: Twin Cities, MN
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For any unit, the accuracy and repeatability will be dependent on the mounting of the accelerometers- if they are not solidly mounted or are otherwise free to vibrate on their own the resultant data will be contaminated. Other factors that can contaminate the data include airframe buffeting from wind and propwash.

My dynavibe has been pretty repeatable - i checked my -6a four months after i originally balanced it and got a reading that was 0.01 ips off; i'd be tempted to attribute this to bug guts etc 😜
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  #16  
Old 08-26-2017, 12:13 PM
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Jesse Jesse is offline
 
Join Date: May 2005
Location: X35 - Ocala, FL
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Quote:
Originally Posted by dtw_rv6 View Post
Can anyone attest to repeatability of the dynavibe? Spent several hours with a buddy who has one and kept trying to improve on 0.16 ips. Gave up after we backed up to a previous weight configuration and the readings didn't come remotely close to the first trial. We removed everything and ran once more and had .6 ips when the original run was 0.42.

Sent the unit back to dynavibe and they found nothing wrong with the unit.

I'm sure glad I wasn't filing on my prop
There must be something else causing the vibration. Only a spectrum analysis can tell you if the vibration is caused by something else, like a plug not firing or something like that.
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  #17  
Old 08-26-2017, 09:58 PM
SHIPCHIEF SHIPCHIEF is offline
 
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Location: Seattle
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I spent 3 days balancing my V530 propeller on 9 cylinder M-14P engine. The Dynavibe I used was very repeatable, and every change I made was sensibly indicated in the next reading I got.
I did expend considerable effort into making a strong & ridged mount for the sensors and followed the instructions closely for distance and size of reflector tape etc..
Jesse's comment about a plug not firing makes sense as well. Perhaps you have a plug with high resistance, a leaking intake tube, of loose propeller bolts? It could be anything. The Dynavibe may be telling you something that you should know? If that's the case, then you'll get double the value!
The next more expensive DynaVibe can help find those pesky hard to find problems. I would like to try one because I have a gear reduction engine and would like to know the difference between propeller vibration and engine vibration.
Meanwhile, I look forward to balancing my RV-8 w/ Catto 3 blade, and my wife's RV-4 w/ Sensenich carbon fiber ground adjustable 2 blade.
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Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)
2019
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  #18  
Old 08-27-2017, 05:52 AM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
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Part of what I do when I do a prop balance (I use a DSS Microvib II which is quite expensive) is the spectrum analysis like you see below. It can definitely show abnormal vibrations and help to figure out what is going on.




Another advantage of the better balancers is I can generally get a balance done in just a few runs. The one below was done is 2 runs, 3 runs is the average.

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EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
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Last edited by Walt : 08-27-2017 at 06:30 AM.
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  #19  
Old 08-28-2017, 12:49 PM
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Chattin35 Chattin35 is offline
 
Join Date: Jul 2014
Location: Boise, ID
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I just flew to Oregon and back over the weekend and noticed my CHTs running about 10 degrees cooler on each cylinder.

This could have been a number of factors like the engine continuing to break in (only ~80 hours on it). But, the OAT was about the same as I've seen lately and I was cruising at the same power settings and altitudes I normally do.

YMMV. But, it was interesting to note the engine running slightly cooler after after balancing the engine/prop.
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  #20  
Old 08-29-2017, 07:23 AM
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13brv3 13brv3 is offline
 
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Location: Tellico Plains, TN
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Has anyone tried the ACES 1015 balancer? It's pretty close to the price of the Dynavibe, but I believe it tells you the weight to use, in addition to being able to split weights over two positions.

Rusty
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