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  #1  
Old 05-28-2018, 07:42 PM
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Sleepy Sleepy is offline
 
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Default Strange discoloration on flywheel after prop removal

I removed my prop the other day to take it up to Northwest Propeller for some edge work. After I got back to the hangar, I decided to take off the flywheel and change the alternator belt. To my surprise, I discovered the two mating surfaces between the flywheel and the crank where stained (see below). The mating surfaces on the other side between the flywheel and prop are clean.

This is off an RV-4 (1992) with about 850 hours on the engine and 300 SOH (2008) on the prop.

While the stains look oily they are not. There is very little build up and they are dry. Any ideas about what is going on?

Thanks,
Scott


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  #2  
Old 05-29-2018, 05:51 AM
vic syracuse vic syracuse is offline
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Default Bolt torque?

Have the prop bolts been torqued properly with every seasonal change? It looks like they have been loose at one time or even for some time. A wood prop that is not properly and regularly torqued can even catch fire from the friction of movement on the flange.

Vic
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Last edited by vic syracuse : 05-29-2018 at 05:51 AM. Reason: spelling
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  #3  
Old 05-29-2018, 07:28 AM
Kyle Boatright Kyle Boatright is online now
 
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Default

Quote:
Originally Posted by vic syracuse View Post
Have the prop bolts been torqued properly with every seasonal change? It looks like they have been loose at one time or even for some time. A wood prop that is not properly and regularly torqued can even catch fire from the friction of movement on the flange.

Vic
Didn't the poster indicate the discoloration was between the crank and flywheel? (Not the prop and flywheel.)

Maybe there is a loose fit between the crank lugs and flywheel? In any case, it does look like a heat related event with slippage between the two surfaces. I'd check the fit and also take a close look at the prop and the bolts.
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  #4  
Old 05-29-2018, 07:41 AM
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Sam Buchanan Sam Buchanan is offline
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Are those oil stains on the inner bore of the flywheel? Maybe the crank seal leaked at some point in the past? Not sure how that would happen but the flywheel looks oily....
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Old 05-29-2018, 08:03 AM
Jpm757 Jpm757 is offline
 
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I agree with the above. Somethings moving!
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  #6  
Old 05-29-2018, 08:16 AM
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az_gila az_gila is offline
 
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Question Paint

Could someone have painted the back of the flywheel where it was not meant to be painted?
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  #7  
Old 05-29-2018, 01:39 PM
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Snowflake Snowflake is offline
 
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Quote:
Originally Posted by Kyle Boatright View Post
Didn't the poster indicate the discoloration was between the crank and flywheel? (Not the prop and flywheel.)
Maybe a wooden spacer?

Seriously though, I agree with the others that something has been moving.
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  #8  
Old 05-29-2018, 07:41 PM
molson309 molson309 is offline
 
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In your first picture it looks like the wood prop has radial stains on it in the area of the lightening holes. Sure looks to me like some liquid/grease spun out from the hub area.
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  #9  
Old 05-29-2018, 08:06 PM
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Arrow

It looks like oil contamination to me but hard to tell.
Clean flange and flywheel, check for pitting, marring, scuffing etc... If something is moving, there should be wear marks.
Check tolerances of bolt holes for flange, flywheel, and prop, have bolts inspected (any prop shop can do this), install reworked prop, then set up an inspection interval. I would inspect at 5 hours, 15 hours, and 50 hours. Those are pretty arbitrary numbers that i would discuss with my AP friends and other resources
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  #10  
Old 05-30-2018, 06:18 AM
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Wood prop or metal? And what is the streaked material and black material visible through the holes in the first photo? The streaked material seems to be completely filling the big lightening holes
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