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  #11  
Old 05-18-2022, 06:37 AM
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AlexPeterson AlexPeterson is offline
 
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Location: Ottertail, MN
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Originally Posted by drill_and_buck View Post
Similar experience. Smooth running prop. After 8 years, 1,000 hours, noticed two rivet heads missing during annual inspection.

Attachment 25948
Attachment 25949
Mike - thanks for posting those pictures. Yours looks identical to mine. The head broke off at the plane of the underside of the head. Meaning, they didn't shear at the plane between the two back plate sheets.

This would seem to indicate a tension related failure, and not a shear failure.

If (when!) I see more of these, I'm going to add a rivet or two in the neighborhood of each of the failing ones.
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  #12  
Old 05-18-2022, 06:39 AM
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DanH DanH is offline
 
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Originally Posted by AlexPeterson View Post
Scott, yes. The strange thing about this is that it went many hours without a problem, then about 50 hours after the backing plate was disassembled/reassembled to the prop hub
Both sets of photos show the failed rivets closest to the prop bolt mount points.

Might want to check torque on the 0.375" prop bolts. They seem to settle in and lose preload after some run time....compression of the new sealant between the hub halves, paint under the heads or nuts, crush of the aluminum sandwich, etc.
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  #13  
Old 05-18-2022, 07:26 AM
wawrzynskivp wawrzynskivp is offline
 
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Default Off the top of my head

Prop balance is the sum of its parts.

Could the spinner be out of true or somehow out of balance?
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  #14  
Old 05-18-2022, 11:33 AM
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AlexPeterson AlexPeterson is offline
 
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Originally Posted by DanH View Post
Both sets of photos show the failed rivets closest to the prop bolt mount points.

Might want to check torque on the 0.375" prop bolts. They seem to settle in and lose preload after some run time....compression of the new sealant between the hub halves, paint under the heads or nuts, crush of the aluminum sandwich, etc.
Excellent idea. I'll pretend I also thought of that...
I do recall checking those torques a hundred hours or so after plane first flew a third of my life ago...
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  #15  
Old 05-18-2022, 11:55 AM
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AlexPeterson AlexPeterson is offline
 
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Originally Posted by DanH View Post
Both sets of photos show the failed rivets closest to the prop bolt mount points.

Might want to check torque on the 0.375" prop bolts. They seem to settle in and lose preload after some run time....compression of the new sealant between the hub halves, paint under the heads or nuts, crush of the aluminum sandwich, etc.
Excellent idea. I'll pretend I also thought of that...
I do recall checking those torques a hundred hours or so after plane first flew a third of my life ago...

Just ran the 4 nuts to 22ft-lbs. They moved maybe 5 degrees.
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