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  #1  
Old 04-10-2021, 10:20 AM
Mark Jackson Mark Jackson is offline
 
Join Date: Oct 2009
Location: Houston
Posts: 70
Default Breaking Bolts

I'm having a problem breaking bolts. RV-8, installing AN3-5A bolts holding the F-843-R-1 longeron to the WD-803-R-1 Engine mount bracket. I've used three different torque wrenches (CDI, Snap-on, and cheapo) in two different holes. Two different lots of bolts to make sure they weren't defective. Torque is set to 100 in-lbs.

Have checked everything many times.

Any ideas?
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  #2  
Old 04-10-2021, 10:30 AM
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Jpm757 Jpm757 is offline
 
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100" lbs. Is way too much torque for an AN3 bolt. It should be 20-25 inch lbs.
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Last edited by Jpm757 : 04-10-2021 at 10:31 AM. Reason: Sp
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  #3  
Old 04-10-2021, 10:30 AM
Ralph Inkster Ralph Inkster is offline
 
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Try 20 - 25 Inch lbs for AN3 bolts.
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  #4  
Old 04-10-2021, 10:47 AM
Kyle Boatright Kyle Boatright is offline
 
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There is a torque chart in section 5 of the build manual. Print it and hang it on the wall of your shop. Follow it. ;-)

It says 20-25 inch pounds on those bolts.
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  #5  
Old 04-10-2021, 10:52 AM
David Paule David Paule is offline
 
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As the others said, but additionally, add the running toque of the nut's locking element, which you'll have to measure.

Dave
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  #6  
Old 04-10-2021, 11:07 AM
YellowJacket RV9 YellowJacket RV9 is offline
 
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I would also go back and replace every AN3 bolt that has already been installed with that torque.
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  #7  
Old 04-10-2021, 11:15 AM
Mark Jackson Mark Jackson is offline
 
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Location: Houston
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Default Brain Fart

I mis-read the torque settings. I was reading AN5 instead of AN3. It was an AN3-5 bolt. Duh.

Threw out all the over-torqued bolts.
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  #8  
Old 04-10-2021, 12:43 PM
salty salty is offline
 
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Ouch! (said the bolts)
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  #9  
Old 04-10-2021, 01:56 PM
Bavafa Bavafa is offline
 
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It is certainly over torqueing but I am not sure if these should break.

Do they break after some use or just as your torqueing them?
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  #10  
Old 04-10-2021, 02:08 PM
rapid_ascent rapid_ascent is offline
 
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They could break in the future if they have been over torqued due to stress.
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