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Old 10-19-2017, 04:40 PM
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Default Sanity Check -- AN6 Torque

For clarification, AN6's get torqued 160-190 inch pounds, right? 180 inch pounds just didn't feel that tight .. for an engine mount .. if someone could verify, just a sanity check
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Old 10-19-2017, 04:47 PM
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https://www.vansaircraft.com/pdf/rev...V-12_05-10.pdf
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Old 10-19-2017, 04:50 PM
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Yep, that's where I got my numbers .. I just expected to have to really muscle these bolts .. guess I'm underestimating how strong these parts are.

Thanks!
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  #4  
Old 10-19-2017, 05:04 PM
BobTurner BobTurner is offline
 
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What you and many people are doing is over-estimating the amount of pre-load a bolt needs, in order to have that maximum strength available when really needed.
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Old 10-19-2017, 05:07 PM
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my seat of the pants observation is that people tend to over torque small bolts and under torque large bolts when relying on feel rather than a torque wrench

erich
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  #6  
Old 10-19-2017, 09:47 PM
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Quote:
Originally Posted by bkervaski View Post
For clarification, AN6's get torqued 160-190 inch pounds, right? 180 inch pounds just didn't feel that tight .. for an engine mount .. if someone could verify, just a sanity check
Depending on the actual friction coefficient present, that torque will result in about 3,000 pounds of clamping force on that size/pitch bolt, which is about 25% of their tensile strength. Lots of margin in bolts holding aircraft together is a good thing! Don't squander the margin by honking down bolts by "feel".

A separate but related fun-fact: Critical bolts subjected to cyclic loads (think about the studs holding the cylinders on) are often specified to be torqued to a value which maximizes their fatigue life. Torqued below or above the spec and their fatigue life will likely be lower.
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Old 10-20-2017, 08:39 AM
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It's the leftover military mentality for me .. give me a hammer and a direction and by God it will get done .. so if the bolt still turns then keep on turnin'

Of course, I'm following the torque specs to the letter (just so it's clear to readers). I just expected to have to enlist the large torque wrench and some muscle and it's simply not the case.

Good information, thanks all!
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