grahamsingleton(at)btinte
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 Posted: Mon Oct 28, 2013 2:39 pm Post subject: Europa-List: AN3 Nut Torque Values…….or any Torque Value |
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Tony
do you still have the bolt? If so put it in a vice and bend it, it should bend significantly without
snapping. Hi tensile steel bolts normally won't bend, that's why we don't use them in aircraft.
Graham
From: Tony Renshaw <tonyrenshaw268(at)gmail.com>
To: "europa-list(at)matronics.com" <europa-list(at)matronics.com>
Sent: Monday, 28 October 2013, 21:58
Subject: AN3 Nut Torque Values…….or any Torque Values depending on type of Nuts
Gidday,
Yesterday I was tightening by hand one of the two AN3 bolts that clamp the flap cross tube to the articulating/hinge arms that are attached in the floor. So, in case there is the slightest movement and this would exacerbate in my flaps I decided to do them up "tight". Guess what, I snapped one, yep snapped. It broke at the top of the shank where the thread started, and did NOT strip the thread as many might have presumed. This got me thinking that normally most bolts are designed to effect a shear load, and not normally a clamping load. Anyway, I know there is counter arguments to all of this, but what matters is the applicable torque loads we use if we torque them using a wrench, and I just stumbled upon a reference I think is important. I found this on an VansForce website, and why it matters is the torque values are NOT for locknuts, which have an inherent friction drag torque value of 14 in-lbs. So, referring to the attached table an AN3 needs 20-25 in-lbw, but in actuality would be more like 34-39 in-lbs.
I think this could be easily overlooked, and if the friction drag torque of locknuts is not taken into account, people are under torquing their bolts.
Regards
Tony Renshaw
Sydney Aussie.
[img]cid:1.930330623(at)web87704.mail.ir2.yahoo.com[/img]
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