One way to deal with temperature cycling is to use the necessary stack
of Belleville washers under the nut to provide the locking tension as
the bolt expands/contracts with temperature. They are used on high temp
process industry pipelines with flanged pipe connections. A325
structural bolts are torqued to near the max as Jim notes, but they
don't experience much in the way of temperature cycling. Like 300
ft-lbs for a 3/4" bolt so you need a serious torque wrench and beefy
ironworkers. The inspector didn't bother to check them in my steel
frame building as one ironworker was 300# plus.
Some A325 bolts are now supplied waxed which reduces the needed torque
by about 1/3.
I've been using Nord-Locks on critical bolts for a while, so far so good.
Grant KZ1W
On 7/24/2016 20:47 PM, jimlux wrote:
On 7/24/16 8:11 PM, Roger (K8RI) on TT wrote:
This video shows the comparison between various ways of locking nuts.
The reaction to a lock washer and vibration was a real surprine. Only
one method actually worked.
https://www.facebook.com/Trustmeiamamechanicalengineer/videos/746827738792165/
Well, there's also using a threadlocking adhesive (Loctite) and safety
wire...
Lockwashers are widely acknowledged to be worthless in actually
locking. What's important is having enough bolt stretch (which in
turn is dependent on good lubrication of the threads if you're
measuring torque). If you have enough bolt stretch, the load on the
"inclined plane" of the threads is sufficient to prevent the nut from
vibrating off.
temperature cycling makes it tougher,of course.
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