[TowerTalk] Lockwasher comparrison

Grant Saviers grants2 at pacbell.net
Mon Jul 25 01:18:25 EDT 2016


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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