Here's a comprehensive guide to fasteners and their use. Includes 11
pages on galling, corrosion, high temperature effects, joint design and
tension control in a bolted joint, including a description of the
tenuous relationship between torque wrench readings and bolt tension.
Oh yes, also marking standards for bolt heads that someone was aking
about recently. The whole thing is a bit over 50 pages so be patient
while Adobe figures out how to get it onto your screen.
http://www.fastenal.com/documents/Miscellaneous/FastenalTechnicalReferenceGuide.pdf
Hope this helps
73 de Jim Smith VE7FO
K7LXC@aol.com wrote:
>In a message dated 6/13/02 2:13:50 AM Pacific Daylight Time,
>w8ji@contesting.com writes:
>
>>You **must** select a bolt
>> that, when tight, pre-loads with tension greater than the zero at the
>> minimum load condition and has know amounts of stretch, otherwise the
>> fastener will quickly work-loose or fail. (Many Caddy V-8 owners
>> learned this when GM used the wrong headbolt design, and anyone with
>> a race car knows it.) Virtually all automotive fasteners stay tight
>> because of stretch, where the bolt or stud actually deforms and
>> elongates. That's true even with lug nuts.
>>
>
> Interesting info. Which brings up a question I've been looking for the
>answer to for several years.
>
> I've installed numerous M2 Orion 2800 rotators over the years and
>invariably the mast turns eventually due to loosening of the mast clamp. As
>you probably know, it's a couple of massive pieces of steel and with six
>bolts it doesn't seem likely that they'll loosen up but they do.
>
> I originally thought the loosening was due to temp cycling of the big
>clamps that was the culprit. Now I suspect that it's bolt stretch that does
>it. The nuts aren't getting loose - I've used double-nutting AND Lok-Tite and
>the danged masts still work loose.
>
> First question, how do I prevent this from happening in the future?
>
> Second question, what's a good sequence to tighten the bolts with? With
>six bolts (2 rows of three bolts) to do and wanting to equalize the
>tightening, I think it should be like the head of an engine where there is a
>sequence that does that - i.e. 1-6-2-5-4-3 or something like that.
>
> Third question, would torquing the nuts help? Since the tendency is to
>REALLY (over)tighten them, maybe that's part of the problem.
>
>Cheers,
>Steve K7LXC
>TOWER TECH -
>Professional tower services for commercial and amateur
>_______________________________________________
>Towertalk mailing list
>Towertalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
|