Towertalk
[Top] [All Lists]

[Towertalk] structural assumptions// bolts - Orion 2800

To: <towertalk@contesting.com>
Subject: [Towertalk] structural assumptions// bolts - Orion 2800
From: jimsmith@shaw.ca (Jim Smith)
Date: Thu, 13 Jun 2002 11:41:42 -0700
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
>



<Prev in Thread] Current Thread [Next in Thread>