[TowerTalk] replacement bolt for Rohn Thrust bearing DE K0FF

[Michael Tope]

Hi Geo,

You are correct, the tensile preload established on bolt is a function of the 
applied torque. The relationship between torque and preload is directly
related to the friction between the nut and the bolt. The specs I have seen
at work for space applications always show lower torque values when the 
fasteners are coated with dry film lubricants. 

Mike, W4EF..............

----- Original Message ----- 
From: "K0FF" <K0FF@ARRL.NET>
To: "Tower Talk (mail list)" <towertalk@contesting.com>
Sent: Monday, October 02, 2000 6:45 AM
Subject: Re: [TowerTalk] replacement bolt for Rohn Thrust bearing DE K0FF


> 
> 
> The question was: where is it published that would substantiate my comment
> about NOT greasing tower bolts?
> 
> Wish I had a full library of data to back up the little things that I've
> learned over the years. As far as not lubing the bolts, I thought that was
> common knowledge. It's been included in  military manuals, and even
> instruction manuals for (farm) equipment that I've assembled, but of course
> I can't lay my hands on it.
> 
> To be politically correct the statement should have read " Don't lubricate
> the bolts, and then tighten without using a torque wrench. Doing so can
> apply undue pressure to the bolt and break it".
> 
> Try it on the bench sometime. Put a grade 2 bolt in the vice by it's head.
> The a spacer, something and inch or inch and a half long. Like a pipe with a
> hole in it (like a tower leg). First tighten a nut on there as tight as you
> can make it. Probably no problem. Now take it off and lube it with motor
> oil. Put it back on and try to break it. You can easily. Stainless steel is
> even weaker. I always though a stainless steel U bolt should be really
> strong, until I started doing a lot of tower work, and now realize how easy
> it is to twist one apart. Actually it's difficult NOT to! Simply stated,
> it's easier to apply excessive pressure to a greased bolt.
> 
> Another fact that many really overlook is on the drill press or metal
> cutting bandsaw, don't use a petroleum  lubrication. The tool simply slips
> and stops cutting. Use a cutting oil instead, it cools, without destroying
> the grip of the tool. There is a certain amount of lubrication going on
> also, it must be so, because the finished hole or cut is a lot smoother with
> cutting oil.
> In some of the factories that I serviced, they used a water based fluid, and
> recycled it. Almost all holes and cuts are made wet in industry.
> 
> Let me remind you all that I'm not an engineer or anything like it. I'm a
> typical Ham, and most of use operate by rules-of-thumb, and cut-and-try.
> Also having said that let me further remind you that most of us don't want
> to spend 10 hours designing something on the computer. We like to take our
> time and build a proven design, and maybe modify it. Therefore, I for one
> would like to see less references to " If you choose the proper core, and
> design the windings with x-y-z in mind , then put that on you $12,000
> spectrum analyzer etc... etc...." and MORE of " Take an Amidon FT-140-43 and
> wind eight turns of wire on one side and 34 turns on the other side, it can
> be used for 'this' purpose and have 'this' result". That's why the ARRL
> handbook is so popular.
> 
> Likewise most of use don't care 2 cents if our PA tube went south because of
> a gold-sputter or an ion pit. We just want someone to tell us what to do to
> keep it from happening again.
> 
> That's just my opinion, but I like to see down to earth tips, and most of
> the engineering arguments get dumped without reading them.
> 
> Geo>K0FF
> 
> 
> >Your bit on not greasing bolt threads as it can allow excess tightning and
> >failure of a bold is interesting.  Where is that printed?
> 
> 
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> 


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