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Re: [TowerTalk] FW: Hindsight: Check your rotator bolts

Subject: Re: [TowerTalk] FW: Hindsight: Check your rotator bolts
From: Kimberly Elmore <>
Date: Mon, 9 Jun 2008 14:45:53 -0700 (PDT)
List-post: <">>
Jam nuts are pretty common devices and are used all the time in things like 
turnbuckles. Here's a simple test: tighten one nut against another on some 
threaded rod, screw or bolt.  Then, try to turn them. You can't. The method 
depends on the elasticity of the threaded rod material: you have essentially 
stretched the threaded rod between the two nuts. As long as the stretched 
material doesn't permanently distort, the tension remains and friction between 
the threads of the nuts against the threaded rod holds the two nuts immobile. 

Kim Elmore, N5OP

----- Original Message ----
From: "Dubovsky, George" <>
Sent: Monday, June 9, 2008 2:23:37 PM
Subject: [TowerTalk] FW:  Hindsight: Check your rotator bolts

-----Original Message-----
From: Dubovsky, George 
Sent: Monday, June 09, 2008 2:48 PM
To: 'Roger (K8RI)'
Subject: RE: [TowerTalk] Hindsight: Check your rotator bolts

> -----Original Message-----
> From: [mailto:towertalk-
>] On Behalf Of Roger (K8RI)
> Sent: Monday, June 09, 2008 2:04 PM
> To: Tower Talk
> Subject: Re: [TowerTalk] Hindsight: Check your rotator bolts
> Dubovsky, George wrote:
> >
> >
> > If you think about it, this accomplishes nothing that a bolt would
> > accomplish in the same application.
> Yes it does.

No, it doesn't. So, there... ;-) My bolt has exactly the same holding
force on the lockwasher/captive plate as your double nut scheme does.
You claim the second nut keeps the first nut from loosening; the head of
my bolt never changes its orientation to the threaded section, so it
never "loosens" either. If my bolt loosens from vibration, so does your
scheme. Check your mechanics again.

> >  The second nut does nothing more
> > than make the first nut "thicker".
> A thicker nut and two nuts "locked" or jammed together are quite
> different in the way they work.
> A thicker nut or rather one twice as thick (two nuts) offers twice the
> area as do two nuts, but the two nuts work against each other by
> preventing each other from turning. The thicker nut does not.
> > If a properly sized bolt with a good
> > lockwasher under the head is not going to hold, than neither is an
> > improperly sized (long) bolt with two nuts forming a new "head"
> > down the shank of the bolt.
> The mechanics of the two are quite different as is the purpose.  The
> problem is not holding, the problem is the bolt coming loose.
> Again two different problems although if a bolt comes loose it won't
> hold, not holding doesn't necessarily mean coming loose.  IOW the one
> can break where the other just vibrates loose.
> >  The second nut only guarantees that your new
> > "bolt head" doesn't move on the threads of the bolt, but the head on
> > hex-head cap screw already has that feature manufactured in.
> >
> >
> Both serve as "heads", but only one serves as a lock.
> The "jam nut" is not nearly as simple as it sounds.
> Roger (K8RI - ARRL Life Member)
> N833R (World's oldest Debonair)
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