[TowerTalk] FW: Hindsight: Check your rotator bolts

Mon Jun 9 20:11:51 EDT 2008

OK, I thought I understood the application, but maybe I don't. I need 
a picture or a sketch or a diagram to understand what I thought I understood.

Besides, I simply slathered the bolts with blue Loctite (tm) when 
this happened to me not very long ago. So far, so good.

Kim Elmore, N5OP

At 06:18 PM 6/9/2008, Chuck Lewis wrote:
>Wait a minute...
>
>We understand jam nuts. A jamnut prevents the pair of jammed nuts from
>moving WITH RESPECT TO THE BOLT or threaded rod; but they don't add any
>additional protection against the jamnut/bolt assembly moving in relation to
>the hole the assembly is screwed into. Jamnuts are useful, but not here.
>
>Here's a thought experiment: make up the jammed assembly as described and
>then weld the nuts to each other and to the bolt. Now you have a permanently
>stable assembly of bolt/nut/nut; but this is now absolutely identical in
>function to the original bolt, with the jammed and welded nuts being no more
>nor less than the head of the bolt. The rotor base and plate can't tell the
>difference.
>
>Jam nuts are useful on turnbuckles because they act as an "adjustable" bolt
>head, locking the otherwise loose eyebolt against the buckle. They are also
>marginally useful with a stud that's otherwise locked in place and where the
>stud itself is NOT going to loosen within its hole, or where (for other
>reasons) it's not advisable to apply sufficient torque to preload the bolt.
>Yes, they depend on applying the correct preload, i.e., stretching the bolt,
>just as a simple bolt, properly torqued. The jamnuts apply preload, too, but
>only in the vicinity of the nuts. The closest nut, or the head of a simple
>bolt still needs (at least) to be torqued to spec.
>
>Jamnuts in this application don't add anything beyond a false sense of
>security. Worse yet, if the first nut isn't properly torqued because it's
>thought that the jamnut will substitute, you'll be worse off. Beware of
>unintended consequences!
>
>73, Chuck, N4NM
>
>----- Original Message -----
>From: "Kimberly Elmore" <cw_de_n5op at sbcglobal.net>
>To: <towertalk at contesting.com>
>Sent: Monday, June 09, 2008 4:45 PM
>Subject: Re: [TowerTalk] FW: Hindsight: Check your rotator bolts
>
>
> > 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" <George.Dubovsky at andrew.com>
> > To: towertalk at contesting.com
> > 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: towertalk-bounces at contesting.com [mailto:towertalk-
> >> bounces at contesting.com] 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
> > not
> >> > 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"
> > further
> >> > 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
> > a
> >> > 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)
> >> www.rogerhalstead.com
> >> N833R (World's oldest Debonair)
> >>
> >> _______________________________________________
> >>
> >>
> >>
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> >> http://lists.contesting.com/mailman/listinfo/towertalk
> >>
> >
> >
> > 
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