Very nice to read the comments from someone who knows of what they speak and
explains it so well. Nicer then reading those comments from .....well
others.
Jim- WA9FPT
----- Original Message -----
From: "Chuck Lewis" <clewis@knology.net>
To: "Kimberly Elmore" <cw_de_n5op@sbcglobal.net>; <towertalk@contesting.com>
Sent: Monday, June 09, 2008 6:18 PM
Subject: Re: [TowerTalk] FW: Hindsight: Check your rotator bolts
> 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@sbcglobal.net>
> To: <towertalk@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@andrew.com>
>> To: towertalk@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@contesting.com [mailto:towertalk-
>>> bounces@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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