Thanks Chuck and George, N4UA, for supplying the correct information. A
jamnut reduces/prevents the NUTS from creeping. The nuts do nothing to
reduce/prevent the threaded rod/shaft from loosening over a single nut
similarly applied.
Doug
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Chuck Lewis
Sent: June 9, 2008 5:18 PM
To: Kimberly Elmore; towertalk@contesting.com
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
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