[TowerTalk] Hindsight: Check your rotator bolts
Roger (K8RI)
K8RI-on-TowerTalk at tm.net
Sat Jun 7 00:39:17 EDT 2008
Rob Frohne wrote:
> Hi Dick,
>
> I used aircraft bolts, after I had re-drilled and tapped the holes. The
> aircraft bolts have wires through them so that they won't turn. I'm not
> sure how Roger does it. He must have a T2X that has bolts all the way
> through the housings.
>
It's not nearly as difficult or awkward as it sounds. Take a bolt (bout
1 1/2" or 2" as I recall). run two nuts up the threaded portion to the
end of the threads toward the head of the bolt. Put a lock washer on
between the nut last nut and the open end of the threads (not between
the nuts. Treat the bolt like a threaded rod which would work just find
if we could get threaded rod made of quality steel. However sawing off
and then properly contouring the end of a grade 5 or 8 bolt is not my
idea of a fun way to spend the evening. SS would be even worse. Insert
the bolt through the rotator plate in into the rotator base. Turn the
bolt in (hopefully by hand) within a couple of threads of bottoming
out. Now bring the nuts up the threads and tighten the first nut
against the lock washer which is against the bottom plate. Now tighten
the second nut against the first as a lock nut, some times called a "jam
nut". This leaves a good portion of the bolt sticking out into open
air. Hence my remark about not looking pretty, but working great. The
first nut is tightened snugly against the lock washer but not over
torqued. That nut is then held with a wrench while the second nut is
tightened against it. This one is *tight* but still not over done.
It's the one that prevents the first nut from loosening. (IE Jam nut)
A remark was made about using a compound to prevent corrosion, or
galling which is a very good/essential point. There are two approaches
and I use both. Never Seize (TM) (not sure about the spelling) works
very well, but you have to be careful about over tightening just as you
do when using any lubricant on threads. It comes in several compounds,
but I've found the one with copper works well with steel and Aluminum,
or at least it has for me. However there is another compound that works
well for this purpose as unlikely as it sounds. "LockTite" (TM). I use
the soft stuff which never really hardens. It grips, more like a Nylok
(TM) nut. I don't remember the color, but I think it's blue. At any
rate it's seems to protect the threads, provide a buffer between the
dissimilar metals, and it keeps moisture out.
Never use SS bolts and nuts without some form of anti galling compound
such as Never Seize. Dry SS to SS will eventually bond and can be a
royal pain in the back side to get apart. Used on a tower the torque
must be adjusted when using an anti galling compound accordingly to
prevent applying too much pressure against the legs.
> 73,
>
> Rob
>
> On Fri, 2008-06-06 at 15:36 -0400, Dick Green WC1M wrote:
>
>> How do you get double nuts on a bolt that has no nuts to begin with? The
>> bolts screw into threads in the rotor casing. There's no way to double nut
>> them.
>>
As I said, sure is. Just put the nuts on a "longer" bolt before
inserting it through the mounting plate into the bottom of the rotator.
Guess I'm going to need to shoot some photos. If I had one of these
rotators I'd set up a demo.
73
Roger (K8RI)
>> 73, Dick WC1M
>>
>>
>>> -----Original Message-----
>>> From: Roger (K8RI) [mailto:K8RI-on-TowerTalk at tm.net]
>>> Sent: Friday, June 06, 2008 2:41 PM
>>> To: Barry Merrill
>>> Cc: jeremy at m2inc.com; 'Towertalk'; n5ya at n5ya.com
>>> Subject: Re: [TowerTalk] Hindsight: Check your rotator bolts
>>>
>>> Just an added note:
>>>
>>> I always use locking nuts (double nutting) on rotator mounting bolts
>>> unless they are the huge bolts as used by Prosistel. I still use lock
>>> washers and locktite on the nuts. I've never had a bolt come out of
>>> one
>>> of the Ham series of rotators or any other for that matter with this
>>> approach. I don't know what size mounting bolts they use with the
>>> Orion
>>> but I'd guess this might apply here as well.
>>>
>>> I'm not knocking safety wires. I fly airplanes and everything
>>> including
>>> oil filters is safety wired<:-)) However in less regulated and much
>>> more environmentally friendly places than aircraft engine
>>> compartments,
>>> lock nuts (double nutting) is very effective.
>>>
>>> 73
>>>
>>> Roger (K8RI - ARRL Life Member)
>>> www.rogerhalstead.com
>>> N833R (World's oldest Debonair)
>>>
>>> Barry Merrill wrote:
>>>
>>>> In 2003, I (actually, I watched, while Bill, N5YA,
>>>> and a 60 ton crane with 161 foot boom did the work)
>>>> installed a US Tower HDBX72 with a 24 foot mast,
>>>> and mounted a 2-el Cal AV 40 at the bottom and an
>>>> OB16-3 at the top, turned with an Orion RC2800
>>>> rotator, and have had zero problems and fantastic
>>>> results.
>>>>
>>>> Yesterday, after a day of 50mph winds, I noticed
>>>> that the antennas were rotated about 45 degrees,
>>>> and then discovered I could not rotate them.
>>>>
>>>> After Reading The Fine Manual and making the voltage
>>>> and resistance checks, which confirmed the motor
>>>> was fine, I called M2 support and received excellent
>>>> support, as Jeremy went thru the system and gave me
>>>> additional diagnostics, in particular, to connect an
>>>> ohmmeter to the counter wires, toggle the rotator
>>>> control, and see if reed switch opened and closed,
>>>> which it did, confirming the rotator electrics
>>>> were not the problem.
>>>>
>>>> Looking at the rotator from the shack (from the West)
>>>> I had seen nothing obvious, but when I then looked from
>>>> the North, I could now see that the rotator was no longer
>>>> in the center of the tower; the rotator was now flush
>>>> with the West side of the tower, and the mast was 2-3
>>>> inches off vertical at its bottom!!!
>>>>
>>>> Clearly, the bolts holding the rotator to the
>>>> tower plate had loosened.
>>>>
>>>> When I called Jeremy back to thank him for the
>>>> excellent diagnostics that eliminated elecrics
>>>> and to report what I had observed, he said that
>>>> this did, very rarely, happen, and that M2 now
>>>> offered a set of bolts that were pre-drilled for,
>>>> and were shipped with, safety wire, and he personally
>>>> packaged a set (only he and the Purchasing manager
>>>> were in the office, so he did it all!) and sent
>>>> them via UPS early AM delivery (promised for 8:30am,
>>>> the doorbell rang at 7:31am)!
>>>>
>>>> On the tower this morning, with the new bolts in hand,
>>>> before the wind kicked up again, Bill discovered
>>>> that two bolts were gone, one was still in place,
>>>> but loose, and one had enlarged its hole in the
>>>> tower plate so that it was above and sitting on
>>>> the plate, cocking the rotator. Fortunatly,
>>>> with ropes on the boom for horizontal pull,
>>>> a jimmy bar in Bill's hand to lift, and a
>>>> comealong strap around the rotator body,
>>>> he was able to realign the rotator and its
>>>> holes, and the new bolts AND SAFETY WIREs were in
>>>> place with only about 2 hours tower time by Bill!
>>>>
>>>> With hindsight, it is now intuitively obvious to
>>>> the casual observer (or more certainly, casually
>>>> obvious to the intuitive observer), that I should
>>>> have had the rotator bolts checked before
>>>> five years had elapsed.
>>>>
>>>> And, now, with the awareness of the alternative
>>>> bolts and safety wires, even at $50.00 for the
>>>> package of six, I'd strongly recommend they
>>>> be purchased if you install the Orion, and
>>>> maybe for all rotators, and, periodically check
>>>> your bolts!
>>>>
>>>> Photos of the original tower installation are
>>>> in the lower left corner at http://www.mxg.com,
>>>> and you can see the load on the Orion is most
>>>> definitely non-trivial.
>>>>
>>>> 73,
>>>>
>>>> Barry, W5GN
>>>>
>>>> _______________________________________________
>>>>
>>>>
>>>>
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>>>>
>>>>
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