Herewith a summary of some of the replies on bolts and elements vibrating
loose on my 204BA. Some great tips here, many thanx to all!...73/Jon AA1K
"If you don't have time to do it right the first time, when will you have
time to do it over?"
(unknown)
----
Well Jon, I long ago discarded using clamps of any type on the elements.
After they're greased with NOALox, I use 2 stainless steel self tapping
screws to hold the thing. Have had a problem with any using that method.
On the boom to mast clamps, I use muffler clamps, and have started
"pinning" them by drilling a small hole through the end of each "U"
about 1/2" from the end ( put the nut on first inside the hole ) and
then, after attaching the thing to the mast, I place very small cotter
pins in each hole. I've never had a nut back off, but using this method,
even if it does, the worst thing which will happen is the thing will
slide down the mast. And even that is limited by a single clamp
installed about 6" under each boom to mast.
73
Ed K4SB
-----
Six or seven years ago I bought an old TH3 tri-bander with rusted
hardware. I rebuilt it using stainless steel hardware gathered locally.
I used stainless hose clamps in lieu of the old C-clamps. No problems so
far. Some of the so-called stainless hose clamps do NOT have a stainless
steel screw and will rust. Be sure to get the ones with the stainless
steel screw.
73,
Jack W4JH
-----
I have had a 204BA for years and years and would answer as follows:
>1) Is the element problem (vibrating loose) common with this type of clamp?
>In neither case where the element worked loose was the clamp noticably
>loose; in fact today I had to loosen the clamp considerably before I could
>re-seat the outer element into the larger, inner element piece.
USE HOSE CLAMPS ALL ROUND, AND FEEL CONFIDENT - ALSO PUT A FEW SS SELF
TAPPERS ON THE REFLECTOR JOINT
>2) Is there some kind of metal fatigue occurring because of the age of the
>antenna?
UNLESS YOU ARE IN A VERY INDUSTRIAL ATMOSPHERE, UNLIKELY (OR YOU WOULD SEE
THE CHARACTERISTIC BLACK OXIDE POWDER)
>3) Should I replace all the C clamps with all-stainless hose clamps? Would
>they be less likely to work loose?
AS ABOVE
>4) Should I insert ropes in the elements to dampen vibrations? (there are
>none now).
GOOD IDEA, ESPECIALLY ON THE REFLECTOR AND ESPECIALLY IN THE OUTER TIPS OF
THE ELEMENTS - I HAVE SEEN THE OUTER SECTIONS BREAK FROM VIBRATION FATIGUE
ON BOTH THE 204BA AND THE 10 MX DIRECTOR ON A TH6DXX/TH7DX
>I checked all the other joints that I could reach from the tower today and
>the outer ones were checked visually. None of these seemed loose. But I plan
>to bring the antenna down to ground this summer and re-check everything.
>Your thoughts on how to improve the antennas durability will be appreciated.
MY COMMENT: Notice that the amount of overlap on the reflector inner joint
is much smaller than the other elements (typically about 2" if you use the
CW settings) - this leads to greater chances of vibration creep over time,
hence the suggestion of a few self tappers on the overlap.
The other point to watch for vibration is the beta attachment to the boom -
I always suggest a bolt right through the boom with the "lock tight" nylon
insert nuts and plenty of silastic around the joint to act as a dampener.
It is a great antenna, which has proved itself over the years to give a
reliable F/B ratio and a fairly good beam off the front
Good luck
Peter VK3QI
------
I've never had stainless hose clamps work loose (theoretically, they can't
because
they are worm gears) on my TH-11 or its predecessor, the TH-7. Both antennas had
the damping ropes in the elements. I'm on a gusty location on the lee side
of one
of the foothills of the Cascade Mountains near Seattle, so I get lots of
turbulence
and occasionally, a 70mph windstorm (two of these since the TH-11 has been up).
I'd say change to stainless clamps and install damping ropes.
One of our 20m monobanders (Cushcraft 20-3CD) at VK0IR had a reflector fatigue
and blow away toward Australia after only 2 weeks in the Heard winds. I
don't think
Cush puts damping ropes in their antennas. We had winds averaging 27mph
(gale force
is 39) with the peak wind at 65mph (the storm that toasted the 20-3CD). Not
that bad,
actually, I was surprised to see the element break.
73 Mike N6MZ
-----
I've had similar problems with my HyGain tribander, and I believe vibration has
something (if not everything) to do with it. Whenever I have a nut/lockwasher
fall off I replace it with a stainless nylock nut. I've never had one of them
come loose. Also, I have never had a hose clamp come loose either. The worm
drive makes them pretty secure. I also believe they are slightly less wind
load (unless you use one too large for the tube size).
73 - JC,k0hps@amsat.org
------
You guessed it....Put ropes in the element ends. The new 204's come with a
rope kit.
Eric, K6GV
-----
Jon, ... My suggestion, consider going to your nearby auto
parts store and picking up a product called Loc Tight (spelling may be
wrong) This product will chemically lock the nut to any bolt. There
are several levels of locking - one requires heat to break loose, real
heat, I use it under the hood of my car to keep the various parts
together. Consider getting a small (but expensive) tube and test it
out.
Ed KE3ZR
------
Yes, happens all the time. You can fix it by putting a #8 stainless steel
machine screw in at each joint. Will never come apart again.
3) Should I replace all the C clamps with all-stainless hose clamps? Would
>> they be less likely to work loose?
YES! Doesn't cost that much and much more reliable. Be sure to use all
stainless hose clamps.
Randy, K5ZD
----
There is only one really right answer for those elements -- throw away the
clamps and use pop rivets. The security of the resulting element assembly
will make you a happy camper, and you'll never have to deal again with the
clamps getting caught on a guy on the way up...
There are some subtleties in the selection of rivets - you want the type
that leave no steel behind when "popped", and that close the hole in the
center. N6BT could probably be persuaded to sell you what you need,
because he uses them in all the Force 12 antennas.
73, Pete Smith N4ZR
n4zr@contesting.com
-----
The problems you describe with the 204BA have plagued
me for years. My beam was on an aluminum mast and thus
suffered from extraordinary vibration as the mast had
a tendency to bounce aorund alot, until it broke a few
weeks ago. Most recently Hy-Gain has replaced all of those
crummy clamps with SS hose clamps. They seem to hold up quite
well. I had placed ropes in the elements and that seemed
to do little to alleviate the vibration problem - the
elements still vibrated loose and fell off.
When I put up my second 205 I pop riveted all the
elements together, ala-Force12. I have had no problems
with the antenna and it presents a slimmer profile and
probably has 1 sq ft less surface area as a result.
Good luck and CU at one of the summer meetings.
73 de Walt - K2WK
----
1 Use hose clamps at the frist element joint. I use Two on the 1.250 to
1.125 element joint. I had a number of the failures at that joint and none
with the dual SS hose clamps.
2. Use dampening rope in the elements. The new ones come with them;it was
only the 10 and 15 that had them in B-4 !!!!
As for the boom bolts I either double them or use salstic RTV on them after
assembly.
3. There are times where the 1/4 X 1.4 lock bolt has scarred the boom and
will loosen up. I have reversed the boom in one case and had to drill a 1/4
hole through the boom to lock an old 204 I had in my old 4/4 stack....
GL 73' Wayne W3EA
-----
So Jon, you want everything to last forever?
I use a drop of sillycone sealer on the nuts and bolt heads of all ants
assembled here. Seems to damp down the vibration run-back of bolts and
even hose clamps. Others have same luck? de K4VUD
------
Loctite(r) products work very well too. Used to use their products on
1960's-era British motorcycles to keep all the screws and access covers from
vibrating loose. Those who owned BSA (especially), Triumphs and
Nortons can probably testify to that!
73, Bob AA0CY <aa0cy@contesting.com>
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