Still hitting hose clamps from the old antenna with my lawnmower. C4XL, C3
and 30mtr Force 12 hasn't shed a rivet in 6 years. Tom at Force 12
conveniently has holes 'pre' pre-drilled in the element/boom bracket on the
40 meter elements to preclude problems associated with a larger rivet
loosening up. I utililzed those features on my 40 meter elements due to
rogue 60 mph sustained winds experienced here on a yearly basis. In windy
conditions, when bored, I sit on the back deck and stare up that the antenna
elements 'surfing' in the wind. No humming or vibrating...
If the rivets are supposed to fail, darn it, I want my money back, cuz mine
has failed !!!!!
Jerry DiPietro K9GD
> From: K3BU@aol.com
> Date: Tue, 27 Mar 2001 18:38:07 EST
> To: email@example.com
> Subject: Re: [TowerTalk] rope in elements
> In a message dated 3/27/2001 13:32:42 Eastern Standard Time,
> firstname.lastname@example.org writes:
>> Is it somehow possible that the mechanical resonances in the elements
>> could feed through to the mounting bracket on the boom and cause some of
>> the rivet failures F12 have had with some of their antennas? For those
>> who don't know what I'm talking about, I'm referring to some of the
>> failures in the rivets that hold the element brackets to the boom. I'm
>> trying to figure out what caused this (so it can be prevented from
>> happening again) and was wondering if resonances could have been a
>> contributing factor (in addition to them using the wrong rivets)?
> There have been discussions how good, beneficial and revolutionary rivets are
> in the Force 12 antennas. I think this is wrong application for use of
> rivets. Rivets should be used to hold two pieces together and be stressed on
> compression, like squeezing two sheet metal plates (airplanes, bridges).
> There is multitude of them squeezing the plates and connection is made by
> friction between the plates. Using rivets as a pivot fastener (not sure about
> English terminology) like in Force 12 elements, or element to boom clamps is
> wrong. There, rivet holds two circular pieces of tubing together with room to
> move. Being in soft aluminum and with all the wiggling and vibrations they
> will eventually work themselves loose. The result is first bad connection and
> eventual divorce. The same goes for element to boom clamps. Whenever there
> are just few rivets and connection prone to some play, vibration or sheering
> stress, sooner or later failure is in store. I bet that many riveted antennas
> will sooner or later fly apart.
> There is nothing better than good old hose clamp with slit tubing. You have
> good all around compression fitting, good electrical contact and continuity
> on the surface for RF to flow smoothly without being forced to go inside and
> out of tubing joints :-)
> Even the old Hygain clamps with screws are not so good, they bite into the
> tubing, bitch to take apart years later and they do not provide full
> circumference contact between two diameters.
> If you see anything vibrating or singing in the wind, take the sucker down,
> before is too late, or you will be looking for pieces in neighbors yards.
> I had commercial antennas fly appart (except 3rd hand TH6), but none of the
> home brewed Razor monsters did. I used tapered booms with only top strut,
> home brewed element to boom clamps with muffler clamps and hose clamps for
> element junctions. Rope inside of Yagi elements.
> Yuri, K3BU
> VE3BMV, VE1BY etc.
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