[TowerTalk] TELREX 40M346 (copy) PROJECT (LONG)

[Mark Nelson]

Muffler shop.
73 AA6DX
----- Original Message ----- 
From: "Brad Anbro" <n9en@hotmail.com>
To: <towertalk@contesting.com>
Sent: Thursday, February 03, 2000 6:41 PM
Subject: [TowerTalk] TELREX 40M346 (copy) PROJECT (LONG)


> 
> A few years ago, I helped a local DX'er friend take down his Telrex
> 40M346, prior to his moving out west in retirement. After we had the
> antenna on the ground, I made rough drawings of the different aspects
> of the construction of the antenna and measured & noted every dimen-
> sion that I possibly could, in hopes of some day building a copy of
> this antenna.
> 
> I have finally got around to getting the project well under way. I
> used 3-1/2" OD x 1/4" wall aluminum tubing for the 22' long middle
> piece the boom and 3" OD x .125" wall aluminum tubing for the 12' 6"
> and 14' 6" boom extension pieces. The 3" OD tubing wouldn't fit into
> the 3" ID of the middle piece, so I had to use a cylinder hone and
> remove enough material for a close fit. I believe that Telrex used
> 3" OD x .090" wall tubing for their extensions but I wanted to go a
> little heavier, as I had planned on putting this antenna on top of
> a 136' tower.
> 
> For the element insulating tubes, where the elements pass thru the
> center of the boom, I used 2" OD x 1/4" wall G10 fiberglass epoxy
> tubing, which I had to bore out a little, as the 1-1/2" OD elements
> wouldn't fit into these without some clearance. Also, I was unable
> to locate the proper size of aluminum tubing for use as "protective
> sleeves," to protect the insulating tubes from being worn by the
> boom, where they pass thru it. I believe that Telrex used tubing on the 
> order of .075" wall thickness for this. I finally settled on
> using material that was salvaged from a used air-operated hydraulic
> cylinder, which I was fortunate to find lying around where I work.
> The "protective sleeves" wound up having a .125" wall thickness and
> I had to machine the hole sizes in the boom pieces and the boom
> "collars" accordingly.
> 
> Telrex originally used 1/4" dia. bolts which passed thru the center
> of the insulators, to hold the elements in place. I decided to use
> 5/16" bolts, instead. Also, for the reflector and the director, 1/4"
> bolts pass completely thru the collars and the boom to help keep the
> elements from rotating. In addition to this, there are two additional
> bolts, lockwashers & nuts which pass thru each collar into the boom.
> These are also 1/4" dia. in size.
> 
> I am having a problem figuring out how to terminate the 1/8" dia.
> stainless steel feed wire stubs on the reflector and the director;
> and also the feed wires for the driven element. With the factory-
> built antenna, Telrex used 7/8" OD tubing which passed thru the boom
> and 3/4" OD tubing fit inside of these. The ends of the 3/4" OD
> tubing were swaged flat, where the wires were fastened. One could
> get the same effect by putting the piece of tubing in the jaws of a
> vise and squeezing the tubing together, but my guess is that Telrex
> used a stamping press and some custom-made die blocks to swage the
> tubing ends. Of course, the Telrex-swaged ends looked very nice and
> I am hoping to come up with something to the same effect.
> 
> Does anyone know of a machine shop that is set up to swage aluminum
> tubing? These pieces are only about 8" long and 3/4" OD x .058"
> wall. If I could find someone who could swage these for a half-way
> reasonable price, I'd much rather have that (than sticking them in
> a vise and "swaging" them that way). If anyone knows of a shop which
> is set up to do this type of work, I'd sure appreciate knowing about
> it. Thank you very much for taking the time to read this.
> 
> 73 de Brad, N9EN
> 
> <N9EN@HOTMAIL.COM>
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> 
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