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[TowerTalk] Re: Ham IV vs. 25G

To: <>
Subject: [TowerTalk] Re: Ham IV vs. 25G
From: (Bob WA1ZJE)
Date: Fri, 24 Apr 1998 15:15:24 -0400

Stan Griffiths wrote:

> >In a message dated 98-04-12 16:41:28 EDT, writes:.
> >
> >>  Can one put a Ham IV rotator in Rohn 25 ?  I'm asking whether it can be 
> >> put
> >>  in a non top sections w/o any alterations to the section.
> >
> >     Yes, the Ham IV will fit in 25G. You can squeeze it through the braces
> >with the proper application of huffing, puffing and liberal use of American
> >colloquialisms.
> >
> >     The question really, though, is where can you fit the AS25G Accessory
> >Shelf/rotator shelf. It will only fit at tower sections junctions or in the
> >open faces of tapered top sections or BAS25G Bearing/Accesssory Shelf.
> >
> >     I think W7NI had a scheme/design for a modified AS way to mount the
> >rotator anywhere in the section. An update, Stan?
> >
> >Cheers,  Steve  K7LXC
> As Steve says, the Ham IV will fit in a Rohn 25G section, but once you get
> it in there, it will not slide freely up and down the tower.  The bell
> housing is too large to get past the horizontal braces and it will hit the
> diagonal braces as it rotates except in a very specific narrow range of
> vertical positions.  So you have to mount it exactly right.
> I made a sample shelf out of plywood just to see if I mounted it on top of a
> set of horizontal braces, the Ham IV could sit on this shelf and rotate
> freely, missing the diagonals.  It looks like it can.  One COULD make such a
> shelf out of steel plate and mount it to the horizontal braces with small
> u-bolts (1/4" cable clamps).  It might not be a good idea, however, since
> all the torsion applied to the rotator by the mast would be transmitted to
> the shelf and then to the horizontal braces and then to the welds that hold
> the horizontals to the tower legs.  The main question is:  Can those welds
> stand up under this type of stress?  I don't know the answer to that question.
> I am still thinking of making a real steel shelf like this and installing it
> on one of my towers.  The next question is:  How long does it have to stay
> there without a problem before we believe it is a good idea?  The REAL way
> to answer that question is to engineer the project and calculate all the
> stresses and know how strong the welds and horizontal braces are in this
> type of service.  This is a job for a REAL PE, which I am not . . . So the
> only approach I can take is to build one, put it up, and wait.  Not really a
> very good approach but I don't see another choice for me.
> You know, if you took a standard AS25G, rotated it inside the tower 60
> degrees, and bolted it to a set of horizontal braces with 1/4" cable clamps
> used as u-bolts (discard the saddle), you could try this experiment
> yourself.  You might have to shim the plate where it rests on the horizontal
> braces of the tower section so it is perfectly parallel with the bottom
> surface of the rotator.
> Try this at your own risk, but let us know how it works out, OK?
> Stan
> --
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    Hi guys, I have a rotator plate available that will fit almost anywhere in 
25 sections.
    It is attached to the legs.
                                          $45.00 plus shipping


                           TOWER ACCESSORIES

       Rotator plate fits almost anywhere in tower section

       Custom antenna mounts made to order etc.

  Bob Feltmate  WA1ZJE             Member of: ARRL, AMSAT, NARC, NEWS
  PO Box 21
  Norton, MA. 02766-0021 FN41jx

FAQ on WWW:     
Administrative requests:

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