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[TowerTalk] rohn flat top sections revisited

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Subject: [TowerTalk] rohn flat top sections revisited
From: (steve sala)
Date: Thu Jun 5 15:54:30 2003
Thanks to all for the input.  A followup question.  I
have the M2 OR2800 rotator to put in the top section. 
If I go for a regular section of 25G for the top and
put on top of it the BA25G bearing/accessory shelf,
will the rotator fit and where do I put the second
thrust bearing plate?  I presume that you want the two
thrust bearing plates to be separated by as much as
possible to stabilize the mast and antennas when the
rotator is removed.  Could (SHOULD) I remove a cross
brace in the middle somewhere of the regular highest
section to put the rotator in?  Does this compromise
the strength?

Steve K7AWB Spokane Valley, WA

--- Robert Peterson - W3YY <> wrote:
> Steve -
> Check the Rohn drawings, but I think you'll get a
> couple of extra feet with
> the new 25G straight section and small flat top
> plate (About 10' vs 8') vs
> the 25AG-4.  Also, if you ever want to grow the
> tower, all you have to do is
> move the small flat plate, rather than removing the
> whole top section and
> reinstalling it later.
> On the other hand, the 25AG-4 may provide some
> better access to rotator,
> etc., since the top two Z brace sections are not
> Z-braced but open.  This
> also allows you to more easily install two rotator
> plates with a thrust
> bearing on the top plate and rotator on the bottom
> plate.  With a second
> thrust bearing the top flat plate of the tower
> section, the mast and
> antennas are now completely supported without any
> rotator.  Removing the
> rotator for maintenance is now no problem (of course
> find a way to keep the
> mast from turning while you do this!).  I use this
> arrangement on my towers
> and it works great.
> The TB-3 is a good thrust bearing.  Have used them
> for years with no
> problems.
> 73, Bob - W3YY
> .
> ----- Original Message ----- 
> From: "steve sala" <>
> > 
> > I am going to exchange my pointed 25AG3 top
> section
> > for a flat section so I can use a thrust bearing. 
> I
> > have two choices:  1)Replace my 25AG3 top section
> with
> > another regular 25G section and use the small flat
> top
> > BPL25G bearing plate with it or 2)Just use the
> 25AG4
> > flat top section.  Does anybody have an opinion on
> the
> > pros and cons?  I have the extra regular 25G
> section
> > here so I would only have to pay freight for the
> small
> > bearing plate to get it here while if I used the
> > regular 25AG4 flat top section, I would have to
> pay
> > the freight for that heavy section.  Would both be
> > comparable for holding the same antennas?  I have
> the
> > 85 foot tower guyed per the Rohn book at 30', 60',
> and
> > 80' (the book published when I put up the tower 25
> > years ago).  Since I will be using a Force 12 5BA
> 5
> > band Yagi just above the top of the tower with a
> > lightweight M2 7 element 6 meter 6M7JHV Yagi
> antenna
> > above that and a M2 9 element 2 meter 2M9SSB Yagi
> > above that, again, would it make any difference
> how I
> > achieve the flat at the top?  Either way I would
> use a
> > TB3 thrust bearing for the 2" OD steel mast.

> > 73     Steve K7AWB  Spokane Valley,WA
> >
> > 

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