[TowerTalk] T500 bearing and rotor placement

[Gene Smar]

Rusty:

      I re-read your original post and now see that you're planning on
installing the rotator in the MIDDLE of the top section.  That should still
be ok, provided you still consider the need to de-rate the tower if you
install loads (antennas) more than a couple of feet above the tower top.

      If you overload the mast, you could, at a minimum, shear the bolts
holding the rotator plate to its angle brackets in the middle of the tower
section.  If you were to install the rotator at the bottom of the section,
more than twice as far below the bearing plate, then the shear forces on the
mounting bolts will be less than half.

     While I'm thinking of it, let me suggest you not rely on the bearing's
set screws to provide support for the mast.  The setscrews have very little
gripping force.  Instead, install a collar clamp of some kind, in addition
to tightening the setscrews,  right on top of the bearing.  I use two
muffler clamp saddles, installed facing each other and connected with
carriage bolts and hardware, to provide vertical support of the antenna
loads on the mast against the bearing itself.

GL es 73 de
Gene Smar  AD3F

----- Original Message ----- 
From: "Gene Smar" <ersmar at comcast.net>
To: <rwb9fiu at earthlink.net>; "towertalk" <towertalk at contesting.com>
Sent: Wednesday, May 26, 2004 1:00 PM
Subject: Re: [TowerTalk] T500 bearing and rotor placement


> Rusty:
>
>      Welcome to the group.  You'll find this one of the most educational
and
> h elpful reflectors in Ham radio.
>
>      I have a T-500-64 at my QTH.  Installing the rotator at the bottom of
> the top section is OK.  The gives you about 8 feet between the rotator and
> the top bearing.  I haven't done the math for this, but but Trylon's info
> (printed and on the web) list no precaution against installing the rotator
> just as you're considering.
>
>      I have my Skyhawk HF Yagi one foot above the top of the tower.  Three
> feet for yours will be ok, but the Trylon series of towers is rated with
the
> antenna load's sail area within two feet of the top.  That is, you'd have
to
> derate the capacity of your Trylon if you start installing antennas more
> than two feet above the top.
>
>      I used Trylon's calculator
> http://www.trylon.com/lightdutytowers/towercalc.asp to determine what I
> considered an allowable load for my T-500-64.  On the tower I now have the
> Skyhawk at 65 feet, a CC D-40 rotatable dipole at 78 feet and a Comet
GP-15
> at 80 feet on a 2 inch diameter mast.  According to my (and Trylon's)
calcs,
> this should survive with a comfortable margin (for me) winds in excess of
70
> mph here in the DC area.
>
>      Remember:  The Titan series of towers is a LIGHT-DUTY design.
Trylons
> says so themselves.  So don't try to put a stack of KT-34-XA's on a long
> mast.  Likewise, I'd give more thought to your plans for installing an
(HF?)
> LPDA above the SteppIR.  If the LPDA is only for V/UHF ( you weren't clear
> what bands the antenna is on) it might be acceptable, but you'll have to
> check with Trylon, etc.
>
> GL es 73 de
> Gene Smar  AD3F
>
> ----- Original Message ----- 
> From: "Rusty Richards" <rwb9fiu at earthlink.net>
> To: "towertalk" <towertalk at contesting.com>
> Sent: Wednesday, May 26, 2004 11:34 AM
> Subject: [TowerTalk] T500 bearing and rotor placement
>
>
> > Hi
> > I'm new to the group and look forward to hearing other opinions on tower
> topics.
> > I have a Trylon T500 up. It came with angle brackets in the top section
> for placing plates under a thrust bearing and rotor in the top and middle
of
> the top section.
> > Would it be better to lower the rotor down into the next section
below,or
> is it ok in that top section?
> > I would also like an opinion on the antenna height above the thrust
> bearing. Will raising it  to 3 ft or more above the bearing have any
effect
> on how low i should nest the rotor? The antenna is going to be a 4 element
> SteppIR,about 10 sq ft. Would like to have a log peridioc for the higher
> bands above the SteppIR,but am not committed to that.
> > Any ideas would be most appreciated.
> > Thanks
> > Rusty
> > rwb9fiu at earthlink.net
> > _______________________________________________
> >
> > See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with
any
> questions and ask for Sherman, W2FLA.
> >
> > _______________________________________________
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>