K7LXC@aol.com wrote:
> In a message dated 3/25/01 8:34:08 PM Pacific Standard Time, wx3k@ptd.net
> writes:
>
> > I acquired a Mosley Pro 95 beam......9 elements...20 through 10.....a
> > monster compared to my TH3JR
> >
> > I presently have a 60 foot Rohn 25G guyed top and middle and bracked to the
> > house. Is it possible to overguy this tower and use an extra house bracket
> > to be able to accomodate the Mosley ???
>
> Maybe. What's your county windspeed? What's your state and county? You
> can look it up on our website under Tech Notes - <A
> HREF="www.championradio.com">www.championradio.com</A>
>
> If your guying and housebracketing are per factory specs for your
> windspeed, then your chances are pretty good based on your windspeed.
> Overguying won't buy you anything since the typical limiting factor to tower
> capacity is leg compression strength - not guys. Another housebracket is of
> no value.
>
> Cheers, Steve K7LXC
> Tower Tech
> Champion Radio Products
I think we disagree on this one, Steve. You say the limiting factor to tower
capacity is leg compression. I can't think of a single tower failure I have
ever
heard of due to too much leg compression. Rohn 25 is good for about 18,000
pounds
in compression, according to the specs in my very old Rohn catalog (1968). They
don't publish that information any more in newer catalogs but I don't think
anything has changed to make those numbers invalid today.
One of the major contributors to leg compression is the downward pull of the guy
wires and Rohn 25 can use up to 6 sets (18 guy wires) according to some of the
configurations in the Rohn catalogs. That is a HUGE amount of downward pressure
on the bottom section but still well under the 9 tons Rohn has said 25G is good
for. More sets of guys will make the tower "stiffer" and less likely to buckle
between guy sets. Installation of a TA25 Torque Arm Stabilizer right at the top
of the tower and the six guys attached to it will make the tower much less
susceptible to failure due to twisting caused by a large beam on top. I would
be
far more concerned about failure due to buckling or twisting than I would due to
too much vertical load on the legs.
A properly guyed Rohn 25G should support the weight of a couple of cars . . .
The important point is that you need a professional engineer to really pass
judgement on your final guy configuration.
Stan
w7ni@easystreet.com
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