Actually a 40ft R25 tower bracketed at 8' would probably
handle 130 MPH with no antennas installed. When I ran
the calcs for my 34ft R25 tower bracketed at 8', it came
out to 150 MPH wind survival (6700 ft-lbs overturning
moment at house bracket) with no antennas installed.
With an Cushcraft A3 tribander on top, it derated down
to ~85 MPH. Nevertheless, if James wants to maintain the
130 MPH rating and actually put an antenna on the tower,
he's either going to need guy wires or a stronger tower.
73 de Mike, W4EF..............................................
----- Original Message -----
From: "Bill Coleman" <email@example.com>
To: "James Brennan" <firstname.lastname@example.org>
Sent: Tuesday, December 28, 2004 6:31 AM
Subject: Re: [TowerTalk] Rohn 25g ennginnering spec. 130 mph
> On Dec 8, 2004, at 2:12 PM, James Brennan wrote:
> > I am looking for some engineering specs forRohnn 25g
> > tower. I need the base diagram and wind load ratings
> > that are the most up to date. I need to show that it
> > rates unloaded to 130mph with engineering specs and
> > drawings to get a permit to put up this tower. I am
> > only going 40 to 50 feet and bracketed to the house at
> > 8'.
> Rohn 25G can't do this. At 70 mph, a 40 foot tower bracketed at 8 feet
> can only hold itself up, much less support any antennas. At 130 mph,
> when the wind pressure is nearly four times greater, it would have all
> blown away.
> I doubt even 55G could hold up in this service.
> The base diagrams and wind load ratings are all available in the Rohn
> Bill Coleman, AA4LR, PP-ASEL Mail: email@example.com
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
> 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.
> TowerTalk mailing list
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.
TowerTalk mailing list