I used an 18 foot section of 1/4" thick chrome-molybdnum alloy
pipe for 13 years (similar to what K5RC is selling). It is strong stuff.
I had a KLM 3 el 40 meter beam mounted 15 feet above the top of the tower. The
tower was guyed 3 feet from the top. Guess what - the top tower section bent,
but the mast stayed straight.
Steve London, N2IC/0
n2ic@longs.att.com
>From Stankiewicz, Warren" <wstankiewi@arrl.org Wed Jun 22 15:57:00 1994
From: Stankiewicz, Warren" <wstankiewi@arrl.org (Stankiewicz, Warren)
Subject: Masts
Message-ID: <2E08513B@arrl.org>
If you're looking for some really good mast material, and money is no
object, I strongly recommend using solid titanium rod. I have a piece that
works really well, is lightweight, and holds up to just about anything
Nature (or antennas) can throw at it. It was really expensive, though--the
35-foot, 1 /14 OD piece I have probably runs close to a kilobuck or more
these days..
Warren, NF1J (wstankiewi@arrl.org)
>From Trey Garlough <GARLOUGH@TGV.COM> Wed Jun 22 16:00:26 1994
From: Trey Garlough <GARLOUGH@TGV.COM> (Trey Garlough)
Subject: Mast question
Message-ID: <772297226.688341.GARLOUGH@TGV.COM>
> I have purchased a 20' mast from Texas Towers. It has withstood my
> requirements for 7 years now. It came galvanized.
Yep. Same here, but as I recall the mast I got from Texas Towers was
2" before being galvanized, so don't plan to use a Rohn 2" thrust bearing
with it.
--Trey, WN4KKN/6
>From Tony Brock-Fisher <fisher@hp-and.an.hp.com> Wed Jun 22 16:35:55 1994
From: Tony Brock-Fisher <fisher@hp-and.an.hp.com> (Tony Brock-Fisher)
Subject: Masts
Message-ID: <9406221535.AA09242@hp-and.an.hp.com>
I have refrained from making my most urgent mast reccomendation until now
because it solves one set of problems at the expense of causing another
set of problems. But now that Trey has us all into 3" thrust bearings,
here goes...
The most inexpensive way of increasing strength of masts is to increase
the section modulus. The easiest way to increase the section modulus
is to increase the OD. So instead of staying below 2" OD, and using
some super-expensive super-hard-to-saw alloy to increase yield strength
to 100K+ PSI, just go to 2 1/2 or 3 inch OD pipe. The strength goes way
up, but the cost is low because any old steel (almost) is strong enough.
Now go get a 3" thrust bearing, redesign the boom-mast clamp, and
use a pipe reducer at the rotator end, and you're in business.
-Tony (not a MEch-ie) K1KP, fisher@hp-and.an.hp.com
>From Bruce Herrick <bdh@mixcom.mixcom.com> Wed Jun 22 17:12:20 1994
From: Bruce Herrick <bdh@mixcom.mixcom.com> (Bruce Herrick)
Subject: Antenna Switches
Message-ID: <199406221612.LAA03966@mixcom.mixcom.com>
As usual, we waited until the last minute...We need a non-shorting 3
position coax switch for Field Day. Looking at the AES catalog, I have a
choice of B&W, Alpha Delta, and MFJ. Although the descriptions do not
specifically state shorting or non-shorting, it appears the B&W and A/D are
shorting types. The MFJ may not be. I called a friend at AES who's going
to grab an ohmmeter and check when he gets a chance, but does anyone on the
reflector have any input?
Please email me direct; I'll summarize to the net. Thanks.
73, Bruce WW1M
--
Bruce D. Herrick bdh@mixcom.com Home: 414.462.1270
Pryon Corporation Office: 414.253.5678
N93 W14575 Whittaker Way Fax: 414.253.2772
Menomonee Falls, WI 53051 PacketCluster: WW1M > NB9C
>From barry@w2up.wells.com (Barry Kutner) Wed Jun 22 16:47:37 1994
From: barry@w2up.wells.com (Barry Kutner) (Barry Kutner)
Subject: Mast strength
Message-ID: <3LTBoc1w165w@w2up.wells.com>
There is a way to calculate the EXACT mast requirements for your station.
I believe there were some formulas published in NCJ several years ago
that shows how to do it.
As an example, the bending stress of a TH7 one foot above the thrust
bearing, with a 40-2CD 12 feet above the TH7 is as follows:
58,590 psi at 100 mph
47,460 psi at 90 mph
28,710 psi at 70 mph
This is why Randy's Texas Tower mast has held up well, being rated at
about 80 Kpsi.
My calculations came with the help of a friend who is mechanical
engineer. Posting the fomulas and calculations would be difficult due to
subscripts, greek letters, etc. If anyone would like to see sample
calculations, send me SASE and I'll send copies to you (2 pages).
P.S. Please don't make any mention of Reunion Island on the envelope. You
know what happens to those... (couldn't resist)
--=====================================================================
Barry N. Kutner, W2UP Usenet/Internet: barry@w2up.wells.com
Newtown, PA Packet Radio: W2UP @ WB3JOE.#EPA.PA.USA.NA
Packet Cluster: W2UP >K2TW (FRC)
.......................................................................
>From drs@ccd.harris.com (Doug Snowden) Wed Jun 22 18:12:54 1994
From: drs@ccd.harris.com (Doug Snowden) (Doug Snowden)
Subject: Masts, More Questions
Message-ID: <9406221712.AA60192@rs2>
Ok, now we have a good idea of what people are using, or recommend
for use as mast material. Now, what is the typical scenario in
getting the mast to the top of the tower, installed, with antennas?
I think we are talking about over 300 lbs (???) of mast if we were
using 3 inch stuff of 20 foot length. My main concern is the
manipulation of the mast while it is on/in the tower and antennas
are being added. You can guess that I have never had more than one
antenna on my mast, and never had a big mast.
Doug, N4IJ drs@ccd.harris.com
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