Date: Fri, 4 Jan 2013 12:26:14 -0800
From: Jerry Gardner <jerryw6uv@gmail.com>
To: towertalk@contesting.com
Subject: [TowerTalk] Source for 2" OD Mast
Anyone know of a source for a 2" OD 5 to 20 foot steel mast in the
vicinity of the S.F. Bay Area? Something with around 87 k psi yield
strength would be ideal.
Lots of on-line places sell these, but the shipping cost is greater than
the cost of the mast itself. If there's someplace close to me that stocks
something suitable, I'll rent a U-Haul truck and go pick it up.
73, Jerry
## which is it you actually want, a 5’ mast.... or a 20’ mast ???
If you are only going to put the yagi 1’ above the top of the tower
even sched 40/80 water pipe will work just fine. BTW, 1.5” water pipe
has an OD of 1.9”. It’s 1.9” OD whether you buy sched 40, (.145” thick)
or sched 80, (.200” thick).
## 1026 DOM is typ 87-90 ksi.
UN heat treated 4130 chromolly is 70 ksi. Heat treated, it ranges from
104 ksi up to 120 ksi.
## 2” OD x .375” thick chromoly weighs 7 lbs per foot. And 2.875 x .25”
thick
1026 DOM also weighs 7 lbs per foot. The 2.875” dom mast is a helluva lot
stronger.
## use the FREE arrl mast software to do the math calcs for you.
Plane jane water pipe is aprx 35 ksi.
## Rohn TB-3 bearing has an ID of 2 1/16. A TB-4 has a ID of 3 1/16”
## 4140 is TOOL steel.
## heat treated chromolly takes place at aprx 1100 deg F. Galvanizing it
takes
place at 900F....and will NOT affect the heat treating per jay at array
solutions..who has
see the procedure done in ohio.
## You can also buy 4130 chromolly masts from UST in california.
## a fellow here in town had a 4 el quad on a 30’ x 3” boom, aprx 9’ above
the top of his
rohn 25 tower. He used galvanized 1.9” OD x .145” wall water pipe... 35 ksi (
sched 40).
It bent badly in a 65 mph gust one day. What a bitch to get the quad + bent
mast down.
## so how high is your yagi/s going to be above the top of the tower ?? The
free arrl mast calculator
will tell u in a few minutes exactly what mast is required for a given peak
wind gust.
later... Jim VE7RF
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