In a message dated 97-06-02 09:25:03 EDT, ea7wa@arrakis.es (Angel M. Claus)
writes:
> I've got a 20 feet long pipe tube, 1.90 OD, .200 wall and would like to
know
> if it is strong enough to support what I'm going to put up there.
Hola, Angel --
What you have is pipe. It is used for transporting liquids and does not
typically have a yield strength rating. It is heavy but not very strong.
What you need is carbon steel tubing. It'll be 2.0 inch OD and will have a
yield strength rating.
>
> The tower is 52 feet long, guyed in 3 points, 18, 39 and 52 feet. My qth
is
> a 70 MPH maximum winds area.
> From the rotor place to towers end there are 3.94 feet, immediately will
be
> a
> KT-34XA, and 12.47 feet above the 6 el, I'll place a 40-2CD, so there will
> be
> abt 15.75 feet of the tube on the air with these two antennas.
>
> Do you think it is OK ?, or should I have to look for something stronger ?
> My dealer does not know to tell me the psi of the tube, only told me it is
> a sch 80
> and the ASTM is A-106. Maybe some of you could tell me the psi of this
pipe ?
>
This is a Schedule 80 pipe and A-106 has a yield strength of 32,000 psi.
> Not to easy to find tubes in my city, so I pray for this one to be the
> adequate, hi ¡
>
According to my MARC (Mast, Antenna and Rotator Calculator) Program,
your proposed setup will have a bending moment on the mast of 22,922 in-lbs.
The recommended mast material should have a yield strength of 46,000 psi and
0.250 inch wall. By using 7 feet separation, the bending moment drops to
12,702 in-lbs with a 42,000 yield strength and 0.120 in wall recommended.
With the closer spacing, your pipe starts to look better and more
reliable. A compromise is definitely called for.
BTW, the MARC Program is available from TOWER TECH. It is US$9.95 +
$2.55 for shipping and handling. The address is Box 572, Woodinville, WA,
98072, USA. It doesn't do metric at this point but you should be able to make
the conversions if necessary.
73, Steve K7LXC
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