help needed

[Bill Coleman]

On 5/25/01 11:57 AM, Ed B Richards at k6uuz at JUNO.COM wrote:

>You don't say what tower you have. If it is a Rohn 25 or so, 30' is
>nothing. I have put them up to 150'.

When propery guyed and not overloaded, this is certainly true.

>If you put the bottom 5' in concrete

Rohn does not specify placing this much tower in concrete. Rohn uses 4
feet.

>they are good to 50' self supporting.

Not according to Rohn. If you look in the catalog, they are only
self-supporting to about 40 feet, and then only with an extremely small
antenna load, and in the slightest winds (70 MPH).

Frankly, I wouldn't climb more than 30 feet of unguyed Rohn 25.

>As a guyed tower, one set of guys
>at the 25' level is sufficient.

Not according to Rohn. It depends on the size of the load and the winds
involved.

>As to repairs, I strongly suggest you
>straighten the legs and assemble it as originally intended. If the leg is
>bent in, try a car jack with a 2X4 across the other 2 legs. If bent out,
>put a long pipe over it and bend it back. Your idea would work for such a
>short tower but not the best way. Good luck.

If the legs are only slightly misaligned, then a bit of bending is OK. If
they are visibly deformed, it might be prudent to buy a new section. A
used bit of Rohn 25 can be had for $20-50, depending on condition and
locale. That might be money well spent.

As for the tower system, your best investment is to spend the $7 it takes
to buy a Rohn catalog -- it has tons of technical information regarding
the proper installation and guying of Rohn tower systems, as well as the
load limits for given installations at a certain wind speed.

Please, don't anyone install a tower system without doing more than this
sort of back-of-the-envelope calculation. For 30 feet of tower, it may
not seem like a big deal, but it's worth the investment to be safe. If
you want to install something unusual, hire a PE and get him to do the
calculations.

Safety is worth any price.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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