On 7/11/13 6:44 PM, Eric Cary wrote:
I have been talking with some friends about setting up a temporary tower on a
trailer something like a boat trailer.
Something like this:
http://home.comcast.net/~k8cc/images/100_0137.JPG
http://home.comcast.net/~k8cc/images/100_0816.JPG
What is the highest you would go with a Rohn 25 or 45 tower with guys of course?
Is the trailer carrying the tower load? or just carrying the tower until
you erect it. I've seen tower trailers that when the tower tilts up,
the base of the tower is in contact with the soil, so the trailer isn't
in the structural picture at all, other than as a prop for the tower
until you get the guys hooked up.
If you're going to use the trailer as part of the structure, you need
something to carry the vertical load to the ground.
Retractable/removable feet or something.
People do build trailers where the unguyed tower is braced to the
trailer frame,but if you do some calculations on tipping it over, you'll
find that the usual 6-7 foot width trailer isn't much base width to
resist overturning, and you have that big lever arm sticking up in the air.
As to how high? What is it going to fall on? Really.. it's a temporary
installation, and sooner or later it is going to tip over, and you need
to make sure that it's going to fall somewhere that the damage is
manageable.
Beyond that, it's more a matter of how will you put the tower up. You're
looking at a non-telescoping stick that you're going to put up all at once.
We've put up 20 feet with a 15 meter multielement beam using ladders and
Iwo Jima style erection at Field Day and it wasn't all that scary.
I've carried around and put up a 30 foot extension ladder and only
dropped it a couple times.
If you're thinking 50 feet, though, some thought is in order of the
mechanics and practicality. Aside from guying (temporary guy anchors
are a chore, and I've seen the bumper ripped off a car by bad choices),
you might think about something like a falling derrick for erection.
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