On 7/4/2013 12:07 PM, PHILIP GRAITCER wrote:
Thanks folks, for the ideas and suggestions.
I am getting the tower from another amateur, so any extra weatherproofing I
will have to do outside the factory. Force 12 has sent me some info, two sets
of drawings, one for the 18x18X36 base that is reinforced with rebar.
Foundation bolts get set in the base. There is also a drawing for a house
bracket - not very detailed, but two pieces of angle iron stick out 24 inches
from the wall and two bolts go through these pieces around the square tower.
In addition there are two 36 inch pieces that run at an angle from the pieces
sticking out to the wall of the house.
I am going to use 2 inch angle iron against the wall of the house, secured by
bolts and a plate inside the wall, and use 2 inch iron for the 24 and 36 inch
pieces. If I can find aluminum that is this stout, I will use that instead of
iron because of the salt air. The tower collapses down to a little more than 13
feet and weighs less than 150 pounds.
I think I have a plan for setting it up, however, I just have to figure out how
to pour the concrete, make the rebar cage, set the foundation bolts, and build
the bracket.
There are many caveats about house brackets.
They run from outright flexible to outright rigid.
Quite often the house moves more in the wind than the tower.
Anyone who has been on top of a house when it's windy can see the house
move compared to the chimney. I've had 3 single story home from 1100 to
2100 sq ft. They all had fireplaces. I could see as much as an inch
movement between the houses and chimneys and these were maybe 30 MPH winds
BTW working on a roof in the wind is likely a lot more dangerous than
climbing towers.
But one thing about house bracketed towers is NOISE. The tower, with a
rigid mount often (but not always) can end up using the end of the house
as a "sounding board", so it might be wise to avoid a wall of a bedroom.
<:-))
The more flexible brackets (like you can purchase at Radio Shack)
provide decent support in a plane from the house to the tower, but
apparently much less parallel to the wall
The last photo on http://www.rogerhalstead.com/ham_files/Dirt_Base.htm
shows a bracket (still undrilled)that was lag bolted to the end of the
shop roof. The end plates are 2 X 10s and form a very rigid structure.
I ended up putting a 1/4 inch of rubber sandwiched between the bracket
and plate for sound deadening.
SOMEWHERE I have a photo of the installation, but have been unable to
find it.
BTW I wonder how many have noticed that this is not a typical bracket in
that it fastens to two tower legs. The tower hinges over from the base
at a 120 degree angle to the wall, due to a tree.
I have used a similar design to hold all three legs. Any bracket that
holds two or more legs requires a very strong wall as the twisting
moment from a large antenna is transferred to the wall.
Where the house bracket may be required to provide substantial support
with large antennas on relatively light duty towers it would be a good
idea to reinforce the wall and use a 3/4 to 1" plate on the inside to
distribute the load across as many studs as possible.
Newer walls using 2 X 6 studs are stronger, even with the wider spacing
and quieter when the inside and outside surfaces are isolated from each
other.
Don't get discouraged from what you hear on here. Let your zoning board
do that. <:-))
73 and good luck,
Roger (K8RI)
Thanks for your tips.
73,
Phil, W3HZZ
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