Bill,
I just finished my house-bracketed 30' tower. The bracket is at about 16'
above ground and bolted into the attic space of my single-story home. I
used the HBU bracket. I had to get the longest one (36") in order to clear
the overhang on my roof eves.
The HBU uses steel "arms" that are 1/4' thick and about 1.5' wide to make
the bracket. In my case, the steel arms on either side stuck out maybe
6-8" past the bracing (made from the same type of steel). The thing had 6
bolt holes in its (wider) base to mount against the house. In the attic,
I added plywood to tie 4 rafters together. On top of the plywood and
against the side wall, I have a 6' 2x6 and a 4' 3x3 steel angle iron. The
bolts from the bracket go through the wall, the 2x6, and then angle iron.
The angle iron is itself bolted to the plywood and the rafters. This
mounting is very solid.
With about 14' of tower above the bracket, there is a _little_ flex in the
bracket arms that stick out past the bracket side bracing. However, even
when I was up on top of the tower, there was not what I considered to be
any significant movement of the tower above the bracket, never any
sensation that the tower was "swaying back and forth" in some unstable
manner -- and at 235 pounds, I was a pretty big weight up on the top of the
tower! If I had it to do over again, I would consider the heavier HBUVTRO
bracket with the increased bracing just because of the roof overhang that I
had to work around. For smaller overhang distances, the HBUVTRO seems like
a lot of overkill.
On the plus side, we had a very windy day this past Saturday. Wind gusts
were probably 25-35 MPH. I was very pleased to see that the tower was not
moving at all in the wind! For all it cared, it might have been a
perfectly calm day.
Hope my info helps!
73,
Nat
N4EL
>I recently purchased some Rohn 25 and am engineering a housbracketed
>tower of about 45 feet.
>
>I have access to a Rohn catalog, but it gives precious little information
>about the three types of brackets available:
>
>* HB25 - three models with 15", 24" and 30" maximum spacing. The picture
>of the 15" brackets looks a little wimpy to me. There's no data on the
>24" or 30" units.
>
>* HBU - the universial house bracket, looks larger, and is built from
>angle steel and not flat straps. More substantial. Goes to 30" from wall.
>
>* HBUTVRO - the heavy duty version of the HBU. This one has cross-bracing
>of the sway braces. The name implies it was intended for big TVRO
>satellite dishes. Goes to 36" from wall.
>
>Does anyone have experience with these? There are no drawings in the
>catalog. What is the span of the wall plate on each, how many bolt holes
>are there and what is their spacing?
>
>Any information would be appreciated, thanks.
>
>
>
>Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@radio.org
>Quote: "Boot, you transistorized tormentor! Boot!"
> -- Archibald Asparagus, VeggieTales
>
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