Imagine this. If the house bracket is perfect and has an infinite
holding power, and the tower is perfect, and infinitely strong, then
if there is a sideways force at the top of the tower (from the wind
blowing on the antennas and mast and everything above the house
bracket), the result will be a sideways force at the bottom. Think
about a see-saw with a balance point (the pivot point or fulcrum) in
the middle. Your house bracket is the fulcrum for the tower's
You need BOTH, a strong immovable base AND a strong mounting point for
the house bracket.
Yes, there is a CYA from Rohn's standpoint, but they know what they
are doing. Follow the manufacturer's directions.
On Apr 1, 2012, at 3:46 PM, Dave Cook wrote:
> But isn't that what the house brackets are for?
>> -----Original Message-----
>> From: email@example.com [mailto:towertalk-
>> firstname.lastname@example.org] On Behalf Of Jon
>> Sent: Sunday, April 01, 2012 12:31 PM
>> To: email@example.com
>> Subject: Re: [TowerTalk] Rohn tower installation specifications
>> The 2x2x4 chunk of concrete is called ballast.
>> Similar to the keel of a sailboat...helps to keep it upright.
>> On Sun, Apr 1, 2012 at 2:24 PM, Dave Cook <firstname.lastname@example.org> wrote:
>>> Hi guys, I'm in the process of relocating my 35' freestanding Rohn
>>> tower after 8.5 years on the air. I figured this time I'll bracket
>>> to the house, which is what I should have done in the first place.
>>> I've run across a few problems with the Rohn specifications:
>>> 1. The tower will be bracketed to the house mid-way up and
>>> the top of the tower with an eave bracket. The specifications for
>>> brackets "must support a minimum horizontal force of 815 pounds". I
>>> can't find any calculations for how they came up with this number.
>>> it seems very excessive for a modest 35 foot tower bracketed in two
>>> 2. The specs also state that the base must be a "fixed base",
>>> than a pinned base. Again, in this case I don't understand why a
>>> pinned base wouldn't be sufficient for a well-bracketed tower. Why
>>> would the base experience any lateral loading?
>>> 3. The specs also state that the base has to be the same 2x2x4
>>> concrete that was spec'ed for self-supporting and guyed towers. In
>>> this case I can understand somewhat having a solid chunk of concrete
>>> for the thing to rest on, but the entire weight of the tower and
>>> antenna will be, by my calculations just a little over 200 lbs. It
>>> doesn't seem to me that it needs a 2000 lb chunk of concrete to keep
>>> that from sinking into the soil.
>>> So in short, I'm just wondering if Rohn is simply CYA'ing
>>> or are these specs really to be taken literally?
>>> Thanks and 73,
>>> -- Dave WA0TTN
>>> TowerTalk mailing list
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