I would never climb 50 ft of unguyed 25. No thanks! Just because it
stayed up 10 years does not mean it was safe.
Mike W0MU
W0MU-1 CC Cluster w0mu.net
On 4/2/2012 10:34 AM, Ro Grrr wrote:
> Dave
> Years ago I put up 50 feet of Rohn 25 and then hung a HyGain TH3 on it. There
> was no house bracket and no guy wires. The installation stood for about 10
> years until the man died. I then removed the TH3 for his widow.
> I know Rohn warns about bracketing and guying but lawyers are the reason for
> all their understating what their product will really handle.
> I would not hesitate to put up the same installation today, either. Further,
> I'm planning to put up 150 feet of R55 here at my QTH and wont put any guys
> on it guy it til I get up to about 60 feet. My base will be probably 3x3x3,
> and I'll ultimately have 3 sets of guys on it, per Rohn's specs. Ground
> here, as it was where the Rohn 25 installation was, is hard clay.
> Roger aka RoGrrr
> KC8HZ
>
>
>> Message: 1
>> Date: Sun, 1 Apr 2012 20:01:44 -0700
>> From: "Dave Cook"<wa0ttn@netdave.com>
>> Subject: Re: [TowerTalk] Rohn tower installation specifications
>>
>> It looks like the comments, both on and off the reflector, have died down
>> for the evening so I'll recap what I've heard so far.
>>
>> 1. None of the arguments regarding the bracketing specs have convinced me so
>> far. For those of you who proposed the "wet noodle" argument, I just can't
>> buy that. This tower is STRONG and I think the topmost bracket is going to
>> take pretty much all of the lateral strain. I didn't clarify, but the eave
>> mount is actually attached to the roof, not an eave, so there's a lot of
>> surface area behind it holding that bracket.
>>
>> 2. The only point made about the fixed base vs. a pinned base is that the
>> base is intended to provide a counterweight to any sway in the tower. But
>> again, with the brackets taking the stress, I don't see any purpose for the
>> base other than to keep it from sinking.
>>
>> 3. And yes indeed, my current tower has a base of 2x2x4 feet, per the Rohn
>> spec on page 25G-4 of my Rohn Consumer Catalog. In retrospect, I see the
>> spec on the self-supporting tower on page 25G-2 does call for 4x4x4. But a)
>> the tower has survived for 8.5 years as is, solid as a rock, and b) the
>> relocation will eliminate this as an issue. Per page 25G-4, a 2x2x4 "drilled
>> pier" foundation is the recommendation for bracketed towers, which is I
>> suppose where I got that spec for the first installation.
>>
>> The last bit of info is that the Rohn spec for a bracketed tower only goes
>> down to 40 feet, whereas mine will be at 35 feet. However, interpolating
>> their bracketing points, which correspond to where I'll be bracketing mine,
>> and with the windloading of my antenna, it should be good for 85 mph of
>> windage, which would be extremely severe in my QTH. In addition to that, the
>> prevailing direction of the wind is pushing the tower and antenna towards
>> the house, so the worst thing I can imagine would happen in a catastrophic
>> failure would be the brackets would collapse and the tower would fall into
>> the house by the few inches (if any) of standoff the brackets are providing.
>>
>> I hope that gives a clearer picture of the situation. I think I'm going to
>> be ok with putting in a 2x2x4 concrete footing, even though our soil is like
>> concrete already to try to dig a hole into. But I still think that Rohn's
>> bracketing specs are just way to arbitrary without some corroborating math
>> to show how they came up with their numbers.
>>
>> Thanks again for all the feedback. I really appreciate you folks' thoughts
>> on this.
>>
>> 73 Dave WA0TTN
>
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