[TowerTalk] Request for Advice - Rohn 25 vs TRI-EX HZN 471

Tue Feb 21 10:29:22 PST 2012

Bruce-

I'd recommend the crank-up.  I recently put up a US Tower crank-up tower in 
my forested area which gets lots of wind.  I thought about a self-supporting 
tower, but something like a Trylon that would handle our local winter storm 
winds would be very expensive.  Also, I figured if the tower was fixed and 
the wind broke the antenna, then I would need to climb the tower and bring 
it down for repairs.  The crank-up can be lowered when high winds are 
predicted, which will greatly reduce the overturning moment on the tower, as 
well as shield the antenna itself behind the tall trees.  Leaving a 
non-guyed Rohn 25 up with antennas on it IMO would be asking for lots of 
trouble.  It will eventually likely fold at the bracket.

73,

Steve
N6SJ
----- Original Message ----- 
From: "Bruce Ward" <Bruce at IPIntel.com>
To: <towertalk at contesting.com>
Sent: Sunday, February 19, 2012 9:56 AM
Subject: Re: [TowerTalk] Request for Advice - Rohn 25 vs TRI-EX HZN 471

>
> I have another friend who is a tower climber.  He is has installed 60'
> freestanding Rohn 25Gs and is comfortable climbing them.  I am not
> comfortable with him doing so.
>
> If I go with the Rohn 25G I will use boom truck to install the steel
> structure (I beam, tubing, pipe, etc approved by engineer).  Then the
> tower can be installed by the climber as a normal bracketed tower.  The
> tower would not extend more than 40' above the top bracket point.
>
> With the TRI-EX he the boom truck would be used to install the tower.
>
> If the tower were to fall over in a storm it would fall into a wooded
> area without damaging any structures.  I really want to avoid this
> scenario so I am investing in the bracketing.
>
> I am in a county, outside the city, that does not have zoning or code
> issues.  Although I do not want to build anything that would not pass
> code inspection.
>
> I am fairly sure my boom truck operator would not allow any riding of
> the ball.  He was very careful while installing the trusses for my house.
>
>
>
>
>
>
>
> On 02/18/2012 09:53 PM, K8RI wrote:
>> On 2/18/2012 8:58 PM, Gary K9GS wrote:
>>> Seems like an awful lot of trouble when you can just buy an extra
>>> section or two of used Rohn 25.
>> Remember he can't guy it.
>> Another problem is standing up this much tower, let along it being
>> unguyed, and having to service it.
>> No way would I consider climbing that much free standing 25G. So it'd
>> have to go up with the coax and antennas in place.
>> In "the old days" we would have had a crane lift it in place and either
>> ride the tower up or climb it while the crane still held onto it. Either
>> way meant "riding the ball" down, or rigging a release we could pull
>> from the ground which with only 60 to 80 feet is not much of a problem.
>>
>> You can use heavy I-Beam with bracing at the bottom welded in place.  I
>> believe they come in 24' lengths like most structural steel.   One 12
>> incher might cost as much or more than your 60 foot 25 G.
>>
>> Another question is what happens if the tower goes over in a storm?  Are
>> there any zoning restrictions? How will you prevent people from climbing 
>> it?
>>
>> Twas 30 plus years ago we had a problem at work that was one of those
>> "how do we get some one up there and back down".  I suggested the crane.
>> To say that was unacceptable would be a vast exaggeration.  Even the
>> suggestion was considered unacceptable.<:-))
>> I always thought "riding the ball" was fun.  Once in a while though
>> you'd find a lot of grease on that sucker just to make things
>> interesting.<:-))
>>
>> Amazing as many of us made "old age" as did.
>>
>> 73
>>
>> Roger (K8RI)
>>
>>
>>> Just saying......
>>>
>>>
>>>
>>> On 2/18/2012 6:33 PM, Bruce Ward wrote:
>>>> Mark,
>>>>
>>>> You make a very sane suggestion.
>>>>
>>>> My reason for putting the tower on top of the building, if I do, is to
>>>> get an extra 8' to 10' of height.  The building will be sufficient to
>>>> handle the 1100 pound weight plus the horizontal wind loads.
>>>>
>>>> The tower site is covered in 60' plus trees and there is a similar
>>>> height hill with similar height trees between my tower and the far end.
>>>> I need to get above the trees plus above the fresnel zone so I want to
>>>> go as high as I can.
>>>>
>>>> If I use the Rohn 25G we will add sections until we are high enough.
>>>> This method could mean that I have to build sufficient structure to
>>>> bracket even higher than 35'.  I would place the bottom section Rohn 
>>>> 25G
>>>> on the ground (a concrete base) and bracket it to a pole embedded into
>>>> the building.
>>>>
>>>> If I use the the TRI-EX I am stuck with its 70' height plus a 10' mast.
>>>> Since it is a one shot deal I would like to start as high as I can.
>>>>
>>>> Thank you.
>>>>
>>>> On 02/18/2012 06:19 PM, Mark Robinson wrote:
>>>>> I am not a mechanical engineer but why don't you put the tower in the 
>>>>> ground
>>>>> and the building next to the tower.
>>>>>
>>>>>
>>>>> Mark N1UK
>>>>>
>>>>>
>>>>> ----- Original Message -----
>>>>> From: "Bruce Ward"<Bruce at IPIntel.com>
>>>>> To:<towertalk at contesting.com>
>>>>> Sent: Saturday, 18 February, 2012 6:53 PM
>>>>> Subject: [TowerTalk] Request for Advice - Rohn 25 vs TRI-EX HZN 471
>>>>>
>>>>>
>>>>>> I am setting up a tower (my first) to get internet service.  The
>>>>>> antennas will be less than 2 square feet of wind loading combined and
>>>>>> could be even less using 2 11x14" grid antennas.
>>>>>>
>>>>>> My plan is to build a 10'x10' 9' to 10' tall block building on a slab
>>>>>> that is larger in all directions.  This building will will have a
>>>>>> concrete roof with rebar and wire in all concrete.  The blocks will 
>>>>>> have
>>>>>> rebar and concrete in every cell.  The structure will use 12  to 15
>>>>>> yards of concrete plus 400 concrete blocks providing an over 45,000
>>>>>> pound base for the tower.  I have a civil engineer friend who will be
>>>>>> involved in the final design of the building.  The building is dual
>>>>>> purpose, it will provide a secure home for my servers and a stable 
>>>>>> base
>>>>>> for the tower.
>>>>>>
>>>>>> Now for the difficult part, I do not have room for guy wires.
>>>>>>
>>>>>> I am trying to decide between two options
>>>>>>
>>>>>> 1. I have 9 full and a top section of Rohn 25G in my yard waiting to 
>>>>>> be
>>>>>> be installed.  Currently Rohn rates the 25G for freestanding use up 
>>>>>> to
>>>>>> 40' with 1.4 square feet of wind loading.  From reading online it 
>>>>>> sounds
>>>>>> like Rohn 25s have been used for decades even higher without guy 
>>>>>> wires.
>>>>>> I do not want to risk stretching beyond Rohns specifications.  I have
>>>>>> access to 40' lengths of 8" pipe. If I go with the Rohn 25G my 
>>>>>> intention
>>>>>> would be to embed a  40' section of the 8" pipe into the building and
>>>>>> bracket to that pipe up to 35' or so then have the tower extend 
>>>>>> another
>>>>>> 35' to 40' above the pipe.  All the metal would be isolated from the
>>>>>> ground and properly guided with a ground rod to avoid corrosion 
>>>>>> issues.
>>>>>>
>>>>>> 2. There is a TRI-EX HZN 471 available locally.  I would have jumped 
>>>>>> on
>>>>>> this one earlier but it is worth more the the current owner than it 
>>>>>> is
>>>>>> to me.  This is a 70' (71'?)  crank up tower with a motorized winch. 
>>>>>> The
>>>>>> motor is broken and would need to be replaced.  The tower is free
>>>>>> standing with the exception of three diagonal pipe braces that 
>>>>>> connect
>>>>>> from the top of the bottom of the 4 sections to the ground around 10'
>>>>>> out.  I like that this tower is freestanding and I believe I could do
>>>>>> away with the braces if I bracketed the tower at the same location to 
>>>>>> a
>>>>>> sufficiently strong structure.  If I used this tower I would likely
>>>>>> build a 3'x3' column of solid concrete into my building and place the
>>>>>> tower on top.
>>>>>>
>>>>>> I would very much appreciate any suggestions and advice.
>>>>>>
>>>>>> Thank you.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>
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