[TowerTalk] tower replacement wisdom

[Matthew Kaufman]

Thanks! This is useful for ballpark costing. Plus who knows what it'll cost
to permit, given its legacy status with the county.

Matthew Kaufman

On Thu, Jul 18, 2019 at 4:48 PM Charles Morrison <junkcmp at gmail.com> wrote:

> Having done a 120ft 140 MPH tower last year I grabbed my costs and applied
> them to your plan:
>
> NEW PARTS  170ft 130MPH 55G 4-guy levels no insulators
>
> $2500 for new Rohn anchor rods  GAC5755TOP  $825 ea +ship
> $400 rebar -pickup
> $200 lumber -pickup
> $6000             17 new 55G sections +ship  (Find used and save 50%, but
> life is reduced.)
> $1500             All other Rohn parts   BPC55G APL55G (4) GA55GD    +ship
> $ 315              700 ft  5/16" EHS  $0.45/ft  +ship
> $ 475             1575 ft 1/4" EHS  $0.30/ft  +ship
> $   48               6  5/16" Guy grips / Big Grips $8 ea +ship
> $ 108             18  1/4" Guy grips / Big Grips $6 ea +ship
> $ ~500           Thimbles, Shackles, End sleeves/ice clips.  +ship
> $ 200              Bolt cutters pickup
> $ 425              12   3/4TBE&J Galvanized Turnbuckles  $35 ea +ship
> $ 100              Safety Wire & parts +ship
> $ ???              Grounding +ship
>
> You build guywires  2-3 days 1 man.
> Tower crew:     Remove ants & cables
>  Tower crew:    Demo tower ( release 1 guy) cut up for scrap, (You could
> do all of this & haul away)
> $500-1000       One day anchor hole prep $500-1000  Rohn AB3
>                         Build rebar cages  1 man 2-3 days
> $ ???                6-to-8 yds 4000 psi concrete  +ship
>  Tower crew:    Erect tower
>   Tower crew:   Install new feedlines and old antennas
> =============
> Totals:
> New Parts discounted retail $13000 + Tower crew ($5000-$10000) + new
> feedlines and associate parts + backhoe + shipping + concrete
> + your free labor listed above.
> Guess: $25000 to $35000
>
> -Charlie N1RR
>
> On Thu, Jul 18, 2019 at 7:01 PM Matthew Kaufman <matthew at matthew.at>
> wrote:
>
>> Hoping to gather some community wisdom before embarking on a tower
>> replacement.
>>
>> I have a 2.5 acre property on a slope with what I believe to be a Rohn 55
>> tower that was installed as a commercial paging transmitter tower in 1971
>> at 150 feet, then extended sometime in the 1980s to 170 feet when they
>> switched from VHF to UHF and then 900 MHz paging. (The top (5th) guy level
>> was quite clearly added using an existing hole on the anchor and a
>> strandvise instead of the big grips that were used for the other guys.)
>>
>> The tower has withstood at least one lightning strike, the 1989 Loma
>> Prieta
>> earthquake, and numerous storms,... but the guys are getting very rusted,
>> the tower is rusting (despite a coating of zinc-rich paint a couple years
>> ago), and the guy anchors are in unknown condition (though visually "ok").
>> I'm not sure how long a tower should last, but it can't possibly be
>> "forever".
>>
>> Two of the guy anchor locations are just above the tower elevation, the
>> third is some tens of feet lower. Each guy anchor has a metal rod that
>> extends 3+ feet unprotected through dirt and then into a concrete block .
>> The tower has a pier pin base on concrete which is below ground level, so
>> is in a bit of a well with retaining blocks around it (had been buried
>> under the earth when I acquired the property and tower).
>>
>> I have the following limitations:
>> 1. I want to have minimal downtime - the tower has a couple of
>> heavily-used
>> ham repeaters, a commercial repeater, and a wireless ISP on it.
>> 2. The county would never issue a permit for a tower like this today...
>> the
>> property has a use permit for the tower, specified as "18 inch face" and a
>> drawing of its approximate location on the property. So I need to somehow
>> permit this work as "replacement in kind". A new tower would be limited to
>> 53 feet in this zoning district, with a possible variance available to 78
>> feet... the trees are taller than that.
>> 3. I have no construction drawings for the guy anchors or the tower base,
>> and have no way of nondestructively testing the strength of the guy anchor
>> rods.
>> 4. I'd like to ensure that the tower can support the existing and future
>> microwave dish loads, and reduce the twist both for those and the fire
>> detection cameras I have up top... so maybe should go to star guying?
>>
>> So... I need to choose a tower that is roughly 18" face width (possibly
>> just Rohn 55 again), and install it at (if I trust the foundation) or near
>> the existing tower location, with presumably new guy anchors that must be
>> near but not at the existing anchor locations (to minimize downtime), and
>> do as much of the removal and installation as possible with a crane (or
>> helicopter?). I also need to not break the bank, as this is really a hobby
>> tower for me, where the commercial customers are mostly to pay the
>> utilities and property taxes.
>>
>> Thoughts? Alternatives?
>>
>> Matthew Kaufman, KA6SQG
>> _______________________________________________
>>
>>
>>
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>