[Towertalk] Lost My Tower Tuesday

[Jim White]

We had a 25G tower that we replaced with 55G......the original 25G base was
a full section that was poured into a sunken 55Gal drum and a square
platform near the surface....after finding a broken top section the decision
was made to replace the tower with 55G and not to have to worry about such
things ever again - 55G is awesome stuff.

At htis point the decision as to how to proceed was one similar to
yours....we chose to pour SOME additional concrete and biscially re-cycle
the existing concrete.  A hole was drilled in the center of the pour for a
base pin and it was set in construction epoxy, the type used to install
rebar in reinforced concrete repairs - now routinely available at bolt
houses and larger lumber yards....

The reason for adding more concrete was due to the original pour being done
so that water would shed off of it and away form the legs of the embedded
25G - it was a "cone head" kind blob and definitely NOT a flat surface to
place a BPG on. A form roughly 4 foot on a side was built that was about 9
or 12 inches higher than the cone head rose up to - this form was centered
over the original pour and bonding agent was added to the pour.

The result is a rather tall square base for the 55G adorned by a BPG and 110
ft of 55G....

This allowed us to maintain the original anchor points and the marriage
between the two generations of pour was irregular enough that I am certain
they are keyed together....and it the benefit of the already oversized
original pour was utilized.

The only downside I have found with this technique involves where the coax
and control cables come up from underground it is far from a tower leg and
there is a tendency to catch ones leg on the resulting coax.....with some
reworking I hope to bury some new coax runs in conduit and will bring them
vertical with  a sweep and a short vertical run allowing for a nice dripe
loop to be formed between the legs of the tower and the outlet from the
conduit.

This was my first experience with a pier pin type base - other than the
hassle of temporary guys until you get the first guy level in place it was
not bad....just a slower start since you cannot gin and go!

Once you are done - you can say nothing about your hybrid base and nobody
will be the wiser :-)

Oh yeah - make sure you finish the concrete where the BPG goes flat before
tapering it off for run off - if the plate is off the slab on one of the
legs it will ultimately be prone to lean in that direction....take some time
to finish that central area off real well - or - use a flowing construction
grout like they do in high rise construction which is a flowable fine
concrete and flood it under the leveled plate after the fact....but this is
high end approach - we are amateurs here just finish that central area nice
and level - carefully striking it off!

 73,

Jim, K4OJ


----- Original Message -----
From: "Mike Rhodes" <weightdn@adelphia.net>
To: "Tower Talk Reflector" <towertalk@contesting.com>
Sent: Thursday, June 27, 2002 9:06 PM
Subject: [Towertalk] Lost My Tower Tuesday


>   The title says it all...  We had an apparent microburst or severe
> downdraft or whatever they want to call it. Anyhow, it took out a
perfectly
> healthy 60 foot Oak which took out a set of guys which in turn took down
my
> 60 foot tower and assorted antennas.
>   My dilemma is, since my bottom section was a piece of 25g that had been
> cut off at concrete level by the previous owner and, my tower bent at
about
> the 5 foot level which - of course - is just below the first joint, what
are
> my best options. I suspect that sawing the remnants off at concrete level,
> plugging the holes, and installing a mounting plate is going to be a lot
> less painful than trying to jackhammer a yard of lazy aged concrete into
> manageable sized chunks. I notice that Rohn offers a Pier Pin mount and
also
> a mounting plate with 4 mounting holes and stubs for the first section to
> mount to. There is about $50 difference in the price so that is not a real
> issue. Just wondering if anyone has any pros and cons to offer on the
> choices.
>   As for loading, I intend to return to the previous 60 foot level and the
> tower was (will be) loaded as follows: Force12 C4 or maybe a C4SXL (C4 was
> the previous installation); Cushcraft A505 6 meter 5 el beam or equiv.; M
> Squared 2M7 7 el 2meter beam; FO25 25el 432 beam; and a Hustler G6270R
> 2m/440 vertical on top. The mast was about 19 feet of 1026 alloy .180 wall
> tubing with about 5 feet of it in the tower. A wooden bearing was on the
top
> plate and a thrust bearing was on the rotor shelf, with the rotor 2 rungs
> below that. Guys were at the 35 foot and top shelf levels.
>   Back on the subject of the mounting plates, what is the proper procedure
> for attaching something like this to a concrete base and where do you look
> for whatever materials are required. I know this has been discussed before
> but I naively thought I would never need to know that sort of thing since
my
> tower was going to stand forever. Oh well, I imagine that's what that 60
> foot Oak thought too.
>
> Thanks,
> Mike / W8DN
>
>
>
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