Fellow tower talkians:
I also used a similar procedure to Bill's.
When I installed my first Rohn 25 tower after digging the hole and putting in a
layer of pea gravel/river rock on the bottom for drainage I put up the 3 foot
base (although I have known some hams that have dug an 8-9 foot hole for the
base
and used an entire section of Rohn 25 for the base) and first 20 feet of tower
and after using a level to make it as vertical as possible I tied off the 20
feet
of tower in several directions (same directions as the guys would be) and then
poured the concrete and periodically checked the two tower sections with a
3-foot
level to make sure they didn't tilt in the concrete as it hardened. Worked like
a
champ.
To keep the concrete from hardening too fast (I put the tower up during a hot
Texas summer) I would sprinkle the surface of the base lightly with water over
several days and then let the whole thing cure two weeks before starting to
install the rest of the Rohn 25.
It was interesting that during the construction several neighbors came over and
said they thought it was nice I was putting up a "bell tower" (The Rohn 25 and a
Ham IV rotor premounted in the top section) in the neighborhood and they hoped
to
soon hear my "bells" chiming out over the neighborhood. Once I put the beam on
top they knew it wasn't a "bell tower". But I kept them satisfied since my XYL
Cheryl (WY5H) and I are storm spotters, besides DXers, and when anything was
brewing in North Texas or near us I'd walk around the neighborhood and knock on
doors to alert them.
As an OT aside, when we'd have a Tarrant County (Fort Worth TX) RACES spotters
callout on Sunday morning I'd always take my talkie to church and listen to our
minister with one ear and the RACES net in an earphone plugged in the other ear.
Yes, our minister knew what I was doing as I had discussed it with him before.
He and I had talked about where to move folks in the church building if anything
happened close by during the service.
Tom, WW5L
Bill Coleman wrote:
> On 8/31/02 1:27 PM, Stan & Patricia Griffiths at w7ni@easystreet.com
> wrote:
>
> >Install the house bracket before you pour the base concrete. This way, you
> >can move the tower base slightly to get it perfectly vertical, and THEN pour
> >the concrete. This is much easier than trying to get the house bracket in
> >exactly the right place after the base is set in concrete.
>
> Sorry for the late reply, but here's what I did.
>
> 1) Temporary mounted a house bracket at 9 feet to the house.
>
> 2) Built a 2' by 2' (interior) frame out of 2x4s. the frame is the top
> form for the tower base.
>
> 3) mounted a centering string on the frame, and another string just
> behind where the legs should go. This gave me the exact center of the
> face nearest the house.
>
> 4) used a plumb bob mounted on the center of the house bracket to locate
> the exact position of the frame.
>
> 5) leveled off the surface of the ground to locate the frame.
>
> 6) dug the hole for the base with the frame in place. (~1800 lbs of
> earth, all with a shovel and a post-hole digger)
>
> 7) put 4-6" gravel in hole.
>
> 8) put rebar cage in hole.
>
> 9) mounted two sections together. Dropped them into the hole, inside the
> rebar cage.
>
> 10) connect sections to temporary bracket.
>
> 11) used plumb bob to get the tower vertical.
>
> 12) got pre-pour inspection by county.
>
> 13) pour concrete. wait 7 days for cure.
>
> So, at this point, the base is in the right place, the first two sections
> are vertical, but the bracket is too low.
>
> 14) stack another section of tower.
>
> 15) mount the lower bracket (18 feet) to the TOWER first, in order to
> locate it on the right place on the wall. Then fasten to the wall.
>
> 16) remove temporary bracket at 9 feet.
>
> 17) stack another section of tower.
>
> 18) repeat process by mounting top bracket (25.5 feet) to TOWER first,
> then fasten to wall.
>
> Note that HB25 brackets allow a little bit of adjustment along the face
> of the wall, but there is little or no fine adjustment coming out of the
> face of the wall.
>
> Oh, and I used a plumb bob before I stacked the top section to make sure
> the tower was true. I made a job out of a piece of wood and nails that
> would fit over the horizonal braces of the tower section and put the 'bob
> right in the middle of the tower.
>
> Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
> Quote: "Not within a thousand years will man ever fly!"
> -- Wilbur Wright, 1901
>
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