Subject: Re: [TowerTalk] Rohn 25 drilling template?
Joe,
I believe you can use one of the bent legs with the holes already in it as a
template for drilling new holes. After you cut off section with the bent
legs, and insure that you cut all three legs exactly equidistant from the
top of the straight section, cut off one of the bottom portions of the
portion of bent tower, with the right hole spacing and distance from the
bottom. Then cut this section lengthwise, slicing it in half approximately
90 degrees from the holes. You can take both of these pieces and using
longer bolts, install the two halves over one of the other legs and tighten
the longer bolts and nuts until the cut sections form around the outside of
one of the other legs. Some light hammering may be necessary until the gap
closes between the two sliced pieces and the other tower leg you are using
to form this "outer clamshell" against the old tower leg.
Once you have accomplished this, take one of these newly formed clamshell
pieces with the proper hole positioning and place it on a leg of the tower
you want to drill. It must be with the tower lying on a flat surface, like
the garage floor, and the new holes to be drilled in each leg should be
vertical to the floor on each leg when the tower is rotated so that the leg
to be drilled is on top. The template piece original bottom should be
precisely even with the bottom of the cut tower and held in place with a
couple of hose clamps against the leg to be drilled. It also must be
positioned precisely with the holes at the very top. Using this old tower
mounting leg as a drill guide, drill completely through the tower while
keeping the drill perpendicular to the floor. A bubble level may help, but a
large drill press would insure straight drilling. Two different size holes
are required for Rohn 25 tower mounting bolts. the smaller would be
clearance for the 1/4" diameter bolt or 17/64" diameter, the other clearance
for the 5/16" diameter bolt or 21/64" diameter. If you have a way to
maintain drilling the holes perfectly vertical, the other side should match
the template also and should fit the stubs perfectly.
If you don't feel confident to drill the new holes truly vertical, you might
want to find a local machine shop with a large enough drill press to
accomplish the drilling and positioning of the clamped template piece. Close
isn't "good enough" in this situation as all three legs must fit the
existing stubs as well as be drilled equidistant from the bottom of the cut
tower. I've done this a couple of times personally, and it has worked out
well but I do remember in one case I needed to enlarge the holes on the
inside of one of the legs, making that hold oblong vertically to line up
with the stub. As I recall, I just used the drill after positioning the
tower section over the stubs and having the other bolts all in place, just
drilled through this last hole that didn't line up well enough to drive the
bolt in and through. Not bad for doing it in my garage though. Good Luck,
Joe. It's not as difficult as it sounds, but you have to take time to get
everything set up right and be able to use a level somewhere on your drill
motor, especially after you go through the top of the "new" base leg and
start drilling through the inside. I had a small bubble level on the drill I
used making it easier than trying to just eyeball if you are perfectly
perpendicular to the floor. This is where a large drill press with a gig and
long table, along with clamps to secure the tower section to the table
and/or an adjustable height floor stand at the far end of the tower to level
the top leg, would be really handy. I once had tools like this at my
disposal, but that was long ago. Most machine shops do, and if you're not
comfortable doing the drilling, you might consider finding a place with the
right tools to make it happen.
73, -=Rog-K9RB=-
----- Original Message -----
From: "Joe Subich, K4IK" <k4ik@subich.com>
To: <towertalk@contesting.com>
Sent: Sunday, March 06, 2005 11:49 AM
Subject: [TowerTalk] Rohn 25 drilling template?
Has anyone made, or know of an easy way to make a template
for drilling Rohn 25 mounting holes?
I have one section of Rohn 25 that has a bend in the bottom
6 to 8" of one leg ... the tower came over in one of the
hurricanes to hit this area ... but it is otherwise in good
shape. I would like to shorten that section by one 'bay' and
use that section just above the new base (I already have a
base - otherwise I would bury this piece in concrete).
I would like to avoid drilling additional holes in the base
stubs but without some kind of template I will be drilling
blind. Any suggestions?
73,
... Joe, K4IK
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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