>From your description, I *assume* your 24 ft mast
that resides above the mast for your 15M beam
is THIN WALL ALUMINUM (a fact you neglected to state)
and NOT a THICK WALL STEEL MAST.
FWIW, we use the opposite approach at Field Day,
inserting 20 ft 1-1/4 inch masts for our 80M antennas
*inside* the short masts for the 20M and 15M antennas.
Tom N4KG
On Wed, 16 Oct 2002 03:12:55 +0000 Dan Robbins <kl7y@alaska.net> writes:
> My 160m inverted vee hangs from the top of a 24' mast. The latter
> sits
> on top of a 125' 25G tower. There is a mast (from rotator) sticking
> up
> about 5' through the thrust bearing on top. A Hy-Gain 155CA beam is
> on
> that mast, just above the thrust bearing. The 24' mast rests on the
> Hy-Gain boom to mast bracket and is sleeved over the rotator mast
> for
> about 4 feet. (The 24' mast does not go into the tower.) To install
> that, not only did the entire 24' mast have to clear the top of the
> tower, but it had to go 5 feet higher to clear the rotating mast
> that it
> had to slide over. No problem for a regular 12' Rohn gin pole....
>
> All you need is a counter weight. With a counterweight and a 25'
> rope
> dangling from the bottom of the 24' mast, I was able to tie the gin
> pole
> rope only 6' from the bottom of the 24' mast. There was 18' of
> free-swinging aluminum mast above the gin pole rope tie-off, 6 feet
> of
> mast below, 25' of rope hanging down and then a hefty counterweight.
>
> With that set up there was no way the mast is going to point any
> other
> direction than straight up. It was actually pretty easy to do and I
> did
> the same procedure when I had to remove/re-install the mast for
> maintenance on the pulley at top. The only real problem was my
> ground
> person who whined about hauling up the heavy counterweight. Of
> course,
> I had to stand on top of the thrust bearing plate (or the boom) to
> reach
> that high, but that's why I buy flat tops instead of taper tops.
> Personally, installing this mast feels a lot safer than wobbling
> around
> on 2 or 3 unguyed sticks of 25G while the section with the guy wires
> comes up the side. Of course, we checked out all the weight and
> balance
> several times before hoisting the thing up.
>
> For those interested, the 24' mast is not secured. The 5' of mast
> inside holds it upright and the weight of the inverted vee keeps it
> pressing down on the boom to mast mount. The 24' mast will
> ocassionally
> wind up a half turn of top rope as the rotator turns, but any breeze
> unwinds it right away and there has never been a problem there. The
> mast is wearing down a bit, and also eating into the boom to mast
> mount. But it has been up there for at least 15 years and the wear
> is
> maybe 1/8" on the mast and less on the mount. I will wear out before
> it
> does. Getting the 160m antenna up above the beam and away from all
> the
> metal of the tower and guy wires really seemed to help the signal
> more
> than expected from just an increase in height.
>
>
> Dan KL7Y
> _______________________________________________
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>
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