<< In a message dated 4/29/01 10:47:13 PM Pacific Daylight Time,
steve@oakcom.com writes:<<
"Mike Wetzel" <w9re@worldnet.att.net> wrote:
>Can anyone point me to a picture or diagram that has a mast to boom
mount
>that will allow the boom to tilt over so that the elements on the ends
of
>the boom are accessible from lower on the tower? I plan to have a 48'
boom close to the top of the tower that I'd like to tilt and be able
to reach an
>element on each end of the boom. The tower is R55 with a stock flat
bearing
>top plate, mast is 3" o.d.
A heavy duty tilt mount can be made from two pieces of steel
channel, four bolts & nuts, & two u-bolts.
Exact dimensions depend on antenna and boom size of course.
The channel should have deep non tapered flanges to allow
fairly close fit. If you don't have a close fit the gap
can be taken up with washers.
IMO the bottom channel is best welded to the mast, but if
this isn't possible, an additional vertical piece welded
to the bottom of the lower channel would facilitate
attachment to the mast with u-bolts.
I scribbled out a crude drawing and posted it as
tilt_mount.pdf at:
http://www.oakcom.com/images/
73,
Steve K8LX >>
In 1958 I needed very this design. A special irrigation clamp was
available in Seattle that enabled me to build this very design all of
aluminum with a hack saw and a drill. I think I can still get them.
Inaddition to being able to tip the boom, I could also twist it without it
slipping.
I needed a way to
1. Install a beam all "by my self" and even with some wind instead of the
usual Saturday morning antenna raising party if weather and people permitted
and
2. Be able to adjust the element tips easily.
The procedure I worked out was this for say a 3 element beam. The boom
was pulled up by rope by hand or a secured pulley and attached to the mast
plate 3/8" pivot bolt. The boom is tipped to the tower, an element is pulled
up and attached. The boom is tipped to the other side by a rope previously
attached to the top of the boom. Another element is pulled up and attached.
The rope is detached and the boom is leveled and 4 bolts secure the boom
mount to the mast Aluminum Plate. The DE is pulled up and attached to the
boom. I have elements mounts I made that are previously aligned. I've done
it in 20 minutes or less many times. With help you only need 1 rope and it's
even quicker. I've done it in just a street light. If there are guy wires,
the boom is twisted so the element can be slipped up and under or away from
them. The mast is oriented is such a way the boom misses the guys. It works
great as the pictures in the original article show.
The article on this mount and procedure appeared in CQ about 1962 +/-
called "One Man Universal Joint Mount". It can be found in the December
indexes. My mags are still packed and I'm not sure on the exact date--only
the Title. I just sent the idea to Barry Briskman editor of CQ at the time
for his use and he prints it. It's a great idea and I've made about 50 of
them over the years. I have heavier duty models now I've used on 44' booms.
I plan another article on this--when I get time. I have a Nikon Digital 990
camera now and will take some pictures and sent you some when I get a color
printer.
I've been waiting to see who would be the first to asked for and see the
full advantage of this design since 1962. You lucked out. "I've been there
and done that." My 7 element 10M beam took 30 minutes--all by myself. The
ease and speed of which I can install a beam has enabled me to quickly
replace and try beam after beam or adjust element lengths safely without any
help from anyone at any time which I did most of the time. I know of no
other such design.
I had a HyGain 2 element beam center loaded one time and one of those
blue insulators shorted to the boom and caught fire. Half of the element
would soon fall to the roof and unbalance the antenna. I zipped up the tower
without a small fire extinguisher and in 30 seconds tipped the boom down to
the tower. I played "Fireman" and peed on the insulator. I then removed
that element for repair in 5 minutes. I still have the burnt insulator.
I've made this design for 1 1/4" -- 6" booms. K7GCO >>
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