The crank on my free standing crank-up, tilt over tower failed with the
tower up at about 50 feet. The crank on the winch that raises and lowers a
Tri-Ex 54 foot tower failed, with the tower raised. The shaft that holds the
crank sheared - when I tried to crank the tower down.
I raise and lower this tower a minimum of four times a year. More often it
is five or six times a year when hurricanes threaten. The tower is 12 years
old and located in West Palm Beach, Florida.
The winch is a friction brake design. That is to say, the friction plates
release only while raising the tower, and brake even during the lowering
process. The tower weighs about 1200 lbs and holds a TH3MKIV, a rotatable
trapped dipole for 30 through 12 meters (WARC bands), a four element cubical
quad for two meters (SSB on two can be fun), and 2/440 Ringo Ranger on the
top. It also supports wire antennas for 160, 80, and 40 meters.
Given this is a three section tower, with two sections raised, my assumption
is that the raised tower sections and antennas weigh about 800 lbs, given
the two raised sections are progressively smaller than the bottom section.
The crank has about a 7 1/2 inches of throw - but from my point of view
should never be capable of generating enough torque to break the shaft. The
crank is also offset to allow it to turn past the outside of the tower.
The first thing I did was call Tashjian Towers Corporation, 2183 S. Highland
Ave., Sanger, CA 93657, Phone: 559-495-0307. They continue to manufacture
and support Tri-Ex towers. Karl answered the phone, and while he could not
provide any real guidance concerning how to replace the wench with the tower
in the raised position, he was able to ship me the replacement winch.
I next started sharing my plight with hams on two meters and HF looking for
ideas on how to go about safely replacing the winch. Several suggested a
cherry picker, others had plans involving using a car to pull a cable to
somehow lift the tower off the lower cable. Still others suggested
hydraulic jacks wedged between tower sections, or using a combination of the
above in conjunction with a gin pole. If you are winching at the various
suggestions, you can imagine my reaction. After all, ultimately, I was the
guy who had to solve the problem.
I finally settled on a set of bolts to attached a chain to the base of the
tower, a 2,000 lbs come-a-long, a 50 foot length of wire rope (cable) the
same diameter as the cable the winch was rigged with, and a dozen cable
clamps. I also place a four by six (dun-age) in the lower section, just
below the second section of tower, as a fail safe should the cable clamps
start to slip.
The concept was simple. I would attach a temporary cable to the permanent
winch cable with cable clamps and use the come-a-long to take the load off
the permanent cable with the temporary cable. Then with no-load on the
lower section of the permanent cable and winch, I would be able to unbolt
the winch, remove the cable from it, place the permanent load cable on the
new winch, and then install the new winch. I was then able to use the new
winch to lift the tower another six inches and take the load off the
temporary cable, so I could then remove the temporary cable and come-a-long,
and associated chain and cable bolts.
It took 30 minutes to rig, 10 minutes to relieve the winch of its load and
another 20 minutes to swap out the winch. It all worked perfectly - as a
one man operation. I have pictures if anyone would care to see them. I can
post them to the web.
A few tips.
Discuss this type of project at length with other knowledgeable hams. You
need to have a clear understanding of what you are doing before attempting
this kind of project.
Buy temporary cable with a lunette pre-installed. One less thing to worry
about.
Buy construction grade, high quality cable clamps. Avoid those available
from Home Depot or Lowes. Be especially careful to avoid stainless steel
cable clamps. The quality of the material is suspect.
I offset the come-a-long just enough to allow the new cable to be near the
winch, but not touch it, once the strain of holding the tower was taken off
of the main cable and shifted to the temporary cable. If the temporary
cable assembly touches the winch under load, you will not be able to
reinstall the winch (bolt holes will not align).
I figured two cable clamps would be enough, but used five.
I had plenty of extra cable, should it start to slip. I also had plenty of
extra clamps should they be needed. There was no way the tower could fall.
I placed substantial dun-age in the tower as a fail-safe against runaway
slip-age should I fail to tighten the cable clamps sufficiently.
I placed the yoke of the cable clamps against the permanent cable to prevent
damaging the cable from the "bite" of the u-bolts of the cable clamps.
I wore a hardhat, just in case something fell from the tower while I was
working below. Even a nut or washer could be deadly at near a terminal
velocity of about 120 mph.
Never fully raise your tower. If I had not had a few feet of vertical
travel to play with, my solution would not have worked so easily.
All queries and comments are welcome.
Terry - W6LMJ
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