[Top] [All Lists]

[TowerTalk] Crank-up Horror => crankup use model

To: <>
Subject: [TowerTalk] Crank-up Horror => crankup use model
From: Dick Green" < (Dick Green)
Date: Wed, 10 Jun 1998 17:30:28 -0400
>My new question is:
>How often do you RETRACT the crank up, and for what reason(s). (My permit
>conditions indicate that they should be cranked down "when not in use". Do
>others have this condition?)


I have a U.S. Tower 70' base-rotated tubular (don't show the town a picture
or they'll instist you put one up -- some people like the slender
"mast-like" appearance.) Fully extended, the tower is rated for 10 sq ft at
50 MPH and I have a 9.5 sq ft TH7DX on top. At 70 MPH, the tower rating
drops to less than half (possibly as low as 2.5 sq ft.) Also, the tower
sways quite a bit when gusts get much over 20 MPH.

For that reason, I normally leave the tower at 50 feet. The TH7DX works very
well for general communications at that height, and the tower is much more
stable. It hardly sways at all when the wind is less than 30 MPH and I'm
sure it would handle the max winds for our region (70 MPH). Still, when the
wind gets much over 25 MPH, I lower the tower all the way. Fully nested, I'm
sure it could withstand 100 MPH+ winds (the antenna would disintegrate
before the tower would fail.)

I only put the tower up to the full height for chasing rare DX (weak signals
and/or a huge pileup) and when making a big contest effort -- but still only
if the winds are below 20 MPH. I never leave it fully extended when I am not
home, and I check  the weather forecasts and my annemometer religiously to
make sure it's OK to leave it at 50 feet when I'm not home.

The town's mandate that the tower be cranked down whenever it is not in use
is both impractical and unsafe. Although there may be some who do it,
cranking a tall tower up and down with a hand winch every day is simply not
practical. I believe one person on the reflector said it took over 400 turns
of the crank to raise or lower his tower. You're going to look like Popeye
the first week! Seriously, it will quickly become a major drag for you and
will probably cause you to use the radio less often. As for safety, cranking
the tower up and down every day will most certainly wear out your cables and
pulleys faster. That will require more frequent replacement, which can be
costly and time consuming. If you are not careful about doing inspections
more often, the increased wear could lead to a tower failure.

This is why I have a motor on my tower (and because it's 250' away from the
house.) I don't want laziness to disuade me from cranking the tower down
when a storm kicks up. If you add up the U.S. Tower prices for what I have
described (plus a tiltover fixture), you will see that a practical and safe
crankup system costs several times as much as a guyed tower for the
equivalent wind load.

Other comments: 1) I don't believe you've shared your wind load and weight
requirements with us -- what are they? 2) You don't need two holes for a
crankup base, only one (but it's true that the amount of concrete needed is
greater than for a guyed tower at the same wind load rating.) 3) You can't
side mount antennas on a crankup. 4) You do have to woory about cranking the
tower down when the wind blows, and 5) You will need some sort of
crane/towtruck/boomtruck/backhoe/excavator and a flatbed or semi for the
tower when you move.

73, Dick, WC1M

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>