Added notes for thoughts.........
-Using the tower cranked down for storm watches, etc., makes the tower very
much more rigid as well as stronger; however, all down and rigid puts all
the wind load on the mast above the tower. Some "up tower" flexing is
eliminated so the only thing left to flex is the mast........ which may get
more flexing than it can stand. Be careful.
-Climbing a crank-up is not to be done due to the added stress on the
raising cables and the falling of the human if that breaks. If you must
climb, do not, but my installer puts 4X4 timbers through the tower at each
joint on the way up. I had my tower fall due to a crank motor failure,
which is something to witness you just do not need. The fall is
spectacular.
-Do not guy a free-standing tower that is designed to be free-standing
because even correctly tension-ed guys will place significant additional
pull down stress on the raising cables, increasing the tower load or adding
load to other type fixed towers. Do not use flopping less-tension-ed guys
due to the whip lash in the wind.
-I use the stop switches top and bottom /fully up and fully down, but watch
the "going up" especially due to not wanting the tower to crank itself up
so far as to come apart. A well designed raising winch with a screw drive
will provide good breaking without an additional break. Replace the gear
box lube due to water incursion over the year.
-Remote up and down, controller inside the shack, sounds wonderful on an
icy day (like Canada note), but I just can not trust that system even on an
unusual ice-free day in Thailand. Maybe you can.
-Use a "positive pull down" winch motor system. Otherwise, like the HyGain
tower without this, even a mild wind can keep the tower sections from
COMING DOWN. That is a disaster because the stuck up (yes it is stuck up)
sections will loosen the drive cables and with a small lessening in the
wind, will allow the tower section to fall and likely break the cable (or
at least will give a smart snap to yagis above). Go out and crank such a
tower down PRIOR to wind and watch for cable slacking. When I saw this the
first time, my body tensors tensed considerably.
-"Hardline" coax is not suitable for crank-up towers because it is not
flexible enough. There are flex brands of hardline, but otherwise, avoid.
Email to me if you are preparing to open any bell-type HyGain rotor. That
is BEFORE opening.
GL, 73, HS0ZCW, Charly (without Whiskey, but catching some zzz's.)
On Mon, Dec 26, 2016 at 8:57 AM, Charles Harpole <hs0zcw@gmail.com> wrote:
> Good question.
> My experience is with TWO 70ft crank up towers, HyGain and US Towers, both
> motorized, over 28 years I used the stand-off arms at the TOP of each
> section to allow full retraction.
>
> I routed the bundle of coax-s and rotor cable through the rings at the end
> of the stand-off arms freely up to the very top of the tower where it was
> taped to the tower fully. The rotor cable went out of the bundle to the
> rotor there.
>
> The coax bundle, taped together, formed a modest coax rotor loop, only
> long enough to allow full rotation and not droop down and wind up on the
> tower top. (Some Yaesu rotors require a larger loop for 450 degrees of
> turning.) The coax is then taped to the mast and on to each antenna
> upward.
> This method puts the load of the down-going coax bundle on the top tower
> tape attachment because the rest of the bundle is free through the
> stand-off arms. Do not use an arm to rotate along with the mast due to
> complicated loop flopping around badly.
>
> For a while, I did measure the coax bundle and tape it firmly to each
> stand-off arm, allowing for full extension, but I found the coax could, and
> did, flop inside the tower as it came down, endangering the coax... thus I
> left the best method be free all the way downward.
>
> I use wide, black cable ties on top of the tape, snugging it so as not to
> deform the coax. I keep the coax-s taped together full length.
>
> Works with 70ft tower also. 73, Charly
>
> On Mon, Dec 26, 2016 at 2:04 AM, Jim George <n3bb@mindspring.com> wrote:
>
>> I've had a three-section crank-up tower (it used to be called the LM-354)
>> that's 54 feet tall when fully extended. For a long time, I used it in a
>> permanent fully-extended manner, with phased ten meter yagis at the top and
>> half-way up. Now, it will have a triband yagi and a two-element 40 yagi on
>> it, above the thrust bearing, and I wish to keep it at least semi-nested
>> between contests to avoid storm damage. What is the recommended way of
>> bringing down two the coax feedlines and the rotator cable for a tower that
>> will go up and down fairly regularly? I'm going to use the three original
>> "stand-offs" to keep the coax and the rotator cable hanging vertically as
>> these three standoffs are positioned such that they nest properly when the
>> tower is down. Is it okay simply to hang the feedlines and the rotator
>> cable down through the top standoff, which seems to rotate around as the
>> rotator moves the mast, and simply let the coax and cable drop down
>> vertically? In this case, there would be no traditional rotator loop. That
>> configuration has worked okayrecently with only the small 40 meter yagi on
>> the top.
>>
>> Another possibility would be to form a five or ten foot "rotator loop"
>> with the feedlines and rotator cable and then route them back up onto the
>> top standoff and down vertically through the other two. In this way, the
>> system would not require that top standoff to move around on its tower leg
>> as the mast and antennas rotate. Not sure if I described this in a clear
>> way. If I were sure that the top standoff would move around on its tower
>> leg, that would work, but if the top standoff got stuck and didn't move,
>> then the feedlines and rotator cable could get stretched and damaged. For
>> some reason, I haven't seen anything on this, or have forgotten. Any
>> recommendations?
>>
>> Thanks in advance, and all the best at the Christmas and other holiday
>> breaks and new year.
>>
>> 73, Jim George N3BB
>>
>> _______________________________________________
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>>
>
>
>
> --
> Charly, HS0ZCW
>
--
Charly, HS0ZCW
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