Ken, From whatever cause, when a cable fails it can be dangerous and
expensive. Some failures take place when the tower is not being raised
or lowered. Irrespective of the cause of this static failure, if the
tower sections were "safed" then damage and danger would be averted.
My current tilt-over/crank-up has only one movable section and my
current refurb action includes adding a lock to take the strain off
the cable and the pulley (which I am changing out for a larger
diameter.) I'm not an ME either but I think keeping the pulley
bearings loaded all the time can't be good for their life span.
By increasing the pulley diameter I hope to reduce wear on the cable
making the turn.
73,
Patrick AF5CK
-----Original Message----- From: Ken Beals
Sent: Sunday, June 16, 2013 5:58 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] How to apply lube to HDX589
Been following this thread with interest even though I donb
Here is a question for the MEs in the group from a decidedly
non-mechanical EE: Why would bthe life of the cable? Since the only
wear mechanism I see is the flexing of the strands and the internal
friction when the cable bends over the pulley when moving. I can only
relate a stationary cable to those used on suspension bridges. Those
seem to last a long time. So I canbadvantage of section locks with
respect to cable life.
I installed towers for a while when I was much younger and I remember
that Tri-Ex had an option to add locks to both guyed and self
supporting crankups They were different since their guyed towers
raised one section at a time rather than all sections equally as a SS
tower does.
Ken K6MR
From: Doug Turnbull
Sent: bTo: 'Patrick Greenlee', towertalk@contesting.com
Chris,
In my experience there was a single brake at the lowest and therefore
stationary level. This counterweighted flap merely takes the strain
from
the lowest wire rope and most importantly from the winch. Some of us
may
add additional stops by carefully climbing the tower and inserting steel
bars on heavy duty rectangular cross arm bracing - obviously such a
tower is
not lowered in a storm.
At this QTH one such tower is stayed as per the manufacturer's
specification - my additional rest / brake between the second and third
section are additional. Imagine the problem which might occur with a
five
section tower using strings to release multiple brakes.
Removing the entire weight of the upper sections from the winch and
lowest rope though makes good sense.
I am not recommending my approach to anyone else. Great care is
taken
when inserting the additional steel bar between the second and third
sections. The larger tower has three sections which are forty foot long
and the manufacturer insisted on stays. I did not intend to ever
depend on
the wire rope when stays increase downward loading.
Why a crank up then. It make is much easier to work on the
antenna and
greatly reduces climbing. I have a bad back and it is not wise for
me to
be up top. Fact is these days I use a rigger.
73 Doug EI2CN
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
Patrick Greenlee
Sent: 16 June 2013 12:51
To: towertalk@contesting.com
Subject: Re: [TowerTalk] How to apply lube to HDX589
*******************
If upper sections also have locks, how is the disengagement cable that
operates the locks managed? Since the tower gets taller, there would
be a
lot of cable that needs to play out as it goes up. How is that kept from
tangling up?
Chris
*****************
Chris, I have a rag sailor background and we lived aboard our sailboat
for 9
years. As you can imagine, minding all the running rigging, ground
tackle,
etc. is not a trivial task and is important to get right and can be life
threatening when fouled up.
A UV resistant very open weave cloth bag to hold the tail of a line
(one per
line) can be real handy. Rain water will not collect in it and permits
moisture to dry out. You just stuff the long line tail into the bag
in FILO
fashion (First In Last Out) and when withdrawn from the bag it virtually
always comes out freely with no tangles.
I can think of hands free systems to take up the slack and pay it out
automatically but they look like they were designed by Rube Goldberg.
Patrick AF5CK
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