[TowerTalk] Strength of installation raising cable for the LM470?

[Don W7WLL]

The 1/4 inch 7x19 SS 304 cable breaking strength I bought for use is 6400 
lbs vs 7000 for 1/4 inch 7x19 galvanized aircraft cable, more than ample for 
my need.  I would not call that difference 'one helluva lot less' unless you 
are referring it to wire rope (winch cable), what the trade calls wire rope, 
which is rated at a lower breaking strength and typically is a 6x9 or 
similar wrap and a lower grade steel. You must know what the cable wrap 
construction (e. g., 1x19, 7x19, 7x7 etc) and wire composition is to 
determine breaking strength vs generalizing.  And there are many different 
wraps and wire compositions out there from the rope/cable manufacturers, 
especially for wire rope. For my crankup tower. I procured my cable through 
the local marine rigging shop in Newport who services the OR central coast 
fishing/crabbing/trawling fleet. These are experienced riggers who deal with 
similar situations all the time. You don't want cable failure on a trawling 
net at sea or on outrigger towers and there is a lot of SS cable at sea.

The comment on the crankup tower attachment point was of interest. I have a 
HyGain HG-70HD which did not come with a welded tower raising ear. Same for 
my TriEx WT-51. Both bottom sections are roughly 21 feet. Using the fixture 
I built with a dual pulleys at the tower and the fixture I set the raising 
point about 16 feet up from the bottom of the HG-70HD. In the HyGain 
illustration it appears to be set about 1/2 way up (10 feet up from the 
bottom). Curious where others have their raising point on a typical 70/90 
foot crankup bottom section. My raising fixture looks a lot like the TRX-80.

Don W7WLL

-----Original Message----- 
From: Jim Thomson
Sent: Saturday, August 27, 2016 9:42 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Strength of installation raising cable for the LM470?

Date: Sat, 27 Aug 2016 19:26:47 -0400
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk at tm.net>
To: "towertalk at contesting.com" <towertalk at contesting.com>
Subject: [TowerTalk] Strength of installation raising cable for the
LM470?

When installing the LM470 using the raising fixture, the retracted tower
is raised from horizontal to vertical.  The cable attaches to the tower
roughly half way out presenting one whale of an initial load on the
cable and winch.
K8RI

##  On the UST towers, the cable attaches to the tower, ALMOST to the TOP of
the very bottom section.  Galvanized .25 inch  winch cable is rated for 5700 
bs.
.25 inch SS  cable is rated at one helluva lot less.   .25 inch galvanized 
aircraft cable
is rated at 7000 lbs  bs.  Although galvanized winch cable  looks identical 
to aircraft
cable, the BS ratings are vastly different.   .3125  or  .375 aircraft cable 
is even stronger
of course.   2-4  pulleys will take the stress off of any cable used.

##  UST welds a small rectangular steel plate to one tower leg, with a hole 
in it. Welded
on all 4 x sides.  IMO,  it would be nuts to terminate the cable only  1/2 
way  along the
bottom section.   You might want to re think what they have done,  esp if 
laying the
tower over, with a mast, rotor,  ant on top.

Jim   VE7RF

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