I think it is important to distinguish between when guys are needed to
support the tower structurally and when they are needed with a trailer
mounted tower for turnover resistance beyond what the outriggers
provide. I also doubt rebar anchors will have any significant benefit
in either case for a 70' tower.
At Visalia DX conference the past few years a 89' US Tower HDX589 (or
maybe the 106') was in use for the convention station. The outriggers
are substantial, about 14' long. The tower is set up to be guyed as it
has the locking swing arm blocking tabs at each level. A non-locking
crank up should not be guyed above the bottom section. The hoist cable
isn't rated for the vertical component of the guy loads. I don't have
the specs, but assume the outriggers are good to xx wind speed, so for a
left in place unattended use, it would be need to be guyed to prevent
turnover at the HDX589 rated loads. Otherwise, it seems to me that the
tower is rated the same as the stand alone equivalent crank up if
mounted to the specified concrete base/base plate.
I've been through similar turnover calculations for a heavy duty 42'
Will-Burt pneumatic mast (non locking) I mount bottom section guyed to
my truck bed. The mast at full rated load (60mph gust, 8 sq ft) will
flip over my 3/4 ton 8' bed HD pickup, so down it comes at 30mph wind
speed. I also have a trailer mount with 5' long 2" sq tube outriggers.
The capacity is a little bit more before the outriggers will bend.
Grant KZ1W
On 7/13/2018 7:14 AM, jimlux wrote:
On 7/13/18 6:11 AM, W0MU Mike Fatchett wrote:
The problem with the trailer is that it should be "guyed" in three
directions 50 ft from the front and the outriggers. I have not found
the original owners manual so I am not completely sure how effective
the guys really are. I found a great manual online that a club put
together for their Field Day ops. They drive rebar in the ground
with a washer welded at the end for the tie offs.
Speaking cynically, I think those "stakes in the ground" are more to
provide a secure anchor point for the guyline so that it holds up when
someone trips over it in the dark. And to mark the approximate "fall
radius" for the tower, so you can make sure you don't set up an
operating tent within that radius.
I doubt they have any signifcant pull-out strength, so if the wind
comes up, the stake will bend, pull out, and over the tower goes.
*real* temporary installations designed to withstand significant wind
(or seismic) loads will use auger screw anchors, or these days, I've
seen a lot of use of "big blocks of concrete" or K-rail/jersey
barrier. The truck drives up with the rented weights, a crane or
forklift puts them in position, and you're done. The purpose designed
weights are about 5000 pounds, with a big steel loop on the top to
attach a guy to. They're roughly a cubic yard in size.
You could probably also use FIBC (Flexible Intermediate Bulk Carrier)
bags full of gravel as weights. They are also in the 5000 pound range.
They're surprisingly inexpensive to rent - $5/day kind of numbers.
It's the delivery cost that might be pricey.
W0MU
On 7/12/2018 8:15 PM, john@kk9a.com wrote:
With all of the HOAs, I'm guessing that this would be more valuable
on the
trailer.
John KK9A
To: towertalk@contesting.com
Subject: [TowerTalk] Mobile Tri-ex 70 tower
From: W0MU Mike Fatchett <w0mu@w0mu.com>
Date: Thu, 12 Jul 2018 18:08:20 -0600
Can you remove the tower from the trailer and mount these on a concrete
base?
W0MU
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