[TowerTalk] [Bulk] Fwd: Attaching winch cable to Universal Tower

[Grant Saviers]

Kirk,

Another idea is to copy the Rohn 65 guy bracket concept.  There are 3 
u-bolts as shown in
http://www.solidsignal.com/pview.asp?p=GA65GD&utm_campaign=base&utm_medium=pla&utm_source=google_base&gclid=CIWE9JXIgcoCFUhlfgodlfAOXg

The concept is the load is transferred to the cross "Z" bracing directly 
with two "u-bolts", not thru the welds of the Z to the legs, or at a 
single plane.  Then the third u-bolt attaches to the leg.  Thus all four 
Z brace members are sharing any asymmetric guy loads and distributing it 
in tension to the other two legs at four points.  No accessory load 
sharing assembly is used on R65 to the max height permitted (500').  
However, the Z brace u-bolts are specially formed to fit, not available 
except from Rohn.  If you can figure out a way to bend some stainless 
rod with threaded ends to shape this might work.

While a 20' up and 20' derrick will reduce the lifting load, a 20' 
derrick is a pretty ambitious length for column buckling loading with a 
backstay.  Side guys are a must, IMO, maybe guys at 10' and the top.  
see http://www.engineeringtoolbox.com/euler-column-formula-d_1813.html 
for some concepts.  I think the derrick for my HDX589 is about 7' tall 
and is braced with 2x2"x.25" tube, uses 3:1 blocks and a serious winch 
that takes a lot of effort for a tower several times the lifting moment 
of what you are planning.

A small disagreement with Hans' - the bending moment on sections above 
is independent of the attachment height of the lifting cable.

Grant KZ1W

On 12/28/2015 16:22 PM, Hans Hammarquist via TowerTalk wrote:
> Hi Kirk,
>
>
> First: I suggest you attach the lifting cable between the third and fourth section (22-TARP and 18-TARP). That will minimize the load on the top sections and at the same time give you a better attach angle on the lifting cable.
>
>
> I am using a plate I custom made that fit between the sections. It has three holes, one for each leg. The legs of upper section fit rather precisely in the holes and at the same time the plate rest in the lower section. I attached the guy cables in other holes, drilled in the plate. That way the guying force is spread between the three legs.
>
>
> I was told that you should never attach a guy or lifting cable directly to a leg as you may pull off the leg from the cross member, some not good. If you want to put a wire to the tower, wrap the wire to include the cross member.
>
>
> If you check through the photos of my tower installations you find a photo of that plate:
>
>
> https://www.facebook.com/media/set/?set=a.10150198503693539.328964.579753538&type=1&l=b4a8463457
>
>
> I know it's not the cheapest way but I think it's one of the better.
>
>
> Good luck,
>
>
> Hans - N2JFS
>
>
>
> -----Original Message-----
> From: Kirk Kendrick <kmkendrick at gmail.com>
> To: towertalk <towertalk at contesting.com>
> Sent: Sun, Dec 27, 2015 10:34 pm
> Subject: [TowerTalk] Attaching winch cable to Universal Tower
>
> To those of you who have used aluminum towers:
>
> QUESTION:  What's the best method to attach a raising cable to an aluminum
> tower?
>
> I'm looking for ideas on how to attach a winch cable to raise and lower an
> HD 21-50 Universal Tower with about 100# of antenna gear at the top.  I'm
> worried that the forces during tilt up/down could damage or deform the
> aluminum tower near the attachment point. Anyone have a design of an
> attachment method/fixture that minimizes this risk?
>
> I'm NOT looking for a "temporary" solution (that is, no "lifting straps"
> that would deteriorate in the weather). The gin pole, winch, and cable will
> remain attached so the tower can be lowered (by one person) whenever
> needed. My hope is that the tower and raising fixture will be up for years
> of service.
>
> NOTE:  My plan is a raising fixture consisting of a 20' gin pole with back
> stay, winch bolted to gin pole, cable from winch through pulley at top of
> gin pole to an attachment point 20-25' up the tower.
>
> I'm sure some of you have already solved this attachment issue...and can
> share successes (& approaches to avoid)
>
> Tnx in advance,
> Kirk KK2Z
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