[TowerTalk] Rohn Tower questions

[T A RUSSELL]

On Fri, 4 Sep 1998 19:05:40 -0600  thomas@cybrzn.com writes:
>
>Gentlemen:
>Have Rohn 25g tower on ground ready to erect. I have the GA25 Guy
>bracket with TB25 torque bars. The holes which are punched in the ends
>of the torque bars seem to have rather sharp edges and I think will
>chafe the guy cables in time. How does one attach the cable to these
>safely?
	First, you did not say whether you were going to use
	Preformed Guy Grips or cable clamps to terminate 
	your guys.  Guy Grips are THE way to go, easier to
	install and they do not work loose over time like clamps.

	Second, you will need to use a THIMBLE to prevent 
	chafing / cutting on the ridge and to maintain the
	MINIMUM termination radius recommended for
	the cable size.  For strength, it is best to use an
	oversized thimble (2 sizes larger  cable diameter).
	This will prevent "crushing" of the thimble and is
	necessary even with a shackle.  

	The ONLY benefit of using a shackle is that you 
	can easily disconnect the guy from the bar, but 
	then if you really want to remove the guy, it is 
	easy to disconnect the bar from the guy bracket. 
	Shackles are EXPENSIVE and you will still need
	a THIMBLE to maintain the proper radius for the
	termination.   I see no benefit to using shackles
	on the torque arms.       de   N4KG
	

>Also, I have a 4' piece of standard 25 tower section which I intend to
>embed in concrete for the base. Any problems with this?
>Can someone tell me which zone I am in for wind loading (60 mi. 
>straight
>north Green Bay, Wi.) Will 3/16 EHS work?

	There must be thousands of towers imbedded in
	concrete.  How tall will the tower be?  If you are
	planning a TALL tower (>120 ft) and lots of side
	mounted antennas, a base plate on a concrete
	pad is best.  I have heard of  heavily side-loaded	
	towers shearing off at the base in very high winds.
	(Well, one 200 ft R45 tower with 4 -  20M beams
	on 32 ft booms side mounted on it.)  The tower
	survived and additional above ground concrete
	was added.  Base in concrete works fine for
	shorter towers.  It helps to form the concrete
	to be above ground and to round off the top	
	for drainage.  Dirt around the legs will retain
	moisture and eventually lead to corrosion.
	NOT a fun thing to realize after 20 years in
	the ground. (come see mine if you are in doubt!)

	The MAXIMUM recommended spacing between 
	guys on Rohn 25 is 35 ft.  Most people install
	a set of guys every third section.   At this spacing,
	3/16 inch EHS works fine.    de  Tom  N4KG

>Any comments would be appreciated.
>Tom Hellem K0SN
>Porterfield, Wi.

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