N4KG response follows background text.
............................................................................
On Mon, 13 Jul 1998 02:52:39 -0400 "Jim White, K4OJ" <k4oj@ij.net>
writes:
>
>An ever recurring topic......4 way guying!
>
>Usually it is for the same reasons, real estate space is at a premium.
>
>One possible solution to a space problem is:
>
>Have you thought about rotating your anchor points by 60 degrees? If
>rotating them by 60 degrees makes your landing points land within your
>yard's boundaries I would encourage you to do the following:
>
>Instead of guy 1 pulling out on leg 1 away from the tower, pass it
>through
>the tower so that guy one passes through the center of the tower and
>then
>exits between legs 2 and 3. You need to use care to make sure you are
>not
>riding on the cross braces when doing this.....I have seen this
>technique
>used many times. The only hard part is the top set of guys - if you
>are
>guying at the top of the tower this is impossible due to the mast
>being at
>the heart of the towers cross section. Alternative solutions for the
>top
>include fabricating a framework like Rohn uses for dish mount tops
>where
>the guys end up coming off at right angle to the face.....or possibly
>having six short lengths of guy wire, two for each face meeting
>several
>feet out from the tower, and those forming the point for the top of
>the top
>guy wire's run.
>
>snip<
>
>....from a mechanical engineering dropout:
>
>
>73,
>
>Jim, K4OJ
......................
AARGH !
Please DO NOT TRY THIS* AT HOME !
*THIS = guying THROUGH the tower.
Conventional guying (3 way OR 4 way) pulls out from the tower.
When a TORQUE (twisting force) is applied to such a tower,
the guy wires tend to oppose the twisting forces, pulling the
tower back to it's resting position.
When guys are run through the tower, the ONLY stable position
is if the guys are spaced EXACTLY 120 degrees apart, crossing
over at the exact center of the tower. When a twisting force is
applied to the tower, or the guys are NOT spaced exactly 120
degrees, the guys ADD to the twisting forces, exacerbating the
load borne by the tower legs and welds.
To picture this, make a drawing for yourselt. Draw 3 legs with
guys radiating out from each leg. Imagine a twisting force
applied to the tower. Notice how the guy tension increases,
opposing the torque.
Now, draw 3 legs with guys going through the tower. Imagine
a twisting force applied to the tower. As the tower rotates, the
guys no longer cross over at the center, but move away from the
center and the guy tension ADDS to the externally applied torque
helping to twist the tower even more.
de Tom N4KG
(Warning: This mechanical analysis was performed by an
Electrical Engineer :-)
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