Gerald,
I believe you should divide by the cosine instead of multiply. Also then
you need to divide by two because the load is shared by two guys. Doing it
this way will show that the four guy system is stronger.
Heinz/NR0X
----------
> From: Texas RF <TexasRF@aol.com>
> To: wa9eka@worldnet.att.net
> Cc: towertalk@contesting.com
> Subject: Re: [TowerTalk] GUYING
To: <towertalk@contesting.com>
> Date: Friday, March 13, 1998 7:15 AM
>
> More on the three way vs four way guying question.
>
> WORST CASE load on the anchor is when the wind blows from the same
direction
> as the anchor (one anchor takes ALL of the wind load). This is the same
in a
> three way or four way guy ststem. By definition, all other wind
directions are
> NOT worst case as the wind load is reduced on a given anchor and
increased on
> the nearest adjacent anchor.
>
> The amount of force on the two adjacent anchors can be determined by
> multiplying the wind force by the cosine of the wind angle relative to
the
> anchor angle. This is the case in any guy system, three way or four way.
For
> example, assuming a 1000 pound wind force, in a three way guy system, if
the
> wind is 30 degrees off anchor #1, the cosine of 30 degrees is .866 and
the
> force on anchor #1 is 866 pounds. At the same time, the wind force on
anchor
> #2 is cosine of 90 degrees X 1000 lbs which is 707 pounds.
>
> Example #2, same wind force on a four way guy system, anchor #1, cosine
30
> degrees =.866 X 1000= 866 pounds. Anchor #2, cosine 60 degrees=.5 X 1000=
500
> pounds load. In this case the load on anchor #2 is less than in a three
way
> system but the load is trivial compared to the design strength of the
anchor.
>
> If you were to plot out the loads on the anchors on a piece of graph
paper you
> would see the shape of the plot to be the familiar sine wave that we
encounter
> so many times in our study of electronics theory. In the anchor case, the
> curve is shifted 90 degrees (that is why it is a cosine function). You
will
> recall that the curve is somewhat broad on top and falls rapidly down the
> sides as you go through the various angles from 0 to 90 degrees. The
forces on
> the anchors also follow the same shaped curve.
>
> Anchor forces are essentially the same in a three way or four way system.
You
> still have to design the anchor for the same worst case loads. Any given
> anchor will be "loafing" when the wind is blowing in the opposite
direction
> plus and minus 90 degrees to the anchor. This is the same for a three way
or
> four way system. In either system the wind load is never applyed to more
than
> two anchors at any given time as all other anchors are in their "loaf"
zone.
>
> Hope this is of interest to some and helps clarify the three way versus
four
> way guy question.
>
> Tnx/73 de Gerald, K5GW
>
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