Your math looks ok; but this is without any wind blowing on the structure!
What will the forces be with 70mph winds?
73/k5gw
In a message dated 7/30/2008 11:18:00 P.M. Central Daylight Time,
K8RI-on-TowerTalk@tm.net writes:
Dan Hearn wrote:
> Dennis: You will find different opinions here on many subjects however I
> believe there is almost uniform opinion on guying crankup towers. Don't do
> it. That puts additional stress on the lifting cables when horizontal force
> is applied to the tower. 73. Dan, N5AR
>
>
(If I did the math correctly)
Think of it this way. Each 1/4" guy wire at 440# tension (10% of 4400#
strength) and 60 degrees at the anchor = 30 degrees angle at the
tower. Neglecting the weight of the guy = 440*Cos(30) = 381#. There are
three guys per level so that would be 1143# vertical load added to the
tower and on the raising cables.
Say a second set at 45 degrees = 440#*Cos(45)= 311# or 933# vertical
load added, so adding just two sets of 1/4" guys properly tensioned will
add 2076# vertical load to the tower and cables. IOW adding guys to just
two levels that move adds over a ton of load on the cables. Using steel
guys would also add additional weight from the cables as would larger,
stronger guys.
The strength of wire rope varies over a very wide range which makes the
selection of the cables a primary consideration and pretty much
eliminates what you find at the corner hardware, or big box store
although the hardware store could likely order it to spec. This is also
why it's important not to oversize the guys on a tower.
73
Roger (K8RI - ARRL Life Member)
www.rogerhalstead.com
N833R (World's oldest Debonair)
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
**************Get fantasy football with free live scoring. Sign up for
FanHouse Fantasy Football today.
(http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020)
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|