Dan wrote:
>
> Ken,
> As an engineer, I can assure you that these fellows are giving you good
> information--the maximum stress on your mast will be at the point it exits
> your tower. The use of an aluminum mast as you describe would be
> considered poor practice (poor engineering, if done by an engineer). You
> may be lucky. If not, the penalty is very high--those antennas are very
> difficult to remove from a bent mast. If aluminum would work in your
> application, these guys wouldn't be spending big bucks to get the chrome
> moly masts. You can get a program called MARC from Tower Tech which will
> make the calculations for you--it's cheap (about $10). (Tower Tech is
> owned by Steve, the guy who runs this reflector.)
> 73,
> Dan
>
> Dan Long (W4TQ)
> 8035 Tokyo Pt.
> Dunnellon, FL 34433
> e-mail: ad4hw@citrus.infi.net
> phone: 352-563-0934
>
> ----------
> | From: Ken Fisher <kfisher@inreach.com>
> | To: T. A. Russell <n4kg@juno.com>
> | Cc: towertalk@contesting.com
> | Subject: Re: [TowerTalk] MAST
To: <towertalk@contesting.com>
> | Date: Tuesday, October 07, 1997 6:52 PM
> |
> | T. A. Russell wrote:
> | >
> | > See additional question at end - de N4KG
> | >
> | > On Tue, 7 Oct 1997 10:15:20 -0700 Ken Fisher <kfisher@inreach.com>
> | > writes:
> | > >> | >I have attached a url with a pic of my stacked beams klm 20m-6
> | > >with
> | > >> | >a klm 40m-4 over it. The mast is aluminum t-6061 3/8 wall 14'
> | > >sticking
> | > >> | >out of the tower. No problems Cost was appx $130 for the mast.
> | > >Ken
> | > >> | >W6FK
> | > >> |
> | > >> | If that is a 2" O.D. 6061-T6 mast, my calculations predict
> | > >> | failure at 55 miles per hour if the wind is in line with the
> | > >> | two antennas. You have been lucky so far.
> | > >> |
> | > >> | Dave Hachadorian, K6LL
> | > >> | K6LL@juno.com
> | > >> |
> | > > If you look real close you will see steel guys from
> | > >the boom ends on the 40mtr beam down to the mast
> | > >just above the 20mtr beam. This is my margin of safety
> | > >and with the top guying on the 40 gives a nice diamond
> | > >effect of guying. Ken
> | > >
> | > >--
> | >
> | > The maximum bending moment will be at the exit point of the tower.
> | > Please explain how guying the boom of the TOP antenna on the mast
> | > back to the mast provides any margin of safety.
> | >
> | > de Tom N4KG
> | >
> | > --
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> | > Submissions: towertalk@contesting.com
> | > Administrative requests: towertalk-REQUEST@contesting.com
> | > Problems: owner-towertalk@contesting.com
> | > Search: http://www.contesting.com/km9p/search
> |
> |
> | My concern is the aluminum mast breaking half way between the
> | 20 mtr beam and the top. Thats why the guys are used. I have no
> | fear that the mast will break just coming out of the thrust bearing
> | or even two feet up where the klm 20m6 resides. This would take
> | one hell of a wind I feel in excess of 55mph and we dont have forces
> | like that in central Ca. Ken
> |
> | --
> | FAQ on WWW: http://www.contesting.com/towertalkfaq.html
> | Submissions: towertalk@contesting.com
> | Administrative requests: towertalk-REQUEST@contesting.com
> | Problems: owner-towertalk@contesting.com
> | Search: http://www.contesting.com/km9p/search
It is t6061 3/8 wall mast, its made it two years so far
without a hint of a failure. I guess thats why Im not an engineer.
Ken
--
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|