[TowerTalk] Mast Extentions

Jim Reid jreid@aloha.net
Mon, 31 May 1999 07:15:34 -1000

Aloha Dick,  You wrote:

> First off, I would call U.S. Tower and/or your dealer and 
>ask their opinion.

I have;  Joel at First Call Comm will be contacting Bruce at
US Tower after the holiday about this issue.  Have also
asked for the price of the 0.25", 20 foot Chromolly mast.

> If they won't comment, I'd have a PE study the question. 
>This will cost some money, but so would replacing a 
>collapsed tower (and you've already had that unpleasant 
>experience!) Seeing how much my MA-770 with a TH-7 
>directly on top sways in a 15 MPH wind, I wonder what 
>15 feet of mast will do to your  new MA-550. The 
>calculation may say that's equivalent to increasing the C4
> windload to 10.8 sq. ft., but I have a feeling there might 
>be more to it in this case. I would be very concerned that 
>the 2" square top section tube would not stand up to the 
>torque of the C4 on a mast 15 feet above it.

> Another question is whether the mast adapter on top of t
>he tower can handle such a long and heavy mast (mine 
>only has a couple of retaining screws, which would seem 
>inadequate.) I'd also be concerned about the extra weight
> on the raising cables.
> 73, Dick, WC1M

Oh wow,  Dick,  you may just have raised the questions,  the
answers to which will quench this mast idea!  Here I thought
I had come up with a way to get up to 65+ feet or so with
the MA-550.  And yes,  I do recall from long ago that at
the top of that square final section up there are just a couple
of set screw bolts,  which I have used to hold a couple feet
of pipe onto which the C4 mounting plate hardware is attached
on the now collapsed 550.

Well,  Burce at US Tower will respond in time I am sure.  He
will be asked about this set up after the holiday by the dealer
through which I am ordering the new 550:  Joel at First Call
Communication,  a really very nice and helpful guy,  I have

And here I was just about to post some questions about
the use of a crane to get this all set up.  Lost some sleep
last night trying to understand how whatever the crane
operator uses to pull the mast up 15 feet above the tower
top would be disconnected!!  Seems somehow someone
would have to get up there to unhook something.  Also,
how does a crane connect to a 2" diameter pipe and pull
it up?  Now such answers may be moot,  hi.  Of course,
would also use the crane to remove/replace the 550 and
antenna on top as long as it was going to be here.

73,  Jim,  KH7M

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.htm