[TowerTalk] Mast Extentions

Dick Green Dick Green" <dick.green@valley.net
Mon, 31 May 1999 04:02:37 -0400

> However,  I am thinking about ordering a "chrome-molly"
> (if that is the correct term)   mast to increase the full-up
> height from about 55 feet,  to more like 65 or 70 feet.
> Assume a 20 foot long mast,  with 5 or so feet down
> inside the upper section of the MA-550?


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

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