There is the assumption, also, that the manufacturers specs are rational. I
have looked at a lot of base-guying-tower combinations that do NOT make
sense. Rohn makes a base plate that is designed to have three custom-made
tubular legs driven into earth. How does this match a 2'x2'x8' concrete
base that will fit the same tower? I know of one Ham that uses a Rohn base
section inserted into a hole and filled with Limestone gravel. (no cement)
This tower base withstood a direct pass by a tornado.
Match the loads on a Pier-pin base under a guyed 25g with the same tower on
a concrete block. As an Engineer (not a PE) I can tell you that the base
load situation in these two cases has no resemblance. So, why does it make
sense to require a heavy block, if the material is concrete, but no moment
support at all if you call it a "Pier-pin" and put it on a flat concrete pad?
Unfortunately, there is little relationship between regulation and reality.
A "wet stamp" by a PE is as good as absolution by the Pope.
Bill
At 12:01 PM 7/11/2005 -0700, Jim Lux wrote:
>At 10:26 AM 7/11/2005, Kelly Johnson wrote:
> >The "drilling rigs" mentioned as of late are all designed to dig a
> >round hole, not a square one. Every tower foundation spec I've seen
> >(USTower, Trylon, AN Wireless) specs a square hole. There are lots of
> >building inspectors that won't accept a round hole when a square one
> >is called out in the manufacturer specs.
> >
> >It would seem to me that these tower manufacturers need to realize
> >that the specs they are creating can't be realized very easily by most
> >amateurs.
>
>
>Bringing up the interesting question of how big a market are amateurs. It
>may well be that the tower company doesn't have much business reason to
>change the design. In a kinder, gentler, less regulated era, it may be
>that the plans were were more guidelines for amateur use, with the
>expectation that the regulators would be working off the "intent" and not
>requiring hard analysis.
>
>If a tower company sells, say, 1000 towers a year, and 950 of them are to
>commercial customers who will be hiring an engineer anyway, then the
>remaining 50 sales may not justify creating a new design, especially for
>use by "non-professionals".
>
>There's all sorts of disincentives to publishing a new design in the
>perceived liability area. Does the new design imply that the old design
>was somehow defective? Maybe the old design wasn't great, but because it's
>40 years old, nobody's complaining, and you've got a big installed base to
>point to for empirical data.
>
>
>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
>any questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
Bill Aycock - W4BSG
Woodville, Alabama
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
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