I think they changed the windload from 75 mph to 90 mph.
73, Dick, W1KSZ
Jim Lux wrote:
> At 12:19 PM 6/26/2007, Clint Talmadge wrote:
>> Bob, AD5VJ asked a question about a concrete base for a Rohn tower.
>> When Bob, NA6T posted this reply I thought the amount of concrete
>> sounded a bit high. I checked the Radian site and sure enough that
>> is what is listed. So I drug out my old Peoria Rohn Catalog, circa
>> 1983 and researched base dimensions. Peoria Rohn specs call for a 2'
>> X 2' by 4' deep hole for the tower that Bob, AD5VJ is installing. It
>> calls for guy anchors of 2' X 2' by 1' deep.
>> Which raises the question: Did Radian re-engineer the base
>> dimensions or did the fear of litigation cause Radian to up the numbers?
> Purely speculation, but a lot has changed in the last 25 years,
> including how windspeeds are specified (or, more properly, what load
> corresponds to what rated speed), perhaps some assumptions about the
> bearing capacity of soil, perhaps standard construction practices have
> One likes to hope that folks aren't motivated by "fear of litigation"
> but, rather, a desire to "do the job right", and if a reanalysis
> shows you need different dimensions, then so be it. I sort of doubt
> they just blindly increased the size in hopes that it would be "safer".
>> I've installed two towers for myself, both Rohn 25G, both in the 30'
>> to 40' range ( I use a full section for the base) and both were
>> planted in 2' X 2' X 4' holes. Neither came down (yet).
> That's not surprising on a sample of 2. The footing design would
> generally not be designed to fail at 1 mi/hr over the limit, but
> would include some margin for things like variations in soil,
> variations in material properties, etc. Failure is a probability
> thing, not a "exceed the limit and total destruction is certain" sort of
> Jim, W6RMK
> TowerTalk mailing list
73, Dick, W1KSZ
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