Thanks Gerald.
W4BOH, in your zip code the 25-year MRI is 84 mph; so, there's a 4%
probability of a storm occurring in a year producing 84 mph winds. Combine
that with Gerald's calulcations and you may want to consider making some
changes.
On Tue, Mar 15, 2016 at 3:36 PM, <TexasRF@aol.com> wrote:
> Hi Ryan, that was the raw data, no safety factor added. The wind speed
> given is actual steady wind speed, no average or gust and failure is
> defined as the point the yield strength has been exceeded.
>
> Gerald
>
>
>
>
>
> In a message dated 3/15/2016 3:12:18 P.M. Central Daylight Time,
> ryan.turner@memhamwan.org writes:
>
> Gerald,
>
> Thanks for providing the numbers. Wind speed here is what -- average or
> instantaneous? How is failure defined? Curious to determine MTBF.
>
> On Tue, Mar 15, 2016 at 2:35 PM, TexasRF--- via TowerTalk <
> towertalk@contesting.com> wrote:
>
>> Google says 1.5" EMT is actually 1.75" OD and .065" wall thickness and
>> yield strength is 35,000 psi.
>>
>> Putting these numbers in a mast analysis program and using a 7 sq ft wind
>> load 24" above top of tower, failure happens at a wind speed of 84 mph.
>> Lowering to 12" above tower top, failure is at 119 mph.
>>
>> So, it could be useful in a modest installation.
>>
>> 73,
>> Gerald K5GW
>>
>>
>>
>> In a message dated 3/15/2016 2:01:59 P.M. Central Daylight Time,
>> infomet@embarqmail.com writes:
>>
>> Let’s not call names.
>> An EMT mast is great, as long as you don’t get greedy and make it too
>> tall
>> outside the tower.
>> Mine is about 2’ above the tower top and I think it will survive any wind
>> likely in my area. And I really won’t cry if the $150 beam is damaged!
>> It’s several years old and shows no sign of deterioration. It cost
>> almost
>> nothing and weighs next to nothing.
>> So I have a used tower, used tribander, used rotator, EMT mast, but new
>> coax.
>> I also have a HB amp made from used components, with an easy KW+ output.
>> It’s a rare pileup I can’t get through.
>> I am VERY happy, but may change to an LPDA so I can get the WARC bands,
>> someday.
>>
>> I also use junk tubing from a kid’s swingset for Field Day. It’s worked
>> fine for a decade or so.
>>
>> Successful systems can be designed around most any components, as long as
>> one doesn’t try to do too much!
>> I’d far rather see a ham put up 30-40 feet of used tower and a used
>> tribander than envy those with more elaborate, expensive setups!
>> A few more hours on the air will make up for a few dB of antenna
>> performance and there will be money left for beer.
>>
>> Wilson
>> W4BOH
>> _______________________________________________
>>
>>
>>
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>>
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>
>
>
> --
> Ryan Turner, K0RET
> +1.901.300.0039
>
> HamWAN Memphis Metro <http://www.memhamwan.org/> - Memphis' Amateur Radio
> Multi-Megabit IP Network
>
>
--
Ryan Turner, K0RET
+1.901.300.0039
HamWAN Memphis Metro <http://www.memhamwan.org/> - Memphis' Amateur Radio
Multi-Megabit IP Network
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