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Re: [TowerTalk] 2" OD pipe.. again

To: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Subject: Re: [TowerTalk] 2" OD pipe.. again
From: "Gene Fuller" <w2lu@rochester.rr.com>
Reply-to: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Date: Fri, 19 Mar 2010 09:53:04 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
If we're really looking for more things to worry about you could add 
vertical loading caused by that heavy steel tubing, and colum strength. You 
may eventually decide to stick with wires in trees. Isn't that where most of 
started a few decades ago ?
Gene / W2LU

----- Original Message ----- 
From: "Gene Fuller" <w2lu@rochester.rr.com>
To: "Tower and HF antenna construction topics." <towertalk@contesting.com>
Sent: Friday, March 19, 2010 9:26 AM
Subject: Re: [TowerTalk] 2" OD pipe.. again


> Depending on where you live, to be really safe, add another0.5 " or so to
> the mast diameter for ice, although you're probably not likely to get ice
> and high wind at the same time.
> I've had "good  luck" (after lots of calculation) with 2"dia x 0.25 wall
> seemless steel tubing, with large LP a foot or two above the top thrust
> bearing.
> Gene / W2LU
> ----- Original Message ----- 
> From: "Jim Thomson" <Jim.thom@telus.net>
> To: <towertalk@contesting.com>
> Sent: Friday, March 19, 2010 1:29 AM
> Subject: [TowerTalk] 2" OD pipe.. again
>
>
>> Date: Thu, 18 Mar 2010 19:12:25 -0400
>> From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
>> Subject: Re: [TowerTalk] 2" O.D. Pipe???
>>
>>
>> Stan Stockton wrote:
>>> Just my opinion....  1.5 inch schedule 40 may be fine if you have some
>>> big tribander or 35 foot monobnder and it is mounted right above the
>>> top bearing.  If you are stacking antennas on the mast, forget it.
>> http://www.rogerhalstead.com/ham_files/Tower29.htm shows a tribander at
>> 100', 7L 6-meter Yagi at 115 and a 14' cross boom at 130' holding a pair
>> of 11L on 440 and pair of 12L 144.  That all on 2" schedule 40 but it's
>> structural steel.  It's a bit flexible with the top looking like a blue
>> gill rod that just tied into a big Bass, but it's withstood over 70 mph
>> winds and many occasions.
>>
>> ##  sched 40  pipe doesn't come in a 2.0"  OD.   It's is 1.9" OD,
>> with a .145" wall.
>>
>> ##  You mean to tell us that you have  30' [thirty feet]  of mast,
>> sticking out the top of the tower ???    Do you ever get ice...
>> or ice  + wind ?
>>
>>
>>
>>
>> I'm going to a heavier wall DOM so it doesn't beat the antennas to
>> death, but strength wise it seems to have been more than sufficient.
>> OTOH it's not ordinary schedule 40 pipe which is relatively soft and
>> easily bent.
>>
>> ## Regular sched 40 pipe  would have been toast, long b4 now.
>>
>> ##  1026 DOM  comes in 60 ksi,  to as high as 90 ksi.
>>
>> ##  IMO... for ants  mounted way up a mast, you had better [A]  run the
>> numbers through the spread sheet.. and [B]  make sure the mast you buy
>> has paper work with it.   Inform your  steel supplier, that it's a legal
>> liability
>> issue... and guess who's liable?     As  far as wind speeds  go.... 
>> unless
>> you
>> have a wireless   wind speed indicator, at the top of the tower,  you are
>> really
>> guessing.   If it's  56 mph at grnd level,  it could easily be 70 mph at
>> the
>> top of the tower.   Talk to anybody who has a wireless wind speed
>> indicator
>> at both the top of the tower.. and also at the  15' level.  You will get
>> an
>> earful.
>>
>> ##  all of this mast issue is really  a no- brainer.  Stuff the numbers
>> into the
>> spread sheet, and see what spits out.
>> http://thebont.com/spreadsheets/AnalysisOfAntennaMastStrength.htm
>>
>> ##  estimate the max wind speed gusts  for your area.... then add a MIN
>> of 25% " to the speed   [and pref a lot higher... like 30-50%].  Then
>> procure
>> the correct mast.   These 1 in a 100 yr wind storms  are too plentiful
>> these days
>> and ditto with ice storms, seismic events, and heavy rains.  WX patterns
>> are
>> changing.. for the worse.  OK, so you buy a mast that's overkill, so 
>> what?
>> Ham's spend $12K on a xcvr, without blinking an eye.  When you  get the
>> crane bill, to remove the destroyed ant's, coax, etc... the pricey mast
>> will look cheap.
>>
>>
>> later....... Jim   VE7RF
>>
>>
>>
>>>
>>>
>>
>> 73
>>
>> Roger (K8RI)
>> _______________________________________________
>>
>>
>>
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