[TowerTalk] [Bulk] Re: Mast Material

Mon Mar 14 16:37:27 EDT 2016

The fence rail can bend a long way and spring back, without damage.

I discovered this the hard way along with never assume the people you 
"thought" were experienced really are.
Always monitor what's going on.
I had to take a short break (nature called).  When I came back out, I 
instinctively looked up to see that gin pole arced over to the side at 
an unbelievable angle
prompting me to shout "stop"!

Someone had figured they could pull the load from the side to under the 
gin pole.  I don't remember the circumstances now, other than seeing 
that gin pole looking like a fishing rod with a "big one" on.  Still, it 
sprang back to straight with the load removed.

They didn't realize the energy stored in that system, had the mast or 
mount broke.
One of the dangers of volunteer help. If you aren't sure what needs to 
be done, find someone who does and put them in charge!
One person, either you or someone designated by you "must be in 
charge".  It's not safe having 5 or 6 volunteers doing their own thing.  
SOMEONE has to coordinate all the work to prevent conflicts

Yes, you will occasionally find a group who work together like a well 
oiled machine, but they are rare.

73

Roger  (K8RI)

On 3/14/2016 Monday 2:21 PM, Grant Saviers wrote:
> "Regular" sch40 pipe is often specified as 30kpsi yield strength, but 
> schxx IPS is available to 70kpsi.  The example fence folks are 
> specifying 50kpsi and a non-standard wall thickness of 0.120" which is 
> in between sch20 and sch40 normal pipe sizes, 0.105" and 0.145" 
> respectively.  If I calculated correctly, the radius of 
> gyration/section moment of inertia is 0.423/0.495 = 0.85 for fence 
> "high strength" vs sch40.  Given the yield stress ratio is 50k/30k = 
> 1.67 then the relative bending yield is 1.67 x .85 or 1.42x better for 
> the 0.120" wall "high strength" fence pipe.  It's an interesting 
> result to trade the amount of steel for better steel to yield higher 
> bending yield stress.
>
> Here is one fence pipe manufacturer's brochure with what they call 
> W40, W30, W20, and W15 grades, with varying wall thickness, usually 
> not the same as IPS sch40, 20, or 10.  Note the W30 which seems to be 
> the pipe mentioned earlier in the post is hot dip galvanized on the 
> outside, but something different inside and also has additional 
> polymer coatings.  The W15 goes down to 0.047 wall.
> http://www.wheatland.com/images/fence_framework/Fence_Framework_Brochure.pdf 
>
>
> if you want to see all of the choices in "standard" pipe here is the 
> USS pipe brochure
> http://usstubular.com/resources/library/brochures-and-catalogs/u-s-steel-tubular-products-standard-and-line-pipe 
>
>
> Yield strength is not the only variable in pipe performance.  High 
> strength tube (not pipe) is Drawn Over Mandrel (DOM) to insure 
> uniformity of wall and strength.  It may have been seam welded or 
> pierced bar to make the rough shape.  Then there may be heat treating 
> to a specific hardness/strength.
>
> Using fence pipe for gin poles which have a significant risk of life 
> hazard, is a risk I would not take.  Rather, a DOM structural tube in 
> an appropriate wall thickness.
>
> Using EMT with a 0.065" wall for a tribander on tower mast, welded 
> seam and electro-galvanized only on the outside is just plain nuts. 
> There are NO specs for the steel properties.
>
> YMMV,
>
> Grant KZ1W
>
>
> On 3/13/2016 18:27 PM, Steve Maki wrote:
>> On 3/13/2016 9:01 PM, Richard (Rick) Karlquist wrote:
>>
>>>> A good alternative to schedule 40 pipe is the tubing used nowadays for
>>>> fence top rails, known as SS40. It's lighter (thinner wall) but 
>>>> stronger
>>>> and actually less expensive than galvanized sch. 40 pipe if purchased
>>>> from the right place.
>>>>
>>>> We routinely use it on cell sites for antenna masts in place of 
>>>> sch. 40.
>>>>
>>>> Here are the specs:
>>>>
>>>> http://www.hooverfence.com/catalog/chart.htm
>>>>
>>>> -Steve K8LX
>>
>>> Note that the outer diameter of fence tubing will always
>>> be the same as the outer diameter of some standard water
>>> pipe size.  E.G. Both "1 7/8 inch" fence tubing
>>> and "1 1/2 inch" water pipe (any schedule) actually
>>> have an outer diameter of 1.900 inch.  Either can be
>>> shimmed with standard 2" OD aluminum irrigation pipe with
>>> 0.050 inch wall to fit standard 2.000" mast clamps
>>> or bearings.
>>>
>>> I don't know why they make fence tubing and pipes the
>>> same size.  One theory is that you if you want to build
>>> a fence on steroids, water pipe can be substituted for
>>> fence tubing very easily.  (Attention:  Donald Trump :-)
>>> Or maybe they make both of them on the same equipment.
>>> (Obviously, I have spent way too much time loitering
>>> in hardware stores.)
>>
>> Hehe.
>>
>> But I'm not sure why substituting schedule 40 for SS40 in fence 
>> applications or any other (except plumbing perhaps) would be an 
>> *upgrade*. A quick search didn't yield specs for sch. 40 that would 
>> lend itself to an applicable comparison, but the fence people claim 
>> that SS40 is *stronger* than sch. 40.
>>
>> In the fence business there are numerous tee couplers, etc. already 
>> sized for stand sch 40 OD's, which probably drove the size 
>> constraints for SS40.
>>
>> -Steve K8LX
>>
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-- 

73

Roger (K8RI)

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