[TowerTalk] Homebrew tower...

[Roger (K8RI) on TT]

On 6/28/2015 1:18 AM, Roger (K8RI) on TT wrote:
> I think, meaning I don't know for sure, but I have the background to 
> make an educated guess, when comparing tubing and pipe, particularly 
> water pipe they are two different animals.  The difference in alloy 
> and hardness is substantial.
>
> If you take one leg of a 25G, I see it comparable to thin wall conduit 
> (not the same, but comparable).  It's fragile, easily bent, or 
> crushed.  The tower gains the majority of its strength from the 
> construction and "Z-braces".
>
> Water pipe OTOH is "relatively" soft like rigid conduit and easily 
> bent.  Compared to a 25G tower leg it's very heavy, so I'd expect a 
> 10' section to be notably heavier than a 10' section of 25G. Per size, 
> or length, I'd expect such a tower to be as durable as a 25G up to 40 
> feet.  BUT...
>
> The idea of using 1" pipe as a sleeve coupling is a sound one  I'd 
> make them about 6 or 8 inches long with 6 being the absolute minimum.  
> Use 2 bolts per section, or 4 bolts per coupling as ROHN does.
> Bear in mind, this is not an engineered tower that "MIGHT" be similar 
> in strength to the 25G.   It's built of a material not designed to 
> support a load.  Based on that I'd be very hesitant to climb one.
>
> As for corrosion, as long as it's well coated with a rust preventative 
> paint ( Cold Galvanizing, or zinc based paint) at sufficient intervals 
> I would expect it to hold up.
>
> As I mentioned earlier, water pipe is relatively soft and bolt holes 
> are prone to "egging out" (holes get larger from wind induced tower 
> movement). A good reason for tight/snug fitting bolts.
>
> For my own comfort, I'd make the "water pipe" tower with the leg 
> spacing of  a 45G, rather than 25G and I would definitely refrain from 
> climbing it.  Using the falling derrick to raise and lower it for 
> maintenance would be my preference.  I think a tower made 3 lengths of 
> 3/4" water pipe 40 feet long plus bracing. antenna and rotator  might 
> be a bit heavy for two to "walk" it up.  Again, the falling derrick 
> sounds good to me.
>
> I have never painted a tower that needed it.  I have painted a couple 
> of the old American Steel as they were beginning to look pretty rough 
> with the original paint peeling off after 20 to 30 some years, or 
> wearing off from me climbing it.  I had 25 to 30 years on a 25G and 
> about 15 on a 45G that never needed painting. However, I'm in 
> Michigan, about 25 miles W of Saginaw bay and over 700 miles from salt 
> water unless you dig a hole. Then it's 200 to 300 feet down.
>
> OTOH Acid rain keeps removing the solder joints from antenna 
> connections around here.  Every C3i antenna I own ( 5 of them) has had 
> the coax come off.  So I resolder the connections and apply several 
> liberal coats of liquid tape which seems to work.  The clear Krylon 
> paint (which is recommended) is completely gone in just a year or two.
>
> With plenty of paint, I think your tower will stand up well. Don't 
> neglect the inside of the pipe.
>
> 73 and good luck,
>
> Roger (K8RI)
>
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73

Roger (K8RI)


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