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Re: [TowerTalk] Tri-Ex HS 588

To: "charles mcneil" <>,<>
Subject: Re: [TowerTalk] Tri-Ex HS 588
From: Jim Lux <>
Date: Tue, 30 Jan 2007 07:46:41 -0800
List-post: <>
At 05:20 AM 1/30/2007, charles mcneil wrote:
>     I am building a wind generator and have bought a Tri-Ex HS 588 
> tower from a neighbor. This was evidently a three section 58' 
> crank-up tower but the top section was missing.
>     I want to weld in some support plates in the top and install a 
> 12' piece of schedule 40 pipe to set my generator on. the generator 
> will weigh about 250 lbs with blades.

water pipe is basically cold rolled steel, and pretty soft, and is 
not made for structural purposes (not that it can't be used.. it 
can.. but it's not specified for it, so you have to do a pretty 
conservative design)

What you really want is what's called steel tubing.  Available in a 
variety of materials and grades, all the way from standard cold or 
hot rolled steel to fancy high strength alloys.

>     The local building inspector tells me I will have to have an 
> engineering report saying the tower can be used for the purpose. I 
> plan to guy the tower at 20' and again at about 40' but have no 
> idea how guying a self supporting tower affects it's wind load capacity.

Guying a telescoping tower changes the loads significantly, and may 
actually reduce the capability (the tower was originally designed for 
bending loads but not compressive (other than weight).. putting on 
guys increases the downforce, so things like the crank up cables get 
loaded more.

(unless you were planning on welding the two sections you've got together.

>     Does anyone have any specs on this tower? Anyone have any 
> suggestions on how to deal with this problem?

Since the inspector wants an engineering report, you need to find 
yourself a local engineer to do the analysis.  Since you'll have an 
engineer, they can run through all your various options for materials 
and construction and come up with something that works. Part of what 
you get from a local engineer is knowledge of what your local 
inspectors' hot buttons are.

>  I have looked into new towers but quickly found out that I would 
> have more money in the tower than I could ever get out of Renewable Energy.

That's true for almost all renewable energy, on a small scale, with 
today's business models. You do it for reliability, psychological 
gratification, etc.

Consider that residential scale solar panel systems, installed, run 
about $8/watt, or $8000/kW.  A 1 kW system, at 4 hours a day, 350 
days/year, that's 1400 kWh/year.  At the $0.30/kWh avoided cost (just 
reducing the bill, as opposed to selling back to the power company, 
for which you get something like $0.06/kWh), that's $420/year... 
quite a while to pay back that $8000 (even leaving aside things like 
interest on the money).

For most small scale systems, the payback period is on the order of 
15-20 years, but with rebates and tax incentives, you get down to 
around 5-7 years.

Jim, W6RMK 


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