Tower Pipe coupling

[imsmooth]

I am probably going to use 3" OD (2.5 nominal) schedule 40 pipe for a 35-40' tower.  I was going to couple two pieces: 21' and 14', or 21' and 19'.  On this site I have seen couplers made with slightly larger pipe and it is bolted tight.  Is this made with one size pipe larger, which in my case would be 3" nominal / 3.5" OD pipe?  I was going to cut a 2' piece of pipe down the side and weld 2" x 1/4" pieces next to the cuts.  I was then going to bolt it tight.  I would also put the guy flanges on this.  Am I approaching this the right way or:

1. is there a different way to do this
   
2. is there a place to buy the couplers already completed?
   

[wpowokal]

OK Allan has a dose of the nasties, your posts here and on the back shed are becoming legend.

Tower joins, well whatever you chose make sure they are tight, so as to not create a area of movement, and do use stay wire at each join to asist in eliminating such movement.

The best advice I can give is machined pieces that fit inside as couplings are the best, but they must be tight.

You have asked a lot of questions about towers and I for one honestly wonder where you are comming from, I will share my experiences with all comers who are sincere, but your questions here and on the back shed are so numerous I am left wondering, I sincerely hope I misjudge your coments/questions.

allan down under

[wpowokal]

This is how I joined my tower, I purchased some thick walled pipe of similar diamiter, machined it down until it just slid inside the tower pipe leaving a 50 mm band in the middle.

Onto the middle band I welded four lugs for the guy wires, this "land" also serves to seat each tower section. The section that slips inside is about 200mm on each side of the centre land.

Not everybodies cup of tea I guess as it requires expending money but......

allan down under

[scorman]

this is another implementation that slips inside and doesn't require all that welding:

http://www.greenpowertalk.org/showpost.php?p=6003&postcount=48

easier to work with small sections like above, but I would put a 1/2 bolt thru whole assembly at each joint to maintain alignment of guy flanges

Stew Corman from sunny Endicott