Advice wanted on welding thin wall tube

admin

I am a new inexperienced welder trying to weld thin wall EMT tube together.I have a wire welder, also does MIG, and a stick welder. The problem I am having is burning the wall on my lowest setting on the wire welder. I'm not sure but I think it might be a combination of heat and wire feed too fast so I have slowed down the feed rate, but still having some problems with burn through. Have not tried the stick at all since low amperage control with my stick is not real good. I have done some tests with brazing this material which I do have considerable experience and got very good results with that. Problem with that is I am not sure how strong it will be and I will be using this for a communications tower at my home. The tower will be nearly 50 feet tall, supported at about 30 feet, but top 20 will be unsupported and will have a platform in the top so I have some concerns for strength of weld. As I said brazing works well on this material but not sure if it is as strong as a weld. Any advice and opinion is welcome. Thanks in advance.
Reply:keep turning the heat down (wire) on the mig and try going faster or weave.  I don't think I could do it with stick.I suggest getting it down pat before you start on a structure.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Already on the lowest setting on my heat now. Any opinion on the brazing?
Reply:Originally Posted by nssaulsAlready on the lowest setting on my heat now. Any opinion on the brazing?
Reply:I will be using sleeves on the uprights where the sections connect. This thin wall is difficult to deal with but is much lighter and cheaper than square tube or angle.
Reply:2 things... what machine do you have exactly and what are the exact tube dimensions? that may help us to help you dial in the correct settings.later,Andy
Reply:Hello,set up a dry tig on a buzz box or gas powered welder and grind the galvanized off in the weld area works everytimeAlways Welding
Reply:Brazing will by far exceed the strength of the tubing itself altho it will put more heat (time) into the weldment. Thin wall EMT is not what I'd use for a tower that I was going to climb as it (EMT) was never nor is spec'd for any type of structural duty.
Reply:nssauls,Sounds like a disaster waiting to happen.You're talking about using material which was never designed for the use you're talking about.  Even if, somehow, you were able to construct the tower, the material would not stand up to the elements.  I suspect it would rust out in less than a couple years.Let's think about this.  If there's insufficient metal present to support the heat of "proper" welding, do you really want to stake your life and equipment on an improperly designed structure.I have a heavy duty Rohn 48' self supporting tower which has been up for nearly 15 years and has survived several hurricanes with an 8 sq. ft. windload.  It was designed and built (not erected) by engineers who know what they're doing.While I may admire your creativity, there are better "projects" to take on which will enhance your welding skills.BOTTOM LINE.  DON'T DO IT.  50' is a long way to fall.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by SundownIIInssauls,Sounds like a disaster waiting to happen.BOTTOM LINE.  DON'T DO IT.  50' is a long way to fall.
Reply:Yep.  It's not just "steel."  EMT Conduit is not for structural strength.  The NEC even forbids using it to support the weight of a light fixture!As for serious stuff, the big difference between it and real structural tube steel is the quality of the welded seam.  This seam can split in EMT conduit when it receives forces for which it was not designed.  All it is designed to do is be an inexpensive metallic path for holding wires.  That's it.Now, as to how to weld thin tubing, did you try becoming your own spot welder?  Give it a pull of the trigger, let it cool for only a second, and give it another, working your way around.  Where you have an edge and you are trying to join it to the middle of another tube, remember that the edge will melt much more easily, and most of the heat has to be concentrated on the body of the other part, washing the puddle into the edge.  Yes, it takes practice.  I'm doing it here, exclusively with a Stick machine now, after mastering the technique with the proper tool, the MIG welder.  But it's definitely possible with Stick as well, when you get the practice.  I also have a Stick machine here that let's me weld as low as 20A, though my smallest rods right now need at least 30A.
Reply:Look into lighting trusses that hold stage lites up behind the stage.. More than perfect for what you want and they bolt together...Come in 10 foot lengths...Get them at any of the bigger music stores......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:OOH... Scary.  EMT is weak.  There's a good reason why they make it so thin.  It's so electricians can bend it with a conduit bender.  It's weak stuff.  Be safe.Also, the fumes created by welding EMT are extremely unhealthy.  My buddy got sick from it.Last edited by DubJ; 11-12-2007 at 06:40 PM.***Stick welding like, woah.***
Reply:Take a look at an AREOMOTOR ? windmill tower. They are meant to be climbed. i sold a couple on ebay a few years ago. They are simply galvanized angle and 3/8 round rod as x braces if i remember Victor SuperRanger O/A                                         Solar migLincoln Powermig 140Southbend 9in lathe350# kohlswa anvilMiller Maxstar 150 stl etc....
Reply:Thanks to all for the comments, suggestions, and warnings. I guess I should qualify what I am doing here. First let me tell you that this is not my first tower built from these same materials, and not without help from mechanical engineers that I work with. I built one of these towers, 30 feet, rather than 50, in 1984 out of 1/2" EMT. It still stands today, has not rusted out, and withstood 80 MPH winds from hurricane Hugo a few years back. The biggest difference between this tower and the first one is 20 feet more reach, larger footprint, with a platform on the top of it. The first one was bolted not welded, and supported at 20 feet from the structure it serves. The new one will also have 3/8" rod stiffeners as designed by my mechanical engineer. I have been working with my welds using some of your suggestion and have had some sucess. I believe I will use a brazing method on the tubing itself but will weld the stiffeners to the tube. Thanks again for all your support in this project. I look forward to learning from all of you in some other projects as well.
Reply:I built one of these towers, 30 feet, rather than 50, in 1984 out of 1/2" EMT. It still stands today, has not rusted out, and withstood 80 MPH winds from hurricane Hugo a few years back.
Reply:I think I forgot to mention the tubes will be sealed from the elements and painted with an epoxy paint.
Reply:Ask your mechanical engineer friend to put his stamp on it.
Reply:After taking a more serious look at this project, and my welds in the EMT I have come to agree with you guys. Although this material worked for a smaller tower that held a single tv antenna, the tower I want to fab here is higher, will have a platform on it, will support 3 sat dishes, and one wireless broadband antenna, so I'm open to suggestion on this. Should I go with angle, square tube, or the DOM tube someone suggested. Thanks for all suggestions.
Reply:Originally Posted by nssaulsAfter taking a more serious look at this project, and my welds in the EMT I have come to agree with you guys. Although this material worked for a smaller tower that held a single tv antenna, the tower I want to fab here is higher, will have a platform on it, will support 3 sat dishes, and one wireless broadband antenna, so I'm open to suggestion on this. Should I go with angle, square tube, or the DOM tube someone suggested. Thanks for all suggestions.
Reply:Originally Posted by nssaulsI think I forgot to mention the tubes will be sealed from the elements and painted with an epoxy paint.
Reply:Originally Posted by EngloidEven still, this pipe is meant to bend easily.  You can bend it with a 3ft hand bender and a 150lb man's weight on it...and you want to build it much longer than that (exponentially higher ....
Reply:Originally Posted by nssaulsAfter taking a more serious look at this project, and my welds in the EMT I have come to agree with you guys. Although this material worked for a smaller tower that held a single tv antenna, the tower I want to fab here is higher, will have a platform on it, will support 3 sat dishes, and one wireless broadband antenna, so I'm open to suggestion on this. Should I go with angle, square tube, or the DOM tube someone suggested. Thanks for all suggestions.
Reply:lets see... 50' high, platform, 3 sat dishes and an antenna. let's figure that we should engineer it for about 2,000 lbs. that will give us a service facto of at least 2.0. if at all possible, i would suggest you take a look at a local comm tower. they vary from location to location. it won;t matter if it's old or new... if it's old and still standing, it's strong enough for you. if it's new, it probably based off of an old design and has been properly engineered for your regional location and has been designed with a minimum service life expectancy. also look into your local building codes and permits. some times permits will tell you (pretty clearly) what you can or cannot have. if possible, go talk to your local community college, tech school or even some high schools. if they have some sort of engineering or drafting program, there is a significant chance that they will help you out. when i was in HS, we had people come in on a regular basis asking for help with things like this... that's how i got a lot of my side jobs. they wouldn't be happy with how the class designed it, but i talked to them on the side and they eventually awarded me the job.just a thought. if you would like, PM me and we can talk some more. most likely, i would reccomend some sort of large, angle iron stock with multiple support cables and some square tube and solid stock for re-inforcement.later,Andyalso... you may HAVE to get the plans signed by a licensed proressional engineer that is registered in your state. especially for something this big. it'd be hard to put it up without someone turning you into the local building authority. technically, if you put in a dog house, or even re-landscape your lawn, you are supposed to get a building permit, but most people don't.Last edited by aczeller; 11-14-2007 at 10:16 PM.
Reply:Check out Rohn Towers on the internet.They have a 48' freestanding tower which comes in 8' sections which are bolted together.  All galvanized metal.  I have one which has been up (right next to salt water) for nearly 20 years.I don't think you could buy the materials for what you can buy the tower for.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.30' will be no problam for square tube, with supports. have your pe do the calc's for 2" to 4" dia x 3/16" wall. use of gmaw with .35" or .045"  90ar-10co2 will work well for this application,in a spray transfer.
Reply:I built a 60 footer out of 1 inch schedule 40 pipe. All butt welder and 3/8 solid round bar bent up to zig zag up each side. The base is 4 feet between each leg and 1 small platform on the top cut from 1/4 plate. Their are only 3 legs. It has been standing for awhile now and you can climb up it. We did at guide wires as a precaution before hurricane Juan went through a few years back. If I get the chance to drive over to it, I will take a pic of it.Miller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.