Bike Frames...Why TIG and not MIG?

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I am a Senior mechanical engineer at UNH and have been getting into designing and building bike frames. I have made 2 or 3 now. However, my TIG welder just died on me and now im wondering if its worth replacing it with a new one, or picking up a mig welder.Is there any real difference strength wise between the 2 welds? Or do they just use tig because its cleaner and looks better?Annnny info would be great.
Reply:Tig is easier to control the heat on thin stuff like bike tubing.Ya gotta spend money to make money!
Reply:Cosmetics and there is zero clean up after with a TIG.....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:Most high end bike frames are of a chrome alloy type material. To best suit the filler metal with the base metal the rod choices are better with Tig. Plus the tig process is a much more controlled process. The heat input can be controled and the welding process actually acts as an annealing procedure. This limits the residual stresses along the heat effected zone. I would replace the tig unit for sure, especially to weld bike frames. The apperance is only 1 of the positves.A young green pipe welder asked an old salt one day...How can I make the weld on the bottom of the pipe look like the top.......The old salt replied....Screw up the top......
Reply:Tig also has a greater versatility if you branch out into more exotic materials... its only a matter of time before you want to branch out.
Reply:Originally Posted by pancakeshakeI am a Senior mechanical engineer at UNH and have been getting into designing and building bike frames. I have made 2 or 3 now. However, my TIG welder just died on me and now im wondering if its worth replacing it with a new one, or picking up a mig welder.Is there any real difference strength wise between the 2 welds? Or do they just use tig because its cleaner and looks better?Annnny info would be great.
Reply:Are you referring to motorcycle or bicycle frames?Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Originally Posted by pancakeshakeI am a Senior mechanical engineer at UNH and have been getting into designing and building bike frames. I have made 2 or 3 now. However, my TIG welder just died on me and now im wondering if its worth replacing it with a new one, or picking up a mig welder.Is there any real difference strength wise between the 2 welds? Or do they just use tig because its cleaner and looks better?Annnny info would be great.
Reply:Originally Posted by Xtreme FabricationAnd people know why I want to off ever engineer I meet.    Here's a prime example of the clueless engineer they are training in college now a days.  You have been trained to design mechanical stuff and you don't know the differences between basic welding processes are?  Its really shows how poor the engineering programs have become in every college now.  I heard a story recently come out of U of MD regarding an civil engineering mid term exam where there was a question along the lines of about how much dirt could a 1.75 yard excavator move in a 8 hour day in hard clay digging 4' wide trench 12' deep and loading a truck behind it.   Almost the entire class failed the question because almost none of them even knew what an excavator was.  A lot of them even wrote on the test what is an excavator? The teacher spent the entire next class teaching all the clueless students what the name was for each piece construction equipment was and what each was used for.
Reply:Are there some dumb engineers out there? Sure and there are plenty of others out there that can show ignorance at times.However, I disagree that the OP's question is a complete damnation of today's engineering programs.XF: Are you a graduate of an engineering program? Just wonderin.CE, Purdue - 1991Last edited by dunemetal; 11-24-2011 at 05:07 PM.
Reply:Not every engineer is clueless, but some are.  It is probably a bit early to throw stones at an ME without knowing what he knows.XF, can you:run a big hairy FEA on a complex partUse numerical methods to approximate a solution to a calculus problemEtc. etc....He probably can. I'm an engineer (actually a graduate of an engineering technology program) and fortunately, I have also been welding for 25 years as well as doing a bunch of rigging, machine shop stuff, fitting, diesel engine maint, and all kinds of other stuff.  I learn something just about every day (lots of stuff right here on the forum)  So he isnt all about welding, doesn't make him a bad engineer.
Reply:some bicycle frames are also made of aluminum.tackleexperts.comwww.necessityjigs.comhttps://www.facebook.com/groups/mach...dingequipment/
Reply:Some companies have even made Scandium frames.... too bad berylium is so tough to work with, that would be the ultimate.
Reply:Maybe OP can elaborate. He says he is a "Senior ME at UNH" I'm taking that to mean 4th yr student at Univ. of New Hampshire. If true, then he hasn't even entered the workforce. Heck, if he was an ME with 20yrs experience, for all we know, he might have spent 20 yrs designing HVAC systems. As such, he might not even come across much in the way of welding. Engineering can get pretty focused depending on where you work. I know guys that do nothing except design bridge foundations, other guys that design specifics for sheet piling. They are engineers with a stamp working in very focused fields. I wouldn't ask them to specify a welding process on a bike frame but that doesn't mean they aren't bona fide engineers.
Reply:Huffy & murray have been migging frames for 30 years.2 OR 3 frames?  That's not a very high number to remember..  So I guess UNH is still a party school, huh?Buy American, or don't whine when you end up on the bread line.
Reply:Alright guys he asked a legit question and there is no reason to jump all over him...Granted I only know 3 engineers that know what a print is let alone draw something that actually works..Give him a break..You have to start somewhere and he is just getting started.I have NEVER seen a engineer that could weld....Or even try.Or actually get his hands dirty so lets leave the negativity out of this and try to help him along..At least he is getting involved....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:the bicycle frames i seen get made on tv one were basically brazed together. thought it was quite cool how they did it.
Reply:Hahahaha, ok guys. Im not at a technical school for welding. We have NEVER even gone over anything to do with welding. And yes 3 frames isnt alot, but thats 10000% funded by me and done at my own house, not at school. I have do do all the cad work, linkage analysis, static and dynamic stress analysis on the frames before I even start. Im talking downhill mtb frames, not road bike frames.Any engineers out there that want to elaborate on fluid mechanics, heat transfer, and the systems classes I have done? Yeah...its not a technology degree where we do algebra problems about excavators...It was a question...dont need a lecture about how "UNH is a party school" and "engineers are r*tards". Im new to welding and was just looking for an answer from people who know what they are doing.Thanks.
Reply:Want to quick whip me up the renolds number for propylene glycol flowing through a 1/8" diameter radiator tube @25lpm?Is the flow turbulent?
Reply:Originally Posted by zapsterI have NEVER seen a engineer that could weld....Or even try.Or actually get his hands dirty so lets leave the negativity out of this....
Reply:D.H.Mt.Bike frame prototypes are a good candidate for tig. If you go into production with the intent of turning every last dollar you can for as little investment as you can, then mig is a good bet for speed. QC is key to creating a durable frame, and that only if you start off with a solid design. Considering the state of the art in bike design today, you have quite a bit of homework to do if you hope to be successful.Brazing also works given good fitted joinery, or braze-welding, oxyacetylene welding could work. But, I would try to stay with tig for your purposes.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Originally Posted by zapsterAlright guys he asked a legit question and there is no reason to jump all over him...Granted I only know 3 engineers that know what a print is let alone draw something that actually works..Give him a break..You have to start somewhere and he is just getting started.I have NEVER seen a engineer that could weld....Or even try.Or actually get his hands dirty so lets leave the negativity out of this and try to help him along..At least he is getting involved....zap!
Reply:I've been brazing bikes for going on 13 years. Most of the bikes have been road bikes silver brazed with lugs, but I've done some few bronze fillet brazed mountain bikes too (the lugs are cast with angles appropriate for road bikes but there aren't any that work with the angles of mountain bikes). In April, I decided it was time to learn to weld. I wanted to be able to build frames faster, start using some other materials, and offer a lower barrier of entry price-wise. To compete in the custom market though, you have to be able to make the joints look beautiful. While they are just vehicles, the owners are fanatical about how their bikes look. So that's one reason you'd choose TIG over MIG. Most of the tubing I use is 0.028" wall or thinner, so the finer heat and filler control afforded by TIG really helps when working with material. As mentioned, if you are talking discount store bikes or some very low end or kiddie bikes in a bike shop, MIG is preferred for speed.MikeUMass Chemical Engineering '99
Reply:Originally Posted by tbone550My immediate family all grew up on the same farm.  One of us (me) is a welder, one of us is a mechanical engineer, and the other two are on the farm.  The engineer can lay TIG welds that look like Zap's (pretty danged good!), and when we all get back to the farm (all too rare these days) he works like a dog with the rest of us.  Proud of my family, regardless of what they do.  For everybody who thinks welders are next to God, I have news.  What we do takes a little skill, experience, and practice, but so does driving a garbage truck.  It ain't rocket science.  If it wasn't for the business side of it, there are times I'd be bored to death with my job.  So I'm with Zap and others, lighten up.
Reply:I'll never understand why some people on almost every forum feel like they need to belittle some one for asking a simple question. If we all knew everything we wouldnt waste our time on these forums. I'm new to welding, and I come here trying to learn all I can from people with experience. It's a shame a guy can't ask a question without having to hear/read a bunch of bsSafety 3rdGumpThe tubesets on bicycles are too thin to risk mig welding them. Overpenetration and possible suckback, as well as coldlap at the Haz and hotcracking at the end of the weld. Especially if you are working with some grade of 4130.Motorcycle frames are mig welded at times, but the heavy walls make them heavy as hell. Your downhill bike would be a bitch to peddle. MOtorcyclists have accepted mig, but bicyclists have not. Not saying you can't do it but your work will look amateurish even if you succeed in adequate welds.With all said, I think you would find learning to tig rewarding, and you won't be ridiculed in your choice of welding process. You might also consider brazing your tubesets.Funny you sound like an engineer.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Originally Posted by GumpI'll never understand why some people on almost every forum feel like they need to belittle some one for asking a simple question. If we all knew everything we wouldnt waste our time on these forums. I'm new to welding, and I come here trying to learn all I can from people with experience. It's a shame a guy can't ask a question without having to hear/read a bunch of bs
Reply:The OP is head-and-shoulders above the typical engineer1) He knows (and admits) welding is outside his area of expertise.2) He's smart enough to start asking guys who know and have experience.3) He has the drive to do something above and beyond the classwork.Dynasty200DX w/coolmate1MM210MM VintageESAB miniarc161ltsLincoln AC225Victor O/A, Smith AW1ACutmaster 81IR 2475N7.5FPRage3Jancy USA1019" SBAEAD-200LE
Reply:Now you got me curious, got any pictures of the frames you have built?  Every thread is better with pictures!
Reply:Originally Posted by pancakeshakeIs there any real difference strength wise between the 2 welds? Or do they just use tig because its cleaner and looks better?Annnny info would be great.
Reply:Originally Posted by Xtreme FabricationAnd people know why I want to off ever engineer I meet.    Here's a prime example of the clueless engineer they are training in college now a days.  You have been trained to design mechanical stuff and you don't know the differences between basic welding processes are?  Its really shows how poor the engineering programs have become in every college now.  I heard a story recently come out of U of MD regarding an civil engineering mid term exam where there was a question along the lines of about how much dirt could a 1.75 yard excavator move in a 8 hour day in hard clay digging 4' wide trench 12' deep and loading a truck behind it.   Almost the entire class failed the question because almost none of them even knew what an excavator was.  A lot of them even wrote on the test what is an excavator? The teacher spent the entire next class teaching all the clueless students what the name was for each piece construction equipment was and what each was used for.
Reply:Sure it can be done, maybe it won't be as pretty, but it will be strong. I read a welding book where the writer had a welding business making certified frames for airplane seats with tig, he could not keep up with production. He had his welders certify on mig and his production went up 400 percent, all still thin tube airplane seats.Lincoln Weld Pak100Lincoln Weld Pak 140 HDLincoln Weld Pak 175Lincoln Precision Tig 185Miller Millermatic 210 mig.
Reply:Someone has been reading Finch. =/ Attached ImagesCity of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Like I said at the first....GTAW is the best process for this application. If you are into making Huffy bikes then what type of degree does that require? I can tell you are leaning towards one off high end racing bike frames...say $3000.00 and up? If you want that type of product then volume is not the direction. Perfection is what you require so the perfect process is needed, and right now that is GTAW.A young green pipe welder asked an old salt one day...How can I make the weld on the bottom of the pipe look like the top.......The old salt replied....Screw up the top......
Reply:Originally Posted by 805greggSure it can be done, maybe it won't be as pretty, but it will be strong. I read a welding book where the writer had a welding business making certified frames for airplane seats with tig, he could not keep up with production. He had his welders certify on mig and his production went up 400 percent, all still thin tube airplane seats.
Reply:@ shovelon books writen by Richard Finchgoogle welding by finch or just his name there are some you can download ebooks of his stuff good read for weldorsidealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:Originally Posted by shovelonIf you remember the name of the book, I would like to read it.