F'd up bicycle

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My brother called to ask if I could fix my nieces's bicycle.  No problem I said....bring it over.Here's what I found.  Whoever the DA was that welded this must have been distracted.....he only welded half the joint.  Now the tube is cracked big time.First pic is the left side of the frame showing the crack.  Second pic is the right side of the joint showing...NOTHING   Hey, at least the fit-up was good!Sticker on the bike says "chrome moly"....OK...maybe.I've never welded CrMo so I did a little research and here's what I've found:Preheat (or maybe just warm it up a bit) which I plan to do as the outside temp is around 45 F here.Move slow.Taper off on the amps at the end...no craters allowed.Cool slowly...no draft or breeze.  Settings:Tig w/ 1/16" ER70s-2.1/16" 2% thor, #6 cup.100% argon, 15 cfm.85 amps.Sound OK with you guys? Attached ImagesMiller 211 w/ spool gunMiller Dynasty 200DXLongevity 60i IGBT plasmaO/A w/ crappy chinese torch/gaugesSouth Bend 10K latheGrizzly 4029 10x54 millGrizzly 7x12 hor bandsawangle grnders, bench grnder, bench belt sndr7.5 hp 80gal cmprsor
Reply:not so fast! hate to take away any excuse to crank up the welding machine but that sounds/looks like a manufacturing defect. refund/replacement maybe??i.u.o.e. # 15queens, ny and sunny fla
Reply:put in a gussetMiller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
Reply:Originally Posted by docweldernot so fast! hate to take away any excuse to crank up the welding machine but that sounds/looks like a manufacturing defect. refund/replacement maybe??
Reply:Originally Posted by BTDAmen on the mfg defect but she bought it used on Craigslist.  But it might be worth looking into.  Good idea!
Reply:Chances are being that's its for a girl she will never put the bike through a lot of stress and it will be alright.  If it was my child I would go on down to WalMart and get another bike.  You never know whose going to hop on here bike and jump that bad boy.
Reply:Started scraping away the paint around the crack.  As is usually the case, the crack was longer than it first appeared.  It starts at the top of the frame at the end of the weld then moves down and to the rear then turns and heads forward back to the bottom of the weld....kind of "U" shaped.  There's only about 1/2' of solid metal holding it together.Miller 211 w/ spool gunMiller Dynasty 200DXLongevity 60i IGBT plasmaO/A w/ crappy chinese torch/gaugesSouth Bend 10K latheGrizzly 4029 10x54 millGrizzly 7x12 hor bandsawangle grnders, bench grnder, bench belt sndr7.5 hp 80gal cmprsor
Reply:On your question of welding moly. I use 3/32 2% red tung 1/16 filler 70 or 80 sd  The bigger the cup you use the better such as a gas lense if not enough gas coverage your welds will be dark gray in color.Set your machine float the pedal its something you cant mash the gas and weld imo.. Good Luck. Clean very well!!Miller 250DX HTP 221 DV AC/DCHenrob O-A Miller 180 MigMiller 150 Inverter   Hobart 10,000 Welder-Generator   Have a good day!!!
Reply:Take the bearing out of the head first ?
Reply:No need to preheat it.  I have performed many repairs on damaged bicycle frames.If you really want to salvage the frame, my advice would be to remove the offending tube, and replace it with another one.  This means cutting out the old one and grinding/filing it smooth, coping a new one to fit, then welding that in.  You will want to remove paint from areas to be welded ~2"+, and you can go as far as to use heat fence mud to prevent additional damage to the paint beyond that.  Chromoly tubing, if cleaned well, is not hard to weld.  I'd suggest .045" ER-70S2, 1/16" 1.5% lanthanated tungsten.  Set your Dynasty to 120 amps, 1.6-2.0 pps, 30% on time, 5% background, don't mash the pedal until you need to. The repair would be best with the headset cup removed, as it will be harboring some grease, but the downside is that the headtube will distort as you weld it.  You might leave the cup, but pull the bearings and degrease the headtube and bearing cup as thoroughly as you can. Keep in mind that in an emergency, if you repair fails, someone could get really hurt.  If a frame failed as they were pulling up to a busy intersection, or down a steep hill, it could be disastrous.  The chances of that might not be high, but if it were someone I knew, I'd want to make sure to do the repair carefully.Miller Dynasty 200 DXMiller CP-300 with 30A feederHypertherm Powermax 900Oxy-fuel w/Harris torchesScotchman Glide-in bandsawMonarch 10EE latheEmi-Mec Autoturn latheDeckel FP2NC milling machinePro-Tools 105 Bender
Reply:I would go on down to WalMart and get another bike.
Reply:Originally Posted by BTDSettings:Tig w/ 1/16" ER70s-2.1/16" 2% thor, #6 cup.100% argon, 15 cfm.85 amps.Sound OK with you guys?
Reply:Originally Posted by brodazhiweiI would go on down to WalMart and get another bike.
Reply:You're probably looking at a tube wall thickness in the .040-.045" range.  I'd second the suggestion to leave the headset cup in place to help prevent distortion.