Stainless exhaust for a KTM motorcycle

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So I mostly lurk here and pick up advice from the various builds and threads and I've done my obligatory "welding cart" thread and now I've moved to a project that is closer to my heart. My bike. So, this is my very brief introduction to me and this thread. Mostly I'd like feedback on my progress. I'm a professional photographer who loves, rides, races and builds bikes. I have a pretty decent shop that is well equipped and I share it with some very talented fabricators and machinists - all building bikes. I've mostly learned to weld from these guys and by just picking up the torch and giving it a go. About a year ago I decided that welding was going to be really important to me and my progress and I buckled down and started practicing and I bought a Dynasty 200. What brings me here is that my main bike, a KTM 950, is in for another rebuild and I've decided to replace the exhaust with one I am going to build. I've designed a few exhausts but haven't welded them - just done the cut and trim. So this is a big project for me since it's the first one that "counts". I figure an exhaust is a good one to start with as opposed to a frame since it's failure won't kill me. So here's me and my bike: Here's a look at the stock system: What is precipitating the exhaust is that I am putting in a new larger 990 engine and decided that since I can't afford to buy a new bike I'd turn this one into something more special. The system I have planned isn't too much different than stock but it's going to be from stainless instead of plated mild steel which I've replaced twice so far. If you'd like to read more about the build I have a thread going here: 950 Refresh or Mission CreepHere's what I got from Burns: mandrel bends in .065 304. The stock is behind.Here's the flanges I machined: and here's why I'm starting this thread: Yes, I know now that I cooked the **** out of them. It was probably 70-80 amps, no gas lens and a 3/32 tungsten. I wasn't happy about it. At least I recognized that I screwed it up but sadly not before I did it. Still usable but not pretty. So, I took a break from building it to take a welding class at the local community college and seek out advice from friends and anyone who can offer it. I know that what I'm trying to do is difficult but I learn best when over my head - it's how I've made such a successful career and I'm not likely to stop now. So, I'll post up some more in a bit but at least that gets me started. Gregor
Reply:So it's obvious I didn't really have a sense for how much heat. I signed up for the local class which was really not much more than an open "practice" with lots of free material. I started with 50 amps and just kept dropping it realizing that less amps finally got me the nice straw color I was looking for. And finally I got a very short bead that looked okay. During this I was told that a gas lens would help. I'd gotten one before but never used it so back at my shop I put the lens on and swapped my 3/32" for a 1/16" tungsten. Then I started trying to weld the actual tubing I am using: 1 3/4" .065 wall 304 stainless.The bead on the right was an early effort from before even the flanges. So I'm making progress. Below is my last try at the tubing. My shop is in NYC and I live in Portland so I only get the chance to work on it about once or so a month when I'm back to my NYC studio for work. We just moved to Portland and until we find a real place my shop will stay there. Sucks but at least I still have a place to work and it gives me something to do with my free time there.So yesterday I got back out to the school and spent some more time just running beads. Lap joint:T-joint - this is really hard for me from some reason. I can't quite get the puddle to stay where I want it. It either stays down or it keyholes. Detail: And finally my best effort at a butt joint which is what the exhaust will be mostly. more to come - there's a 10 photo limit...
Reply:Here's the front header tacked up: and the rear:So next week I'll head back and start work on building an "X" collector which I need before I can finish the mock up of the rest of the system. Here's an example of a beautiful one:  I'd like to get that fabbed and tacked and then build the rest of the system and get it all tacked up and then buy some more tube to take to my class and practice before I actually start with the real thing.  Oh, and yes, I know I'll need a back purge. I have a splitter on my argon tank but not a second regulator. I'm hoping that will be fine. One of the things I have a really hard time with is getting more than 1/2" of bead on the tube. Is there a trick to that? Are you free handing the torch or are you braced? I've tried to look at as many videos as I can but there's not much out there for stuff as small as I'm doing. When I get there I'll need advice on heat management (in terms of not letting the system warp or distort) but for now I'm still working up to getting good bead and I don't want to weld the real thing until I think I won't screw it up (too badly). Thanks for any advice. Gregor
Reply:Gregor, are you going to back purge?HammerFile Big Hammer------------------------------Here, let me Google that for you...
Reply:Yes, I have a splitter for my tank but not a second regulator. I have only done one test with it so far but I'll try to get that working before I start.
Reply:You probably don't even need to backpurge running For your application, butt welding with fusion, properly back purged and gas covered, will give you all the strength you will ever need.  Many high end aftermarket systems are fusion welded with an robotic (orbital) welding process.
Reply:awesome thread . team orange!
Reply:Originally Posted by dave powelsonMany high end aftermarket systems are fusion welded with an robotic (orbital) welding process.Yeah how true the above is---these high end systems have precision fitting--which the orbital process requires. Without the precision fitting and fixturing, things can go to pot very quickly as I've mentioned.The orbital process achieves a higher order of precision torch movement that surpasses what an ordinary or high skilled weldor can achieve by hand;additionally the orbital weld parameters can be programmed and refined--oftendegrees above the parameters available in conventional machines.You're trying to compare 'Perfect World' robotic conditions to manual autogenous welding--especially by one lacking in bench time, fixturing and fitup methods....and in SS, which isn't-at all, forgiving to errors.
Reply:The rest of the pics:6.  Weld wire brushed7.  Fusion weld interior closeup8.  Fusion weld interior mid distance9.  Orbital weld interior mid distance10 Orbital weld interior closeupI take nothing away from a filler weld.  It can be stronger, when strength is the critical factor.  For this application, though, my experience is that the fusion weld is easier to master for some one with no experience in this particular application,  and provides no lack of strength with full penetration.  Hope this helps someone trying to figure out this option. Attached ImagesLast edited by Mr. Moose; 05-01-2012 at 08:45 PM.
Reply:Since nobody caught this and mentioned it I will..GET RID OF THAT WAY OVERSIZE CUP!!!!!!!What a waste of gas.Blowing around everywhere except where you need it...I would just use a #5 regular cup and everything would be so nice....That's what I would do....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:Those are great pics and detailing of the 'how?'---Moose.You obviously have ability.I understand as you mention--that these were 'quick and dirty' setups...but:In the outlined pics below, are undercut areas.The inside pics show sagging-further confirmation of undercut on the outside.Doing a butt weld via fusion is fraught with this undercutting problem. Back off on the heat, etc. and poor fusion/penetration results. It's a very thin red line to walk.http://weldingweb.com/attachment.php...1&d=1335931432http://weldingweb.com/attachment.php...1&d=1335931455http://weldingweb.com/attachment.php...1&d=1335931465 Attached ImagesBlackbird
Reply:Originally Posted by zapsterSince nobody caught this and mentioned it I will..GET RID OF THAT WAY OVERSIZE CUP!!!!!!!What a waste of gas.Blowing around everywhere except where you need it...I would just use a #5 regular cup and everything would be so nice....That's what I would do....zap!
Reply:I've welded with a few different cups and I like the pyrex for both the coverage and the visibility. It does seem my welds are better with it but perhaps it's psychological or it could just be hood time. I do see how it could be very tricky to get the adequate penetration without undercutting. I'll do some coupons of a fusion once I get back to the shop and post up some shots for critique. My impression from testing my fusion welds (flat coupons) was that they were easily as strong as the parent material provided a got full penetration. .065 wall is considered pretty heavy for a bike exhaust so I should be good.
Reply:Getting every last shred of strength is not even remotely an issue here lol, Just ignore the armchair warriors that tell you so.Welding/Fab Pics: www.UtahWeld.com
Reply:There is some good info here. I have built exhaust for bike a time or two and done a couple in stainless. I always use a back purge... be it .065 304 for pipes or sched10 316 at the refinery. Just sayin' my bikes experience some violent vibrations that are transfered from the flange to the end of the pipes......actually through the whole bike including the rider On the .065 I fit it with no bevel and use filler wire off a spool that actually mics out to 065. I then hand file and polish. Thats just me and I do it scratch start with an old pipeliner hood, I don't have a pedal or wah wah bar or any kind of fancy machine. Not knocking that equipment or anybody that has it....just sayin'
Reply:I just noticed a good example of how gas coverage and weld color correlate...See the horizontal line below dividing colorful weld from not colorful? that's because when you stopped welding that area that had gas coverage. It had coverage for longer that the weld right before it where the torch was moving past. Do whatever you can to keep oxygen in the atmosphere from hitting the hot metal near the weld and you'll get pretty gay rainbow welds. Imagine if you had an inch-or-two long trailing shield on your torch... it would probably look like that all the way around.Welding/Fab Pics: www.UtahWeld.com
Reply:Originally Posted by MikeGyverI just noticed a good example of how gas coverage and weld color correlate...See the horizontal line below dividing colorful weld from not colorful? that's because when you stopped welding that area that had gas coverage. It had coverage for longer that the weld right before it where the torch was moving past. Do whatever you can to keep oxygen in the atmosphere from hitting the hot metal near the weld and you'll get pretty gay rainbow welds. Imagine if you had an inch-or-two long trailing shield on your torch... it would probably look like that all the way around.
Reply:Hi again. Sorry for the delay, I forgot the cable to my camera and I couldn't post up images and I just sort of plowed ahead. Anyway, here's some photos. Here are several fusion or autogenous welds - non purged. I was running low on argon, couldn't get my second tank filled and didn't have a second regulator so I skipped it. And here's the inside of those welds. Here's a filled weld (.034 308) at 40 amps I think with pulse turned on to 100pps 80% peak and 50% background... I think. I didn't write it down. It seemed to focus the arc a bit better and give me a bit better control over the puddle. I'll keep it on pulse I think. Here's that same weld on the backside - it was my back purge test.But, I did those Friday and was hoping to post them to get some feedback but couldn't upload them so I plowed forward rather than lose time. What's that saying, there's never enough time to do it right but there's always enough time to do it over? Hmm. Thursday night I went and picked up a new belt/disc sander (thanks for the encouragement Mechtician) as the one I had was crap and I hated it. Never buy cheap tools - you regret it every time, at least I do. Anyway I picked up the new sander and got it set up here behind my cold saw. Anyway, I had it in my head to make the X crossover I wanted. I knew it would be hard but it was the thing holding me up and, heck with it, I wanted to just plow forward. I am sick of welding coupons. I wanted the pressure of welding something that counted. So I was going to use a friends bandsaw and make a jig to cut the tubes but decided that I own a far better saw in my cold saw and so I spent half of Friday making a jig to hold the "U" bends perfectly in order to make the first 2 into 1 join. It's basically a clamp to replace the vice of the saw and hold the tube flush to the table. Here's what that looked like.My first cut didn't account for the right spacing so I needed to remove about 1/4" and I was pretty damn happy with my set up when I got this. Two perfect 1/8" slices.And finally here are my four tubes. The cold saw made perfect, square and repeatable cuts. Okay, gotta split this into two posts...Last edited by sakurama; 05-07-2012 at 01:04 AM.
Reply:Here are my two "2 into 1" tubes tacked up. And that is the idea so I just eyeballed where I'd want to cut them - basically halfway. Of course I couldn't cut them unless I welded them so I decided to just go for it - damn the argon - full speed ahead! That's my purge set up. I just turned on the argon for a few seconds to flood the tube (there were a few 1/16" holes pricked in the foil) and then turn it down to just about 3-4 CFM. And here is my first weld. I really had no idea how to weld into that super tight space but I just kept extending the tungsten and welding about 1/2" until I had the tungsten out almost and inch or more and it was a real trick to get the arc to go into the gap but I did get it. It seemed I had to have the tungsten less than 1/32 or 1/64 - almost touching before the arc would go into the gap and melt the tubes. I fusion welded the tops and the inside and added filler to the sides. Not sure if that's right but it worked. Here they are cut and dressed on the belt sander. And so I went ahead and just welded them up. I had one instance where it seemed there was some contamination and the arc just turned into a green bubble and the weld spit back and turned black - I have no idea why. I cleaned the inside and outside with alcohol and even wiped down my filler and tungsten with alcohol and ran a very fine point on the tungsten which I kept dressing since it seemed that welding the tight interior stuff seemed to make it dirty even when I didn't touch it or dip it. Oh, anyway, here it is: Critiques on my welds or methods is welcome. Gregor
Reply:When you purge you need to put argon in the lowest point and have a hole in the highest point so the the lighter air can be pushed out of as the pipe fills with heavier argon. Also you need to purge more than a few seconds, more like a minute on a pipe that size... and you cant just crank up the flow to make it purge faster or it will just just stir up the air and mix.Welding/Fab Pics: www.UtahWeld.com
Reply:Originally Posted by MikeGyverYou probably don't even need to backpurge running <40 amps on .065" material. Look at the inside, if it's not sugaring w/o a purge then doing so will probably just be a big waste of time/argon.Remember, getting colorful stainless welds is primarily about gas coverage, and in a cause and effect way, secondarily about heat input. You can put in all the heat in the world as long as you maintain gas coverage until it cools down to a certain temperature, and you'll still get colorful welds. Keeping the heat low only gets you so far if you want full penetration with 1 pass. Past that you need to find a way to sink the heat out of the metal and maintain gas coverage until the temperature that corresponds to your desired oxide color.
Reply:Originally Posted by MikeGyverWhen you purge you need to put argon in the lowest point and have a hole in the highest point so the the lighter air can be pushed out of as the pipe fills with heavier argon. Also you need to purge more than a few seconds, more like a minute on a pipe that size... and you cant just crank up the flow to make it purge faster or it will just just stir up the air and mix.
Reply:Since you mentioned pulse a couple times lately, it might be useful to you to think about the effect on pulse mode.  You want to have enough heat in the high setting of the pulse to get the full penetration you need, but drop it enough to reduce the heat input, which is critical on SS, since it holds heat much more than mild steel.  I suspect you would get results you'd like better by reducing both your 80% peak / 50% background quite a bit.A common setting keeps the high setting on 1/2 of the time, and then drops the "background" setting much lower.Here's a weld (the lower one in the pics) of a fusion weld with a setting of 75A / 50% peak / 25% of peak for the other 1/2 while the pulse is at background / 2 pulses per second on .065 SS tubing.  This would be the equivalent of 1/2 times 75A (37.5A) plus 1/2 times 25% of 75 (18.5) = about 56 amps average heat input.You can see the pulse gives full penetration  on the interior, which stays silver because of the argon purging.  The outside shows a very small undercut (remember these welds are about 1/8" wide) and work very well for a .065 wall tube project.Your cold saw gives you the ability to do setup which is essentially perfect for butt welds.The upper weld is an machine made orbital weld.  Just happened to be on the scrap I had handy. Attached Images
Reply:I haven't given up! I got some tips from a friend who does a lot of titanium and he convinced me that I really should just go fusion on this. I took some of his tips and in my welding class I used a Lincoln Invertec V205 so I could experiment with pulsing on something similar to my Miller Dynasty 200DX. Here's where I ended up on my settings: I was using a 3/32" red tungsten with a gas lens, 70 amps, 20 background, 50% cycle and 1.5hz with .035 rod. Above I was experimenting with torch angle but......this was where I ended on flat coupons feeding rod. I picked up some practice tubing from Columbia River Mandrel Bends (thanks Brandon!) and after playing with my settings and making my fit good I got to this: I feel pretty good about where I'm at. The pulse does wonders for control and I'm just barely getting full penetration. It's certainly more than strong enough and I'm convinced of doing the exhaust as pure fusion. Gregor
Reply:Looking good man. Try adding just a tiny bit of small filler with each pulse so the weld just barely bumps up and see what kind of results you get.Welding/Fab Pics: www.UtahWeld.com
Reply:Originally Posted by MikeGyver... getting colorful stainless welds is primarily about gas coverage, and in a cause and effect way, secondarily about heat input. You can put in all the heat in the world as long as you maintain gas coverage until it cools down to a certain temperature, and you'll still get colorful welds. Originally Posted by TuscanyThat's not true when you get stainless too hot it burns the chromium out of it giving it that carbon steel look afterwards.
Reply:Originally Posted by MikeGyverSo you're telling me getting the actual part "too hot" will burn the chrome out when that didn't just happen in the much hotter actual molten weld? Chromium doesn't burn without and oxidizer. Argon coverage until the part is cool enough will displace oxygen from the atmosphere and not allow the chromium (or anything else) to burn. Gas coverage is king.