[JCmotoTIG]

Hello All,

I started welding about 2 months ago and have been doing a few hours every other day to get some practice in since then. The sole purpose of this is so I can design and build my own motorcycle exhaust. I'm a design engineer by trade, so the design bit was easy, just need to learn how to weld!

So can I get some professional feedback please on my efforts so far, just so I know what direction I'm going in? See the picture attached.

20140930_174808.jpg (41.78 KiB) Viewed 744 times

Here are my setup details;

1.5" (38.1mm) OD x 18 gauge (1.2mm) 304 SS pipe
Pulse settings are: 6A (Machine minimum) to 30A, 25hz (Machine max), with pulse width at 0.4 seconds
Using the 4T torch button function on this machine has an automatic 0.5 seconds of pre-flow, and I set the Up-Slope to 3s, Down-Slope is 3.5s.
Post flow is around 4-5s
100% pure Argon at 10cfh (4-5lpm)
0.06" (1.6mm) 2% thoriated tungsten, sticking out of a 1/2" No. 8 cup by around 1/4", large gas lens, on a WP-9F torch.
Not using any filler on this as the individual pieces were nitrogen laser cut and line up perfectly.

I appreciate any advice you can give me. Cheers

[dsmabe]

I'm no professional but can at least get started on replies. Overall probably better than me right now, just work on your consistency. One question though, did you purge the pipe beforehand? If not, from what I've been told, the outside may look fine but the inside can have contamination that will shorten the life of your welds.

[dirtmidget33]

Don't take offense at this comment. Consider reengineering the bends. Simplify whole process instead of doing the armadillo thing will be smoother and create more even flows too. From what it looks like to me a good tubing bender Will save you hours of time and material.

Just my .002 cents

1001142039.jpg (38.65 KiB) Viewed 726 times

Odd coloring is from being heat cycle over and over again

[Otto Nobedder]

Welcome, JCmotoTIG,

Glad to have you among us.

I don't see anything wrong with those welds that time and practice won't fix. I'd think they're pretty solid as they are, and you need only to work on the cosmetics. This is a matter of training your hands to repeat the motions in small, consistent steps. Sound simple, but it still takes time.

dsmabe's comment has merit; Backpurge is not required in exhaust systems, but you'll get greater efficiency (no "sugar" sticking out into the pipe to disrupt flow), and, as he suggested, longer life.

Steve S

[Otto Nobedder]

.... Consider reengineering the bends....

Good suggestion for a typical exhaust.
If he's building an expansion chamber/exhaust for a two-stroke, this would be impractical, though.

Steve S

[dirtmidget33]

If he's building an expansion chamber/exhaust for a two-stroke, this would be impractical, though.

Steve S

Yes expansion chamber totally different animal. Looked to me like a s bend maybe collector in one. If expansion chamber then I would start considering flat sheets and building into cones if doing weird bends in cones. . . well then I would be looking for an old timer that used to build old aluminium body panels on race cars to form that stuff and to learn from them. Hard to find guys that could teach the art of an English wheel.

[weldin mike 27]

This "pie cut" or lobster back method is very popular in Australia at the moment, and if you are building a custom exhaust/or piping allows for almost infinite adjustment of the direction of the pipe.

Mick

[TRACKRANGER]

@JCmotoTIG:

Keep in mind restrictions caused by eddy's at all the individual changes in direction, especially if you are looking for ultra-efficient scavenging, low / no back pressure. Less joins might be better under some circumstances. Also need to be mindful of any internal obstruction from weld deposits, not perfectly aligned joins etc.

Good luck though, it's a worthwhile approach.

[JCmotoTIG]

Thanks for all your thoughts, I really appreciate the feedback.

@dsmabe & @Otto Nobedder
For the project work shown here I have purged the pipe, and compared to the first practice welds I was doing without purging, I've been able to see first hand how advantageousness it is.

@dirtmidget33
Way ahead of you! I thought this way would look cooler and knew it would cost more in time and money than using mandrel bends, but didn't realise just how much more! Put it this way, for my next project I'll use bent tubes! Although, doing it this way has forced me to complete a lot of welds in a very short amount of time, which is great as I'm still learning.

@Otto Nobedder
Tis' a 4 stroke exhaust, for a Honda VFR400. Not much space going on around the rear bank and single sided swingarm, so have been tacking it a single pie cut at a time to make sure it fits. I'm also trying to make the silencer exhaust under the seat rather than out the left side, which again reduces the amount of space to play with round the side of the swingarm.

@TRACKRANGER
I've tried to place the pieces as closely aligned as I can for that exact reason, I guess 'the proof will be in the pudding' as we say over here!

Thanks again. Any more comments are welcome.

[kiwi2wheels]

http://www.burnsstainless.com/tubingmain.aspx

[Otto Nobedder]

JCmotoTIG,

Sweet! I like that approach. Putting time in to build it "the hard way" is an investment in your skills that will pay dividends, and you still get exactly what you want on your motorcycle.

Well done.

Steve S