Making up exhausts - any tips?

[Mr Fro]

Hi guys. I made up an exhaust system for the generator the other day to make it sound less obnoxious in the pits.

I was intending on TIG but someone forgot to get a new bottle of argon so had to make do with MIG...

Cutting and fitting up was fine but I struggled a bit welding it up - it's got a few bends in it so I couldn't run a bead all the way round some of the joints in one go so ended up stitching it together.

I think MIG ended up the better route for this application as I reckon I would have really struggled getting round the pipe with a TIG torch.

I'd have preferred the look of TIG but the MIG looks pretty seamless once it's been knocked back.

I've seen any number of beautifully TIG welded bike exhausts and would love to know how the heck they're made - is there some sort of trick that I'm missing or are the fabricators the most flexible people in the universe?!

Cheers,
Fro

 

[slim_boy_fat]

Setup, technique and robots

And maybe a turntable?

 

[Richard.]

Setup, technique and robots

Actually the really good bike exhausts are hand welded by gifted torch holders. Yes rotators are used but not often automated welders. The cheap ones that are produced by the truck load are made by robots.
Austin racing, Akrapovic, Arrow are titanium and stainless hand welded Tig

 

[Richard.]

That's why I included 'setup' and 'technique'

Yes your right there. Set up and technique. They just don't weld with robots. Or at least the good ones don't any how.
Tbh cylindrical tig welding in a smooth rotator is easy to get perfect once you master the speed to your comfortable welding pace. You don't have to travel anywhere or worry about angle changes. Not hard at all to get perfect looking results.

 

[sardine]

I get all my exhausts for various projects from the scrap bin. You usually find they are 90 % sound with just one end rusted out, chop it off and hole saw a bit of 2mm sheet to fit the tube, and weld it up.

In fact I thought it would make a money spinner selling welded recon exhausts.

 

[Brad93]

I weld the exhausts for these guys now. All mild steel. Just playing with some stainless ones now. http://www.gibsonexhausts.co.uk/

 

[Mr Fro]

This was an adaptation of a CBR600rr exhaust. Took a couple of bends from the downpipes, couple of straight bits, an expansion chamber and then to the box. I thought about a turntable but how would you go round the pipe some 18" up a not straight pipe?

 

[Richard.]

but how would you go round the pipe some 18" up a not straight pipe?

It's not always possible to do on a rotator which is where your skill needs to come into play for angle changes to maintain your arc length. If your an outfit making these professionally then you'd be surprised at what you can rotate and how. As Pdg said it's very much in the set up. I have welded lots of stainless exhaust joints to what I would say are a lovely standard. I'm not a professional outfit and have a few basic jig arrangements that I've made in the past to hold sections on the bench. It's not difficult it just needs practice to keep your angles the same around the tube.

 

[Mr Fro]

I can see an awful lot of practice on the horizon.

 

[Richard.]

Of course. It's a skill it's not meant to be easy. Don't be in a rush, post your results up. I'm sure you'll do fine.

 

[Kent]

Do something eight hours a day for a few years and you can get pretty darn good at it.

I might be alone but to me personally I rate a weld by its strength fusion and the fact that I don't notice it. Not the patterns In the bead.

To this end a nicely formed mig bead with a good transition at the stop/ start. Nice toes is the equal or better as a pile of pennies with pretty colours

 

[Richard.]

While I agree the fundamentals of a weld in general are function over visual appearance. I still and always will prefer the Tig adopted method for thin wall tube over mig.

 

[Mr Fro]

I'm with you on that one Kent, much prefer something that works than something that is pretty but pants.

I still class myself as a noddy welder so I expect it to be a long time until I get these things mastered.

It hasn't stopped me eyeing up the wife's sewing machine as a good donor for a rotating table build though!