Exhaust expander

[Ed Womer]

I am working on a project and using 1 1/4" stainless steel exhaust tubing with .065 wall thickness and need to weld straight tubing to a cut off bend. Problem is the bends OD is distorted probably because the manufactures mandrel is getting worn and allowing the tube to distort. Does anyone know if and where you could get a tube expander that will do 7/8" to 1 1/4"? I have bought cheaper ones but they don't work so I am looking for something that would expand the tube to it's straight length and only maybe a 1/2" of tube since it is in the bend area and it is 2" CLR.

Thanks, Ed

Yes I have made a tapper and been hammer it in the end but I haven't been able to quite get it to the straight OD.

[S Lathrop]

If I was facing the issue you have, I would machine a tapered plug that I could drive into the distorted bend. With the plug and a sheet metal hammer should do the job. It won't be fun or easy but it will work. The taper wants to be as gradual as the bend will allow.

[mikey]

What about asking your local exhaust shop to put it on their expander for you?

[Ed Womer]

Yeah Steve that is what I have been doing. Took some different sizes of DOM tubing and welded one inside the other and tapered it on the lathe. You are right that the tapper needs to be slight and it is working but not fun.

I noticed on Amazon kits that are for copper, aluminum, titanium and mild steel. They look nice but it doesn't say stainless so they might not be worth the expense but look like something that would work if strong enough.

Mikey the issue with the local exhaust shop is they usually start at 1 1/2" or larger for their stuff.

Thanks guys, Ed

[Hardingfv32]

The reduction of the diameter is standard on all retail exhaust U bends, not a tooling issue. If you are trying to expand the area where the bend transitions from a radius to straight, you are going to have a had time with any type of expansion tooling. I always reduce the diameter of the mating larger (straight) tube.

Just a tip: Are you using a stainless welding backup flux instead of purging?

Brian

[Ed Womer]

Hi Brian,

I have been back purging when doing stainless collectors that I have made. I did make a copy of a plumbing tool that I have that is used to install or remove the tub drains and I used 3/4" threaded rod and made the tooling to fit inside the stainless tubing and turn the rod to expand the ID of the tubing. It is working better that hammering a taper into the tube and is faster. I would like to get just a few thousands more and it will be close enough. Still looking at alternative methods.

I realized that the old Zink vee I bought from a local Porsche shop that he wanted to get rid of had a lot of extra parts and I saw some bearings since I think the previous owner was experimenting with intake work and I might see what size they are and if I could try that method.

Ed

[J Leonard]

How about a split collar clamped on the outside to hold it round?

[Ed Womer]

I don't think a split collar would do the job since the OD has been reduced due to the die forming the bend and it also deforms the tube not consistent so it needs to be expanded to get back to the original OD. Fortunately there is YouTube and if you watch enough video's you will get to see how they make the expanders. Now I just need the time to make the parts and hope it works.

Ed