Thin-walled exhaust tubes

[R. Alexander]

Did a search on this, was surprised to not find anything.

How thick are your exhaust tubes? It's hard to find anything thinner than .049" in constant diameter tubes and that size is way overkill.

Moving to titanium poses some welding issues so I want to find thin steel ones.

Has anyone found suitable exhaust tubes that are .035" or thinner?

[kapps]

Not sure if the big production houses have found ways around it but we've had serious issues trying to bend .035 past 10 or 20 degrees.

[Mikey Antonakakis]

I'm gonna get in on this discussion because I'm wondering the same thing.

[TimR]

We looked into titanium, but the problem was bending the tubes rather than the welding.
The thickness may look like overkill but take into account the whole manufacturing and handling process and you'll most likely see that the reason nobody has thin walled exhaust tubes is that its not feasible

[Kirby]

Originally posted by R. Alexander:
Did a search on this, was surprised to not find anything.

How thick are your exhaust tubes? It's hard to find anything thinner than .049" in constant diameter tubes and that size is way overkill.

Moving to titanium poses some welding issues so I want to find thin steel ones.

Has anyone found suitable exhaust tubes that are .035" or thinner?

The smallest I've seen was a 1.2mm (0.049") 304-STST. But then all the bends had to be purchased from burn stainless because no one wanted to bend such thin wall section for us. No one we could find would weld smaller than .049" either.

Waterloo did have Ti exhaust at one point sponsored for supply and I understand CNC bending, it was very time consuming getting reliable bends out of the thin walled ti.

[Mazur]

A PTG M3 header I saw had, I believe, .028'' wall thickness inconel tubing. Just by flicking it with your finger you could tell that it was very thin.

[Drew Price]

Burns Stainless stocks slash can make 90 and 180 degree bends of the small stuff, like 1.25" - 1.75" diameter, I'm sure there are other exhaust supply and race houses that would have similar. Haven't seen this year's Pegasus catalogue, but places like that. Maybe even try Jegs or Summit. Or call McMaster and special request it, see what kind of quote they come back with.

Burns has 0.035" wall 321 and 304 tubing in 1.75" diameter (1.5" for 304), and it's not cheap....

Best,
Drew

[Adam Vaughan]

For our 2009 4-1 headers, we used GR2, 1.25" OD, 0.035" wall seamless titanium tubing.

I know this topic is about wall thickness, but I thought I'd also share some of my own experience to help you guys out. First off, we decided to go with Ti primarily to drop weight followed by thermal reasons. Ideally, you want to go with 1.375" OD for a ~600cc engine, but it's not a standard Ti size to purchase and most benders won’t have the die for it (but they'll be happy to charge you to make one with a long lead-time). Getting the tubes CNC bent was definitely the biggest hurtle--don't even bother trying to do it yourself unless you really know what you're doing. I spoke to about 20 different bending houses before finding one who would consistently return my calls, had Ti experience, be willing to do the one off run in Ti, and also would sponsor us with a discount. Don't forget to keep your bend radii standard sizes and doable for the diameter of your tubing (this makes packaging lots of fun). Then there's the whole welding of the headers, which is not exactly a walk in the park because of embrittlement. It has to be done in an inert atmosphere. Even through their customer service could use some work, I'd recommend getting your headers Jet-Hot coated. It drops the surface temperature to ~450F, making thermal management somewhat painless.

Ultimately, the headers weighed ~3lbs. In retrospect, I'm not sure the extra effort to get them done in Ti was worth the cost or weight savings.

[Adam Vaughan]

As a proud parent, here's how they came out:
http://i649.photobucket.com/albums/uu213/adamv61243/FSAE%202009/Fabrication%202009/exhaust.jpg?t=1255852393

And this is after sprinkling "Precision Blingology" on them:
http://i649.photobucket.com/albums/uu213/adamv61243/FSAE%202009/DSC02810.jpg?t=1255849306

I wish I could say our muffler and collector setup worked out just as well. But I suppose that's best left to the history books as we were understaffed and out of time.

[Kevin Dunn]

In 2008 we used 0.065"x1.5" T304 stainless for our turbo manifold. Obviously, this made it quite a heavy piece. I went and talked to Reid at Reid-Washbon Racing in California (they stock high grade SS, inconel, ti, etc). Our 2009 manifold was made with 0.035"x1.5" T321 stainless which we purchased all of the bends from him directly. Stuff retained so much more heat than the 304 despite having half the wall thickness AND cut 3 pounds off of the old manifold...Pricing wasn't too bad either.

We'd like to do inconel one day but that probably won't be this year due to $$$.

[VFR750R]

Originally posted by Kevin Dunn:
In 2008 we used 0.065"x1.5" T304 stainless for our turbo manifold. Obviously, this made it quite a heavy piece. I went and talked to Reid at Reid-Washbon Racing in California (they stock high grade SS, inconel, ti, etc). Our 2009 manifold was made with 0.035"x1.5" T321 stainless which we purchased all of the bends from him directly. Stuff retained so much more heat than the 304 despite having half the wall thickness AND cut 3 pounds off of the old manifold...

Why do you think it retained more heat? Did you coat them? The thermal conductivity is within 1%.

[Kevin Dunn]

Ah, yes. Failed to mention we had it ceramic coated also. Just working with the tubing (cutting and grinding it) compared to the 304 we noticed a lot of difference. Probably mostly due to the decrease in wall thickness though. 30-thou is quite a bit.

[RenM]

Originally posted by Kevin Dunn:
We'd like to do inconel one day but that probably won't be this year due to $$$.

Of what use would inconel be for Formula Student?
You can´t reduce the wall thickness any further then with Stainless or Ti.
Inconel is heavier then both.
You dont need the high temperature stiffness inconel offers.
And the whole thing is a lot more expensive then stainless.

[Brett Neale]

UARC's 2006 and 2007 car (same exhaust) had 1.2mm wall thickness mild steel exhaust. The material was a BHP product called "Ezyform" I believe. There was only one place in Adelaide who would bend it, everyone else thought it would split.

Dropped the exhaust weight by 4kg over 2005's exhaust.

[VFR750R]

Originally posted by RenM:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kevin Dunn:
We'd like to do inconel one day but that probably won't be this year due to $$$.

Of what use would inconel be for Formula Student?
You can´t reduce the wall thickness any further then with Stainless or Ti.
Inconel is heavier then both.
You dont need the high temperature stiffness inconel offers.
And the whole thing is a lot more expensive then stainless. </div></BLOCKQUOTE>

Somewhat agreed. For road racing at these exhaust heat levels, inconel is more of a liability. It will work harden to failure if it is never run above it's annealing temperature (>1800F), making it not have any more durability, or perhaps less so, then 304 or 321.

But...inconel is routinely run as thin as .019" wall, making it as light as .035 Ti, and stronger at temperature.

At those thin wall thicknesses, you have to be careful not to 'ding' them, they become very crushable, not to mention the difficulty in welding tube that thin.

I can't see NA headers for fsae ever being made from it, but serious turbo headers could be made from inconel.

Inconel is ~3 times the expense of 321.

Ti really doesn't seem like a bad option for NA cars. Ti has an embrittlement problem when run above 1600F, but none of these cars should be running EGT's that high (at least for long enough to heat the Ti to 1600).

[JamesWolak]

Originally posted by VFR750R:
QUOTE]

Why do you think it retained more heat? Did you coat them? The thermal conductivity is within 1%.

Yeah, I am on Kevin's team and must admit that the EGT data has never been closely reviewed to prove that we retained more heat (even with the coatings). The only thing that suggests this is the lack of burns from our drivers back but we also ran different timing/EQR/ waste gate strategy/packaging/heat shielding so it’s not a good A to B comparison.

I would also like to point out that a decent amount of weight is wasted in the exhaust attachments not just the exhaust tubing, sizing these correctly will pay off.

[RenM]

bending 1mm or 0.8mm stainless steel tubes is no problem at all.
But be sure your tubes were heat treated before!

[Chris Allbee]

For a given alloy heat treatments will increase the yield and tensile strength at the expense of total strain capability. Are you sure you'd want to heat treat the material before bending? Why not just anneal or normalize the material?

I understand that both require heat, but the implications of a "heat treatment" are very different from an annealing.

[R. Alexander]

thanks for the input.
the stuff from burns looks promising.

[wweissin]

There is also Simpson Race Exhausts in the UK.
They can bend 1.5" dia. .020 wall with a center line radius of 1.5". I have no clue what the cost of that would be. They also have extensive experience with inconel in F1.

Simpson Race Exhaust (http://www.simpsonraceexhausts.com/index.html)

[RenM]

I meant annealing. I wasn't able to recap the English word so i tried to simplify. Sorry for that http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Jon Oneill]

Due to time, money and skill restraints, we decided to use pre-mandrel bend sections which we would then weld together ourselves. We went a slightly larger wall thickness on our steel tubing (.9mm) mainly because we did not have any custom mandrel places around who would do 1.25" tubing according to our design requirements.

If we did not go this way and had to get custom mandrel sections made up, our bend radius would be much larger and that would have significant packaging and weight disadvantages.

Its also worth noting that even MotoGP bikes still use welded sections for their exhaust headers. They actually use increadibly short tube sections throughout the bends which then enable them to clean up the inside surface of the weld to optimise flow as they go. We aplied the same thinking this year with our extractors however, we used much longer sections due to time restraints. https://s3.amazonaws.com/basec/473504/2160868/Simo2.jpeg?AWSAccessKeyId=1RF809NDDCNB7616HJ02&Expires=1256087700&Signature=yt4KK9tjdiFyF%2F4nngaQXe2GVAA%3D

[mbzimmerman3]

In the past we have been able to use mandrel bent j-bends manufactured by hooker headers with 1.375" OD and a 2" bend radius. Our header design for this year uses this same tubing but hooker has temporarily stopped making this specific j-bend (back order date continually being pushed back since august).

I have searched all over the internet for the same spec j-bends but the closest thing I can come up with for 1.375" OD tubing is a bend radius of 2.5". So, I tried emailing a few places including burnsstainless, and a few other places I found that do custom headers. No one seems to be able to bend that small a radius.

Does anyone know of any companies that can, at the least, bend this size tubing or a place that manufactures it already?

Thanks for the help.

Mike
University of Pittsburgh
Panther Racing

[TeamRX8]

Several more T321 mandrel bend resources for you below in addition to Burns Stainless. I built my own 18/20 Ga. manifold and exhaust systems for Mazda rotary applications:

http://www.customaircraft.com/index.html

http://www.spdexhaust.com/TubingB.html

Unfortunately with the economy being what it is most places are cutting back on their inventory. You'll have to call and verify which specific parts are available off the shelf.

Best Regards

[BuckeyeEngines]

Ak tube in cleveland Ohio makes aluminized steel in 1.5 id with .032 wall thickness. I dont know the radius of the bends but normal 4130 .045 thick tore when our sonsor tried to bend it.

[TeamRX8]

this company can likely do what many of you are asking about, but they only stock 16 ga T304 parts so you're going to pay some heavy setup expenses just to run a few elbows in the diameter/gauge/type you want

http://www.woolfaircraft.com/index.html

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