Exhaust Why only steel for expansion pipes?

[FurryOnTheInside]

Not much else I can add to the title lol. Hmm..

So I was looking at tubing to make a second muffler or tail muffler to eventually go on the end after a tuned expansion chamber I'll hopefully be making at a later date, and I'm even looking at silicone tube for that, but aluminium looks okay.
The 50/51mm steel tube I'm finding online is way too thick 1.5mm, I have 1mm already from an old bunk bed frame so I know it's very heavy so I would probably be choosing the aluminium for my muffler.

So that just got me wondering what is the actual reason for only ever using steel for the expansion chamber? Is it that aluminium will fatigue and crack if used for the X chamber itself?

But I'm still okay to use ally for the tube of my muffler though, right? I'll just be bolting on two end caps from the spare stock mufflers I have using threaded rod, and stuffing some muffler packing inside with a bit of a rolled up oven chips (fries!) mesh to make the perforated tube through the middle.

 

[Will'smotobikes19]

Well expansion chambers vibrate a lot atleast the "thrust racing mufflers" if you rev up the engine and take a look at it you can see the whole thing move. Steel is also cheaper than aluminum. Aluminum is also not as strong. It could get pretty weak if you went on very long rides and that thing gets too hot. What's the word? annealing? something like that. I mean throw an aluminum can into a fire for a second and pull it out it will be half melted. If you throw a steel can into a fire it won't be melted. I suppose thickness of the aluminum would help. That's why the aluminum frames are thicker than steel to make up in strength.

 

[FurryOnTheInside]

Well expansion chambers vibrate a lot atleast the "thrust racing mufflers" if you rev up the engine and take a look at it you can see the whole thing move. Steel is also cheaper than aluminum. Aluminum is also not as strong. It could get pretty weak if you went on very long rides and that thing gets too hot. What's the word? annealing? something like that. I mean throw an aluminum can into a fire for a second and pull it out it will be half melted. If you throw a steel can into a fire it won't be melted. I suppose thickness of the aluminum would help. That's why the aluminum frames are thicker than steel to make up in strength.

Aluminium conducts heat much faster than steel, works well for my camping cookset so I thought perhaps it would cool the exhaust gasses too much, and that makes it ideal for the tail pipe muffler. Idk if the X chamber gets hot enough for the aluminium to crack but perhaps the header does. I don't think I have ever even got my engine up to a high temperature, I'm always stopping it to pedal past other cyclists lol.
Anyway I was only wondering. I'm not going to be starting work on the X chamber for a little while yet. Muffler first.

 

[zippinaround]

stainless works quite well for pipes some may disagree but from my own experimenting it was better than mild or cold rolled bright steel, aluminium no good the heating and cooling will make it fall apart along with vibration, if you want to cool your pipe you can always weld fins on the outside but will need to carefully tig it so as not to disturb your perfectly tuned pipe. and dont forget if you have a scrapyard nearby you can find bits of scrap stainless to use for a fraction of the cost.

 

[FurryOnTheInside]

stainless works quite well for pipes some may disagree but from my own experimenting it was better than mild or cold rolled bright steel, aluminium no good the heating and cooling will make it fall apart along with vibration, it you want to cool your pipe you can always weld fins on the outside but will need to carefully tig it so as not to disturb your perfectly tuned pipe.

I actually have no objections to using steel. Standard, normal steel expansion pipes for other bikes/ scooters, chopped up and joined with high temp hose (like the SBP pipe is) will do for my purposes.. I just wondered what the actual reason for them all being steel is.
I definitely want to try an aluminium cylinder for my tail pipe muffler with two stock muffler caps, as it'll just be held together by a threaded rod through the centre.

 

[zippinaround]

the reason i think my stainless pipe was better than the normal steel was one side of the sheet i used was highly polished i put that on the inside so very little carbon will stick to it making it resonate better. even as a muffler unless you buy some high grade aluminium pipe that is thick i.e. expensive as f*ck the pipe will split in no time where the seam is. hell you should just try it if you have some alu pipe lying about but i wouldnt pay to test it.

 

[FurryOnTheInside]

the reason i think my stainless pipe was better than the normal steel was one side of the sheet i used was highly polished i put that on the inside so very little carbon will stick to it making it resonate better. even as a muffler unless you buy some high grade aluminium pipe that is thick i.e. expensive as f*ck the pipe will split in no time where the seam is. hell you should just try it if you have some alu pipe lying about but i wouldnt pay to test it.

The smooth polished surface definitely makes sense for an expansion chamber.

I'll be wrapping the tail muffler, so.... Well I guess I'll find out. I have 50mm x1mm steel bed frame lying around so I'm going to use that first and then try the alu later (spent too much money already this month lol).

 

[HeadSmess]

i know it runs a bit cooler, but um...

alloy is fine. if youre building from scratch you can always change the dimensions slightly to compensate for any excessive cooling. and you can wrap it without it rusting.

joining the stuff is the tricky bit... i doubt that technoweld zinc solder stuff is up to the task, its TIG all the way.

allowing for vibration with spring mounts and graphite bushes at the joins... dont make it all in one piece.

pipes dont get hot enough to affect the aluminium that much. its cooler than what the piston and head is experiencing.

you usually still run a steel header though, as the first bends do bear the brunt of the hot exhaust gas. i can only think of one twostroker that runs an alloy header pipe... (cr125 and related, with the ATAC valve) wasnt an issue with these bikes (except for that ATAC valve!) despite pumping out far more heat than any china girl can.

you could make a pipe out of copper or brass sheet if you so desired, just silver solder it all together...

just dont do what i did, which is start making tags for lap joins, give up, and just butt the steel sheets up, expecting that tiny sliver of silver to hold it together...it doesnt!

vibration is the killer. no rigid joins!

 

[FurryOnTheInside]

i know it runs a bit cooler, but um...

alloy is fine. if youre building from scratch you can always change the dimensions slightly to compensate for any excessive cooling. and you can wrap it without it rusting.

joining the stuff is the tricky bit... i doubt that technoweld zinc solder stuff is up to the task, its TIG all the way.

allowing for vibration with spring mounts and graphite bushes at the joins... dont make it all in one piece.

pipes dont get hot enough to affect the aluminium that much. its cooler than what the piston and head is experiencing.

you usually still run a steel header though, as the first bends do bear the brunt of the hot exhaust gas. i can only think of one twostroker that runs an alloy header pipe... (cr125 and related, with the ATAC valve) wasnt an issue with these bikes (except for that ATAC valve!) despite pumping out far more heat than any china girl can.

you could make a pipe out of copper or brass sheet if you so desired, just silver solder it all together...

just dont do what i did, which is start making tags for lap joins, give up, and just butt the steel sheets up, expecting that tiny sliver of silver to hold it together...it doesnt!

vibration is the killer. no rigid joins!

Probably beyond the intended scope of this thread but...
My idea for a stealthily slim (tuned length) pipe was to use a 2" tube and cut a triangle out of each end then bend into a cone (I actually want one side straight so it lies close to the frame for stealth) and then take it to a welder to be TIG welded by someone competent. There would then be only a small amount of welding needed so it would be less expensive for me.
Would it have to be a lap joint? Because that would be tricky with it being a tube already. Would it be okay to have that seam just butted? If so it would be a lot easier, and I would be able to use high temp silicone hose and pipe clamps to join the sections (like the SBP pipe). The clamp would help keep the narrow end together and the tube is already machine welded so that holds the top of the seam together.

 

[HeadSmess]

if its tig welded from tube, no need to lap. lap joins just if you go the silver solder/brazing route...