Copper exhaust pipe... how to bend?

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silverbear

silverbear

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I have a question maybe one of you electricians could answer for me. I want to experiment making exhaust pipe from 3/4" copper water pipe and am wondering if a hand held type of conduit bender could handle copper as well? I'm guessing yes, but don't want to waste money on a bender if it won't work for copper. I wouldn't need to use double wall copper pipe as strength is not an issue. Thanks,
SB
 
Kevlarr

Kevlarr

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One type they don't list is soft copper tubing, it comes in a roll so in a way it's already pre-bent. :D

What you can do with soft copper is use it for your bend then transition to regular copper pipe if you want a long straight by "swedging" the soft copper to fit over the copper pipe.
 
silverbear

silverbear

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Thank you both for your input. I knew about double wall water pipe, but wasn't aware of the other types. I imagine most of those do not end up at Lowes or the local hardware. I've worked with both copper water pipe and the soft kind mentioned in a coil used for propane. If I could use the water type and get a nice, smooth bend with no unnecessary unions, that is what I'm looking for. If it would bend like conduit, then its a go. Don't know why I like copper so much, but I do. Maybe in a former life I worked in a copper mine. But then I probably wouldn't like it. Maybe I owned a copper mine and it reminds me of all the gold it got turned in to. If I could bend it I'd sure like to fool around with fabricating something.
SB
SB
 
2door

2door

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SB,
Just thinking and realized that you might have some problems using a conduit bender due to the inside-outside diameter thing. Typically conduit benders come in 1/2", 3/4", 1", etc. Copper pipe/tubing in measured two ways depending on who uses it. Plumbers measure it by inside diameter and pipe fitters (air conditioning guys) look at the outside.
Electrical conduit is measure by the I.D.. If by chance there is an air conditioning supply near you they will carry benders specifically made for copper. The conduit bender will not fit the tube exactly but maybe well enough for your purposes. Truthfully, I've never tried to bend copper with a conduit bender so I can't with any accuracy say what will happen but my feeling is you might get some kinks in the tubing.
Tom
 
silverbear

silverbear

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2door said:
SB,
Just thinking and realized that you might have some problems using a conduit bender due to the inside-outside diameter thing. Typically conduit benders come in 1/2", 3/4", 1", etc. Copper pipe/tubing in measured two ways depending on who uses it. Plumbers measure it by inside diameter and pipe fitters (air conditioning guys) look at the outside.
Electrical conduit is measure by the I.D.. If by chance there is an air conditioning supply near you they will carry benders specifically made for copper. The conduit bender will not fit the tube exactly but maybe well enough for your purposes. Truthfully, I've never tried to bend copper with a conduit bender so I can't with any accuracy say what will happen but my feeling is you might get some kinks in the tubing.
Tom
Click to expand...
I hadn't thought about the inside/outside measurements. Yes, my copper pipe is 3/4" I.D. So the fit in the conduit bender would have something to do with how thick the copper pipe is, or does the o. D. remain the same and with double wall it has a smaller I.D.? If the outside changed with wall thickness then the fittings would need to be different, right? Wish I knew an electrician and could just try it. I'll see if my brother has one he can send me. He has a shop in Iowa with over a half bazillion things in it. As he says, he buys junk and sells antiques. Worth asking. it would be cool if it worked. Or I think it would be cool anyway. This would be for my 50 Schwinn Motorbike build with a four stroke. It already has a copper drop stand and copper jewel running lights, so I might as well carry on the theme. Thanks, Tom.
SB
 
Kevlarr

Kevlarr

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Forget the bender altogether SB, take your length of pipe, sweat a cap on one end, fill the pipe with sand (packing it tight), sweat a cap on the other end then bend around a block of wood cut to the curve you're looking for. The sand will keep the pipe from collapsing.
 
silverbear

silverbear

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Ooohhh I like that! You really think it will work? Sounds like it should and if it doesn't, I'm just out a section of mangled copper pipe. I think I'll try it this week and will let you know how it goes... pretty cool. Thanks! Now I have to give some thought to making the form, something like a sandwich of three layers of (one by) wood with the grain going opposite crosswise in the center section or better yet use plywood scrap for the center The two outer pieces would form a lip so that the center was in a kind of trough. Something like that.
Thanks, Bud!
 
2door

2door

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Let me emphasize Kev's suggestion about "packing the sand tight". Pour some sand in and using a tool of the right diameter, tamp it down then add more sand, tamp etc, etc until the pipe is full and "packed solid'. The more compact the sand the less chance you'll have of kinking the pipe/tube. If you've ever seen the old movie, 'Flight of the Phoenix', the original version, they show this method during the building of the airplane.

There used to be a product called Cerro Bend. It was a lead allow that melted at about 190 degrees. You could melt it in boiling water then pour it into whatever tubing you were bending then cool it with cold water. It was like bending a solid rod. When finished you only had to submerge the tube in hot water and the Cerro Bend would melt and pour out leaving no residue. It was probably a victim of an EPA ban on lead so it might not be available anymore. I haven't seen or used it for many years.
Tom
 
silverbear

silverbear

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2door said:
Let me emphasize Kev's suggestion about "packing the sand tight". Pour some sand in and using a tool of the right diameter, tamp it down then add more sand, tamp etc, etc until the pipe is full and "packed solid'. The more compact the sand the less chance you'll have of kinking the pipe/tube. If you've ever seen the old movie, 'Flight of the Phoenix', the original version, they show this method during the building of the airplane.

There used to be a product called Cerro Bend. It was a lead allow that melted at about 190 degrees. You could melt it in boiling water then pour it into whatever tubing you were bending then cool it with cold water. It was like bending a solid rod. When finished you only had to submerge the tube in hot water and the Cerro Bend would melt and pour out leaving no residue. It was probably a victim of an EPA ban on lead so it might not be available anymore. I haven't seen or used it for many years.
Tom
Click to expand...
You guys are the best! I think this is going to work, but may not be able to get to it until I get back to Maryland, a couple of weeks. I'm finishing up a build and packing for the trip first to Omaha to visit family and then on the mountains in Maryland. Do you think the form is still necessary? I'm guessing it would be best, but what about bending it free form using a telephone pole or tree? Bend a little bit and then bend a little bit more. If I don't have to make a form I can do it sooner rather than later.
SB
 
2door

2door

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SB,
I've used both methods and had good results. As you said; "go slow, bend a little at a time" and don't rush it. Keep in mind that the surface you bend against needs to be as smooth as possible so you don't damage the outer surface of your pipe which would detract from the appearance. Tele poles tend to be a bit rough so maybe a short length of metal pipe of the right diameter would work better. Or, wrap the pole with tape and a rag or something to keep it from making dents/scratches.
Tom
 
silverbear

silverbear

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2door said:
SB,
I've used both methods and had good results. As you said; "go slow, bend a little at a time" and don't rush it. Keep in mind that the surface you bend against needs to be as smooth as possible so you don't damage the outer surface of your pipe which would detract from the appearance. Tele poles tend to be a bit rough so maybe a short length of metal pipe of the right diameter would work better. Or, wrap the pole with tape and a rag or something to keep it from making dents/scratches.
Tom
Click to expand...
Good point, Tom. I think I'll find a paper birch tree and give it something like a sweatshirt for padding. Nothing rough on the birch tree and being alive it has a slight bit of give due to the cambium layer under the outer bark. Don't want to hurt the tree either, so easy does it, a bit at a time.
SB
 
silverbear

silverbear

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Here's my update. I tired the bend against a birch tree of the right circumference. It did not want to bend at all... until it finally crimped. Bummer.
So I thought I'd try making something up using 45 degree angle unions. Got busy and made a pipe with nice silver soldered unions. Fired it up and the bike sounded gooood! Gave it throttle and I could feel more power. Woohoo! And in no time the pipe came apart. I looked and the pipe gets so hot up at the manifold end that it melted the silver solder. Dat's hot! So, the ony way it could work is one continuous piece clamped to the manifold fitting (little bit of the stock pipe with a coupling) with a nice sweeping bend to it. At the other end you could solder something I imagine, as it is less hot there. So I figured that was the end of this experiment.
Then Fasteddy suggested heating the copper pipe first, good and hot, to remove the temper, and of course that is the answer. I'll experiment more later in the fall and will post results on this thread, positive or negative. Now I've got to know if it will work.
SB
 
BarelyAWake

BarelyAWake

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Jus' FYI in case anyone is interested in combining the packed sand & heat ideas - make sure the sand is completely dry (and/or a pinhole vent in the endcaps) else you've just made yerself one heck of a steam-powered pipe bomb O.O

Another possibility that might work (tho I've not tried it) is to use some of that flexible conduit over the copper pipe to prevent kinking, much like the springs provided in the less expensive tubing/brake line bending kits...

I unno if it'll fit or if you'll be able to get the copper pipe back out, but I figure it's worth a shot if ya have some around anyway *shrug*
 
silverbear

silverbear

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Good point on the pipe bomb. No, I would heat it up with nothing in it... takes much less time and propane to heat the copper without all that sand in it. Hadn't considered it exploding if capped. That would be a disaster for sure. Good heads up. That's a thought about the flex pipe. On my propane lines I have different sized spring sheath deals to keep it from crimping in tight bends.
SB
 
Goat Herder

Goat Herder

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Bailing wire works like a champ when custom bending brake lines. Would wrap it it tight and even on the brake line Tubing. Then bend them the way ya need them last take the wire off. [like the springs that come with those tubing kits]

I imagine it might not be heavy enough though for the scaled up size of you copper though.

Yet if you have a bunch of thicker wire on hand its a thought.
 
Russell

Russell

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SB,
Couldn't find your posting where you built the copper fuel filter. I liked it and said I was going to copy it(a year ago). Finally got around to it! Thanks for the info. Couldn't find the ss wool, so went with ss filter mesh.

Thx again

Jim
 

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silverbear

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
Russell said:
SB,
Couldn't find your posting where you built the copper fuel filter. I liked it and said I was going to copy it(a year ago). Finally got around to it! Thanks for the info. Couldn't find the ss wool, so went with ss filter mesh.

Thx again

Jim
Click to expand...
You are welcome, sir. Boy, that turned out nice. You made the deluxe version!
SB
 
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