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Posted by Dave on July 24, 2007, 11:57 am
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First off, I have zero experience brazing (or welding for that matter)
anything.
I've got a motorcycle with a few significant holes in one of the mufflers.
Given the advanced age of the cycle and the prohibitive $$ of a new muffler,
I'd like to try my hand at brazing and cover the holes.
the muffler is thin (< 1/16") chromed metal. I've got a small dual-gas
torch setup, and could use either propane or MAPP with oxygen for brazing.
I'm looking for recommendations on:
1. type of gas to use
2. Type of brazing material. As I noted I have no experience brazing. I'm
guessing there's probably different types of brazing filler for different
applications, temperatures, etc.
3. Type of flux. See #2, above.
4. Tip size to use... I'm guessing the smaller the better given the
thinness of metals I'll be working with.
I'm planning to use some scrap metal for my patches (have yet to search my
basement for supplies) and I'm thinking something thin enough to bend by
hand or with a mallet and wood form like a coffee can. Would this work?
Any tips on brazing, DO's and especially DON'T's greatly appreciated..
thx
Dave
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Posted by Grant Erwin on July 24, 2007, 12:08 pm
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Dave wrote:
> First off, I have zero experience brazing (or welding for that matter)
> anything.
>
> I've got a motorcycle with a few significant holes in one of the mufflers.
> Given the advanced age of the cycle and the prohibitive $$ of a new muffler,
> I'd like to try my hand at brazing and cover the holes.
>
> the muffler is thin (< 1/16") chromed metal. I've got a small dual-gas
> torch setup, and could use either propane or MAPP with oxygen for brazing.
> I'm looking for recommendations on:
>
> 1. type of gas to use
> 2. Type of brazing material. As I noted I have no experience brazing. I'm
> guessing there's probably different types of brazing filler for different
> applications, temperatures, etc.
> 3. Type of flux. See #2, above.
> 4. Tip size to use... I'm guessing the smaller the better given the
> thinness of metals I'll be working with.
>
> I'm planning to use some scrap metal for my patches (have yet to search my
> basement for supplies) and I'm thinking something thin enough to bend by
> hand or with a mallet and wood form like a coffee can. Would this work?
>
> Any tips on brazing, DO's and especially DON'T's greatly appreciated..
Oh, boy are you signing up for a buncha misery. Oh well - you will learn. The
very easiest way to solve your problem is to go find the money for a new muffler.
As soon as you heat the rust-holed muffler to hot enough to melt the brazing
rod, it is going to start deforming is my guess. If you did manage to braze on
some bits of steel, they will very very shortly rust through given the
temperature of motorcycle exhaust systems. The old stuff was chrome-plated and
it rusted through, how much quicker will non-chromed steel rust?
GWE
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Posted by Dave on July 24, 2007, 12:26 pm
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> Oh, boy are you signing up for a buncha misery. Oh well - you will learn.
> The very easiest way to solve your problem is to go find the money for a
> new muffler.
Yeah. I kinda figured that. But, nothing ventured nothing gained.
>
> As soon as you heat the rust-holed muffler to hot enough to melt the
> brazing rod, it is going to start deforming is my guess.
Theoretically, at least what I've read, the idea behind brazing is that I
don't have to heat up the metal to be joined hot enough to melt it. Just
hot enough to melt the brazing rod which, again theorically, should melt
significantly lower than chromed steel. No?
If you did manage to braze on
> some bits of steel, they will very very shortly rust through given the
> temperature of motorcycle exhaust systems. The old stuff was chrome-plated
> and it rusted through, how much quicker will non-chromed steel rust?
Hmm, I didn't think coffee cans rusted, at least not for awhile. I don't
suppose it would do much for the cost-effectiveness of my project to buy
some titanium or SS plate. How 'bout aluminum? Can it be brazed? I've got
lots of aluminum cans. Hmmm, and they're pre-curved too...
Maybe I'll swing by the motorcycle junkyard first, just for fun to see what
they've got for used mufflers.
Dave
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Posted by Leo Lichtman on July 24, 2007, 7:20 pm
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"Dave" wrote: (CLIP) How 'bout aluminum? Can it be brazed? I've got
lots of aluminum cans. (CLIP)
^^^^^^^^^^^^^^^
If you can ask a question like that, I think you need to re-read what Grant
wrote, and double it. First of all, aluminum cans are OUT OF THE QUESTION.
Second, chrome is an obstacle--things don't stick to it very well. If you
grind off the chrome on a muffler that's already rusted through, what will
you have left? Some steel that's so feather edged that as soon as you start
to heat it, it will start to sparkle and burn back, making the holes bigger.
Coffee cans DO rust after the tin plating is gone, which it will be after it
has been heated to brazing temperature.
If you are lucky enough to have a motorcycle wrecking yard in your area,
that's your best bet. But if yours is an old bike, then the bikes like
yours that happen to be in the wrecking yard are also going to be old.
Chances of getting a good clean strong muffler seem slim.
If you were my neighbor, I could fix it by welding, but I wouldn't guarantee
the looks. Where are you located?
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Posted by on July 24, 2007, 7:48 pm
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> Maybe I'll swing by the motorcycle junkyard first, just for fun to see what
> they've got for used mufflers.
>
> Dave
If you can't find a good mufler at a junkyard, I would try an
automotive parts place and see what they have for repairing car
mufflers. I think they sell something like fiberglass tape with a
thermosetting adhesive. If that fails think hose clamps and some high
temp gasket material ( higher than silicon gasket stuff ) and some
bent metal. One of the local hardware stores sells wood stove door
gasket stuff.
Dan
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> anything.
>
> I've got a motorcycle with a few significant holes in one of the mufflers.
> Given the advanced age of the cycle and the prohibitive $$ of a new muffler,
> I'd like to try my hand at brazing and cover the holes.
>
> the muffler is thin (< 1/16") chromed metal. I've got a small dual-gas
> torch setup, and could use either propane or MAPP with oxygen for brazing.
> I'm looking for recommendations on:
>
> 1. type of gas to use
> 2. Type of brazing material. As I noted I have no experience brazing. I'm
> guessing there's probably different types of brazing filler for different
> applications, temperatures, etc.
> 3. Type of flux. See #2, above.
> 4. Tip size to use... I'm guessing the smaller the better given the
> thinness of metals I'll be working with.
>
> I'm planning to use some scrap metal for my patches (have yet to search my
> basement for supplies) and I'm thinking something thin enough to bend by
> hand or with a mallet and wood form like a coffee can. Would this work?
>
> Any tips on brazing, DO's and especially DON'T's greatly appreciated..