Can a Smith AW1A be used to heat up a Bottom Bracket?

[Amir Avitzur]

I use a Smith AW1A for fillet brazing racks and stems.

Can it also be used for heating a heavy bottom bracket with internal lugs?

If so, what mixer and tip should I use?

--

Amir Avitzur
R"G Israel

[Skip Montanaro]

I use a Smith AW1A for fillet brazing racks and stems.

Can it also be used for heating a heavy bottom bracket with internal lugs?

If so, what mixer and tip should I use?

I would think an AW1A would be sufficient, though you'd likely want to use a rosebud tip to increase the flame size.

Skip

[Mark Bulgier]

Amir wrote:

> I use a Smith AW1A for fillet brazing racks and stems.

> Can it also be used for heating a heavy bottom bracket with internal lugs?

> 

> If so, what mixer and tip should I use?

Amir, remind me, what's your fuel gas?

If acetylene, I can't recommend a large tip unless you have really big fuel bottles.  Do you know about the max withdrawal rate?  It's expressed as a fraction of the bottle size.  But basically there's a max flame size you can run, based on the bottle you're withdrawing from.  That makes any tip bigger than maybe a 205 sketchy for people with small-shop sized bottles.  And if you have the tiny bottles that come with jewelry kits, then jewelry is about as big as you can go.

If you're using propane, LNG, methane and the like, that takes away the withdrawal limit, so big rosebuds become feasible.  In that case I'd use the AT-61 mixer, with tips from Paige Tools in Seattle.  Let me know if they don't ship to Israel, I can 'broker'.  Paige aren't the only propane tips, but they're really good.  Endorsed by Doug Fattic as well, the gold standard. 😉  If using an AT61 neck, get the "NK" adapter, which stays on the neck, and all the other tips attach to the NK.

At the risk of repeating what everyone knows: 

Despite its lower temperature flame compare to O/A, Propane is really good for soaking in a lot of BTUs.  Especially if you'll allow yourself the luxury of two torches.  I tend to hold a torch in each hand to get the heavy part up to temperature quickly, then hang the rosebud on a Gasaver, a switch that turns the torch off when you hang it on the hook.  Then you have a free hand for holding the rod during the actual brazing.  Though with pre-placed rings or other preforms of filler inside the joint, you may wish to just keep using both torches until the joint is finished. The Gasaver is optional; you can also just turn the knobs off on the torch you're setting down.

Is your BB being brazed in a fixture, or can you point the flame inside, through the openings where the bearings go?  I always point the flame on the inside of the shell for at least part of the heating cycle, if I have access to it.  So, not in the tacking jig, but yes after tacking, brazing the joint outside the jig.  Watch out for the chimney effect, if your frame is anything like a normal one with a seat tube open at the top for a seatpost, the entire seat tube can get hot when pointing the flame inside the shell.  Can melt plastic repair stand jaws, or burn you if you forget and grab the seat tube to move the frame around.

Without flame access to the inside:  Since you have a thick inside lug with (presumably) thinner tubes outside, you will have a challenge to heat those inside spigots without overheating the tube.  You'll have to apply the flame mostly to the shell, far enough away from the tubes to avoid overheating them.  And keep the heat on the shell long enough for it to conduct to the inside spigots.  It helps if the tube to spigot fit is snug, but it can't be a press-fit, you need clearance for the filler, so direct transfer of heat to the spigot through the tube can only really start after the filler is moving into the gap.  Which does happen, you do get direct heat transfer in the area already brazed, through the filler, but your spigot better be pretty close to brazing temp already before you start letting the flame play on the tubes at all.

I saw your Q about induction brazing, but I know practically nothing about it except it is used in industry.  Not in the bike biz though, that I know of.  Rumor I heard was Trek was experimenting with it way back, like late '80s?  But they dropped it and no production models were made that way.  This rumor I heard could be totally wrong, so don't believe it! 

Mark B

[John Thompson]

On 2/18/24 13:43, Amir Avitzur wrote:
> I use a Smith AW1A for fillet brazing racks and stems.
> Can it also be used for heating a heavy bottom bracket with internal lugs?
>
> If so, what mixer and tip should I use?

Yes. At home, with oxy-acetylene, I use an AW207 tip. At Trek, with
oxy-propane, I cobbled up a rosebud tip. You need a pretty hefty flow
rate for the rosebud, and the tanks I have at home can't provide that.
But if you can get enough flow, the rosebud is super-sweet for that kind
of work.

--

-John (JohnDT...@gmail.com)
Appleton, WI USA

[Michael F.]

Dear John Thompson,

Those pics you sent  are interesting - that's an old piloted Goss brand  tip for Propane / "Alt. Fuels".

I have two of those, and they are some of the best Propane tips I have. Very wide range of adjustment from big to small, and IMHO a really nice 

flame shape for brazing. Goss (and probably a few other companies BITD) made a neat adapter piece that had 3/8-24 threads, and you could braze it onto a

tip for use on whatever torch you had. There seemed to be a much better selection of just about everything back when torch welding and brazing was still a popular

and common industrial process.

 

Unfortunately, I think they haven't been made for 15 or 20 years, now. I never even see them on Ebay, either.

Back to the original topic - Smith makes a nice Rosebud for the AW torch - the AT-605. Smith says it is for Acetylene, but like most  multiflame tips, it works fine with Propane

for the light to medium-duty stuff bike folks do.

Good Luck !

MF in SF

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[Jon Norstog]

I forgot at useful "tip:"  When using the rosebud to heat a BB shell from the inside, thread in an old, steel BB cup on the side away from the flame.  It will keep more of the heat inside the shell, where it belongs.

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[good friend]

I'm reminded of the issue that acetylene creates a "gas shield" around the work, and other gases do not...
   I'm curious to hear from people who have used both propane (or map) + oxy how it compares in real-world to acetylene in these terms...   clean-up, life expectancy, etc.    anything you can think of
It is time for me to get a torch and I'm curious what I will end up with    =}

noMadic  Thomas

(suggestions appreciated, I'm thinking mini-tig and/and-or some flame maker...   sized for bicycle frame/rack and jewelry)

[Duane Draper]

This is the first I have heard of Acetylene forming a shield.  I assumed only inert gasses would do that - but I was an econ major so, what do I know about such things! 

There are a couple really good threads on other forums so I would suggest you search out those.  Doug Fattic has contributed an encyclopedic amount of information to the topic. 

I can say that between O/A and propane, I notice no difference in outcomes.  I use propane with a big tip for big parts (crowns, shells and lugs) where lots of heat needs to soak into the part and I use O/A for fillets and braze-ons.  Clean up, longevity of torches/hoses etc seem the same.  I worry about my Oxy concentrator giving up the plot at some point but that’s not related to propane or acetylene.  I’m probably a bit more cavalier with how I treat my propane/Oxy Concentrator set up.  I give my O/A tanks and regulators more respect.

 

I haven’t really tried fillet brazing with propane but many do with good success.  If I was just getting started, I would go with propane and oxygen concentrator – no question.

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[Eric Keller]

My understanding is that if you want to weld, propane isn't
appropriate because it doesn't offer a "gas shield" (and the weld
oxidizes too quickly?) Seems like I have seen that from reliable
sources, but I don't recall for sure. Obviously, propane is fine for
brazing. With tanks the size that I have, it's too frustrating to weld
anyway. Someday I'm going to get a Tig welder.
Eric Keller
Boalsburg, Pennsylvania

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[John Thompson]

On 2/20/24 13:00, good friend wrote:
> I'm reminded of the issue that acetylene creates a "gas shield" around
> the work, and other gases do not...
>    I'm curious to hear from people who have used both propane (or map)
> + oxy how it compares in real-world to acetylene in these terms...
> clean-up, life expectancy, etc.    anything you can think of
> It is time for me to get a torch and I'm curious what I will end up
> with    =}

I've only used oxy-propane at Trek, where we also used in-line GasFlux.
That combination worked well.

[Jon Norstog]

Oxyacetylene welding!  If you have a slightly reducing (Acetylene-rich) flame, you get a smoother, prettier weld joint.  Probably stronger too.  If you overdo it, the weld becomes carburized and brittle.  Do that on a bicycle frame and it will probably crack at the weld.  It takes a little skill and practice to get it right.

jn

"Thursday"

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[Mark Bulgier]

Yeah I'm happy with propane + oxygen generator for everything.  I still have an O/A rig, that I had before getting propane.  I have multiple torches, regs and hoses, so I can have them both set up and flaming at the same time, but if I were just starting out it'd be just propane/O2 for sure.

Propane run thru a tip made for acetylene will make a flame that detaches from the tip and blows out too easily.  Usable but annoying.  There are ways to mitigate that such as counterboring the tip slightly so the orifice is recessed, but I'd recommend just getting proper propane tips from Paige Tool, they're better.  Oops I said that already.

Get any smallish "aircraft" style welding torch.  Name brand recommended for availability of spare parts and accessories.  I like Smith's AW1A (well mine is really the older AW1 but it's pretty much the same), or the Meco Midget.  Lots of FBs like a Victor J28.  You can't go wrong with any of them, differences are slight compared to the similarities.   The Meco stands out for its small size in your hand, but it can take large tips too, and they even make long extension tubes for when using big heating tips.

For my biggest propane rosebud, I have a killer Harris torch with a long  tube from the handle to the tip to keep my hands further away from the Great Balls o' Fire, but that's seldom needed on bike frame sized jobs.  It is nice for heating a lug/crown/BB shell to almost brazing temperature, then using the aircraft torch to finish the job.  But having two torches going at once is a luxury almost nobody needs.  I just ended up with all this stuff — some free cast-offs, some bought used on CL or ebay — so I use it.

That "gas shield" with O/A is only relevant for gas welding, not a factor in brazing.  I think that's been covered already, but yes, it's true that propane can't be used for gas welding of steel, the welds are too brittle.  But almost nobody gas-welds anymore (apologies to Thursday), not in industry, welding is all done with electricity.

Mark B in Seattle

[Andy Newlands]

Howdy,

What Mark said.  For heating multi port work I use Harris oxy/propane Classic handle model 43-2, “F” low pressure injector mixer B-43-N, 10-1/2” bent heating tip tube no. 2393-4F and heating tip 2290-1H (103,000 BTU).  For single point brazing I have the model 2000 which is no longer available but is another heavy duty torch and a bunch of tips 2N-10N.  Great products in my opinion and available worldwide - been using Harris products since 1971!  Go with heavy duty torches as you never can tell when the wife might surprise you with another child and you might have to braze up a bigger baby buggy.

[leonard hanson]

👍😉

Sent from my iPad

On Feb 20, 2024, at 5:50 PM, Andy Newlands <strawber...@gmail.com> wrote:

Howdy,

What Mark said.  For heating multi port work I use Harris oxy/propane Classic handle model 43-2, “F” low pressure injector mixer B-43-N, 10-1/2” bent heating tip tube no. 2393-4F and heating tip 2290-1H (103,000 BTU).  For single point brazing I have the model 2000 which is no longer available but is another heavy duty torch and a bunch of tips 2N-10N.  Great products in my opinion and available worldwide - been using Harris products since 1971!  Go with heavy duty torches as you never can tell when the wife might surprise you with another child and you might have to braze up a bigger baby buggy.

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<Amir 02.jpeg>

Best regards,

Andy

Terra Nova Cycles LLC

1535 SW 17th. Ave.

Goose Hollow

Portland, OR 97201

503-224-1215

an...@strawberrybicycle.com

www.strawberrybicycle.com

www.torchandfile.com

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<50 year sticker.pdf>

  

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[Jim Adney]

On 20 Feb 2024 at 11:00, good friend wrote:

> I'm curious to hear from people who have used both propane (or map)
> + oxy how it compares in real-world to acetylene in these terms...  
> clean-up, life expectancy, etc.   

AO has higher temperature and can apply a more pinpoint flame, making it
better for applying braze-ons, for fillets, and for welding. PO has a larger,
more diffuse flame with more heat content, making it better for sweating a
large joint. I use both, as appropriate. I've never used MAPP, so I don't know
anything about it.

Note also that acetylene has gotten really expensive over the last twenty
years. I've never heard of a "shielding" effect from acetylene; that sounds
like it might be more appropriate for propane.

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Jim Adney, jad...@vwtype3.org
Madison, Wisconsin, USA
*******************************

[Alistair Spence]

On Tue, Feb 20, 2024 at 11:00 AM good friend <tho...@kokopedli.com> wrote:

I'm reminded of the issue that acetylene creates a "gas shield" around the work, and other gases do not...
   I'm curious to hear from people who have used both propane (or map) + oxy how it compares in real-world to acetylene in these terms...   clean-up, life expectancy, etc.    anything you can think of
It is time for me to get a torch and I'm curious what I will end up with    =}

noMadic  Thomas

The gas shield in an Oxy Acetylene flame only applies to gas welding akaik. The combustion of Acetylene in Oxygen creates a reducing zone, which minimizes the oxidation of the metals being melted. An Oxy Propane flame doesn't have this reducing zone. I'm not exactly sure why it doesn't, but it means that Oxy Propane isn't suitable for gas welding.

I built a dual fuel brazing rig set up some years ago, in order to take advantage of the benefits of both fuel gases. I didn't get to use it much before it was destroyed in a wildfire, along with the rest of my shop, but initial tests were very promising. Here's a couple of pics, dredged up from ye olde Flickr,

https://www.flickr.com/photos/duncancycles/14118477333

https://www.flickr.com/photos/duncancycles/13911832738

I'm a little rusty on all this stuff now, but generally speaking Propane puts out more heat per unit of fuel gas burned than Acetylene does, but it takes more oxygen to do it (something like 4 times more). An Oxy Propane flame temperature is a little lower than an Oxy Acetylene one (something like 2800 deg C vs 3200 deg C), and it releases about 10 percent of its heat in its inner cone, whereas Acetylene releases 40 percent of it's heat in its inner cone.

Basically, Acetylene has a much more pinpoint "punch" to its flame. Propane is much less localized. Broader. Personally I found Propane to excel at brazing things like BB shells and fork crowns. Acetylene was better for me for fillet brazing and fussier lug work but really, you can do it all with either one. It's just a matter of adapting ones technique. 

I perhaps should mention that I was doing mostly brass (aka nickel bronze) brazing with this setup, so bear that in mind when reading the above. I'm sure it will still all apply with silver but I didn't do much of that, so I can't speak from first hand experience.

Alistair Spence,

Seattle, WA

[good friend]

Really usefull and informative responses.
   Thank you !!!    Many of you.    Much appreciations

noMadic  Thomas