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  1. #1
    Senior Member Oldpeddaller's Avatar
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    Novice Question, Brazing with Propane or Butane - Is this feasible?????

    Having looked at some threads in this Forum, I can see that for brazing up a new frame, a proper bottle set-up is required to ensure enough heat to get the filler to flow from one side of a lug to the other.

    However, what about smaller and simpler jobs?

    If the job is just, for example, to braze on an additional bracket or stop (non-structural), or to mend a steel rod carrier rack, could a butane or butane/propane mix cannister torch be used with flux and nickel/silver solder rods?

    If this is at all feasible, any tips or advice on the best way to proceed, the best choice of kit & materials or anything else I should be thinking of?

    Thanks, would appreciate your expertise.
    Oldpeddaller - The older I get, the better I used to be !!!" ***** If at first you don't succeed - hit it with a hammer.

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  2. #2
    Senior Member Nessism's Avatar
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    Try MAPP gas, it's hotter than propane (not sure about butane).
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    Senior Member scbvideoboy's Avatar
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    Yep a benzomatic Mapp gas (yellow bottle) and Oxygen (red bottle) setup will do the trick, you can buy silver wire and flux in little kits for about 15 bucks. Safety Silv 56. For silver all you need is to watch the flux turn wet and watery looking and you'll have enough heat to flow. Lots of flux aids cleanup and avoid over heating (cherry red)

    Just spent the past weekend doing this!

    Dave

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    Any fuel with Oxygen is playing with the big boys. Can you get by without oxygen is the question, and the answer as mentioned above is that one can. All common fuels, possibly most flames, have the required heat. to get the job done, the problem is what happens to the heat produced. An example of this, in the extreme, is the use of a propane torch without O2 to forge fairly large pocket knives possibly even forge weld damascus (though my experiments don't support he latter, however designs can vary enormously). The trick there is insulating the heated area. Check out coffee can forge, or one brick forges. These could hearth braze lugs, but they are a little clunky.

    If one is using an open flame the problem is whether the rate of transfer is fast enough. A flame of several thousand degrees is hot enough, but it is dissipating as quickly as it is transferring. This means difficulty hitting peak heats, and the heat that spreads out can carry heat beyond the flux with flux burning working back from the edges and other bad things. It is also harder to pull the solder, because the heat is going to be very even, best case. Moving the flame to the off side doesn't do much to pump up the volume. Keeping heat in a particular place will require overheating to have enough stay as one moves away to heat another part.

    The solution is smaller parts, when working with an open flame. And it is hard to give solid rules since the heat properties of parts varies a lot. Stuff like bottle mounts and racks are reasonable with an un-insulated propane, or mapp. People have done frames. One problem is that the people pushing this envelope may be newbies, so they are both learning and using far harder to use formats. There are a few people who have been around doing this stuff for a long time and have it nailed. Just as there are people who have nailed stick welding bike frames.

    Butane seems to be liquid at lower pressure making it easy to use in stuff like cigarette lighters and soldering guns. I don't think it has what it takes to do hard solders, unless the parts were miniscule.

  5. #5
    Senior Member Oldpeddaller's Avatar
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    Thanks guys, that's given me a lot more really helpful information and detailed description to help me understand the process better.

    I think I'll experiment on the broken steel carrier rack and any bits of scrap I can find to get a feel for the capabilities and limitations of the kit I have before considering going anywhere near a bicycle frame! It looks as though a Mapp gas set-up is going to be an absolute minimum requirement and I'll have to consider cost and learning curve so may well be passing my frame work on to a professional!

    Much obliged for your help!
    Oldpeddaller - The older I get, the better I used to be !!!" ***** If at first you don't succeed - hit it with a hammer.

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  6. #6
    Senior Member DannoXYZ's Avatar
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    Implicit in Peter's post was basically BTU/second of the torche in question. You need to spit out enough BTU per second to counteract the wicking/cooling for the surface-area in question. The other issue is silver vs. brass and you have to consider the tolerance of the contact-area as well as its surface-area. I wouldn't do fillet brazing with silver.

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    Good points Danno. I probably wouldn't do silver for someone else's bike. I am a big believer in doing the conventional thing with adhessives and welding type stuff, where commerce is concerned, it will be tantamount to malpractice to be offside on those practices if one appears in court. The most reactionary industry voice is the kind of person who will appear as an expert witness.

    I wouldn't hesitate to do silver fillets for myself. I don't see any evidence that they fail. I'm not saying there isn't that evidence, or theoretical descriptives, but I searched pretty hard to find info on the process when I got interested in it, and I didn't find anything serious. What I found was that a lot of big names did a lot of frames this way. It reminds me of the monohull multihull arguments where the big deal is that multihulls flip and capsize (big deal back in the 60s). But that reputation sticks to them, while a million mono wrecks on the bottom of the ocean and nobody is bothered. There are thousands of bust up frames with joints that failed for one reason or another, one process or another, doesn't bother a soul. Meanwhile there are a few rumours on silver fillets and some people declare it usafe. When the process was popular there were probably thousands of silver fillet bikes out there, where is the smoking ***? So the Italians stopped doing it and moved to another process. Industries change processes all the time, doesn't mean the original bikes won't still be spinning in 100 years. Most frames stay togethere regardless of the process so even the very worst imaginable process will probably see one through if one sweats the details. It is hard to see it as a best practice, but for people who like playing with marginal stuff, it could be fun.

  8. #8
    Senior Member Nessism's Avatar
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    MAPP gas won't generate as much heat as oxy-acetylene which suggests silver, on the other hand silver is not as strong as brass or nickle, and strength is what you need for brazing rack eyelets or adding structural attachments to a frame.

    Just my opinion but I'd restrict MAPP to simple, non structural type projects using silver or small sectional area parts, like a rack for example, if using a higher temp filler material.
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  9. #9
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    I agree with Nessism, though the fact that there are lots of builders picking silver for highly loaded bikes out of preference makes me believe it will never be an issue to go silver. Think Beckman/Sakkit. So yeah, brass is currently the go to filler, but I really wouldn't worry on silver either, most people just don't have a reason to go there.

    I also agree on MAPP, since this is always really a discusion about using the little plumbing torches from the hardware. However, even propane without oxygen is hot enough to melt steel frames down into anchors if you use enough of it. Think hybridburners.com (proud supplier to NASA ), and the kinds of burners ganged in factory settings. So in the real world under which this discusion comes up where people are trying to press hardware store torches, there is a razor's edge ballance to getting that right, but for completeness sake, it isn't the gas as much as the size of the torch. MAPP in a big torch would be even hotter.

  10. #10
    Senior Member Oldpeddaller's Avatar
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    Thanks again gentlemen for your interest, experience, expertise and opinion - being a total novice I've been lacking the latter three!

    As an experiment I've just tried out a butane/propane mix canister torch with fluxed silver rod on a broken rear rack frame. This involved joining two 5/8" round steel rod sections together end to end under sprung tension. The result is encouraging, a very neat. strong and solid join that appears to be stronger than the adjacent rod.

    Learning points were:

    1) As stated, heat seems to be crucial - the whole working area must be thoroughly and meticulously cleaned first in order to get a workable heat with this type of torch, which takes minutes, not seconds, to attain and maintain working temperature.

    2) A lot more gas and silver rod is needed than I anticipated - 4" of rod flowed into and across this join, which was less than half an inch across the whole job. Half a can of gas was used for pre-heating and brazing.

    3) For both these reasons I would now only consider using this kit for small jobs and allow plenty of time - I don't believe I could build a frame or do major frame joins using this.

    4) It's essential to plan the whole job before starting and the clamping & positioning of parts is a big factor in how well it will turn out. Access to the whole joint from every angle with the torch flame is required. First attempt with the join held in Mole grips was a disaster - the joint sprang apart as the metal expanded during heating. Starting again and clamping the whole assembly in a big vice worked a treat!

    5) For jobs any bigger than this, "grown up" equipment will be required - any suggestions short of a full large bottle oxy acetylene rig?

    6) The job was satisfying and actually quite fun!

    Are there any fundamental points I've missed that I should have learnt or should be aware of for future projects?

    Again, thanks for your time and trouble in answering my rather ill-informed and naive questions. I've got an old scrap frame (seriously bent top & down tubes) that I intend to practice upon; making and fitting cable stops, brackets and so on and if this works for me I might then try similar small additions to a "real" frame. If it doesn't work, nothing lost!

    Happy 2009
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    I think if you really want to do this kind of stuff at some point you need to bite the bullet and spring for the real gear. It shows up here in Can. periodically on Craigslist, for cheap, though I bought mine retail. I like propane oxy, because it is arguably better (as is OA), and most homeowners over here have a BBQ that runs off propane for starters. So the total cost is a torch at around 100-150 dollars, a regulator for the OXY, and I purchased an OXY tank. It all ads up, but it's the right gear, and in the end is far more useful that the endless kludges that are possible. I think it would be possible to build using a hearth set-up and propane only, and a home made burner. Check out hybrid, and ron reil, but while this is possible, nobody I know of is doing it so you have to invent your own universe. There are people doing it but not present on any lists etc... A torch set-up, and using it in a residential setting is a serious risk issue, and needs to be carefully investigated before considering it. Around here in the country probably every third farm has an OA torch for cutting and brazing farm machinery, but in the city, it is a little more out there.

  12. #12
    Senior Member Oldpeddaller's Avatar
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    Peterpan,

    Points taken - I'm getting to like this type of job so will be looking out for oxy-propane. I've realised that I too already have a huge propane bottle & regulator for our barbecue so if I look out for an oxygen bottle & regulator, hoses and torch I may be lucky in putting together an outfit quite cheaply. I'll talk to some of the ship repairers in the docks where I work to see if they know of any good used/surplus sources. Over here in the UK at present there's unlikely to be too much regulation at least in the area I live, but sensible precautions are naturally necessary at all times, better to be safe than (stupid!). Thanks again for your help, advice and encouragement!
    Oldpeddaller - The older I get, the better I used to be !!!" ***** If at first you don't succeed - hit it with a hammer.

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  13. #13
    Randomhead
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    oxy/acetylene is not that expensive. I have been thinking about oxy/propane. I'm going to try it first though.

  14. #14
    Senior Member scbvideoboy's Avatar
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    I bought a small bottle ox/ace portable kit at Northern tools for $300 and they fill the tanks up too.
    However I need more practice with it as my sample test work was getting too hot and burning up the flux and not wicking well at all. So I switched to the mapp/ox setup and have been using for my frame. Silver for me allows some room for heating error as the tubing can handle brass temps.

    DH

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    Senior Member PaPa's Avatar
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    Be advised, that oxy-propane is different in many ways than oxy-acetylene.

    1. Propane has a greater stoichiometric oxygen requirement than acetylene; the ratio of the volume of oxygen to fuel gas are 1.2 to 1 for acetylene and 4.3 to 1 for propane.

    (a) This means you'll typically use 4 times more oxygen with the oxy-propane setup.
    (b) Oxidation is much easier to induce - which requires complete and uniform use of quality flux, proper flame adjustment and diligent use of the torch to avoid. Dilly-dally or char the flux and you're screwed. Oxy-acetylene is much more forgiving in this regard, and therefor easier to stay out'a trouble.

    2. You can successfully burn oxy-propane with oxy-acetylene tips, however, you'd be wise to spring for the correct, 'alt fuel' tips. If for no other reason, the flame is much easier to light and adjust.

    3. Use a "T" rated fuel hose, not the more common "R" acetylene hose.

    4. With smaller 20 pound LPG bottles, you'll experience line pressure fluctuations using single stage regulators. Unlike acetylene, this is due to the refrigeration effects of propane, causing a drop in bottle pressure. Get a dual stage reg.

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    "4. With smaller 20 pound LPG bottles, you'll experience line pressure fluctuations using single stage regulators. Unlike acetylene, this is due to the refrigeration effects of propane, causing a drop in bottle pressure. Get a dual stage reg."

    I was warned this would happen with my propane forge, which sucks down a lot of propane running flat out. I didn't have that problem, I think it would be pretty unlikely at the fuel rates required here, if it happens one option is to put the tank in a tub of water. The other solutions suggested are better, but if you are already caught offside...

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    Senior Member PaPa's Avatar
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    Quote Originally Posted by Peterpan1 View Post
    I didn't have that problem, I think it would be pretty unlikely at the fuel rates required here
    What size of burner are you using and what is the reg's output pressure set at? If you are pushing 5 PSI or more at your forge, then you'll rarely notice pressure fluctuations of 2 PSI or more - it's not critical, especially when you can't see the burner and it appears to be doing what its supposed to do. With #4 Victor tip, trust me... you'll instantly notice (well, I do) a pressure drop as small as .5 psi. Since switching to a Victor VTS-710A over 6 years ago, I've not replicated the problem. But hey... I'm pickier than most.

  18. #18
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by scbvideoboy View Post
    Yep a benzomatic Mapp gas (yellow bottle) and Oxygen (red bottle) setup will do the trick, you can buy silver wire and flux in little kits for about 15 bucks. Safety Silv 56. For silver all you need is to watch the flux turn wet and watery looking and you'll have enough heat to flow. Lots of flux aids cleanup and avoid over heating (cherry red)

    Just spent the past weekend doing this!

    Dave
    +1 -- there's no such thing as "too much flux."

    BTW, didinium tinted safety glasses will let you see the pink color more clearly than a traditional green lens.

  19. #19
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by Peterpan1 View Post
    Any fuel with Oxygen is playing with the big boys. Can you get by without oxygen is the question, and the answer as mentioned above is that one can.
    Yes, but you can do the job much quicker with a fuel/oxygen setup, and that means a smaller heat affected zone on the tubing.

  20. #20
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by unterhausen View Post
    oxy/acetylene is not that expensive. I have been thinking about oxy/propane. I'm going to try it first though.
    Oxy/propane isn't as hot as oxy/acetylene, but it works fine. You do have to use a somewhat larger tip with oxy/propane. At Trek we used oxy/propane through a manifold system. You can run propane at higher pressures than acetylene which makes it good for things like manifold distribution and flame cutting.

  21. #21
    Senior Member PaPa's Avatar
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    Quote Originally Posted by JohnDThompson View Post
    +1 -- there's no such thing as "too much flux."
    I disagree.

    Excessive flux is no excuse for controlled and diligent use of the torch to prevent charring in the first place. Too much flux also obscures the puddle and makes post clean-ups much more time consuming. A thin, but complete and uniform coverage is all that's necessary.

    Quote Originally Posted by JohnDThompson View Post
    Oxy/propane isn't as hot as oxy/acetylene, but it works fine.
    There is less than 400f flame temperature difference between O/P and O/A - Both being well over 5000f. I have successfully O/P brazed nearly 1/4"" thick stock with a tip as small as a Victor #4 (the same tip I occasionally use for lugs).

  22. #22
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by PaPa View Post
    I disagree.

    Excessive flux is no excuse for controlled and diligent use of the torch to prevent charring in the first place. Too much flux also obscures the puddle and makes post clean-ups much more time consuming. A thin, but complete and uniform coverage is all that's necessary.

    There is less than 400f flame temperature difference between O/P and O/A - Both being well over 5000f. I have successfully O/P brazed nearly 1/4"" thick stock with a tip as small as a Victor #4 (the same tip I occasionally use for lugs).
    Having brazed probably several hundred frames -- maybe even over a thousand -- I have never found too much flux to be a problem. And a 400F difference at ~5000F represents about 8% difference. I think this is significant.

  23. #23
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    FWIW, I've built several complete frames and forks (lugged and silver brazed) with MAPP gas and a Bernz-O-Matic torch. It takes about two $10 bottles of gas for each frameset. The torch is capable of getting even the thickest assemblies -- bottom bracket shells and fork crowns -- cherry red, which is too hot for silver.

    I have tried the Bernz-O-Matic oxy/propane torch and while the flame is hot enough for brass brazing or even welding and cutting, it is a tiny flame unsuited to heating areas of any size, and doesn't last more than ten minutes or so. IMO it is nearly useless for framebuilding.

    HTH!

  24. #24
    Senior Member Oldpeddaller's Avatar
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    Update - I bought a small butane/Propane mix cannister torch and a packet of pre-fluxed silver rods for the jobs mentioned. After a few false starts on the rack it is now fully repaired and the cable stop on the frame went without a hitch - really pleased with both jobs. However, for anything larger I appreciate that a hotter flame will be needed and I certainly won't be using this set up for major jobs. With the recession now in full flow over here, sadly a lot of small firms are going belly up - but it does mean that good used professional gear is now going at stupidly low prices, so will be looking out for something suitable. Thanks again for all your advice, I've learned an awful lot.
    Oldpeddaller - The older I get, the better I used to be !!!" ***** If at first you don't succeed - hit it with a hammer.

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  25. #25
    Senior Member wirehead's Avatar
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    You know, I suspect that the hidden problem with using a air-fuel torch of any sort is that you are going to have a much larger heat affected zone than if you get in and out with oxygen-fuel. So... joints that look right but a frame that wouldn't hold up long-term.

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