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  1. #1
    Senior Member calstar's Avatar
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    Opinion on lugged brazing penetration

    This was from a thread in C&V.

    "And all mass produced items in which are brazed/soldered (same joining process, different temperatures) will be less than perfect. Soldering/brazing is highly dependent on the perfect fitting of parts. Brazing/soldering can not fill gaps (unlike welding) and so unless each part is milled or machined to perfect fit (nearly impossible in a factory setting - or any other for that matter), there will always be gaps in the joining process. So even if you inspect a brazed lug and it looks perfect doesn't mean that the unseen part of the joint is perfect, in most cases I seriously doubt that at any time there is a 100% bond in almost any mass produced bike frame from any time period.

    Mind you I'm not a frame builder. But I am a welder by profession"


    Thoughts??

    Brian
    "The older I get the better I was" (from Old Guys Rule t-shirt)

  2. #2
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    Twaddle. Brazing is very good at filling gaps, small ones via capillary action, larger ones with a fillet. A good fit for tubes is important, but if anything more important for welding.
    http://www.kinetics-online.co.uk

  3. #3
    Randomhead
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    I'm not a big fan of "process wars." I have this ridiculous bias that TIG welded frames aren't as strong as brazed frames, but I know it isn't based on reality so I don't go saying that it's true in public forums. When I first started riding bicycles, welded frames were bad, full stop, and everyone knew it. It's hard to get over that sort of thing.

    lugged construction can hide a lot of flaws. In fact, I suspect when people first invented lugs they were intended to be the structural element at the joints and perfect mitering wasn't really considered necessary. All the pictures of cut apart mass produced bikes I have seen have major discontinuities of the tubes at the junctions. I think most of the Treks I made were pretty good at the miters, but when a person is producing 30 bikes a day there is some potential for a miter mismatch. And I think occasionally the machinist would get some of the TT miters out of phase.

    Having said that, a lot of welders are very ignorant about brazing and yeah, they should stick to welding unless they want to perfect the craft of brazing. The proper way to braze a lug is to flow the filler across from one tube to the other. This is really hard to do unless the miters are good. If you are going to look at mass-produced frames then the comparison has to be like-like. Mass produced welded frames have some really nasty flaws too, and I would rather have a lugged frame produced by someone that wasn't that good at what they are doing than a welded frame built by someone that didn't know what they were doing.

  4. #4
    coprolite fietsbob's Avatar
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    Mind you I'm not a frame builder. But I am a welder by profession"
    of what? thin wall Tube, TIG? like all the factory based Taiwan Builders by the thousands, do all Day long ..

    Or Boat Trailers? thick structural steels .. allow bigger gaps in fit, stick welding.

    [ it really doesn't matter]

    I found a visit to a production bike frame building shop interesting , Gazelle in Dieren NL,

    the building of a torch array jig focused domestic natural gas flame on the joints from all directions
    and brought the steel evenly up to temperature and then the brass filler was added ..

    then the hot frame was moved to an alignment jig till an indicator light lit.

    the production set up was quite efficient .

    and then racked to cool.. this was their Reynolds 531 road race frames.. main triangle.

    Cold joints are 1 cause of poor penetration, often, or contaminated surface.
    Last edited by fietsbob; 03-17-13 at 12:59 PM.

  5. #5
    tuz
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    Some guy on a forum said:

    "And all mass produced items in which are welded will be less than perfect. A good weld is highly dependent on the perfect fitting of parts. Welding cannot fill gaps that brazing can't and so unless each part is milled or machined to perfect fit (nearly impossible in a factory setting - or any other for that matter), there will always be gaps in the joining process. So even if you inspect a welded joint and it looks perfect doesn't mean that there was no burn-through or overheating, in most cases I seriously doubt that at any time there is a 100% penetration in almost any mass produced bike frame from any time period.

    Mind you I'm not a welder. But I have brazed a few frames"
    homebuilt commuter, mixte, road and track (+ Ryffranck road)
    bla bla blog

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    Who knows what the dudes point was in his statement. To say "there will always be gaps in the joining process" means he hasn't seen the many fine examples of tube joinery amongst our fine framebuilders. And of course we don't know his definition of a gap.

  7. #7
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    [/quote]I'm not a big fan of "process wars." I have this ridiculous bias that TIG welded frames aren't as strong as brazed frames, but I know it isn't based on reality so I don't go saying that it's true in public forums."

    Obviously if one is talking about frames that would not be an accurate position, because frames can be adapted to any process, or there may be no reason why a particular frame would even be limited by the joints the failure point might only be one joint, which could be beefed up, etc...

    On the other hand, merely at a joint to joint level, one thing about brazing or lugs is that they are much heavier and overbuilt that a weld, and even the average TIG weld is overdone, if one just looks at tube joinery specs. With fillet brazing in particularly they sometimes throw in a chunk that could join a 1/4 wall sewer pipe if it was a weld. So is some fillet brazed frame with a fillet radius of 1" stronger that TIG, quite likely, but only because the guy doing the work was on no budget whatever. Probably a belt and suspenders guy.

    I'm near a nuke plant, one of the old welded ones like most of NA. I am no down there every day with a placard begging them to get the welds out and replace them with lugs or brazing. Of course, the welds are bad news also.

    When I first started riding bicycles, welded frames were bad, full stop, and everyone knew it. It's hard to get over that sort of thing.
    And the reasons for that were that the people making bikes at the time were a) as ignorant of welding as the welder in the quote here is of bikes; b) scared their process would loose out, and they were right to be scared of that.

    I know you know all that U...

  8. #8
    Randomhead
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    actually, at that time TIG didn't really have that wide of an influence, and nobody was doing it on bikes until (? speculating) Teledyne stunk up the bike world.

    I think it's funny about my bias about TIG, because I know TIG welders that have an equal and opposite bias against brazing. At least I recognize my bias is wrong.

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    I think the guy has a point when taken into the 70s, stuff was crap back then, in many cases. There is another post in that thread where a guy reports Raleigh engineers telling him that 70% penetration was near 100% strength. It is funny, modern day guys often build perfect workmanship, but have no ideas what the numbers are. While back then they often turned out very poor workmanship, but they had engineers on staff, and did testing, and knew their numbers.

    If that 100% number is real, then since welds never reach 100%...

  10. #10
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    Quote Originally Posted by unterhausen View Post
    actually, at that time TIG didn't really have that wide of an influence, and nobody was doing it on bikes until (? speculating) Teledyne stunk up the bike world.
    I bought my first nice bike, a Peugeot, back in the early 70s. I remember around 1980 seeing a Kelty back packing frame and trying to figure out what this TIG was. The first Aircraft tubing was welded back in world war 1. And bikes followed not long after, probably not even in 4130 at that time, don't know. Not sure how they built stuff like penny farthings, maybe someone even forge welded them.

    I think it's funny about my bias about TIG, because I know TIG welders that have an equal and opposite bias against brazing. At least I recognize my bias is wrong.
    Brazing is cool. I can't do without it. Like you I think the process wars are pointless. Mainly because it is obvious they all work.

  11. #11
    Randomhead
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    I knew that people were "heliarc welding" aluminum back then. That term has pretty much gone away, although if you search for it you will find it. I don't know when people started TIG welding steel bike frames, I always figured it started with mountain bike frames.

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    Quote Originally Posted by unterhausen View Post
    I knew that people were "heliarc welding" aluminum back then. That term has pretty much gone away, although if you search for it you will find it. I don't know when people started TIG welding steel bike frames, I always figured it started with mountain bike frames.
    Funny- No one calls it "heli-arc" any more. Same-same though. Tungsten electrode- inert gas. I grew up on the welding bench starting in the mid-late sixties as a kid. We had the only "heli-arc" in town and I spent most of my work day doing repair on crusty old aluminum and mag castings on logging and fishing equipment. Tig'ing bicycle frames? I don't know, but we were using tig on kart frames in the mid sixties, and motorcycle frames in the late sixties. But, bicycles back then were only transportation- not sport, at least not in my neck of the woods.

  13. #13
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    GTAW seems to be the current acronym. Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding. To quote WIKI. Well I am sure glad the industry cleared up that confusion... That is OK for them, but I'm just going to stick with TIG.

  14. #14
    coprolite fietsbob's Avatar
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    I've heard it said by some Skilled welders they can tell how many cups of coffee
    you may have had, by the bead you lay down ..

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    Quote Originally Posted by fietsbob View Post
    I've heard it said by some Skilled welders they can tell how many cups of coffee
    you may have had, by the bead you lay down ..
    I've heard it said about some really good welders that "that guy could weld soap if he had the right rod." I wasn't one of them- LOL.
    -

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