Arc Welding bicycle frames possible?

Discussion in 'Painting, Welding, Bending and Gas Tanks' started by cheap ride, Apr 11, 2007.

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  1. Steve Best

    Steve Best Well-Known Member

    Another ancient post drug up for perusal.
    Most bikes these days are aluminum or chrome-moly.

    Aluminum will require either fitted joints and aluminum braze or MIG or TIG.
    TIG is best because it is the only weld that doesn't undercut at the edges.

    Aluminum, bronze or silver braze works great if you have enough overlap.
    Because the overlap surface area exceeds the material cross section the brazed joint is stronger than the tube.
    It gets questionable when you do butt or fitted joints. Fillets are not too bad if cleaned, fitted close and lots of fill.

    Chrome-moly will temperature harden at the edge of most arc or gas steel welds.
    The weld holds but will crack just outside it. I have experience with MIG, TIG and gas on thicker chrome-moly motorcycle frames.
    Fluxcor is garbage for this work, except for maybe a tack during assemble, but no more than a tack.
    Braze is my favourite, just don't get the chrome-moly too hot.
    MIG and TIG work well with pre-heating and then insulating after the weld.

    Proper flaring and fitting so there is enough overlap and no holes.
    Thorough cleaning, minimal heat, and slow cooling are the rules what ever you use.
    Stick can be done with tiny rods but on chrome-moly it will likely crack on the margin of the weld.
    Try pre-heating frame and insulating after weld, but I'm not hopeful.

  2. Frankenstein

    Frankenstein Well-Known Member

    I stick welded numerous times several forms of steel, generally speaking they held up just fine when laid right. Probably close to nothing that can't be arc welded. Just takes lots lots lots practice.

    I find that busting the Flux off a rod and making collar that goes along the seam to be welded works particularly well with thin tubes and low heat. High heat seems to melt the extra metal away from where I am working (like a melting string gets shorter) and so I usually 2 hand it and cut my welding stick in half and knock the Flux off half and manually feed it into my pool as I'm working. Sometimes a preheat with a torch is useful but mostly isn't needed unless it's really too f***ing cold out and the welds cool too quickly (Flux pops off on its own and the metal makes plenty of crackling sounds)

    Arc is completely reliable if you do it right, don't forget to add gussets or collars if you think you need it, better to have it and not need than to suddenly be riding 2 machines traveling away from each other when you least expect it.
  3. butre

    butre Well-Known Member

    older steel frames are more than thick enough for a stick welder at low amps, especially if you sleeve or gusset the joints. personally I like to just braze them though. it's easier than fiddling with amperage until you stop blowing through the steel or not holding an arc well
  4. V 35

    V 35 Member

    I was told to * never * use an Electric [ Mig or stick ] Welder on steel bicycle frames . The current from repair to ground inductively hardens the metal, leading to cracks. If the factory used an electric welder, you can too. If the frame is brazed, repair with braze. I brazed Chain Tensioners on several bikes, they all lasted .
    Can't say that about the ' death pops ' that come with most kits . Ditto for drilling, to drill is to invite cracking .
  5. Frankenstein

    Frankenstein Well-Known Member

    Well sure, heating to molten steel temps and cooling it too quick will make for brittle steel. If you are honestly worried then heat the joint to about 500 for an hour or 2 and cool it slowly by packing it in hot sand that you left in an oven at 500-600 degrees for a couple hours.