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  1. #1
    Junior Member
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    First bike frame

    Hello iv decided to build a mountain bike frame and need some help.
    But first little about me I'm a welding student at mt sac in socal I'm GTAW(haven't started the class yet) I'm currently taking oxy,beginner arc, and basic electric arc welding. With that out of the way here are my questions

    -witch should I use GTAW,oxy or braze
    -if I use oxy or braze will they holed on mountain bike ( rather not kill my self going down hill)
    -material and cost what my material should use, I want something strong and light weight not super expensive, and where to get it (not online)around chino)
    -general cost of material (exclude welding supplies I'll be welding at school)

  2. #2
    Randomhead
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    GTAW or fillet brazing are both mainstream methods for building mtb frames. People use oxy, but I wouldn't suggest it. If you are going to buy locally, you are pretty much stuck buying 4130 straight gauge. The tubing isn't cheap, usually bike specific tubing is actually cheaper

  3. #3
    Senior Member
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    Regardless of which method you use for joining tubes (tig or fillet braze) the biggest obstacle you'll likely face is fitting and holding tubes to produce a strong and straight frame.

    For a first timer you'll spend a lot of time mitering tubes, and then devise some way to hold the tubes for welding. I can't imagine doing this in a classroom environment unless you can leave you workpiece "set-up" while you go home for the night. It's a PITA to teardown, clean up, and set up at the begining of the next class. IDK, maybe your class setup will accomodate this.

    Local supplies, if there are any, will most likely be expensive. If you source straight gauge 4130 from someone like MetalSupermarkets, or Aircraft Spruce, it is considerably less than bike specific tubes from someone like Nova or Henry James. All the sources mentioned have outlets in CA, just not close to you.

  4. #4
    Randomhead
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    Nova sells some sets that are less than $100. Building a frame is going to take about 20 feet of 4130 at an average cost of $6 a foot so you are money ahead buying a set.

  5. #5
    Andrew R Stewart Andrew R Stewart's Avatar
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    reddog3- There are both low cost and portable fixturing methods that one can use to build a frame from. Most start with a full scale drawing and then add devices to stand off the tubes above a flat surface (not necessarily a precision surface plate). A few pins in the lugs (or hose clamps) hold the tubes lengthwise WRT each other. Simple triangulated measurement points will hold the angle. (As an example for main triangle construction, other methods exist for forks and rear triangles). In a couple of hours one should be able to do a step or two and over many sessions end up with a frame. Slow, yes, but not complicated or needing a dedicated spot to leave untouched till next session. See my posts in this thread for more details. http://www.bikeforums.net/showthread...ed-Some-Advice

    I do agree that using bike specific tubes makes sense, as long as they're basic grade steel and not the thin wall super high strength stuff for the first frame or two. Andy.

  6. #6
    Junior Member
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    In class I have every tool I need ( Aka disneyland for welders) I can ask my instructor if I can leave in the shop since I'm there mon - sat. I may ask my instruct when he doing a bike build class.

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