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  1. #1
    Senior Member DigitalQuirk's Avatar
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    Mig Welded ChroMoly

    Greetings. I'm new here, but I've been rebuilding bikes since I was a kid. My latest project is what was my workhorse in my lean years; my Miele Astro road bike. It was my 4 season primary mode of transportation for a few years until I finally broke down and bought a car. Now I'm restoring it to take the place of my car (though, admittedly, not when the weather gets nasty anymore; I'm getting too old for that crap).

    Here's a shot of the rear drop that broke:



    I have some good friends at work who are good at mig welding (I do some myself, but I'm not as good as they are). We broke it off, pounded it back to shape, and mig welded it back on (lots of thanks goes to Rob and Reid). Here's the result:



    I'm just curious if anyone has tried anything like this before, and how well will it hold up? Does ChroMoly take well to a mig weld? I plan on repainting the rear drops, but since it'll be my commuter bike, it's going to be parked where it could get stolen, so they're getting the black TremClad treatment.

    Here's a shot of the stripped frame:


  2. #2
    me have long head tube TallRider's Avatar
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    That's a pretty cool job your friends did on the frame. I worked a welding job back in 1998, but don't know anything so technical as how chromoly steel will work with mig-welding.

    For the time being, I'd say you just ride the thing, and inspect it periodically for cracks in the weld. My guess is that the dropout will hold - my biggest worry (which isn't all that big) is that the brazed connection between frame stays and the dropout might have loosened while the welding was being done. Ask your friends about this too.

    You should probably post this in the framebuilder's forum - more knowledgable folks are there (though some here will be knowledgable).

  3. #3
    Senior Member DannoXYZ's Avatar
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    Chromoly was designed to be gas-welded for aircraft frames, so it's pretty tolerance of welding techniques. Super-thin tubing really should be brazed to keep peak-temperatures low and to spread out the HAZ. But the thick dropout shouldn't have any problems. Good job!

    BTW - make sure you align the faces of the dropouts to be parallel. Then clamp a wheel in and align the RD hanger.

  4. #4
    Senior Member DigitalQuirk's Avatar
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    Thanks for the tip; I'll do that.

  5. #5
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    They MIG weld stock car frames using 4140. Usually TIG is a better process for the scale of a bike frame. But if the welds worked, the result is just as good with any type of welding process. The problem is getting a good weld in, not whether a good weld will hold better from one process to the next, not in CM anyway.

    MIG welds can look great without actually being solid. If your friends are pros, or otherwise skilled, they will know their limitations, and the settings on the machine, and should have done a good job.

  6. #6
    Banned. sngltrackdufus's Avatar
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    "The appearance of the face are not as important as the root & the toes" - Google

  7. #7
    Banned. sngltrackdufus's Avatar
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    Too many amps,too much deposition,joint wasn't prepared correctly,it shouldn't need to be ground.......
    Last edited by sngltrackdufus; 02-12-06 at 08:30 PM.

  8. #8
    crusty jbrians's Avatar
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    The Miele CroMo frames where very good ones in their day. It's still going to work well for you, even with the fix.
    Around and around we go!

  9. #9
    Senior Member DigitalQuirk's Avatar
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    Quote Originally Posted by sngltrackdufus
    Too many amps,too much deposition,joint wasn't prepared correctly,it shouldn't need to be ground.......
    Hmm...I didn't post specific details on how the joint was prepared prior to welding, so please elaborate...how was the joint prepared incorrectly, and how should it have been prepared? How many amps should have been used, and how many do you think were used?

  10. #10
    Senior Member DigitalQuirk's Avatar
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    Quote Originally Posted by jbrians
    The Miele CroMo frames where very good ones in their day. It's still going to work well for you, even with the fix.
    I agree; being a tall rider (6'4"), theirs was one of the few frames I could get real comfortable with. It's hard enough finding a good road bike that isn't an ultralight racer or overpriced these days; even harder finding one with a frame of these dimensions with the shifters where they ought to be (on the down tube). One of the reasons why I opted to try to repair it, since the original company that made the bike don't seem to be in business anymore. If I wasn't so abusive with the bike and thought to keep an eye out for fractures, the repair probably would have been a lot easier.

    I just finished sanding the drops with 400 grit sandpaper; time to mask off the rest and break out the Trem Clad.

  11. #11
    Bike Junkie aadhils's Avatar
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    Get a mod to move this to the framebuilders section, and see what the pros think...

  12. #12
    Banned. sngltrackdufus's Avatar
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    Quote Originally Posted by DigitalQuirk
    Hmm...I didn't post specific details on how the joint was prepared prior to welding, so please elaborate...how was the joint prepared incorrectly, and how should it have been prepared? How many amps should have been used, and how many do you think were used?
    I have xray vision. I can see things.
    Just posted my comments with honesty that's all.

  13. #13
    Senior Member DigitalQuirk's Avatar
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    Quote Originally Posted by aadhils
    Get a mod to move this to the framebuilders section, and see what the pros think...
    Excellent idea; it appears that I'm even getting advice from a dog breeder here on dog breeding for some strange reason. I asked koffee brown to move it.

  14. #14
    Banned. sngltrackdufus's Avatar
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    Quote Originally Posted by DigitalQuirk
    Excellent idea; it appears that I'm even getting advice from a dog breeder here on dog breeding for some strange reason. I asked koffee brown to move it.
    You funny

  15. #15
    Rider Up!! Hardtail Guy's Avatar
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    Sorry I digress.
    If it works for you then great. I hope it does but I am not sold on that weld job. I did that for years with a gas torch on aircraft. Old ones that is. Too much heat. Try a heat sink next time. I hope you let the area air cool rather than quenching it. I feel your pain I have had old frames that I love too.
    If you know me you will see me. If you see me then you will know me

  16. #16
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    You can tell by looking at a weld, up to a point, whether there were too many amps, too much deposition, and so forth. What really counts is whether the little bit of metal that you rejoined in that photo has enough strength. There is a fair bit of material kinda clomped on everywhere in areas that don't look like they were in need of repair. That can weaken the overall result, but the key issue is whether the broken piece is actually fused back together. It is pretty comon with bad MIG work to just end up hosing the whole area with filler with little actual welding happening. Sometimes this work looks really neat. But at the same, particularly if fighting the machine a little and it's capabilities, if the welder actually gets good penetration at start up you can have a good part.

  17. #17
    Banned. sngltrackdufus's Avatar
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    Quote Originally Posted by aadhils
    Get a mod to move this to the framebuilders section, and see what the pros think...
    Yeah, see what the "pros" think

  18. #18
    Banned. sngltrackdufus's Avatar
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    Quote Originally Posted by DigitalQuirk
    Hmm...I didn't post specific details on how the joint was prepared prior to welding, so please elaborate...how was the joint prepared incorrectly, and how should it have been prepared? How many amps should have been used, and how many do you think were used?
    Pretty good guesstimation for a "dog breeder", eh quirk.......
    If you weren't such a wise a$$ , i probably would have told you exactly how to do it.

  19. #19
    Banned. galen_52657's Avatar
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    Not a frame builder or welder but had a similar issue with Bianchi steel frame - dropout cracked. Bianchi USA repaired the frame by welding the dropout. It lasted about a year and then cracked about a quarter of an inch away from the repair. Took it to the local frame builder. He ground out the crack and brazed it back together. That lasted about a year than cracked at the repair.

    Put an end to all that assembling/disassembling by buying a new frame...!

  20. #20
    Banned. sngltrackdufus's Avatar
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    Quote Originally Posted by galen_52657
    Not a frame builder or welder but had a similar issue with Bianchi steel frame - dropout cracked. Bianchi USA repaired the frame by welding the dropout. It lasted about a year and then cracked about a quarter of an inch away from the repair. Took it to the local frame builder. He ground out the crack and brazed it back together. That lasted about a year than cracked at the repair.

    Put an end to all that assembling/disassembling by buying a new frame...!
    The third crack,was that on the braze or next to it?

  21. #21
    Senior Member DigitalQuirk's Avatar
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    It's done.

    Working on it in my spare time (of which I have very little of), I prepped the metal and gave it the flat black tremclad treatment. I reassembled everything. I'll go to more detail in another post later; suffice it to say, with a new rear brake cable, deraliur, and chain, it rides very good and solid:



    Rode it all over the neighbourhood today. Didn't really push it much beyond its limits, since the old tires need replacement (showing cracks in the sidewall). Didn't want to put on new tires until I tested it, though. So far, so good!

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