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  1. #1
    Senior Member Kactus's Avatar
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    Is this frame ruined?

    Frame has been exposed to high temperature from close by fire. Is this frame ruined or was the temperature low enough not to destroy the temper?

    1974 Motobecane Champion Team
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    1983 Sekai 4000
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  2. #2
    Super Moderator no1mad's Avatar
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    Moved from C & V Appraisals.
    Quote Originally Posted by Cyril View Post
    Ride what and in what manner pleases you. Those that mind don't matter, and those that matter don't mind. srsly.
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    Look around the lugs to see if the brazing material melted.

    The brazing material (likely brass) has a melting point lower than the steel (or steel ally) used in the tubes, and the steel tubes (at least the ends of them) were heated to above the melting point of the braze material when the frame was made. Plus carbon steel frames can be repaired by heating the lugs to melt the braze material, allowing a damaged tube to be removed, and a new one inserted. So if the braze material did not melt, the steel tubes were not heated by the fire to a higher temperature than they were when the frame was made.

    Steel and steel alloys can lose strength if they are kept for a long time at high temperature that is lower than their melting point. For structural steel building I think the rule of thumb is 1 hour at 900 degree F will start to weaken the steel. Plain carbon steel will regain at least some of its strength when cooled. Some steel alloys may not regain strength when cooled, but I think these alloys have to be kept at a temperature close to what was used to temper them in the first place, and I’m pretty sure that is above the melting point of brass.
    Last edited by 0.2HP; 08-08-13 at 02:55 PM.

  4. #4
    7-speed doomsday prepper ThermionicScott's Avatar
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    Unless that's the original paint, the blueish coloring on the seat tube is the definition of "lost its temper."
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  5. #5
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    The bluish coloration means that if the tubing was harden and tempered (which it may not have been then the temper is lost. I don't know if that means the bike was ruined. Though I would agree with the prior posters concerns about the brazing of the lugs; however, the heat source doesn't seem to have affected the whole bike and bluing can occur at much lower temperatures than required to melt brass or silver solders used in brazing.

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    Quote Originally Posted by PlanoFuji View Post
    The bluish coloration means that if the tubing was harden and tempered (which it may not have been then the temper is lost. I don't know if that means the bike was ruined. Though I would agree with the prior posters concerns about the brazing of the lugs; however, the heat source doesn't seem to have affected the whole bike and bluing can occur at much lower temperatures than required to melt brass or silver solders used in brazing.
    To me, the frame appears to have been chrome plated. If so, chrome will start to discolor in the 500°F range and above. So, while it got toasted, it may not be toast, remelting silver or brass happens much higher. An uncertain element would be how fast it was cooled. Which if in a burning building, might have been pretty rapid had it been exposed to a fire department hosing. I would have the frame alignment checked, put it together and ride it if things look good dimensionally.

  7. #7
    Senior Member Kactus's Avatar
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    Quote Originally Posted by repechage View Post
    To me, the frame appears to have been chrome plated.
    It is chrome plated. The brazing does not appear to have melted from what I can see from photos.
    1974 Motobecane Champion Team
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    1983 Sekai 4000
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  8. #8
    Senior Member mikemowbz's Avatar
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    Fire "next door", eh? A little far down the I-5 to evaluate in person, perhaps.

    Looks cool in it's way...could be worthwhile.

  9. #9
    Senior Member clasher's Avatar
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    Frames get exposed to heat in the middle of the tubes when a builder adds water-bottle braze-ons or anything else and I've never heard of anyone heat-treating a frame after doing that.

  10. #10
    Senior Member Kactus's Avatar
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    Quote Originally Posted by mikemowbz View Post
    A little far down the I-5 to evaluate in person, perhaps.
    A little bit!
    1974 Motobecane Champion Team
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    Personally, I wouldn't mess with it.

  12. #12
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    Quote Originally Posted by Kactus View Post
    It is chrome plated. The brazing does not appear to have melted from what I can see from photos.
    Caswell plating advises that chrome turns blue at 900°F. Getting close to silver melting but quite away from Brass. My advise is the same if you already own it. Verify dimensions and try it out. If you are considering a purchase, just smile and wave.

  13. #13
    Decrepit Member Scooper's Avatar
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    Do you know what the tubing is?

    As an example, 753 is the same chemical composition as 531, but is heat treated to gain higher tensile strength and can therefore be drawn thinner than 531 so the tubes are lighter. Subjecting heat treated tubing like 753 to high temperatures weakens it. In fact, Reynolds certified 753 brazers to ensure that the work never exceeded the temperature that would lead to loss of strength, and insisted that 753 be silver brazed because of the lower temperatures. Reynolds wouldn't sell 753 to builders who weren't certified.
    - Stan

  14. #14
    Gearhead old's'cool's Avatar
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    To me, it seems your problem is right out there in the middle of the grey area, between the "frame is trashed for sure", and, "heck, no problem". That means you won't be able to get a definite answer on the internet, but maybe we can point you down some avenues that will provide the information you need to determine whether the frame is good as-is, needs to be refurbished, or is now wall art. BTW, I think it looks pretty cool, and I hope you keep it that way regardless of the outcome.
    Off the top of my head, perhaps a Brinnell or Rockwell hardness test would tell the true story. (probably Rockwell, because I think Brinnell will not work due to the thinness of the tubing - not even sure about Rockwell). Because the temperature exposure varied over the extent of the frame, this would have to be done in many distributed locations on all the tubes.
    I also don't know if there is readily available test equipment that can be used on an arbitrary shape like a bike frame tube. I would suggest calling around to local machine shops. Most of them may not have have any hardness testing capability, but odds are they'll know someone to put you onto.
    The test is not completely non-destructive, as there will be a small indentation left behind at each test location. But generally, you could place them in relatively discreet locations, i.e. on the bottom side of the top & down tubes, and the rear side of the seat tube.
    A little more research will be required to determine what the desired minimum hardness is, for the 753 tubing, but that information is available, surely.
    Another way to ascertain the condition of the tubes, it seems to me, would be to have a frame builder check it out on a straightening jig. First of all, to see if it's still straight, but secondly, to input a specific amount of displacement, to the expected limit of the elastic range. If the frame returns to its original shape, I say it's good. This should be done in as many iterations, in different axes, as necessary to verify each of the tubes.
    I don't have any other ideas at the moment, but if I think of anything, I'll let you know via this thread.
    Geoff
    "I think that I think, therefore I think that I am"

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