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  1. #1
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    Removing Cantilevered Brake Lugs

    Is MAPP gas hot enough to de-braze cantilevered brake lugs from a frame?

    Someone said a hacksaw and a files are all that's needed. I was thinking of removing the fitting first, then smoothing the spots with a file and sand paper.

    How is it done?

  2. #2
    Framebuilder
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    I did this last week. It went like this- angle grinder, file, and 80 grit...15 min tops. A torch wouldn't make it any faster and it saves the stays from a needless heat cycle.

  3. #3
    Randomhead
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    the problem with using a torch to un-braze canti posts is that they are probably put on there with brass. The remelting point of brass is high enough that it's fairly easy to rip the tubes if there is a small part that isn't loose when you start tugging on it.

  4. #4
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by unterhausen View Post
    the problem with using a torch to un-braze canti posts is that they are probably put on there with brass. The remelting point of brass is high enough that it's fairly easy to rip the tubes if there is a small part that isn't loose when you start tugging on it.
    Position the frame so the bosses are pointing straight down, with a bucket of water underneath. Keep the flame on the bosses as much as possible while heating. When the brass is fully melted the boss will just fall off into the bucket. At that point you can use a wire brush and/or a solder wick to remove residual brass from the stays. If you're lucky/good enough you will have minimal clean up afterward.

    N.B. Mapp/air may not be hot enough to melt the brass effectively; if you can use Mapp/oxygen or oxy/acetylene you will have better luck, and it will be much faster meaning the heat-affected area on the stays will be much smaller.

  5. #5
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    I knew you were going to say that. I think they sell small DIY MAPP/oxygen torches at Home Depot. Do they also have DIY oxy/acetylene? I think not.

  6. #6
    Randomhead
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    they do have DIY O/A at home centers, but they are pretty expensive for what you get. MAPP/Oxy is hot enough, MAPP will probably be somewhat frustrating

  7. #7
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    I just unbrazed some brass brazed braze-ons (how's that for a fun sentence?) with Oxy/MAPP. Just getting the braze-ons red hot is adequate. The frame tubing doesn't need to be that hot and is somewhat insulated from excess heat. But to be honest, I normally go the grinder route. In this particular case it would been a long and unpleasant task with the grinder, so...

  8. #8
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    Lowe's has a MAPP/oxy kit that cost $60. I also thought that was "too much for what you get". I do have a grinder and some disks, so that's always an option. I hope it doesn't come down to that, but it might.

    If I can ask another question, is MAPP/oxy hot enough to remove and replace rear dropouts, too? I'd imagine that'd be a problem, given it's just barely adequate to remove a surface mounted boss.

  9. #9
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    Quote Originally Posted by JohnDThompson View Post
    Position the frame so the bosses are pointing straight down, with a bucket of water underneath. Keep the flame on the bosses as much as possible while heating. When the brass is fully melted the boss will just fall off into the bucket. At that point you can use a wire brush and/or a solder wick to remove residual brass from the stays. If you're lucky/good enough you will have minimal clean up afterward.
    Yamaguchi did that, but also clamped a very small set of vice grip pliers on the part as well. The extra weight helped it fall off a bit sooner, but didn't impart any undue stress.

  10. #10
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    Oxy/MAPP is hot enough for just about anything you'd like to do with steel, including welding it. The only trouble is that the little oxygen bottles are good for 10-15 minutes tops.

  11. #11
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    So, listen, If I do this to an otherwise 100% totally serviceable frame, does that qualify me for the "Drew of the Month" award?

  12. #12
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    What is it?

  13. #13
    Randomhead
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    I don't think I would remove canti bosses from an otherwise serviceable frame. If the reason you want to remove them is just because you don't like cantilever brakes, get some Paul's or sell the frame. Cheaper than a new paint job
    Last edited by unterhausen; 06-06-10 at 12:04 PM.

  14. #14
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    Gentlemen,

    I have been shopping for a frame ever since I started this thread. I still haven't found one yet. I have been focussing on 29er frames because they seem to have the best combination of features to do what I want. They almost universally use disk brakes, so I may have to go that route, instead of the internal hub brakes I want to use. One wierd part of the 29er world is frames are sold without a fork. So, even if I find a frame, I still need to find a fork. In the end, I may end up buying a complete bike and just swap out the rear hub.

    P.S. - I even found a new bike, a complete bike, with the infinitely variable rear hub for as little as $400. I haven't found any inexpensive Rolhoff hubbed bikes. :-)

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