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    • CommentAuthorNikola
    • CommentTimeNov 8th 2012
     
    I recently got an old road frame from a neighbor of mine. It has a bottom bracket with plastic cups, and they are damaged, so I can't remove the bottom bracket to replace it. I was considering using a propane torch to melt the cups. What do you folks think?
  1.  
    get a junior hack saw, use the triangle filer, OR use dremel
    • CommentAuthorrollins
    • CommentTimeNov 8th 2012
     
    I've dealt with this before, believe it was on the non drive side. I think I pried it out with a screw driver, which broke it in half and then reinstalled without it, which I was surprised to find out actually worked with no issue at all.
    • CommentAuthorthrub
    • CommentTimeNov 8th 2012
     
    Remove bottom bracket from the drive side. With the pressure removed from the non-drive side, the cup will unscrew fairly easy. If it's really trashed, used the screwdriver approach. Replacements cups cost between five dollars for a Delrin cup, and twelve/fifteen dollars for the alloy cup.
    • CommentAuthorCeya
    • CommentTimeNov 8th 2012
     
    Post a picture ( picture is a thousand plus words).

    S/F,
    CEYA!
    • CommentAuthorShaku
    • CommentTimeNov 9th 2012
     
    I got the person to use a flat file, manual one, so that they had more control how far they cut into the plastic cups.

    I also had someone else just use the blade of a hack saw, and cut it in one place and fold it down on itself.

    CAVEAT: if you cut too deep, you will destroy the threads, or damaged them, cut JUST ENOUGH.
    • CommentAuthorNikola
    • CommentTimeNov 14th 2012
     
    Both sides are damaged, so I probably will melt the cups, and mount some "real" bottom bracket after that.
    • CommentAuthorthrub
    • CommentTimeNov 14th 2012
     
    If you go that route, I suggest using a heat gun rather than the torch. Things start softening up around 350° F. The heat gun will give you more control heating up things through and through without setting plastic on fire.
    • CommentAuthorNikola
    • CommentTimeNov 14th 2012
     
    I was planing to use a campers' gas stove, I think it's not to hot.
    • CommentAuthorthrub
    • CommentTimeNov 14th 2012
     
    I believe I would attack the bearings with a twist bit to disassemble and remove the axle and gain a purchase on the cups before I attempted a stove approach. By hook or crook, once the spindle has been driven out you can insert and jam in a long tapered steel wedge and unscrew the cups.

    Even better, bore two pilot holes between the bearings and the cups and run in a pair of large screws, then throw a large adjustable wrench on and unscrew.
    • CommentAuthorNikola
    • CommentTimeNov 15th 2012
     
    Done, I've melted the cups. Next thing is cleaning the residues of the melted plastic, and painting the frame.
  2.  
    or... do what ever the hell you want, ignore everyones advice, we'll assume your muttering to yourself, and then ask for help when it goes to crap.
    Which you will probably ignore as well.

    If you had provided the relevant information that you were going to paint the bike anyway, ten of us would have suggested you use some gas (or I think for you, petrol) and burn it out. be sure to leave a window open as the soot will make a mess in your mom's basement.
  3.  
    Maybe I should have saved that for a what grinds my gears rant?
    • CommentAuthorveggie
    • CommentTimeNov 15th 2012
     
    Haha
 
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