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German FAG bottom bracket
#1
Hello folks.

This is about a bitchy seized and insisting bottom bracket. It is from a 85 german hercules bike and the BB is the standard german F.A.G by that times. http://de.wikipedia.org/wiki/Innenlager#mediaviewer/File:Fag-g.jpg  well in my case both plastic sides are broken after trying to remove it. I have the appropriate tool but the BB was seized so it's jammed and broken in there. After reading some forums I got a soldering tool to melt the plastic. It works. The bearings are exposed from both sides and I have started digging in the plastic to the area between the bearings and the threads. It melts i remove the melted plastic out with a pair o pliers. Problem is that the soldering tool cannot reach further in anymore. I got a small hole around the metal bearing and still the BB is not coming out. I tried hammering really hard with a big mallet, nothing... any suggestions? Vice is available , blowtorch no. I could easily burn the plastic out with the torch, that was my idea but i dont have one sadly....
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#2
Does not sound great. Whatever you do do not damage the BB threads. Get a good penetrating oil like Liquid Wrench that is readily available.(there are better available mail order), soak everything over night or more and gently try again. You can use a hairdryer on the outside to heat it up some and expend. Replace with a shimano UN54 or such. Your BB should have size stamped on it.
Never Give Up!!!
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#3
Do you have any idea what kind of resin the BB cartridge's housing is made of?  Depending on the plastic, it may not be hard to find a solvent that will attack it - unfortunately, the same solvent will probably attack the paint, but not the metal.....

Another suggestion: pack the area in dry ice; hopefully the plastic will get very brittle, and a couple of hard wacks with a hammer will cause it to shatter.  Wear gloves!!  

This is a really crazy design from a Mechanical Engineering standpoint; definitely flunks serviceability.
Nigel
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#4
(02-23-2015, 08:54 PM)nfmisso Wrote:  Do you have any idea what kind of resin the BB cartridge's housing is made of?  Depending on the plastic, it may not be hard to find a solvent that will attack it - unfortunately, the same solvent will probably attack the paint, but not the metal.....

Another suggestion: pack the area in dry ice; hopefully the plastic will get very brittle, and a couple of hard wacks with a hammer will cause it to shatter.  Wear gloves!!  

This is a really crazy design from a Mechanical Engineering standpoint; definitely flunks serviceability.

Hmm i do not want to risk the paint. Luckily as a chem. engineer i could get my hands on some oxy acetylene from the lab i work but hmm it will destroy the paint in seconds as well. It is a last option...For the time being I will insist with a smaller edge on the same soldering iron. It can go further in and melt it. Luckily with patience this thiner nose and more whacking it will come off Sad

As for attacking it with chemicals...It is a good idea. It is supposed to be polyamide (nylon!!) reinforced or very hard probably or at least thats what i could find....hmmm chlorine then!! and maybe at a next step some stronger acid....through the seatpost ....
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