German FAG bottom bracket

[Konstantin]

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....

[GeorgeET]

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.

[nfmisso]

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.

[Konstantin]

(02-23-2015, 04:54 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

---

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 ....