Retrobike Forum Index

It is currently Fri Dec 09, 2016 5:14 am

* Login   * Register * Search  * FAQ



Post new topic Reply to topic  [ 71 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8  Next
Author Message
 Post subject:
PostPosted: Thu Jan 24, 2013 10:33 pm 
Dirt Disciple

Joined: Wed Jan 23, 2013 12:54 pm
Posts: 28
Location: Bedfordshire
Hmmmm, so I can either try the bolt hole technique and possibly have all the caustic run straight back out again, or just chuck it in the top and hope the BB has no aluminum it it... All good fun indeed! What did you use when you attempted to seal it?

It does at least look like the original BB on mine so it would presumably be full of nice steel parts...


Top
 Profile  
 
 Post subject:
PostPosted: Fri Jan 25, 2013 10:36 pm 
Dirt Disciple

Joined: Wed Jan 23, 2013 12:54 pm
Posts: 28
Location: Bedfordshire
Thinking of trying this tomorrow. What's the consensus on the bottom bracket, is it likely to have any alu in it? It's a 1992 (or thereabouts) Specialized Rockhopper if that helps, quite certain it's the original BB in there too.


Top
 Profile  
 
PostPosted: Tue Feb 26, 2013 4:40 pm 
Dirt Disciple

Joined: Wed Jan 23, 2013 12:54 pm
Posts: 28
Location: Bedfordshire
Finally finished! Took quite a few rounds of caustic to get the little blighter out (a dodgy batch of crystals that didn't want to dissolve delayed things further), but it's done. Went for integerspin's bottle hole method in the end, took some doing but worked nicely.

I've put a thread up about it, rather than continue to hijack this thread:

viewtopic.php?f=1&t=245226


Top
 Profile  
 
PostPosted: Sun Mar 31, 2013 9:51 pm 
Retro Guru
User avatar

Joined: Tue Nov 23, 2010 9:00 pm
Posts: 392
Good work! When I was blocking the seat tube I crammed rubber strips down there, and it pretty much worked, but it sounds like plasticine worked better.

In this video I was pouring it in and collecting it in a bucket; guess I went through a few litres before the thing plopped out:
http://www.youtube.com/watch?v=NJVAU0GXMcY&feature=youtu.be


Top
 Profile  
 
PostPosted: Wed Nov 27, 2013 9:02 pm 
Retro Guru
User avatar

Joined: Sat Feb 12, 2011 6:39 pm
Posts: 1182
Location: wales
my B.V. will be rescued by this treatment, yes boss.


Top
 Profile  
 
PostPosted: Thu Nov 28, 2013 12:36 am 
Old School Hero

Joined: Fri Sep 07, 2012 12:05 pm
Posts: 243
Location: Auckland NZ
You can measure how much seat post is in the frame with 2 spokes and one nipple screw one spoke halfway into the nipple then screw in the other insert into seatpost(obviously clamp is out at this point) until the hook in the spoke finds the bottom,mark the spoke and measure.


Top
 Profile  
 
PostPosted: Sun Jan 11, 2015 7:23 pm 
Retro Guru
User avatar

Joined: Tue Nov 23, 2010 9:00 pm
Posts: 392
joe careless wrote:
my B.V. will be rescued by this treatment, yes boss.


Yeah do it. DO IT. Then take some pics and let us know if it worked. I mean, it worked for me, but bloody hell it's 90% risky craziness.

Especially if you've got as much beer in your bloodstream as I had whilst melting/filming the process


Top
 Profile  
 
 Post subject: Re:
PostPosted: Mon Jan 19, 2015 7:02 am 
Dirt Disciple
User avatar

Joined: Thu Jan 27, 2011 1:47 am
Posts: 21
Location: New Zealand
Just been reading this, and as a former chemist/corrosion scientist I feel compelled to add a couple of other points, which may or may not be useful.

Firstly, caustic soda is VERY nasty stuff. Most people kind of ignore that because it's not an acid, but in lots of ways it's worse. So - if you tip it town the sink when you're done, make sure you flush it away with loads (and loads) of water. Don't want it sitting in the pipes, especially if they're copper...

Secondly, and somebody touched on this - the coefficients of thermal expansion for steel and aluminium are very different. For a nice steel frame with a decent paintjob, getting a blowtorch onto the outside isn't too useful since it will make the alloy post expand even more than the steel. And burn off the paint :(

But you can still use that property - if you live anywhere near an industrial gases plant, you'll probably be able to get hold of some liquid nitrogen. A couple of thermos's full should be enough to shrink the seatpost out, if you organize a plug and put it in via the BB etc etc with the frame upside down. I did it once years ago at university (where LN2 is freely available 8) ) and worked a treat.

This might be my second or third post in the four or so years I've been a member - it's the first time I've felt like I knew something useful...there are a lot of smart people on this forum!!


Top
 Profile  
 
PostPosted: Mon Jan 19, 2015 9:07 pm 
Retro Guru
User avatar

Joined: Fri Jun 12, 2009 11:58 pm
Posts: 803
Location: Quantocks
Nice advice Big Sud.


Top
 Profile  
 
PostPosted: Mon Jan 19, 2015 10:53 pm 
Retro Guru
User avatar

Joined: Wed Feb 20, 2013 8:23 pm
Posts: 2000
Location: Durham
Very intresting method BigSud will have to look into that myself .


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 71 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: fitzroybikeco and 11 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

About Us

Follow Retrobike

Other cool stuff

All content © 2005-2015 Retrobike unless otherwise stated.
Cookies Policy.
bikedeals - the best bike deals in one place
FatCOGS - Fat Chance Owner's Group

Powered by phpBB® Forum Software © phpBB Group