<VV> freeing stuck parts
djtcz at comcast.net
djtcz at comcast.net
Fri Aug 15 21:10:40 EDT 2008
snipped and bottom posted
-------------- Original message --------------
In a message dated 8/11/2008 9:01:35 A.M. Pacific Daylight Time,
dkdewald at pasty.net writes:
At 21:20 8/10/2008 -0400, Marc Sheridan wrote:
>My bicycle has an aluminum seat post in a steel seat tube. While looking
>creaking noise, I discovered that I forgot to use anti-seize in this
>situation, because the seat post won't budge
>Has anyone found a way or a chemical that will break that bond? I've been
>shooting PB Blaster on it everyday for weeks and it still won't move. Heat
>is out of the question because it would ruin the paint and I can still ride
>it the way it is. I'd just like to get it freed in case I do want to
>it for some reason.
I've had pretty good results heating bolts that were stuck, then letting things cool off. I believe it works so well on steel parts because iron oxide is less dense than the steel it came from (more volume, and why things ge tightened up and seize ) and weak, so when the hot bolt swells up the rust is crushed to some extent, reducing the "press fit" when temps and dimensions return to normal.
I could not find if aluminum oxide is less than dense than aluminum (2.7 g/cc), but I'm thinking the steel frame ID may be what rusted anyhow.
I'd remove the seat, and heat the aluminum post aggressively with a propane torch being careful to keep the temp near the epoxy cooler than I can touch (I'd keep a bucket of water with a few rags in it close by to limit the frame temp). Let cool for an hour and repeat a few times.
Sometimes impact breaks rusted parts free, but sometimes a steady force is better. If the steel post is welded to the bottom set I might try "torquing" the post to loosen with the crank held n a vice
Is there a hole in the alum seat post? Maybe it can be tapped 1/4 inch or bigger to provide a good purchase for a puller made from a bolt, thick washer, and a steel tube that just slips over the alum post to push against the frame.
It does not take much bolt torque to exert 1000s of pounds of force.
Westford, Massachusetts, USA
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