On 9/17/2017 11:48 AM, wrote:
On Saturday, September 16, 2017 at 8:47:25 PM UTC-7, John B. wrote:
On Sat, 16 Sep 2017 13:30:10 -0700 (PDT), wrote:

On Friday, September 15, 2017 at 7:30:42 PM UTC-7, John B. wrote:
On Fri, 15 Sep 2017 19:59:27 +0100, "Ian Field"
wrote:



"John B." wrote in message
...
On Thu, 14 Sep 2017 21:33:17 +0100, "Ian Field"
wrote:



"Joerg" wrote in message
...
On 2017-09-14 10:42, AMuzi wrote:
On 9/14/2017 12:32 PM, Ian Field wrote:
The bike I built up on a frame I dragged out of a hedge has
a seized seat post.

So far; I've slackened the clamp bolt and give it a squirt
of PTFE penetrating oil at least once a day - is there a
reasonable expectation that it might work loose?

Thanks.

Yes.
The vibration and cyclic loading of the post can free them.
Not always but well worth a daily shot of penetrant and some miles.
Leave the bolt out and cross your fingers!


Might sing soprano after it let go all of a sudden :-)

Its seriously stuck, it'll probably need a lot of twisting to shift it at
all once it starts to loosen.

If I still had a welder, I'd weld a lever arm to it so I could apply
enough
force.

If it is an aluminum seat post in a steel frame and you can't budge it
with a, oh say 24 inch pipe wrench, after a few days of penetrating
oil then it probably won't come out without some serious attention.

I once spent nearly a week to make a boring bar and boring out a stuck
seat tube after all else failed however after reading the Internet I
discovered that dissolving the aluminum tube using lye would have been
much easier :-)

No aluminium - and I wouldn't want a glob of corrosive **** running down
into the BB bracket if there was.

You are supposed to disassemble the bicycle before you start :-(

From the Internet:

As a strong alkali, sodium hydroxide will attack and dissolve the
following metals: Tin, Aluminum, zinc, cadmium - behaves closely
enough to zinc. It will also attack chromium plating and copper,
although ammonia is far better at dissolving copper:

The reaction with those metals releases hydrogen gas.

Sodium hydroxide will not react with iron or steel, in fact the
alkaline conditions will not allow rust to grow;

What would you use in a frame that has been fully chromed?

Well, not lye :-)

Sheldon writes that "Fortunately, aluminum oxide can be dissolved like
magic by using ammonia" however Brandt disagreed :-)

I have no idea whether ammonia attacks chromium and "chrome plating"
is often several metals rather that just one so regardless of whether
something did or did not attack chromium it might attack an underlying
metal.

Pinarello frames are often completely chromed under the paint. Somewhere there was a video of them using baking soda to allow rechroming. I know that the fork on the Pinarello I'm restoring was pretty badly rusted in places. The chrome shop perfectly restored it in one day. There are pin holes here and there but I can't remember any rechroming that didn't have those. Oddly enough the pin holes are not anywhere near where the rust was. Those areas are perfect.


not 'baking powder' but rather reversed polarity in a
caustic soda (lye) bath.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971