Stuck seatpost - a new idea?

Stuck seatposts have been discussed here many times over the years.
Apparently, the most common situation is an aluminum post stuck in a
steel frame.

I've never had the problem, but a good friend of mine who lives over an
hour away has the problem now. He's not an expert on mechanical things.
(For example, after he sent me a photo of the seatpost/seat tube
juncture, I said "Well, your seatpost is aluminum..." and he replied
"How do you know that?") Penetrating oil and much tugging and twisting
on the saddle has done him no good.

Anyway, I pointed him to Sheldon Brown
http://sheldonbrown.com/stuck-seatposts.html
and I think he may now be trying to have some ammonia trickle into the
joint.

But I'll be visiting in a couple weeks, and I'm wondering if this has
been tried: Finding or boring a section of steel pipe with an ID just
larger than the seatpost diameter (27.2mm in his case), splitting it
longitudinally, re-assembling and very lightly clamping it around the
protruding seatpost, then using it as a support to pry, lever or jack
the saddle and seatpost upward. The pipe would transfer the compressive
reaction load to the top edge of the steel seat tube.

I imagine I'd need a steel plate under the saddle. I can conceive of an
arrangement of screw threads to do the lifting, using nuts welded to the
steel pipe so as to support the lower end of bolts. But again, I've got
no experience with this repair, so perhaps the force doesn't need to be
very great?

I'll be visiting only for a few hours, so I'll have just one chance to
help him out. Anybody know if this method has ever succeeded?

--
- Frank Krygowski

uh yeah look thru RBT archives there's long uh you know post on this.

I deal with rust doing auto maintenance and restoration. In the rust belt, I had mated steel and aluminum as splash guards. The ion trading between steel and aluminum goes way beyond rust in mass, solidity and adhesion: beyond concrete into a very hard successful epoxy bond worthy of orbital use ages.

http://goo.gl/sRRslq

I've soaked forks/head tubes, in ammonia and oils (separately) for weeks: solid tight not map gas and 02 with leverages world nit loosen the bond ...over a significant surface. Remember the surface.

I haven't figures the molecular weights of the steel-aluminum ion deposit but you're encouraged to weigh the reactions and report back. Comparing against a few oxygen and water molecules

On 10/11/14 13:13, Frank Krygowski wrote:
Stuck seatposts have been discussed here many times over the years.
Apparently, the most common situation is an aluminum post stuck in a
steel frame.

I've never had the problem, but a good friend of mine who lives over an
hour away has the problem now. He's not an expert on mechanical things.
(For example, after he sent me a photo of the seatpost/seat tube
juncture, I said "Well, your seatpost is aluminum..." and he replied
"How do you know that?") Penetrating oil and much tugging and twisting
on the saddle has done him no good.

Anyway, I pointed him to Sheldon Brown
http://sheldonbrown.com/stuck-seatposts.html
and I think he may now be trying to have some ammonia trickle into the
joint.

But I'll be visiting in a couple weeks, and I'm wondering if this has
been tried: Finding or boring a section of steel pipe with an ID just
larger than the seatpost diameter (27.2mm in his case), splitting it
longitudinally, re-assembling and very lightly clamping it around the
protruding seatpost, then using it as a support to pry, lever or jack
the saddle and seatpost upward. The pipe would transfer the compressive
reaction load to the top edge of the steel seat tube.

I imagine I'd need a steel plate under the saddle. I can conceive of an
arrangement of screw threads to do the lifting, using nuts welded to the
steel pipe so as to support the lower end of bolts. But again, I've got
no experience with this repair, so perhaps the force doesn't need to be
very great?

I'll be visiting only for a few hours, so I'll have just one chance to
help him out. Anybody know if this method has ever succeeded?



Seat posts are cheap. Why not cut the end off so that the steel tube
can slide over the seat post without needing to split it longitudinally,
which would weaken it I'm sure.

I'd then tap a thread inside the seat post, and with the tube slightly
longer than the seat post, and with a plate with a hole as a stiff
washer, try to pull the seat post out as you describe.

--
JS

On Sun, 09 Nov 2014 21:13:07 -0500, Frank Krygowski
wrote:

Stuck seatposts have been discussed here many times over the years.
Apparently, the most common situation is an aluminum post stuck in a
steel frame.

I've never had the problem, but a good friend of mine who lives over an
hour away has the problem now. He's not an expert on mechanical things.
(For example, after he sent me a photo of the seatpost/seat tube
juncture, I said "Well, your seatpost is aluminum..." and he replied
"How do you know that?") Penetrating oil and much tugging and twisting
on the saddle has done him no good.

Anyway, I pointed him to Sheldon Brown
http://sheldonbrown.com/stuck-seatposts.html
and I think he may now be trying to have some ammonia trickle into the
joint.

But I'll be visiting in a couple weeks, and I'm wondering if this has
been tried: Finding or boring a section of steel pipe with an ID just
larger than the seatpost diameter (27.2mm in his case), splitting it
longitudinally, re-assembling and very lightly clamping it around the
protruding seatpost, then using it as a support to pry, lever or jack
the saddle and seatpost upward. The pipe would transfer the compressive
reaction load to the top edge of the steel seat tube.

I imagine I'd need a steel plate under the saddle. I can conceive of an
arrangement of screw threads to do the lifting, using nuts welded to the
steel pipe so as to support the lower end of bolts. But again, I've got
no experience with this repair, so perhaps the force doesn't need to be
very great?

I'll be visiting only for a few hours, so I'll have just one chance to
help him out. Anybody know if this method has ever succeeded?

It depends greatly on how long things have been assembled.

Some time ago I bought a used Japanese bike, that from the derailers
and other bits seemed to be 20 years old or thereabout. In trying to
get the seat post out I tried everything I could think of and finally
resorted to making a boring bar with a cutting head the diameter of
the I.D. of the seat tube and boring it out. Things didn't go
perfectly and I was left with a paper thin layer of aluminum bonded to
part of the lower portions of the seat tube which I was able to chisel
out (with a specially made very long chisel :-) From the remains it
was apparent that the tube had essentially bonded to the steel seat
tube.

I do not believe that the frame will withstand the force needed to
pull a firmly stuck seat tube.

I did read an article about a couple (I think it was) that removed an
aluminum seat post by plugging the frame tubes and pouring in some
chemical that reacted with aluminum but not with steel.

I did try a acid, I don't remember what now, but it didn't seem to
accomplish much, but the article I mentioned (it might have been a you
tube) definitely ended in success.

I tried: adapting an impact wrench to the seat tube, a rivet gun
applied to drive the post into the frame - thinking it would "break
the bond" so to speak, and finally a 24 inch pipe wrench on the post,
which after all the other tortures finally twisted the post off.
--
Cheers,

John B.

ah frank, ura machinist ?

fab a holder for a narrow hacksaw blade stick into the seat post ID...

cutting seat post wall in 2-3 places then adding ammonia then tapping with a punch is the way togo.

while there build a small shop for eyeglass and helmet mounted mirrors from solderable unbreakable aluminum.

the ammonia problem is elementary...there's no way to deliver ammonia to the ion exchange areas !

n not an H202 level reaction eg

On Monday, November 10, 2014 7:30:43 AM UTC-5, wrote:
ah frank, ura machinist ?

fab a holder for a narrow hacksaw blade stick into the seat post ID...

cutting seat post wall in 2-3 places then adding ammonia then tapping with a punch is the way togo.

while there build a small shop for eyeglass and helmet mounted mirrors from solderable unbreakable aluminum.

the ammonia problem is elementary...there's no way to deliver ammonia to the ion exchange areas !

n not an H202 level reaction eg

nnnnnnnnnnnnnnnnn

linseed oil mixed with aluminum antiseize

or

https://www.google.com/#q=dissolving+aluminum+hydroxide

On 11/9/2014 8:13 PM, Frank Krygowski wrote:
Stuck seatposts have been discussed here many times over the
years. Apparently, the most common situation is an aluminum
post stuck in a steel frame.

I've never had the problem, but a good friend of mine who
lives over an hour away has the problem now. He's not an
expert on mechanical things. (For example, after he sent me
a photo of the seatpost/seat tube juncture, I said "Well,
your seatpost is aluminum..." and he replied "How do you
know that?") Penetrating oil and much tugging and twisting
on the saddle has done him no good.

Anyway, I pointed him to Sheldon Brown
http://sheldonbrown.com/stuck-seatposts.html
and I think he may now be trying to have some ammonia
trickle into the joint.

But I'll be visiting in a couple weeks, and I'm wondering if
this has been tried: Finding or boring a section of steel
pipe with an ID just larger than the seatpost diameter
(27.2mm in his case), splitting it longitudinally,
re-assembling and very lightly clamping it around the
protruding seatpost, then using it as a support to pry,
lever or jack the saddle and seatpost upward. The pipe
would transfer the compressive reaction load to the top edge
of the steel seat tube.

I imagine I'd need a steel plate under the saddle. I can
conceive of an arrangement of screw threads to do the
lifting, using nuts welded to the steel pipe so as to
support the lower end of bolts. But again, I've got no
experience with this repair, so perhaps the force doesn't
need to be very great?

I'll be visiting only for a few hours, so I'll have just one
chance to help him out. Anybody know if this method has
ever succeeded?


If you're going to attempt a mechanical removal at that
level of corrosion ( and I heartily encourage you especially
since owner seems not to have much experience in the area)
you might cut the top of the post and slip a steel bar
inside so the post doesn't crush and tear when you clamp and
twist it.

In my experience the last infallible resort is that the
aluminum post melts well before any damage to the steel frame.

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

On 11/9/2014 9:59 PM, wrote:
uh yeah look thru RBT archives there's long uh you know post on this.

I deal with rust doing auto maintenance and restoration. In the rust belt, I had mated steel and aluminum as splash guards. The ion trading between steel and aluminum goes way beyond rust in mass, solidity and adhesion: beyond concrete into a very hard successful epoxy bond worthy of orbital use ages.

http://goo.gl/sRRslq

I've soaked forks/head tubes, in ammonia and oils (separately) for weeks: solid tight not map gas and 02 with leverages world nit loosen the bond ...over a significant surface. Remember the surface.

I haven't figures the molecular weights of the steel-aluminum ion deposit but you're encouraged to weigh the reactions and report back. Comparing against a few oxygen and water molecules


Oxides are bigger than metals.
There's the problem in a nutshell.

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

For your reference, records indicate that
John B. Slocomb wrote:

From the remains it
was apparent that the tube had essentially bonded to the steel seat
tube.

I wonder by what process. What we really need is a material scientist
who can say what is actually happening so that we can devise a proper
solution.

I tried: adapting an impact wrench to the seat tube, a rivet gun
applied to drive the post into the frame - thinking it would "break
the bond" so to speak, and finally a 24 inch pipe wrench on the post,
which after all the other tortures finally twisted the post off.

Not yet mentioned: heat and/or chill the frame so that there is a
significant difference in the thermal expansion of the two metals.

--
"Also . . . I can kill you with my brain."
River Tam, Trash, Firefly

On 11/9/2014 11:52 PM, James wrote:
On 10/11/14 13:13, Frank Krygowski wrote:
Stuck seatposts have been discussed here many times over the years.
Apparently, the most common situation is an aluminum post stuck in a
steel frame.

I've never had the problem, but a good friend of mine who lives over an
hour away has the problem now. He's not an expert on mechanical things.
(For example, after he sent me a photo of the seatpost/seat tube
juncture, I said "Well, your seatpost is aluminum..." and he replied
"How do you know that?") Penetrating oil and much tugging and twisting
on the saddle has done him no good.

Anyway, I pointed him to Sheldon Brown
http://sheldonbrown.com/stuck-seatposts.html
and I think he may now be trying to have some ammonia trickle into the
joint.

But I'll be visiting in a couple weeks, and I'm wondering if this has
been tried: Finding or boring a section of steel pipe with an ID just
larger than the seatpost diameter (27.2mm in his case), splitting it
longitudinally, re-assembling and very lightly clamping it around the
protruding seatpost, then using it as a support to pry, lever or jack
the saddle and seatpost upward. The pipe would transfer the compressive
reaction load to the top edge of the steel seat tube.

I imagine I'd need a steel plate under the saddle. I can conceive of an
arrangement of screw threads to do the lifting, using nuts welded to the
steel pipe so as to support the lower end of bolts. But again, I've got
no experience with this repair, so perhaps the force doesn't need to be
very great?

I'll be visiting only for a few hours, so I'll have just one chance to
help him out. Anybody know if this method has ever succeeded?



Seat posts are cheap. Why not cut the end off so that the steel tube
can slide over the seat post without needing to split it longitudinally,
which would weaken it I'm sure.

I'd then tap a thread inside the seat post, and with the tube slightly
longer than the seat post, and with a plate with a hole as a stiff
washer, try to pull the seat post out as you describe.

You're right, that would be easier, if he's willing to destroy his
seatpost.

It occurs to me, I don't know if the lower saddle mounting lug (or
whatever you'd call it) is cast as one piece with the seatpost tube, or
simply pressed in. If it's the latter, that joint might not resist much
tensile force. So I might end up drilling a transverse hole through the
post anyway.

Bonus! His bike would then be 3 grams lighter!

I wish I had an idea of how much force is needed. On one hand, it's
clearly more than he could exert by twisting and tugging on the saddle.
On the other hand, the bike's (IIRC) only about 3 years old, so
corrosion etc. shouldn't be very bad.

--
- Frank Krygowski