Stuck Seatpost Blues?

The seat post man website indicates that our hero (yes, if he is very successful at removing stuck seat posts than he must be a hero) has some special tools of his own design. I would love to see these tools and watch him pull a recalcitrant seat post. I have found a few custom made tools in YouTube videos (see links below). They have made a puller that pushes on the bottom bracket and lifts the post. They use a great deal of pressure and I suppose that (occasionally) the frame might yield before the seat post. Some videos show burly men using a giant pipe wrench and freeing the post while beating the wrench with a large hammer. I shudder to think what this might do to frame alignment. Some show filling the seat tube with ammonia or Coca Cola as a solvent, but they seem to fail. Sodium hydroxide dissolves aluminum and melts the post; nasty stuff.

You took the words out of my mouth there Brian - ditto

October 29, 1941

"Know when to hold 'em, know when to fold 'em
Know when to walk away , and when to run" - Kenny Rogers 1978

Not sure that song was about stuck seat posts , but I heed that advice if after 30 mins I have made no progress . But I have great respect for those who keep at it.

Excellent!

My somewhat brutal technique is to first pry the seat tube open a bit at the slot, then seep the best penetrating oil on hand into the opening. That can sit overnight. Next day, after the usual hammer whacks, post in the vise twists, etc., I just pull out the drill and use a grinding bit to thin the seat post wall, by a lot, with emphasis on one side; I want it as thin as possible somewhere, rather than uniformly thinner. That heats the post and frame up quite a bit, so frequently a dousing with ice water will break the bond. If not, back in the vise. the thin wall of the post will collapse at some point and from there it should just come out, or you can use a really long, thick screwdriver to get in there and pry more. It will come out.

Only rarely does a bike require that total brutal job. The post usually gives up after the drill - ice water - vice routine.

But I haven't done this in years. I can pick what bikes I'll work on, and one of those won't be it.

Cheers and good luck,
Frank

I have to admit I've had no success with temperature change and I've tried extreme versions ...
-18C brine from the freezer, and boiling water from the kettle don't make enough of a difference
because the aluminium and steel are too similar in their respective expansion, and usually in
intimate contact, so it's hard to get a temperature contrast (ie, shrunk post, expanded tube).

I've also had little success with twisting ... if it won't come out using the saddle to lever on it
then spanners, moles, or even a vice seem to make little impact. I have even tried setting up some
tension while heat cycling, and while this worked after ~20 cycles on a stuck pedal (small mass)
I gave up before seeing benefit on a seatpost/frame (big mass, so hard to cycle by many degrees).

I'd also caution against hammering inwards (the post fattens and grips more), or threading the post
(pulling a thread exerts a slight outward pressure). In theory, a slide hammer might help but in
practise I've not met a big enough one to succeed this way.

Even adding lubricants is an "all or nothing" affair ... they fill the oxidised space between post
and frame, and if insufficient to loosen the post, they now block the penetration of something
that could have reduced the oxide. Because of this my first attack on a stuck post is phosphoric
acid (you can use hydrochloric if you have drain cleaner), knowing that if it won't release by the
morning, there was nothing that could have done better. This works, maybe half the time ...

... and if that lot doesn't work, the post is trash ... either slot the inside until it weakens
(difficult) or if it's an aluminium alloy post, dissolve the post with caustic soda (dangerous -
but this really works). Beware, grinding or drilling or milling out the post is a lot of work,
and if you have to use caustic do it slowly with ~10% mix, pre-dissolved, because it will get
hot and that damages the paint. It will take repeated doses (up to a week), best done outdoors,
and you must dress the part!!!

I mean rubber boots and gloves, eye protection, old clothes that you can afford to throw away ...
Keep a bucket of water on hand, and watch out for bubbling and spewing of corrosive effluent.

I prefer to plug the post, invert the frame, and feed the mix in via the bottom bracket. If the
frame gets warm just wait. When it goes cold (an hour or so), pull the plug over a bucket, rinse,
replug, and top up. About a mugful each time works well ... as does a funnel and plastic tube to
get it in the seat tube. This will definitely work if you have the patience, and what's really
nice is that caustic soda wont's damage the frame. Once washed, and re-waxed inside (waxoyl!),
you can put the whole debacle behind you.

Rod, nice write-up and if that photo is your dissolved and extracted post, congratulations. I have been wondering about reversing the galvanic weld by filling the tube with a suitable electrolyte and applying a small voltage between the seat tube and the seat post. The problem is the dead short wherever the non-corroded metals are touching, but some current would still flow through the welds and possibly dissolve them.

You could also immerse the frame in seawater. The aluminum seatpost (as well as any other aluminum or zinc parts) would function as a sacrificial anode like they put on boats. This would protect the steel from corrosion but dissolve the seatpost over time. An applied voltage with the right polarity might speed things up. Any chemists on this forum?

Brian

Thanks Jem ... re-reading my post, maybe not! ... it's one of the hazards of following WC's advice.

Thanks Brian too; you raise some good points on galvanic corrosion but I think (a) aluminium has too
similar an electropotential to iron to be an effective sacrificial anode, and (b) the non-conductive
oxide and metal-metal contact conspire to leave no current to remove the oxide. Usually magnesium is
the preferred sacrificial metal for yachts and steel water tanks.

You're definitely onto something with using electrolysis to clean up old parts though. Use a plastic
bucket and sodium carbonate to improve conductivity, and a car battery charger can turn rusty into
pretty in a few hours! Some polishing is needed afterwards, but far less elbow grease than before 👍

Does this mean that Viscounts have aeroplane-standard frames and USN-standard seatposts?