seat post (Alum)+carbon stl. frame= HELP!
 

Hello all!

I really love reading this place when I get the chance. I finally got my MEL PINTO SPECIAL tandem back from the shop with a whole new set of mechanical upgrades. Well, they "almost" got everything done.

First off, the biggest reason I'm attacking this post is because I can barely finish my downstroke when pedaling. My leg is almost straight out when down. :(

The previous owner put a Kalin seat post into my Mel Pinto carbon steel frame! Well, as you enthusiasts and mechanics know, this will create one HUGE headache trying to get the seat post to move, let alone come out.

Thus far I've tried ammonia, penetrating oil (I'm using PB Blaster now, cause I read that's the best on another forum), and the preverbial monkey wrench. I have not tried heat or cooling it as of yet, nor have I tried to start doing any cutting. This puppy won't budge. I'm afraid I'm gonna have to cut or ream the thing out of there.

What I'm after here, advice-wise, is... do I continue the penetrating oil treatments? Should I go for the big one and start cutting out? Or would just adding some wood blocks with zip ties be my best bet (yeah, it'll look goofy, but it would at least make it able to ride). I live in Goshen, IN, so if anyone near here knows of some Zen-master of problems like this, I sure would appreciate a name or number!

Thanks and hope to hear some good advice here soon.
~hoosierref

I have fixed this many a time. It is a pain, no doubt. You are correct in that the post is corroded into the seat tube. Essentially it is poorly welded in there.

Let the penetrating oil work a while (like a week).

Next, get some way to hold the bike very well and then get a big assed pipe wrench and honk back and forth on the post, this will destroy the post, but rarely is there any choice. If it lets go at all you can add some more oil and work it out of there with back and forth movements.

If this doesn't work you are going to have to cut it out. Cut the post off near the top of the seat tube and then get a slitting hack saw and make 4 cuts around the inside of the post until you have nearly gone through the aluminum but not all the way through. Then take a big drift punch and hammer one section out. Once that is done the others should come out fairly easily.

Some try the cold treatment also. That is freezing the aluminum with CO2 or dry ice etc. Aluminum contracts more than steel so this may help, but it never worked for me because the corrosion holding the two items is usually too much.

Hope that works.

Dave Bohm
Bohemian

Try several cycles of heating the post with a propane torch and letting it cool completely. Use some care to not let too much heat transfer to the steel frame as aluminum conducts heat pretty fast. Maybe keep your hand on the seat tube and when it gets warm stop heating the post. Soak it good in penetrating oil between cycles. Wipe off the excess before reheating-don't need any flames. After several heat-cool cycles and some good soak time get your pipe wrench out and see if you can break it loose. Might try cutting off the post and whacking it with a hammer a bit driving it a bit further into the frame as well-your goal being only to break it loose.
BTW my favorite penetrating oil is a John Deere branded aerosol that I picked up at a local Deere farm equipment shop. That stuff seems to really work. Kroil is another favorite.

I'm impatient with things like this so when I've encountered a stuck aluminum post in the past I've hacked off the top of the post about 1" above the seat tube, split the seat post down to the mast, then used a pair of vice grips to "coil" and tear the two "ears" inward so the post begins to collapse into itself. Once you get that crease or split to start moving down the shaft, the post usually breaks free.

Thank you so very much people! I really really love this bike and having just got it, we want to enjoy it so much, but I just want to be comfortable doing it, and right now, I am sooooooooooooooo not comfortable.
My wife and I have looked forward to getting this back and just going. I can do some, but no way can I go long distance.

I will keep everyone up to date on my progress.
~hoosierref

Try boiling water.
Take a face cloth with ice in it and wrap it around the seat post and let it sit for a while. Then boil up some water in a tea pot and pour it on the frame. You will probably hear a "tink" sound as the 2 dis-similar metals unbond.
If you have access to a/c refrigerant, dry ice or co2...it works even better than the ice

That sounds like a good idea also... to go one better, I have access to liquid nitrogen! A very good friend of ours is a science teacher! :)

dbohemian... i read you've tried it but didn't work. did you do cold then hot, or just cold shots?

with the access, I'm almost up for doing that, BUT I also don't want to hurt the seat tube and it's welds to the frame by doing the supercooling and then heat... one weld break there and that would not be a good thing.
~hoosierref

I wouldn't heat-cycle the seat post. I would cool the seat post and warm/heat up the frame at the same time (as "the mayor") suggests. I would start with just ice and hot water and if that doesn't work I would try the nitrogen. With the liquid nitrogen it might work to just cool the seat post and have the frame at room temperature.

Here's some *unhelpful* suggestions...

Put the wood blocks on the pedals. Use carriage bolts like my dad did on my tricycle 30+ years ago.

Wear the KISS platform cycling shoes just like Gene Simmons. (Works best if you and the stoker also wear black and white grease paint makeup.)

Use shorter s. You didn't really want to make those big circles anyway did you?

Remove the s completely and let your stoker do all the pedaling. After all you are doing the braking, steering, etc.

Cut down the seat post and weld it back together shorter. Maybe while doing this the welding heat will magically make the bond break anyway.

Get a shorter seat to put on the too long seat post. You don't really need all that soft, plush, cushion on your bicycle seat do you?

Sneak up on the tandem late at night with the light off in the garage to see if you can surprise it. Maybe it will not be holding onto the seatpost so tightly if you catch it unawares.

Sell the tandem and buy a new tandem. But make sure you only sell it to someone with the correct inseam measurement though.

Sorry, couldn't help myself. I'll punish myself later, maybe make myself ride without the seat on the seatpost...