Hudson308 

It is one of the rare Columbus-tubed early Treks. I subsequently had it powder coated, then applied decals from Velocals and Cyclomondo.
A forum member in California currently has it.

Since selling that one, I've stumbled across another one... a '78 TX770. And, you guessed it... the seat post is stuck.

Iowegian

I've used lye to dissolve a stem that was stuck in a fork but I hated working with something so dangerous so this time when I had a stuck seat post I tried something else.

First, I cut the post off until just about 1" was sticking out. Then I drilled a hole through the post so I could try to twist or pound it out. No luck. Then I started with a hacksaw etc and managed to cut into the seat tube for about 1 or 2 mm until I quit. I was just about to toss the frame when I decided I had nothing to lose. So I got out the sawzall and a loooong blade made for wood, not metal. This cut through the rest of the post easily! Then I pounded a couple small nails down between the post and tube at the top and poured a mixture of acetone and AT fluid down the tube until it wicked in. Finally I pounded the seat post and it came out. Made my day. There were NO discernible marks anywhere on the inside of the seat tube from the saw that I could see or feel. I think the blade only cuts on the upward stroke so it never had any purchase on the steel.

I took the frame to the co-op to find a post and their seat post gauge said 30.4mm. WTF! I think the inside of the tube was so corroded that what I assume was originally a 30.6mm post would no longer fit. Rather than spend hours with a hone, I lucked out to have a 30.6 to 28.6 seat post shim. I pounded that in (it's not coming out....) and now a 28.6 post works beautifully. This was such an easy extraction I put the sawblade into by bike tool box. It really worked like a charm!

unterhausen

when I worked at Trek, the 900s had fastback stays. Was this prior to the fastback stay models, or afterwards?

I have a dime-sized scar on my face because of a tiny splash of drano. I'm lucky nothing happened to my eye. I washed it with soap and water right away, but the next day there were four little red dots and it just kept getting bigger. Fortunately, it stopped eating it's way through my face before it hit anything important. Nowadays I would call poison control.

I think I'll try boring out the next stuck seatpost I come across with a boring bar. I tried drilling one out in my lathe, but that didn't work. I think the trick to any such approach is to thin the seatpost. The drillbit I used in the failed attempt was close enough to 27.2 that it made huge chips that ruined the seat tube.

52telecaster

I had a stuck seatpost on an old chromoly schwinn traveler. I though it might make a nice winter bike. Reading this thread made me afraid to do the lye thing so i walked downstairs with a large hammer just now and started hitting the nose of the saddle and damned if it didnt break loose. You guys inspire me one way or another. Ty!

Hudson308 

Your memory isn't failing! The TX900 from '76 through mid-'78 had fastback stays. There were a number of cracks/failures with this early seat cluster design, so Trek went back to more traditional "feather" stays for the 900 for a few years.
They returned to an investment-cast one-piece "fastback" design for many models in 1984.

TriBiker19 

I'm wondering if it would easier for me to try the hacksaw/sawsall method. The stuck post I have has ridges on it. If I was to cut the post on the thinner sections, maybe I can get it out and have some fair warning that I'm going to hit the frame before I actually hit the frame.

Or, I do what I have been doing and just have my husband work on it while I look on longingly.

52telecaster

If i weren't hetero i might get one of those myself.

TriBiker19 

A hacksaw?

52telecaster

Husband. Hell if he would do the dishes and change the oil i would for sure.

TriBiker19 

I'd like that, too! This one is very mechanically handy and makes sure there's a roof over our heads, so it evens out. And he doesn't complain about me taking over his half of the garage for bikes. (Although he might start to grumble once the snow flies.) Or when I bring home foster kittens. Lots of foster kittens.

52telecaster

My gf is the adopter of cats at our house. One of them loves me, the other thinks im a monster.

TriBiker19 

Only two? We were up to 5 for quite a while. My husband started making comments about six pushing me into "crazy cat lady" territory. I've fostered 309 in the past 16 years, kept 6. As for the one who thinks you're a monster--there's hope. Hubby had a cat, I'll call her "Princess". She hated me. HATED. Many years later, she was cool with me. It only took a little over a dozen years to be her friend--there's still hope for you.

Unless the cat is Siamese. I gave my Siamese a bath and he still hasn't forgiven me for it. The bath was in 2007.

52telecaster

My gf says the older cat(the one who loves me) wont tolerate more cats or we might have them. We are babysitting a dog this weekend. She loves torties but these torties dont love her.

Guerc 

I followed the instructions from this thread on my ‘92 Marinoni. Indeed, the lye dissolved the seatpost. It also peeled the original paint right off, but appears to have had zero effect on steel and chrome. Cool trick.


(paint was already terrible and the bike needed a good powder coat anyway)

dddd

Alkali solutions, even mere alkali cleaners, are known to embrittle steel.

Reports of chains and cassettes that broke or crumbled in use after being soaked in such cleaners turn up occasionally.

I've used a long, narrowed (to make it fit through the post ID) metal blade in a Sawzall to remove a few posts and which didn't even begin to notch the ID of the seat tube.
The trick is to probe the slot with a sharpened, bent spoke periodically to know when the entire slot in the post is free of any aluminum "bridge" (which will prevent it's extraction).
One must also prevent the stroke of the blade from catching on the upper end of the seat lug, to prevent paint loss. The slot in the post doesn't need to extend above the slot in the seat tube anyway, so this is easy if one simply familiarizes themself with their saw's stroke length and then pays attention to what they are doing.

With the mandatory, fully continuous slot, cut to the bottom of the seat post, some twisting action typically breaks the post free of the inside of the seat tube with only modest torque applied. Penetrant and thermal cycling makes this even easier, as the heated aluminum post expands lengthwise relative the the steel set tube.

The Lye is scary stuff, dangerous for anyone who is not familiar with handling the dry material or the liquid or the vapors.
NEVER add water into any contained dry lye crystals or it will tend to literally explode with the expanding gasses from the exothermic mixing reaction!!!

RandolphCarter is correct that, unlike many other caustics, caustic alkali solutions can/will actually dissolve skin tissues without any stinging being felt.
This makes them (well, household bleach anyway) useful for the small skin-removal surgeries ("accelerated dermabrasion") that I've occasionally performed on myself to remove growths or thickened skin.





Failed method:


Success removing an over-sized STEEL seatpost that apparently got pounded in back in the '60's(???)

xiaoman1 

Success removing an over-sized STEEL seatpost that apparently got pounded in back in the '60's(???)


[/QUOTE]
Lye is really a dangerous product to use......I am glad to we able to remove it. mechanically, in the photo with the crescent wrench what you trying to do? I did see the strap but curious about its purpose, were you standing on the board for the extra umph?.....BTW, did the whiskey harm the paint?
Best, Ben

dddd

Lye is really a dangerous product to use......I am glad to we able to remove it. mechanically, in the photo with the crescent wrench what you trying to do? I did see the strap but curious about its purpose, were you standing on the board for the extra umph?.....BTW, did the whiskey harm the paint?
Best, Ben[/QUOTE]


I knew that someone might wonder what all was going on in that photo!

The horizontal wood "bar" (and the wrapping around the seat tube) was there so I could pound on the seat tube with a 2# hammer without damaging the tube or the paint.
Such pounding was what finally got the steel post out of the red frame (while a couple of tons of tension was pulling on the post)!

And the strap supported the bike's weight (plus some weight applied by my foot on the frame) to produce bigger torque on the alloy post while I beat on the seat tube. I could have easily achieved more torque than that using my two hands, but which left no hand free to beat on the seat tube!

I also then reversed everything, flipped the frame over and got the wrench to apply reverse-torque, while hitting the other side of the seat tube, also to no avail, before I resorted to the Sawzall and the long blade (that I first narrowed slightly at the bench grinder to fit through the post ID).

Here's the photo of the "hanging" procedure reversed, evidence that the post was mightily stuck (had been soaking in PB Blaster for years, and had resisted all previous attempts at removal, even using dry ice):


The Sawzall made short work of this stubborn post, and left no discernible scar to the inside of the seat tube. If you've tried cutting good steel with a Sawzall, it's apparent that it takes some minimum of contact force at the teeth to begin cutting, force that is seemingly impossible to generate with even the saw's sharp teeth at the tip of the blade. However, if one were to lean into the Sawzall such that the blade contacted the seat tube opening edge, or contacted the edge at the bottom of the clamping slot, surely one then could easily generate sufficient contact force for the blade to dig into the steel. So always just stay away from the seat tube's edges with the blade teeth and then it's a seat-tube-safe procedure.

Oh, and the whiskey and ice was to chill the post of course...

xiaoman1 

I knew that someone might wonder what all was going on in that photo!

The horizontal wood "bar" (and the wrapping around the seat tube) was there so I could pound on the seat tube with a 2# hammer without damaging the tube or the paint.
Such pounding was what finally got the steel post out of the red frame (while a couple of tons of tension was pulling on the post)!

And the strap supported the bike's weight (plus some weight applied by my foot on the frame) to produce bigger torque on the alloy post while I beat on the seat tube. I could have easily achieved more torque than that using my two hands, but which left no hand free to beat on the seat tube!

I also then reversed everything, flipped the frame over and got the wrench to apply reverse-torque, while hitting the other side of the seat tube, also to no avail, before I resorted to the Sawzall and the long blade (that I first narrowed slightly at the bench grinder to fit through the post ID).

Here's the photo of the "hanging" procedure reversed, evidence that the post was mightily stuck (had been soaking in PB Blaster for years, and had resisted all previous attempts at removal, even using dry ice):


The Sawzall made short work of this stubborn post, and left no discernible scar to the inside of the seat tube. If you've tried cutting good steel with a Sawzall, it's apparent that it takes some minimum of contact force at the teeth to begin cutting, force that is seemingly impossible to generate with even the saw's sharp teeth at the tip of the blade. However, if one were to lean into the Sawzall such that the blade contacted the seat tube opening edge, or contacted the edge at the bottom of the clamping slot, surely one then could easily generate sufficient contact force for the blade to dig into the steel. So always just stay away from the seat tube's edges with the blade teeth and then it's a seat-tube-safe procedure.

Oh, and the whiskey and ice was to chill the post of course...[/QUOTE]

ddddl,
Whew...that was a great Rube Goldberg approach.....and the use of your favorite beverage to cool the post was genius!

Best, Ben

Xavi.steel

is there a way to preserve the paint using this method? ie masking or something?

WGB 

FWIW, a local mechanic leaves the seat post as long as he can and then heats the end of the post with a torch.

He swears that since aluminum melts at about 660c and steel melts at 1500c he can heat a post enough that the post will soften to a point that he can twist it and out it comes without damaging the frame. Obviously this won't work with a slammed seat post.

For a seized stem, I have twice cut off a stem at the bars and done the lye method with great results. I first wrap the steerer with a rag and then put cold water in a container, added crystals and then inserted the wrapped stem into the container. Both times I did this outside in February. The rag prevents splash-back.

I told the above mechanic my method and he laughed at me. He said that a) no one can see the steerer tube as it's hidden inside the headtube and b) its often not painted anyway. He simply cuts off the stem, heats the stub at the steer tube and out it comes.

I have sworn that the next time he does one I will video it for posterity.