Will heating a steel frame up, damage its strength?

[simon the viking]

I have a stuck seat post on the spare bike and I'm about to do a hybrid conversion on it. The seat is at about the right height but I would like the option to alter it if possible.

I've tried post in vice, soaking in plus-gas, Freeze type sprays and everything on Sheldon Brown...... but I'm not going to the extreme of hack-sawing downwards or reeming it out, but if I heated the frame gently with a blow torch would it damage the integrity? and would it stand a chance of releasing it? I think someone in past has mentioned that the alloy seat post would expand more than the steel but would'nt the steel expand first and therefore release it....

I know I might blister the paint but I could touch that up (oh ahhh missus) later, the rest of the paint and stickers are a bit tired anyway.... what I dont want to do is damage the paint and then still have a stuck seat post

any thoughts?

 

[Drago]

Depends on the particular steel blend and whether it was heat treated or not.

If its an alloy post then caustic soda will dissolve it out without harming the frame.

 

[fatboy123cycling]

Heating a steel frame past its critical temperature will ruin the frame. A steel frame is extremely thin and will not take much heat to reach that temperature One way would be to use a hair dryer - that should heat it enough to expand the material - however, I guess the reason it is seized is that they are dissimilar metal i.e. steel and aluminium alloy - classic for seizing

 

[Shut Up Legs]

I have the same problem, the seat post on my touring/commuting bike has been stuck for so long, I doubt it will ever move again.

 

[simon the viking]

I have the same problem, the seat post on my touring/commuting bike has been stuck for so long, I doubt it will ever move again.

I recall you having the same problem.... I offered to come over and test out your theory of leaving it a baking conservatory to heat up......

 

[simon the viking]

Heating a steel frame past its critical temperature will ruin the frame. A steel frame is extremely thin and will not take much heat to reach that temperature One way would be to use a hair dryer - that should heat it enough to expand the material - however, I guess the reason it is seized is that they are dissimilar metal i.e. steel and aluminium alloy - classic for seizing

It is the classic alloy/steel corrosion problem I think I'll try the hair dryer and leave it at that if it don't work

 

[MrWill]

I've personally got one out by tacking a bolt to the top of the seat post then using an electric impact wrench to release the bond. Worked brilliantly.

Must be very careful to get the bolt dead centre!

 

[simon the viking]

I don't NEED to raise the seat I just WANT to have the option.....

 

[simon the viking]

I've personally got one out by tacking a bolt to the top of the seat post then using an electric torque wrench to release the bond. Worked brilliantly.

Must be very careful to get the bolt dead centre!

We (me and LBS) had seat post in the vice and it was clear the frame was going to bend before the seat post freed!!!!

 

[MrWill]

A pipe wrench on the seat post would also work.

 

[simon the viking]

Depends on the particular steel blend and whether it was heat treated or not.

If its an alloy post then caustic soda will dissolve it out without harming the frame.

I had thought of caustic sode in through the bottom bracket then leaving it upside down....

 

[MrWill]

We (me and LBS) had seat post in the vice and it was clear the frame was going to bend before the seat post freed!!!!

Ah ok. An impact wrench would shock it free, wouldn't bend the frame.

 

[Shut Up Legs]

I recall you having the same problem.... I offered to come over and test out your theory of leaving it a baking conservatory to heat up......

Sure, come on over, I see flights from London to Melbourne are only about 600 pounds at the moment! Actually, my seat post is like yours, it's pretty much spot on, so I also don't need to move it, I just wanted to regain that option.

 

[simon the viking]

A pipe wrench on the seat post would also work.

might try that with a long bar on the pipe wrench.....

 

[MrWill]

Sorry I meant impact wrench not torque wrench! On another planet.