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Also, I heard heating is a no go with alu on steel. Alu expands more than steel, so it gets tighter. You want to freeze it, as alu will contract more. Some folks mentioned using a CO2 canister, or dry ice, to shock freeze the post so it breaks the galvanic weld.
Scrabble-
I heard heating is a no go with alu on steel. Alu expands more than steel, so it gets tighter.
I watched a youtube video once that claimed this was a bit of a myth.
Yes ali does expand more but where its expansion is restricted it can expand in the other direction so instead of getting wider it'll get longer.
The best bit is that when it cools and contracts, it does so regardless of which direction it was able to expand in so it will pull away from the sides and loosen.
The example being demonstrated was an ali fastener in a block of steel so I don't know if a seat tube would restrict the expansion the same or not.
bigshape
M_Vatwork
nice! what ratio caustic / water did you use?
i take it you bunged up the inside of the tube somehow?
the fabricator i spoke to about removing my post said they'd heat the tube to get it out, thus wrecking the paint, so going to see if any other local companies can do it on a lathe...