-
if aluminium expands faster than steel when heated, why has everyone (2 companies) I have asked to get my seatpost out suggested that they can do it but the heat from melting out the seatpost would destroy the paint job? Surely they need to cool, not to heat?
The following is a hypothesis, I haven't tested it and it doesn't seem to appear in the literature:
The aluminium expands, the steel tube can happily stretch to accommodate that, but the brittle oxides which are gluing them together will shatter, allowing the post to be extracted. You might be able to achieve the same effect with cooling, but everybody has a blow torch and hardly anybody has ready access to the liquid nitrogen you'd need to get a similar effect, and compressing the oxide bond layer might not even break it as they are quite strong in compression but weak in tension.The other possibility is that they have just explained the process badly, and that they plan to apply the heat directly to the seat tube while cooling the seat post.
You are reading a single comment by @gbj_tester and its replies.
Click here to read the full conversation.
gbj_tester
fredtc
danb
if aluminium expands faster than steel when heated, why has everyone (2 companies) I have asked to get my seatpost out suggested that they can do it but the heat from melting out the seatpost would destroy the paint job? Surely they need to cool, not to heat?