Re: [CR]reply to stuck seatpost discussion

(Example: History:Norris Lockley)

Date: Fri, 04 Jul 2008 11:03:18 -0400
To: <classicrendezvous@bikelist.org>
From: "John Betmanis" <johnb@oxford.net>
Subject: Re: [CR]reply to stuck seatpost discussion
In-Reply-To: <BAY102-W2382ABB2ABF6D66E27E1B9B2980@phx.gbl>
References: <MONKEYFOODeCs6CGFvY0000200e@monkeyfood.nt.phred.org>


At 09:18 AM 03/07/2008 -0500, Manfred Hegwer wrote:
>
>Heating the aluminum seat post may very well work but don't heat it to the
>point of trying to melt it. You can use a torch like the one a plumber wou
>ld use to sweat copper pipe. Heat the exposed aluminum post long enough to
> allow it to conduct the heat down into the seat tube. The different metal
>s have different rates of thermal expansion. This movement will often brea
>k the bond between the two metals. I recently used this method to remove a
> pedal stuck in a crank arm.

In the case of the pedal in the crank arm, you (usually) have steel pedal spindle in an aluminum alloy crank, so heat will loosen the bond due to the higher coefficient of expansion of the aluminum. With the seatpost you have the opposite. However, heat could still help break the bond due to the difference in expansion crushing any corrosion products in the interface. Repeated heating and cooling is always good.

John Betmanis
Woodstock, Ontario
Canada