Stuck seat post: Reversal!

[Canuk]

I have one of these very elegant BMC frames with the big aluminium lugs. Unfortunately the seat post system is a disaster, two bolts on a relatively thin aluminium structure, obviously eventually it's cracked!

It will hold a seat post, but it'll slip after a few days. I'm looking for a method to permanently secure a post into this frame, at my desired height, forevermore! I don't really want to go down the route of bonding a carbon post into the frame, if I have to I will though.

Is there another method to ensure the post stays put, and can be eventually retrieved (mechanically, or with heat, or penetrating fluid etc etc). I want to use this bike as an early season mileater, one which I can ride in rough weather and not bother too much about cleaning! It is quite a ridiculous design, thanks Swiss engineering...

 

[jim haseltine]

I'd be inclined to try a Vitus-style grub screw setup, maybe by bonding an internally threaded sleeve into the stress-relief section of the seat lug.

 

[Harvo]

A sleeve or collar attached to the seat post would prevent slippage.

 

[Canuk]

Someone suggested a coke can sleeve, but I guess I'd be concerned it would bond permanently with the aluminium lug.

 

[Canuk]

I've thought about perhaps drilling a very fine hole in the opposite side of the lug and fashioning a metal wire binder, or a machining a very thin jubilee clip to fit. I'm not sure how much extra torque it will take to hold the seat post in place but I'm guessing it won't be much?

 

[Canuk]

This is the side on view of the complete l seat ug assembly.

 

[sunympholepsy]

Someone suggested a coke can sleeve, but I guess I'd be concerned it would bond permanently with the aluminium lug.

Anti Seize Compound is your friend, if you wanted to use a shim. Otherwise, skip the shim and use Loctite 638 + activator to glue it in for good?

 

[Canuk]

I've seen the Loctite 638 used on bottom brackets so I guess it would be sufficient to hold a seat post in place. I'm not sure how much holding force the two bolts give with the cracked lug, but I don't reckon it will be much.