Right, it's done! Yay! I've put some photos & a video below, but I learnt quite a few things, so here's my top tips:
- The paintwork's not going to be happy (particularly around seat tube), but you can mostly protect it
with electrical tape. Gaffer would probably work too. CS doesn't melt the paint, but if it gets under it it does seem to 'enhance' scratches & chips
- You can probably do the whole job with 1kg of CS;
I got through 2kg in the end, but I wasted loads with it too dilute and pouring it through a non-sealed frame
- Mix it way more concentrated than it says;
you know it's the right strength when the plastic bottle you've got it in starts to shrink away from it's wrapper from the heat!
- Mix and pour it in batches of about 250-300ml at a time;
I was doing it pint by pint but it gets weaker after about 5 minutes so it's a bit of a waste to mix too much. If it drips through like it did with me, you can re-pour the stuff you collect, but it does get weaker
- If you can remove the BB and do it upside down, or seal the tube properly it'll be much more effective than the way I did it.
Whilst pouring the final lot, the seattube did seal itself properly as it filled up with gunk, and the melting process got much quicker then. I initially tried to seal it by packing the seat tube with strips of rubber and it sort of worked ish
- Remove the whole of the visible part of the seatpost
with a hacksaw before you start; there's no point melting stuff that's sticking out anyway. In my initial videos you can see I left loads sticking out - this was in the hope of wrenching it out, but was pointless; just cut the lot off
- When you're nearly through, the whole frame made a weird cracking sound.
I now realise this was the seatpost melting through and releasing itself from the walls, but it sounded like the frame was doooooomed. When you hear that sound, you'll be able to lift the remains out - I carried on assuming it was still trapped until it basically floated out [see video!
After about 300ml more CS from the last session, I was able to just tear the top pieces of alloy off and I mangled the alloy in the tube as much as possible to increase surface area:
Ten minutes later:
Five minutes after that:
Here's a video of me pulling the final sliver out:
(Warning: contains victory swearing)
One happy, freshly-oiled frame:
'03 Cannondale Jekyll & '00 Cannondale F500
Previously: '97 Cannondale F1000, '94 Kona Lava Dome, '03 Cannondale F800, '99 Marin Mount Vision, Custom Brand-X, '97 Marin Monocoque, Custom Merlin Hardtail, Falcon Stealth, Raleigh Grifter, Raleigh Burner