I've used a pedal spanner as a lever against the bb casing before - twice! Just lodge it in and lever until you hear a bit of a creek, turn the crank 45 degrees lever again and keep going til it pops off. I've found that a reasonably reliable way of doing it, and even knowingly put on some stripped cranks on a beater bike with the knowledge (hope) that I could eventually get them off again this way.
I've used a pedal spanner as a lever against the bb casing before - twice! Just lodge it in and lever until you hear a bit of a creek, turn the crank 45 degrees lever again and keep going til it pops off. I've found that a reasonably reliable way of doing it, and even knowingly put on some stripped cranks on a beater bike with the knowledge (hope) that I could eventually get them off again this way.