Twinkle Toes
Growing old disgracefully
It sounds to me like the cotter pin might have gone in at a sqewed angle & has understandably become seriously jammed on the crank/pivot shaft. Have you tried putting a pair of mole grips on the unthreaded end & see if you can turn it slightly? If that doesn't work, I'd refrain from using a drill if I were you - as you are in serious danger of wrecking the end of the chainwheel axle. If using something like Plus Gas (WD40 ain't good enough here) & drift n hammer doesn't shift it, I'd take it to a local engineering workshop & get them to press the bugger out hydraulically.
Here's hoping one of the above suggestions works!
Here's hoping one of the above suggestions works!