I bought a load of aluminium from a scrap yard, a mixture of engine parts and wheels. The engine parts were easy to cut up with an angle grinder into sizes that would fit my crucible. The wheels were more of a problem. I know that I could heat them enough to make them brittle and break them with a hammer but I have never found that to be very convenient. Instead I obtained an oil drum, dished the bottom and made a hole in the centre. I set it up on some bricks and built a wood fire in it. Once it was burning nicely I dropped the wheels in with more wood between them and on top. After a while molten aluminium was dripping out of the hole. I placed my ingot mould underneath and after about a hour the 4 wheels were reduced down to a pile of ingots plus a few runs were I overfilled the moulds.
All in all, a good couple of hours work and it kept me warm!