Here are more detailed instructions showing my furnace in use.
You can see how with careful design using waste motor oil is not dirty to use which was one of my concerns before doing this project.
More furnace details can be seen here http://myfordboy.blogspot.co.uk/p/development-and-construction-of-my-oil.html
The casting shown is for my Stove fan https://www.youtube.com/watch?v=ISDJWZPigQc
Castings and plans available for sale.