I built this Gingery style dual fuel, propane/used motor oil, furnace last summer. It runs flawlessly and have melted 5 lbs of aluminum in under 15 minutes and even 12 lbs of iron on used motor oil. It will take a max. #10 clay graphite crucible or A steel crucible for aluminum with a capacity of over 20 lbs. I run 2 burners, a combined propane and waste oil burner with blower and a atmospheric burner in the Riel Mongo burner style. Both heat up very fast the combined burner can run on just propane or waste motor oil with propane to get it started, I have melted 12 lbs of iron in a little over an hr. on just motor oil after starting with propane.The Riel Mongo style burner is a monster melting 5lbs. of aluminum in 12 minutes, my fastest time.
For full build documentation the following link will take you to my site, "Hobby Workshop Projects.com"
Hobby Workshop Projects