This instructible has no photos, only drawings. This unit I Built in the late 70's for melting aluminum transmissions, bumpers and such.
The unit was about 4 ft square and 6 ft tall, would accept whole transmissions that that had been drained of oil, and automobile bumpers thru its 36" feed chute. the continuous flow of molten aluminum was poured into 1/2 ton molds.
The burner unit which is the main focus here can be scaled up or down for your particular needs. This size unit when burning uses about 7 gals used oil an hour, at 20,000 btu per lb, that's equivalent to 1.12 million btu an hr. much more than most garages need.
A 1.5" x 12" unit was placed in a barrel stove in a garage, it produced as if the barrel stove was running wide open, and burned thru in 5 mins because there was no fire brick. So be careful and have fire extinguishers handy, if you decide to build a unit like this.
Step 1: Continous flow Smelter
This pic shows the 2 main tubes and how the holes are drilled and assembled with fuel inlet and end caps. Muffler tubing, low carbon steel tubing is fine. Size will depend heat output since size determines how fast the oil can be broken down to lighter fuels.