Oh yeah, I guess I'm suppose to set forth some sort of disclaimer...
Working with molten metal can be hazardous so if you're an idiot and cause yourself serious harm or death don't blame me!
Nuff said.

I got involved in casting out of a necessity to make new tools for my lathe as well as custom parts. My first furnace (shown in the first 3 images) was a square box fueled by naturally aspirated propane and it worked quite well but, being human, I had to improve upon it (I haven't reached the point of destruction yet).

The next stage (images 4 to 6) was to go with forced air aspiration and a cylindrical design that would offer a swirl chamber effect. This worked quite a bit better than the square design and, because I used a 1" ceramic paper refractory, gave me a fairly large internal space for it size. The refractory was rated for 2600° F. The parts list in image 6 is as follows..
1. Furnace body (that was obvious)
2. Burner
3. PVC air intake with a choke for easy lighting.
4. Coleman air mattress inflator
5. Rheostat switch to control air speed

I played with a few other designs before going to a waste oil burner and they had pretty much the same results... Good melting for aluminum and brass, the ability to use large quantities of propane with the ability for the propane tank to freeze up and cause a loss of performance in mid melt.

Going to the waste oil system opened up a lot of doors, so to speak. Not only was the fuel free but it also had enough calorific value to melt cast iron. The design is based on Colin Peck's book and I whole heartedly recommend the purchase of said book if you are interested in this fine hobby. I used professional refractories in the way of bricks rated at 2600° F and a hot face rated at 3200° F. I also added a propane preheat (red hose inlet) which runs for about 5 minutes before going full on oil.

I use two 100 liter propane tanks for my oil storage. These are kept in the heated shop since I found the oil got too sluggish to flow in the winter if kept them outside (I lose more shop space this way). I rigged up plastic tubing so I can see where my oil level is, have to be careful the oil doesn't have a lot of solvents in it. The hose for connection to the burner just makes it to my roofed open air station maitaining a downward slope all the way.

I built a sand muller out of an old 2 horse compressor. The motor is a fractional horsepower though. The tines are sloped in a manner to cause a compression of the sand during mix. There are 4 tines, 2 per row set 180°. The rows are at 90° to each other. The pulley system sets the speed at about 120 RPM. It takes about 5 minutes to do what use to take me a couple of hours by hand so I really like this thing. The one drawback is that being driven by belts it will only handle about a gallon or so of sand at a time, this works out to be one of my 12" flask sections full. I'm definitely not going to complain about that. There is a trap door at the bottom to let the sand out when finished. I set the muller up on a rack with a catch basin underneath. See it in action (opens new page).