The Burner
Cue dramatic music
So, one of the most important things for a foundry's furnace is a heat source. When I decided to scale up from pewter to brass, I didn't realize exactly how much of a differece in energy output the heat source would require.
Previously I had been melting pewter on a propane-powered radiant heater (which was handy, because it also would heat my shop in winter.) After perusing a number of sites, I had decided to go with a forced air / coal furnace. This was primarily for 2 reasons:
1) It was free (I had access to lots of coal, a blower, and firebrick)
2) It was technologically simple. IE, less work building it.
Well, to make a long story short... I did manage to melt both aluminum and brass on the coal. But not with a reliability to call it functional for actual casting.
So, at this point I happened across Lionel's site, www.backyardmetalcasting.com . An awesome (and incredibly helpful) site. I decided to build a propane burner, and make a furnace out of homeade castable refractory.
In the process of design, I made some modifications.
While assembling the parts to build the burner, I kept looking at this part and thinking that drilling a hole in the side of the tube wouldn't be ideal. So I decided on this configuration, with the nozzle tube mounted on-axis with the burner tube. The black pipe to the side there is the future burner tube. The nozzle is a #57 hole, as was reccomended elsewhere.
This is me tapping the burner tube for the set screws to hold the nozzle centered. Because the nozzle tip is hexagonal, I decided to use 3 screws placed at 120 degrees around the pipe to center it, and then a second set of screws also spaced 120 degrees, but offset 60 degrees from the first screws, to help hold the nozzle pipe.
This image is looking down the burner tube at the centered nozzle. Somthing I didn't think of when designing this was that with the set screws holding it like this, it is possible to alter both the centering and the aim of the nozzle down the tube. I have endeavored to make it as dead-center as possible.
Here is the completed burner, minus a flare. I had all kinds of plans as to how to adjust the air flow, but as of yet I haven't really needed to.
I couln't wait to get my high-pressure regulator, so I connected the burner with a standard fixed-pressure barbecue regulator. This is the flame I got, nice and lazy but plenty hot and brighter than you'd think from this picture. Note that there isn;t a flare, and the flame is igniting inside the tube.
After I got my regulator and built a crude sheetmetal flare, I had to test it at full power to see if it would actually work. As you can see, it burns great.
