The exterior structure of the Breath of Fire is a ten foot tall black obelisk made of a wooden 2×2 frame covered with a thin plywood skin. The tip is covered with sheet metal, and has a crafty custom pilot light enclosure. the BOF can be set on wheels to be mobile or sit stationary on the ground. on the front of the structure at about 4′ from the ground is the main control interface with the LCD readout, the blowhole, start button and indicator LEDs. on the backside is an access panel for changing propane tanks, and accessing the manual valves and electronics. The BOF is transported partialy disassembled and is assembled in a cryptic order that somehow seems to work.
fuel is propane fed from standard (BBQ) 20lb propane cylinders. the propane starts as liquid in the cylinder, and when the valve is opened the liquid boils into a gas and is piped through 3/4″ brass into an expansion chamber. At 70 degrees propane will expand to about 130 PSI, higher the temperature the higher the PSI. the BOF is equipped with quarter-turn manual shutoffs both before and after the expansion chamber. the output from the expansion chamber is controlled by an ASCO 8210 solenoid rated for propane well above 130 PSI. the pilot is fed from the main supply tank via 1/4″ copper tubing to a custom made pilot light just below the output at the top of the tower.
Propane MSDS (.pdf) Material Safety Data Sheet for Liquid and Gas Propane
Creating Dangerous Art Safely From burningman.com
NFPA 160 National Fire Protection Association, Standard for Flame Effects Before an Audience
The brains of the BOF is a Parallax Basic Stamp II (BS2). The input comes from a Figaro TGS2620 ethanol sensor with integrated heater. The sensor is interfaced with the BS2 via an National Semiconductor ADC0831 analog to digital converter. The LCD panel is a Matrix Orbital LK-202-25 2×20 serial LCD display with backlight. the BAC is calculated on µM-FPU math coprocessor. the formula to convert from the sensor output to blood alcohol content was borrowed from the breath-o-matic.
Flowchart (.pdf) Overview of electronics functionality.
Skot Croshere, Adam Bannister, Dave Croshere, Ria Blackburn, Katie Wilson, and more!