[TheForge] blown forge

[Jerry Frost]

Once you've attained a proper fuel air ratio how they're brought together
and introduced into the forge chamber isn't very important and not at all
relevant to the final temperature. My 3/4" "T" burners melt the 3,000f split
fire brick floor in my forge if I leave them turned up any length of time.

There are significant differences between gun and naturally aspirated
burners of course. Guns are easy to tune but require turning every time you
change the gas or air input. Naturally aspirated (NA) burners are a PITA to
tune till you get the hang of making them but once tuned changing the gas
pressure changes the air entrainment on a near flat line curve so that
part's easier. Guns are NOT very sensitive to outside conditions, breezes
especially and are a lot less sensitive to back pressure so that opens the
way for some really cool burners not very workable with NA burners. Ribbon
burners and chip forges for example don't make NA burners happy.

Mixing air and propane is problematical in most devices. I know so don't
tell me propane is a GAS, however it acts like a mist so tends to separate
from air unless actively mixed. This is another place where NA burners don't
work as well as guns. Mixing in a gun is best accomplished by introducing
controlled turbulence, the little propeller blades, (I don't recall what
they're called, but they do have a proper name) for instance is an industry
standard. Introducing the propane in front of a 90* bend has more than one
advantage. First it mixes the air fuel, and it prevents back fires from
traveling as far as the blower. I don't know why but air gas explosions
don't make wave fronts that go around sharp corners well. The last method
for introducing propane is my personal favorite, put the gas jet in the air
intake and let the blower's impeller blades mix it.

Jerry