[TheForge] Gas Forge "Chuffs"

[Scott Lane]

Greetings,
	I participated in a gas forge construction workshop this weekend, in which 
we build 14 new double burner atmospheric gas forges.  They are made out of 
10" thin wall pipe, with two non-blown burners coming in horizontally near 
the top of the forge.
	Got mine home and fired it up.  Runs great at 20lbs gas, but when I reduce 
the psi down to 5 or 7psi the combustion "chuffs" (surges) and does not 
burn completely.  There is a massive amount of blue flame coming out the 
front, no matter how far I open or close the air gates (adjustable disks on 
the end of the burner pipes).
	I have seen a number of these exact forges run well, so I don't think it's 
the design.  However, with any mass construction effort there is bound to 
be minor differences.  For instance, most of the forges built had the 
burner pipes running slightly "down hill" into the forge, where mine run 
slightly "up hill".
	Any suggestions on the combustion problem?

Thanks,
Scott