Thanks Steve, Grant, John for your replies.
In reading articles on gas forges with blowers the words"flash back or Back pressure"is mentioned, I guess I put in the term "mode" and what i should havesaid is the word "problem"....so what i am talking about is when thefan blower LP gas forge is working fine and every thing is heating up andeverything is sounding good,,, Then all of a sudden a large roar starts and youcan hear that sound that you hear with a acetylene torch, when you get flashback. All I have to do is cut the gas valve for a second and turn it back onand it works till the next time it feels like doing the roar..
As far as the question on what are the "end of theburner tube restrictions" well it is the sane exact design as I have usedsince 1986 when i built my first Hans Peot designed LP gas tube forge..
His burner end uses concentric tubes 3 inches long startingat the outer main tube 2in dia. the next is 1 1/4 then 3/4 then a solid 1/2 rodall are separated with a series of 5/32 spacer rods.
The flame at the end of the tube looks great and the forgeheats up fast and gets hot. but you never know when it will flash back..
I have built many of these forges at least 8 over the last 25 years, yes I have had someflash back problems over the years but not like this forge and burner,
By the way this is a big forge it is 24 inches long... 12inch in diameter, and uses 2" thick Kao-wool, half thick fire brick floorand fire brick ends,
See attached drawing...
Again any input would be greatly appreciated,,,
Thanks,,, Mike