Propane forge burner design and tuning

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Thought I would share what I did right and what I've done wrong building gas forge burners and get input from others on there experience and have a place to answer related  questions ............I wanted to build decent forge burners for blacksmith work in the winter when it wasn't practical to use my coal forge outside .I work on ag specifically orchard sprayers so we have a ton of pipe fittings to experiment with I came up with a decent calculation for a basic burner I found that the inlet Venturi should be about double the nozzle size the length should be about 2-1/2 times the inlet minimum and the tube needs to increase by about  1/8 every increase in inlet example 1-1/2 inlet 3/4 tube but a 3 inlet will need 1 tube and so on.... the first ones I built have a 1-1/2 to 3/4 reducer inlet with a 3/4 by 6 tube and a 3/4 female coupling nozzle with the threads drilled out be sure to clean the inside of any burs rough edges for these I decided to use mig tips for the orifice to be able to tune them you want a neutral clean flame that extends just beyond the nozzle or it will heat the burner red hot the actual final nozzle ends up being your refractory with a slight air gap between it and the nozzle to pull in air and keep the burner cool ....next thing to remember is just cause the burner works great in the vise it may not in the forge due to the rapidly expanding gas mixture causing back pressure this is where  the tuning comes in you can start small and up the mig tips till you get the flame at the right spot in the forge (burning in the refractory not nozzle ) once you find a good fit this one uses a .030 I remove the burner and hook it to a garden hose and aim the jet of water coming out the orifice or mig tip centered straight down the tube this will give the best possible mixing effect ............. probably should have been mentioned before but you will need a high pressure regulator and a shut off valve mounted near the tank and a pressure gauge near the burner I highly recommend at least two 20 lb tanks tied together or else the valve will freeze up after about 45 minutes run time ..........the first set of three burners I have detuned so that I can leave steel in there with no worries it will burn up I use this one for production work cold in one side hot out the other ........the next burner I built was to be more like the coal forge under fired cause heat rises much larger and faster and with bricks that can be rearranged easily for doing forge welding or heating small areas like to do a twist in the middle of something longer it uses about the same formula and a slightly different orifice since I just want it to run Full on  always  the inlet is a 3 -1 inch reducer the outlet is 1x 1-1/2 reducer with the threads drilled out and the tube is 8x1 inch with all burs cleaned out I used a larger nozzle hear because there would be no refractory to hold the flame and being upside down it doesn't get too hot I then centered and drilled a small orifice in 1/8 pipe I wound up at .062 or 1/16 for the final size but started at .035 and worked up then again ran water to center the stream and locked it in place this style forge and burner has almost no back pressure so it can be tuned in the vise ......I run both at only about 5 psi so two tanks will last for about 20 hours depending on outside air temps hope all this rambling helps some one get started if anyone has any other ideas share them your results may vary this is just what worked for me be patient it's not going to work perfect the first time I spent about a week of evenings on each till I was satisfied thanks for reading
Reply:Wow!  Looks like you are into gas forges big time.  If you haven't done so, I recommend you swing over to www.iforgeiron.com blacksmithing forum and check out the info on gas forges.  There is a ton of info there and lots of guys who are very knowledgeable about gassers.  Sign up and join the group, you won't regret it.  Be sure to put your location, of some kind, in the signup or the boo-birds will hound you...LOL.  There is a section devoted strictly to gas forges, so spend some time reading through it as well.
Reply:Great post Mike, thanks for taking the time. I'll be trying to make one of these before long, and your info should be real helpful.K
Reply:As you can read lol there's alot more to it than grabbing some fittings
Reply:Another good site for info is the Blacksmithing for Beginners page on Facebook. The discussion is kind of painful, but there's some good info in the archive pages.250 amp Miller DialArc AC/DC StickF-225 amp Forney AC Stick230 amp Sears AC StickLincoln 180C MIGVictor Medalist 350 O/ACut 50 PlasmaLes
Reply:Knife maker forum is excellent for such. Bladeforums.com I think they call it