Hello all,
Just a followup (for anyone who may be interested) about my recently built forge. Following a suggestion that I aim the burner a little more towards the back yeilded some pretty amazing results. The tubing that I used to mount the burner to the forge is a little larger than was neccessary to allow the burner to slide in, so I had a pair of washers filling the gap and keeping the burner at a right angle to the side of the forge.
Taking out the burner and removing the front washer so that I could use the set screws to set the burner at a slight angle towards the back (at an estimate, I'd say 3-4 degrees) made all the difference in the world.
Where it was very impressive before, with gouts of fire coming out the front and it's relatively loud presence, it is now very obviously a signifigantly hotter forge. With the gas swirling backwards and then reflecting and travelling the full length of the forge before exiting, I was able to set it so that I had a purely blue flame inside, and no flame escaping the outside edge. It's also a little quieter.
That alone doesn't mean all that much to me, but the real convincing came when I took a look at the 1/2" rod of A-36 that I stuck in there before I lit the thing. I'm not going to claim it did anything spectacular or unbelievable like melt the steel into a little puddle- but I did time how long it took for the bar to get to a bright orange color. It only took about three minutes from the initial firing, and it appeared to be a uniform color throughout from the tip at the very back of the forge to about 1" from the outside edge (about 17 inches). By that time, the firebrick on the bottom was well on it's way to fully glowing as well.
I'll note again that I am using a 0-60 psi regulator, and this was with the regulator and the blower gate both open to almost full-bore. That alone should account for some of the extra heat, but angling the burner back seemed to be the thing that really made it hum.
So, if anyone is still reading this after all that- despite Pete S.'s fantastic help and advice, I think I may have to disagree that the pipe forge design is signifigantly better without an insulated and air-tight back- it just requires a little minor tweaking to get it to work really well. Obviously, angling the burner on a forge with two open ends will not do a guy much good, but where the back is closed, it seems to do the trick really well.
Of course, I still have virtually zero experience with the total blacksmithing experience- so if I do find that there is a problem with what I've got set up for whatever reason later on, I'll take back the statements above cheerfully. But if it works as well as it apparently does, I figure it can't hurt to share this minor modification (which may already be common knowledge, as far as I know!)