Gas forge exhaust opening

[MonkeyForge]

So, I modified my current forge by moving the burner from the back to the front, I also placed it at a tangent across the arched ceiling and slightly toward the back. You can see it running in the picture below. I got a nice even heat. I ran it with the original burner port open which seemed to 'pull' the flame to the back (the back is closed). Plugging the burner port in the back also works but the cool spot will be larger. I have to run it a bit longer to be sure what the difference is. I guess I am just wondering about the advantages/disadvantages of having a small exhaust in a long narrow forge like mine. (chamber is 12 cm wide 6 cm high about 25 deep). I imagine there will be a marginal heat loss. 

[Buzzkill]

Personally I'm rather pragmatic about these things.  If it does what you want it to do then it's good in my opinion.  If it doesn't then it needs modification.  If having the exhaust port open gives you the characteristics inside your forge that you want I'd say leave it open.   Nearly everything is a balancing act.  I have a pass through at the back of my forge.  I lose some heat through it, but I wouldn't build a forge without one.

[Frosty]

The trick is tweaking your forge till it's doing what you want and need. There's only one hard and fast rule as far as I'm concerned, that it NOT scale the stock in the fire. After than we're just talking performance characteristics, control and longevity.

The only thing I see to comment about is how deep you have your burner set in the picture. It LOOKS awfully deep into the forge to me. How far is the output end from the chamber? I have my burner ends BARELY inserted into the Kaowool outer liner. (backer in furnace terms)

My recent burner mounts are floor flanges and I sheet metal screw them to the top of the shell. The burner stops right at the shell, the liner is the nozzle, flare, etc. I'm always tweaking the technique but it works very well for me. I haven't had a burner tube or thread protector (flare) burn out in going on 15 years now.

From what I can see of your forge I could use it,

Frosty The Lucky.

[Mikey98118]

My favorite solution is always "have your cake and eat it too." If you get the best performance from your burner with the exhaust wide open then leave it wide open. If you  are fighting a cold spot from doing so, try separating exhaust losses from radiant heat losses by putting up  a movable barrier of brick or a drilled kiln shelf, at a small distance from the opening, to allow exhaust gases to move upward and out, while bouncing radiation off of an ITC-100 coating, and back into your forge. Move the barrier closer and farther away from the forge opening, depending on how high you are running the burner.

[MonkeyForge]

Thanks for you input guys. Seems we think along the same line. If it works it works. And I like cake occasionally. It is my inexperience that sometimes makes me unsure. Frosty: the burner is inserted less than an inch into the lining, because it is angled toward the back the picture shows the "short" side, if that makes sense. I had to reapply some if the kaolin/zirconium coating where I cut the new burner port. That should be cured tonight so I can get a better picture.