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New Forge Troubleshooting


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Hello, Bladesmiths

I'm new to this forum and to knifemaking and bladesithing in general. Recently, I went through the process of making my own propane forge, but I'm having some problems with it. It sputters and sounds like the propane is burning inside the burner tubes. I tried turning the pressure up (I only have a 0-10psi regulator) but it still makes that sound and it seemed like the whole forge tube was acting as its own burner since orange flames were shooting out from either side. I thought that maybe there wasn't enough oxygen so I cut out the divets you see in the adapter where the propane injector is held by screws. Then, I did some research and found that there could be back pressure building up in the forge from all of the gas, so I turned the pressure almost all the way down. It stopped sputtering, but the flames were orange and small, so I don't think those will be hot enough. Also they would not hold up well when even the slightest breeze came by (This is all outdoors)

My burner design is based on Grant Thompson's video (https://www.youtube.com/watch?v=eO8NwseRxSA). Except I didn't use a welding tip for my propane spray, but instead used a 1/16" drill bit to make a hole. I used this design along with his vertical "" video and it worked great (Although I didn't use a reducer coupling but a t adapter instead)

The burners you see in the pictures use 3/4" black iron pipe and the air intake coupling is a 3/4" to 1 1/4" 

As you can see, the forge is made inside of a Home Depot bucket which has a ~12 diameter and is ~14" deep. I made the hole in the center by using a 4" PVC pipe which gives the center a 4 1/2" diameter. Each of the holes drilled for the burners is a 1" diameter, but I was planning on filling the gap once I could get the burners to work properly. The burners are placed roughly 5-6 inches away from each other and about 3 inches away from the ends on the tube.

A few more quick points: The burners do not have an end nozzel on them; I didn't know if it was necessary since the burner I made the "foundry" with did not use one and worker perfectly fine in and outside the walls of the vertical "foundry."

I realize there is a lot of wood around this "flamethrower" And I'm working on another way to hold up the furnace that doesn't use wood. Also I have made bricks that I can place around the forge to keep in the heat.

Can you guys help me fix my forge?

(My images won't load and the double click to edit image options isn't working, so yeah there's that)

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I also saw this video, a friend of mine built his burner based on it.  as I've begun to build my own, I threw out this idea.  a shut off valve above a 4 point system to hold the orifice - although it may work fine, to me it's not the safer way to build it. 

further more, the orifice from what i understand of them should be a #60 bit (like a .0040 of an inch).  And yes finding one isn't easy, yet just this past week at harbor freight I found one. 

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Without pictures it's hard to guess what's happening, but I suspect the large orifice and low pressure is one problem.  With that big a hole you need a lot of pressure to entrain enough air fast enough to keep the flame out of the burner tube.  That's why most people like a 0-30 psi regulator, sometimes you just need more high-pressure gas.  

The gas also needs to be aimed straight down the center of the burner tube.  A bit off to one side and the mix gets wonky.  A burr in the orifice will play havoc as well, which is why mig tips are recommended over just drilling a hole.  A burner flare does help, but you can mold one into your forge liner if you don't want to make or buy one that attaches to the burner end.

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It seems that you guys were right. I changed the orifice to a 0.035" welding tip and added an end nozzel to my burners. I also had to change my burner length to 10" which, I think, allows for better fuel/air mixing and therefore better combustion. All of these together gave me a really nice, working forge. Thank you very much!

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