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I Forge Iron

Ran the blown propane forge


bigb

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for the first time. I got the regulator that was suggested and a pressure gauge from Mcmaster Carr. Just fiddling around with it it seems that 5 PSI is plenty, it gets really hot. I noticed it belched "dragons breath" out of one side only but I could change that by rotating the blower in the tube. Did some searching and read that I should first set the propane PSI then adjust the air till it is the loudest, does that make sense? On my maiden run it got really hot at 5 PSI and was difficult to approach with the work piece. I could actually get the work piece to forging temp by just laying it on a fire brick in the dragons breath.I also read about a needle valve for the propane but not sure what kind and how to fit it. Also, how much can I block off with the fire brick? Do I need to leave some opening on either end?. And where exactly is the "sweet spot"? I noticed a cylinder of blue flame about 1.5-2" and the width of the forge (about 4-5").

I want to see if this forge will serve me while I rebuild my coal forge. Funny a couple years ago I didn't even have a forge now I have to have a backup!

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Most of the answers to your question amounts to "it depends." You are going to need  some time playing with the forge, and will then be able to answer most of your questions on your own.

The valve you're trying to think of is a needle valve, and isn't strictly needed; it's more of a luxury for people who want to fine tune performance. Before you even ask, yes you can fine tune performance without one; they just make it faster to accomplish, and end minor pulses in the flame by providing some back pressure that regulator alone can't provide.

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OK thanks. Will have to fiddle around with it some more when I have time. Too many irons in the fire right now!

I wanted to try closing off one end with fire brick but not sure if that would be OK

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IMHO you are using way more fuel than needed.  The pressure of propane tells us nothing without knowing what is restricting the flow.  I used an unrestricted line from the regulator to the inlet on the burner and would never show any pressure no matter how far I opened up the regulator.  If flames are shooting out the openings to the point where it's hard to approach the forge from that direction, to me that would indicate that there is a whole lot of wasted heat just going out into the open air rather than heating your steel. Since you said you can heat the steel to the desired temperature in the dragon's breath outside the forge my guess is you can cut back significantly on your propane and air to the point where you have only a few inches of flame exiting the forge and still easily get the temperatures you want.  Closing off portions of the front and back should also keep a lot more heat in the forge.  Obviously what you're doing works, but you're probably using something around twice as much gas as you need and that costs you money.  It may also wear out your forge lining faster.

For tuning a blown forge, setting the propane and adjusting the air till it's loudest should give you somewhere near a neutral flame.  However, that neutral flame can still be way more output than is needed.  Personally I set for the loudest flame then cut the air back until the noise decreases and the flame gets lighter in color.  Then I increase the air a little until I hear the volume of the flame increase again.  I like to stay on the reducing side of the mix just a little to keep scaling in the forge to a minimum.  If after a couple minutes I think it's too hot, I reduce the propane flow and adjust the air again.  If not hot enough I increase the propane and adjust again.  I haven't forge welded with mine, but I've never had the need for a dragon's breath like you show in the top 2 pictures to get the temperature I wanted.

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Yup; try starting it at 2 psi and adjusting the air and closing up most of the ends---blown forges tend not to be as fussy about back pressure as NA forges.  If 2 psi works for you for regular forging then try a bit more for welding, etc.

And yes I tune by "loudest roar" and "brightest impingement" for the neutral/oxidizing burn and restrict the air a bit more for a reducing forge.

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Their answers to you both line up nicely with your question about partially enclosing one forge, end and completely enclosing the other. The answer is yes, but not  before you back off the air and gas quite a bit. Just as the air and gas inputs need to balance with each other, the amount of back pressure that comes from partially enclosing the forge ends need to balance with the amount of flame being produced; not too much or too little.

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Fired it up again tonight, blocked one end and about 1/2 of the other (I need more fire bricks). I changed the gauge from a 1-60 to a 1-15. Buzzkill what you say about pressure makes total sense, without knowing what is at the other end it doesn't mean a whole lot. In my case just under one PSI seems to work fine. I was definitely using way too much fuel on the first run, just like when I first used my coal forge I wasted fuel with too big a fire, This time I had no dragons breath, the forge was completely approachable and I heated a piece of 5/8" rebar orange in about 1.5 minutes. How does the color of my flame look?

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This brings up a good occasion to  revisit the much reviled hard fire brick; of which I have been a chief reviler. But, in the case of a standard fan-blown forge, such as this is, I believe that they could be used at the exhaust opening instead of insulated fire bricks without harming performance, if the forge side of the bricks were painted with a high emissive coating.

Why the apparent turnaround?  This kind of forge has a very fast exhaust, pushing a lot of super hot gas past the brick face for the coating to encounter and bounce radiant energy back into the forge from; so much that I think it worth while to give up some insulation in this area only, in order to game the physical toughness and resistance to breakdown from thermal cycling this kind of barrier will show, compared to soft bricks.

Note: I would not make any such prediction with any other kind of forge, including ribbon burners.

Oh, what a bad taste my mouth has in it; essence of crow pie, I believe:unsure: 

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