Small soft brick propane forge build

[Frosty]

Looks good, is it doing what you expected? Will you be coating it with a high alumina kiln wash? It wwill act as an IR re-radiator and protect the brick from the chemical erosion caused by caustic molten borax based fluxes. Silicates dissolve in bases and molten borax takes base to a very caustic extreme.

Thanks for the stills.

Frosty The Lucky.

[Mikey98118]

Well, this is one those times that the video actually showed me more than the stills

First; I noticed a shorter flame than usual; is this from installing a Hybrid burner sans its flame retention nozzle, is is the gas pressure turned way down? Either way the flame looks perfect in his forge.

The second video shows how rapidly the forge is heating up; and this with it running wide open at both ends .

If nothing else he now knows that his design is a success.

[NicZa]

Is it doing what I expected? Well it's too early to tell, but then again I'm amazed how promising it looks!

I'm really happy how fast it gets up to temp, how easy it is to fire up, how compact and light it is and how quiet it is!!

I don't know how much gas it uses yet but my guestimate is that it uses below half of my old forge, how much below? I can't wait to figure it out!

And I haven't tried to get it to welding temp yet, but I'm guessing it will get there by the looks of it.

Biggest question yet is how it will last, time will tell 

 

I would like to coat it with a high alumina kiln wash since I've heard only good things about it, but I haven't managed to locate one from Europe.

The coating I'm using have to suffice for now. I had to reapply it yesterday since it started to flake. But I think I shouldn't have used the adhesive sealer, and I did the initial coating with the bricks cold and room temp round 10 degrees Celsius.  Now I reapplied it while to forge had cooled down to around 200 degrees Celsius, let's see how it holds up this time.

 

Thanks for the reassuring words Mikey, and yes I'm running the forge on quite low gas pressure. How low? I don't know yet, but the dial at the bottle is at 1bar (~15psi) and the needle valve before the burner is barely open. At times I'm questioning if I'm running it too low. 

(I wouldn't say I'm running it completely wide open at both ends. I have the back closed off with a small window at the top, maybe it still qualifies as wide open?)

// NJ

[Frosty]

Check with a ceramic shop about where they get kiln building supplies, if they carry them you can call around other suppliers and compare prices. What you need is a high alumina air setting kiln wash. A high alumina wash that contains zirconium is pretty common and outstanding for a blacksmith's forge for slightly different reasons. Ceramic kilns use a zirconia wash because ceramic clays and glazes don't stick to it but it's excellent in a forge because zirconia is a superb IR re-radiator. Zirconia is a very poor IR conductor so it's better at collecting heat than conducting it more deeply into your refractory. The easiest way the heat can escape the zirconia is as radiation back into the forge chamber, where it can heat your work. So keep watch for a high alumina kiln wash containing zirconia.

Please clarify, what do you mean by adhesive? The word brings to my mind products like wood glue, construction and silicone adhesives, not things that would survive more than seconds in a blacksmith's forge. OR do you mean masonry cements like mortar? Mortaring the bricks together in your forge could be a really bad idea. Not being carved from a single piece the bricks in your forge MUST have room to expand contract and shift against each other. Mortaring or cementing them together could lead to them cracking and breaking up from the thermal cycling.

One last thought, I'd put the hole in the back wall at the bottom so it can act as a pass through for heating back from the ends of long stock. Heat also rises and while it's minor compared to the utility of a pass through it is a factor.

Frosty The Lucky.

 

[Mikey98118]

Frosty covered things pretty well. I would only add that your next step should be a brick baffle wall in front of the forge, to allow stock to pass through, and exhaust fumes to escape upward between its near side and the forge, while bouncing back radiant energy into the forge's interior. You will find that it saves you plenty of fuel, and glare in your eyes.

For this wall, you are better off to use plain old hard clay firebricks, and coat their forge facing sides, just like the forge interior.

Once you add a baffle wall, that forge should use about one-third gallon of propane per hour, at welding heat. There are other steps you can take to reduce fuel used, like adding an idler circuit to your forge. However, most people with a small efficient forge, just don't bother going that far

[Mikey98118]

On 10/1/2023 at 2:09 PM, timgunn1962 said:

You (probably) won't just be able to just turn it down because there's a limit where the flame-speed through the gas:air mixture matches the mixture speed through the burner tube. If the flame-front moves faster through the mixture towards the Venturi section than the mixture is moving through the burner tube towards the forge chamber, the flame will run back down the burner tube. Not A Good Thing. 

The limit on turn-down range for that burner is just above 4 pounds per square inch gauge pressure. At 4 P.S.I. it begins to huff, as the flame starts burning back into the mixing chamber. If allowed to continue, the mixing chamber begins overheating and the huffs become bangs; finally, the flame is blown out.