Of course much depends on how much clinker is being produced.  With the best coal I've used I could forge for 6-8 hours and have a couple of tablespoons of ashy clinker.  With poor coal I had to pull out a glassy hunk every 15 minutes or so.  This of course was for regular forging.  When billet welding; the flux and extra fuel consumed and scale generated could produce stalactites from the tuyere grate... 

It also depends on the material of the firepot. A dirt- or sand-filled side-blast forge will see some amount of that fill becoming clinker as well, in addition to the noncombustible material in the coal itself.

Charcoal made from scrap or dirty wood has its own challenges. Ash isn’t much of an issue with charcoal but old nails and dirt form clinker 

Run a strong magnet through the charcoal after it comes out of the retort? Sweeping old pallets would take care of the worst of the dirt.  Pressure washing would be overkill but maybe not.

Frosty The Lucky. 

You are missing the rest of what makes a dirty fire. Thats the fly ash, fines, small bits of clinker, scale etc. That big clinker is only a small part of it. 

And you are right. A difference is that with a bottom draft all the "stuff" falls straight down. With a side blast, It falls down below the air inlet. Both solve this problem differently. With a bottom draft with a "clinker ball" and handle, I constantly flip that handle and the ash etc are gone. And thats what you cant do with a grate. With a side blast eventually you are going to have to break down your fire and shovel it clean. 

I shouldnt of said fire control. Maybe I meant thermodynamics.  Where the air goes because of a triangular ball. The air goes up the sloped sides and no air goes straight up. This makes an envelope around the heart of the fire,radiating in, and no hotspot anywhere. With a sideblast, the air comes out 1" dia and hits the coke. And this is the hot spot. With fire control, you can control the size, but it will always be hottest right where it comes out. 

This has been good for me. I've been thinking of a side blast these last few months. This and one other thread have given me good info on side blast. Its a bottom blast for me. What can i say.    The air envelope idea and getting rid of fly ash, not sweeping it into a corner waiting for the ash bunnies to.... 

 

 This style of bottom blast fire grate does basically the same thing in regards to the air flow with a ducks nest pot. However the clinker does have to be dug out. With coal that produces a large clinker, I can use the pick-up tongs and lift it out without killing the fire.

If my fire clinkers up enough to be a problem I slit the mound just above the clinker with a shovel, lift it enough to hook the clinker out and let the fire back down. A couple swats with the shovel and some air and it's rolling along.

I don't burn coal often and what I can collect is clinkery,  I can't find the seam with the world class smithing coal so I collected what I could get to. 

The ease of cleaning the clinker is another reason I prefer a duck's nest and a few fire bricks rather than a fire pot. 

Frosty The Lucky.

On 7/12/2021 at 3:23 AM, DHarris said:

This is it now. The top is 2.75 inches from the top edge of the fire pot. The top of the bullet grate is two knuckles on my middle finger to the bottom of the pot. 
 

It does work. Clinker forms and falls down in a ring around the grate.  Clinker does form and clog the opening, but my poker can clear it without disturbing the fire. 

 

 

How has that worked out?

Mine is simply too deep. I’ve considered clay, but I am likely going to just make a new pot with a “ball” clinker breaker. 

On 12/14/2021 at 6:32 AM, DHarris said:

How has that worked out?

Mine is simply too deep. I’ve considered clay, but I am likely going to just make a new pot with a “ball” clinker breaker. 

HOw much is too deep 5 inches ?

 

Depth is determined by the size stock you use. Any depth will heat any size stock, more or less. the shallower your firepot, the longer it takes to heat larger stock and the number of irons in the fire decreases. 4" is a good depth for most contemporary shops of any sort. It will easily and rather quickly heat multiple pieces of 1" square stock. Multiple pieces over this size start to take noticeable more time. If I were to heat over 1" square on a regular basis, I would add an inch more, 5" depth. The Railroad firepots I've seen are 5" or more. Never forget, the initial heat is the longest. Doing multiple pieces basically take the ~ the same amount of time for the initial heat as a single piece. Always do multiple pieces when possible. Once all are up to a working heat, when you finish working the first, the rest are ready. Width and length tend to limit the number of irons and the length of heat. Centaur Forge rectangular firepot is a good example for most contemporary firepots. 

I still need to add clay, but I now have a shallower fire pot. I had planned to chop the bottom off and just reinsert it from the top, but that left it too deep still. I wanted 3.5”. So I welded strips of steel around the bottom and snugged the bottom of the pot to that. It is ugly as heck, but I don’t get points for that, so I am fine with ugly. 
 

What I am not fine with is losing my two favorite shirts in the process. I had the pot laying on its side on a welding table while cutting it. The shape of the pot was funneling all the heat and fire to the tails of my shirts. During the second cut I thought I smelled something burning. A few seconds later, I no longer thought something was burning. I knew something was burning: me. Luckily my skin didn’t get burned. 

Your wardrobe will soon look like mine. Most of my shirts also have a bunch of little tiny holes in the front by my waist line from flux coming out when welding. The wife is a manager at a thrift store so when i need "new" work cloths i just tell her. 

Ever light the fuzz on a new Chamois shirt of fire? I love the reaction from non-welder fabricators who see it. A good friend about slapped the stuffings out of me once. 

Frosty The Lucky.

Those fuzzies go up quickly especially if you use fabric softener sheets in the dryer. 

Pnut

Well this one about got yanked off. I slapped and slapped. It just kept on burning.

Tragic thing is I have a leather apron. I custom made it myself. But it is too tight to wear with more than a t-shirt on. I need to adjust both the waist and leg straps. My belly has grown to be huge over the past three years.

My light weight HF welders leather apron has saved me more times than I can count. That is if I remember to wear it.

Short of welding strips of steel to close off that big gap between the inner and outer pots, how can I keep water from pooling between them? I assume just clay will not do that?

Water pools between your belly and the apron?  

I'd say yes, welding strips of steel on sure would stop water from pooling. You'd be running WAY too fast for water to settle.

Frosty The Lucky.

Lol, I just have to compliment you on your "Firepot from Hades"! 

seems there should be enough heat in that area to keep water from being a problem.

Personally, I'd solve that dead space problem between the insert and the outer old firepot before doing anything else. 

Funnin aside D. If you weld a flange to your insert firepot and make the flanges wider than the old one and slope them down slightly it will shed water away from them and make a little ramp so raking coal in is a little easier. Not a great plus in either case but it's easy enough to get the benefits of both it's a why not in my books.

Frosty The Lucky.

 

My forge stays outside in the weather. The pot is pretty thick, almost half an inch, so it would take quite some time for moisture under the clay to rust through. Still I would like for “some time” to be as long as possible. 

Welding in strips to cover those gaps would definitely help keep the water out. Clay would absorb water from any precipitation you might get, which could cause problems both from expansion and contraction working it loose and breaking it down and also from the water turning to steam when you fire up the forge.

My recommendation would be to weld in some metal that's sufficiently massive to keep from getting burned away by the fire, and then to build a removable cover for the firepot to keep the weather out when you're not using it. Something like a big metal trashcan lid would be perfect.

Use it often enough that it stays dry!

Put a trash can lid over it when you aren't using it?

Frosty The Lucky.