Forges and Fires

[SReynolds]

I was simply agreeing with you. Air induced burns fuel/makes heat. 

And I like what Glenn mentioned;  I agree with that unless you are a mathematician then I could see becoming obsessed with how much fuel you consume per work performed. 

[TechnicusJoe]

On June 16, 2016 at 4:18 AM, gote said:

I have high regard for Technicus Joe and his videos but he is wrong when he states that more fuel means more fuel burnt. More air means more fuel burnt - at least when using coal or coke. I always pile up so much fuel that I hide the fire ball just as in Glenn's pics. It preheats/cokes the fuel and keeps the heat where it belongs also I am not tempted to gaze into the fire.

Ermm.. how can I say this the best.

Are you 100% sure you got the context I advanced in the video, or tried to?
You know...., making a big fire only to heat for example 3/8" stock, working this all day only, no professional speed applied or production.
Thus more fuel is more fuel consumption.
Plenty of beginners do this ----> goaled audience. This is an attempt of mine to save them money. In many areas coal isn't cheap.

I haven't seen any smiths making their fire bigger than it needs to be.
There is a balance to this, you make a fire suited for the stock size. Making it bigger than this wastes fuel.

Or please, make a fire the size big enough to forge a sword in. I'd suggest the type and size used by Japanese swordsmiths and then only forge nails.
Without putting multiple bars in, just 1 of, say 3/8" cross section.
But that's awfully wasteful isn't it? All that energy released and not used to heat more stock.

Well then you come to my statement more fuel = more fuel consumption.
Either load up your fire or bring the size of your fire down.

I hope this clarifies it.
 

[gote]

I am referring to your statement: " The larger and higher you pile up, the more fuel gets consumed." Not to the video. I love our videos especially that you also use text  (please put in even more) Far too many videos are just someone staring into the camera and moving the lips in a deafening background noise.

You cannot consume more fuel than what can be burnt by the air supplied - that is a basic scientific fact. If the fire grows because you pile more fuel, you are feeding it excess air - something that increases the scaling and fuel consumption. If the air supply is limited to support the size of fire ball that you need for your work you can pile as much fuel as you want without increasing consumption. If you do that, (pile up) you will use the extra heat above the fire ball to coke the fuel, you will have less radiation heat loss, you will have less scaling in the upper part of the fire ball  and you will have less IR reaching your eyes. Since you coke with heat that is above the stock and since the unused fuel decreases radiation heat loss you are in fact more fuel efficient if you pile up - providing you have means to limit air supply. The drawback is that you cannot directly see the stock and how hot it is. Personally I am happy to pull it out or raking a hole to look.

I definitely agree that fires should not be bigger than necessary but the way to keep size down is is to limit air (and fuel size) not fuel. Many of those who seek advice on IFI are proposing too big fans and are told to limit the air supply. What is not so often discussed is fuel size and, as Charles pointed out above, fuel type.

 

[TechnicusJoe]

Thank you for the compliment! I'm glad to hear you like them. And the more text suggestion has been noted, cheers!

The first statement " You cannot consume more fuel than what can be burnt by the air supplied "  I cannot disagree with statement, it's fact that it works this way.
So, we're on the same page regarding this.
But I have to add there is a lot more to it than just that. Yes, this is fact, though a lot more things happen in a forge.
The statement you make applies when there is no other possible source for oxygen to react with the fire. But the forge is in open air.
Oxygen is all around the fire, so there is always a source apart from the forced air we use to heat up stock.
Even if you pile up, coke and the other solid fuels are porous and/or have gaps everywhere where air can move through.
It will reach it.

This is not as apparent with coke, but clear with bituminous coal that is coked or being coked during forging, charcoal, wood that is charred to charcoal as you forge.
Low quality coal turns into ash rather quickly in this case.
Coke will die out rather quickly without much ash when air is stopped. Bituminous coal, coal, charcoal and wood will continue to be consumed at their corresponding rates.
You can water the fuel in various ways at various stages, but I want to leave this out of the equation for now.

Coke you can rake over the fire, it's all the same fuel. With bituminous coal, which I address in the video, it is not desireable to rake over fresh fuel.
This will litter the fire, make it dirty - this is especially important for forge welding. Fresh coal is favorable to have around the fire so the heat can coke it, so you can have clean coke by time it reaches the center of your fire. The center of a coal fire tends to be left "open" - by this I don't mean a opening down to the tuyere, but the top layer of coke glows.
This will burn off the gas released by the coking coal.
If you want to you can smother the fire and create HUGE plumes of whiteish to green and yellowish smoke. Though this is not favorable. Certainly when you do demonstrations with bituminous coal!!!

Something else that also affects the fuel consumption in a fire is thermal dynamics. A coal forge lit 10 minutes ago will heat stock more slowly/differently than a forge that has been fired for 6 hours. Heat/energy wants to find equilibrium: heating some 3/8" rod, say 1 foot long, heating it at the end. After some time, you will feel the heat at the other end.
On a cold day the top portion of the anvil may become very warm during forging, but the feet are still cold. After a certain amount of time you can feel the heat in the feet.
Piling fuel ontop of the fire does this too.

It will always search for equilibrium. So heat wants to go into the cooler piled fuel. Now there is also more to it than how I just phrased that.
Coke is a porous material, so it can insulate the fire. Which is what we smiths try our best to do. Though the heat still moves outward, even with very little air.
If you leave it as is, the fire will become a big glowing pile, rather than having all heat contained at the core.
You're heating the fuel too, the forge etc., rather than soley the stock.



So, back to my statement. Making a larger fire (mostly emphasized on making it bigger than necessary) will result in more fuel consumption.
I will agree again, it won't go any faster than you feed it air.
But it's not a perfectly closed system. More things affect the fire.


I'll also happily go the other way around. Say that piling and closing the fire keeps all heat it in and doesn't bring up fuel consumption.
I wonder then why I don't see smiths making a large fire by default. It will save time and effort scooping fuel.
When I studied blacksmithing at the Herefordshire College of Technology - today Hereford and Ludlow College, the beginning smiths were informed to not make a (an unnecessarily) big pile of coke on their (water cooled side blast forge) fire. Rather, make a suitable sized "mole hill" that is fit for the stock to be forged. But no excessive piling. 

Here comes my statement again - If you make the fire larger and higher you will consume more fuel. The college very much tries to keep the coke consumed in the forges down.




 

[gote]

It seems - as can be expected since we both have experience of actual forging - that we agree on many things. I think that it might be unwise to use the word "fire" in a discussion like this. To some people that word means a pile of combustibles even when not actually burning. To me the word means something so hot as to actually radiate visible light. For that reason I use the word "Fire ball" I could as well say "Burning zone" but zone suggests a flattish shape.

I agree that it is wasteful to make the fire ball bigger than is needed. That does not mean that more fuel means larger fire ball. I habitually keep a 3-10 cm layer of non burning fuel on top of the fire ball and that does NOT start burning until the material below is consumed to the extent that it moves down - at which time I pile more on top. Even if I happen to rake up a burning piece of fuel into the top layer it will stop burning. NO! Oxygen does not enter from the sides. The N2, CO2 and CO going in the other direction prevent this. Please understand that this is not conjecture - this is observation. The extra fuel does not ignite.

I do not get HUGE wisps of smoke (=volatiles) when I put more coal on top. I sometimes get some but not all that much and quite often it goes up in flames. I get more smoke when starting the fire - probably because there is not enough heat to ignite the smoke. However, smoke generation is beside the point we discuss.

Yes the circumstances at the start of the fire are different from steady state. However, I fail to understand the significance to the point of discussion. Personally I use more air at startup because I want to increase the fire ball from scratch to the size I want. I then close down on the air to keep it that size.

 Coking is the driving off of volatiles. The incombustibles (=ashes) stay inside the fuel regardless of where the coking takes place. They are released when the carbon is consumed i.e. in the fire ball. Ashes do not migrate from the inside of the pieces of fuel on top of the fire ball into the fire ball and make the fire less "clean".  

Regardless of where it takes place, driving off volatiles is an energy consuming process. If it is done using the heat of the gases leaving the fire ball, less energy is wasted but that is also beside the point.   

Yes heat moves by conduction in steel and in fuel and I think you are right in that coke conducts less than coal but coal conducts much less than steel and the steel does not heat up all that fast outside the fire ball. This means that heat lost by conduction in the fuel is insignificant compared to that lost by convection (carried away by the exhaust gasses) and by radiation. By keeping the fire "black" I stop radiation losses. I cannot do much about convection losses but I can use them for coking.

I and some smiths prefer to keep the fire black - You and some smiths prefer to keep it red. I think you are wasting fuel and inviting IR-damage to your eyes doing this but there are more consideration to be made and your forge may be different.

Yes I agree with you that the fire ball should be kept to the minimum size needed but I disagree with you in that this is achieved by limiting fuel supply. My view is that it is better to limit air supply. I also think that this should be clearly spelled out to newcomers to the art.

    

[TechnicusJoe]

(I have dropped a lengthy text responding to our (expanding) discussion)

Even when you said disagreed and wrong, I think we still agreed from the start. let me explain.

Everything is so dependent on context. By my statement: " The larger and higher you pile up, the more fuel gets consumed."
I aim at a situation that a higher and more piled up fire, the actual the fire ball that is larger in size; the actually glowing and firey part.

Soley, I aim at what you refer to as "fire ball". I can happily concur with this word.
Getting an enlarged fire (ball) very easily happens with bituminous coal, charcoal. Coke and anthracite will do too, but slightly slower/differently. All of them have different fire maintenances. I address I use bituminous coal and in what kind of fire pot it is fired in.

So what do we have and what do I aim at: an over sized fire ball: we agree this is wasteful. I quote you: " I agree that it is wasteful to make the fire ball bigger than is needed."  
Thus it's larger, and often higher piled up - You got more fuel consumption. This is with the perspective that the fire ball can and will grow


Your perspective is at a different point than mine. From what I can read from your posts we are still agreeing, only looking from different perspectives. What doesn't help is our differences in fuels used and corresponding observations. I have used coke, bituminous coal, charcoal, anthracite, lignite, wood. But I don't get the impression you have used bituminous coal that swells up into coke as it burns (often). My video mainly deals with this fuel, bituminous coal.
You include the layer of fuel that isn't yet used inside the fire ball, I exclude this. It's not the part of the fire that supplies the heat. It's not fire or the glowing embers.  And the fuel you use, and right now I have to assume it from what you say - correct me if wrong, is coke. Coke works different in it's fire maintenance than bituminous coal. 
There are enough similarities though. Because from the start we agree that making a fire (ball) bigger than the work at hand, is wasteful.

The way smiths pull fresh coke over your fire (ball) - I did the exact same thing when I was in England; using a side blast forge and coke - I had better not done the same with bituminous coal. I can, as in I am able to do it. But it is not desireable.
You can ask all smiths who use bituminous coal that you had better not done that.
With coke you can just pull it over the fire. With bituminous coal is it better to make 2 fresh coal piles left and right of the fire ball, so it can coke the fresh coal and help keep the heat in as much as it can, whilst burning off the smoke. Or you can make an alround soft of volcano-like structure. Though this last one brings some undesireble effects I will leave out of this discussion. 

Coke you can choke down, if you do it right, exactly like you describe. Then you can indeed mount it higher, but still only have the fire ball small down inside. But a look around in forges in the main part of Europe and in the US and Canada, you will find many use bituminous coal. If you do the same thing, the fire will spread. you can water it down and extinquish it. But this cools down the fire and makes it inefficient with large piles. The coal will ignite, burn to coke first, but then continues to glow at dull red; burning (if not extinguished.)
If you allow the fire (ball) to become larger and have glowing fuel ontop of the fire core, it is very wasteful. It's more apparent with bituminous coal than with coke.

By limiting the amount of fuel you have on your fire, you limit the fire (ball) size and already converve a lot of fuel - all proportional to the stock heated.
Further fuel conversation can be done with exact amount of air fed into the fire.
 

[gote]

I repeat wit the tenacity of a lunatic. I put coal Not charcoal not coke, directly from the sack, on the top of my fireball and the fireball does NOT expand. Fire does NOT spread. Observation!!   I prevent the fireball from increasing by limiting the air. I do not care what "all the smiths" say. I am able to see what is actually happening and I trust observation more then hearsay. If you do not believe me that is your problem.

[Charles R. Stevens]

Gote,

Well that explaines things, they do have medications that help....

With much respect and all kiding aside, when we talk about fire spread in fuel it is dependent on 3 factors, fuel type, air and temp. Fuel type is a spectrum, charcoal at one end and coke & andradicite coalat the other.  Under most conditions found in a solid fuel forge fire will spread threw a charcoal pile readily wile coke and andricite coal are very risistant of spread. Wind and exesive stack draw will of corse effect this, but usualy coke and andricite will go out even in the presence of a good breeze. Bitamith may spread in the presence of a strong breeze or a strong blast, this is one of the reasons water is used for fire management with it. 

The 100 degrees we see in temp isn't generally going to cause much in the way of creep, but the diference between a forging fire and a welding fire certainly will, not only are you adding more air, but the fire itself is generating more heat, again, coke and andracite it isn't a real issue, but bitamith can see a bit of spread.

That said, the generalization that fire will not spread in coal is a good one (tho their are mountains smoking in Kentucky...) but if the generalization failes you can figure out why and how to manage it. 

As I am not a commercial smith, and I don't have a power hammer a fire ball over 6-8" is a waste of fuel, and as I started with gas and charcoal I generally don't load my table with fuel when using coal.

[gote]

Yes Charles I agree to what you say. Outside the controlled situation in the center of a a forge, (such as in a barbecue or open fire) coal and charcoal even more so, will burn by itself and fire will spread. The reason why I do not have spread of fire in my forge is that he gases coming from the fire ball are depleted of oxygen and have enough bulk to prevent oxygen coming in from the sides. I can even sometimes see blue flames (which I assume are burning CO) hovering over the (black) pile. I agree with you in what you say about "good breeze " and "adding more air". That certainly will tend to increase the fire ball but that is precisely my point. The fire spreads because there is more air not because there is more fuel. When the blast is running, there is fire close to the tuyere. Air is entering through it and the oxygen is consumed as it passes through the fuel. No oxygen comes in from the sides because the oxygen depleted gases are in the way. If the blast stops, there is no longer  exhaust gasses preventing oxygen from entering the fuel pile from the sides and the top and nothing prevents the fire to spread through the whole pile of fuel. My experience - and the discussion is about about coal. I can imagine situations where charcoal might so to say burn beside the fireball.   

[Charles R. Stevens]

Each fuel has its particulars, lol.

[swedefiddle]

Good Morning Gote,

My understanding of the little blue flames, is that is the Coal Gas burning off. When you choke a fire and get the very thick smoke, when you sometimes add a little fresh air, you can get the Coal Gas explosion as well (with a bang).

I add the new Coal to the sides and slowly push in into the center. I never add new Coal to the top center. If you use a lot of air blow, you can move the Fire-Ball up higher above the Tuyere. I like setting it up this way, if i am getting ready for some welding.

Greetings from Canada, my fathers family lives mostly south of Stockholm (Tystberga).

Neil Gustafson

 

[TechnicusJoe]

Gote,

you mention "coal". But it is rather confusing, because I have no idea what type? The type of fuel affects the fire.
The discussion isn't just "coal".
There is:
Brown coal
Flame coal
Gas flame coal
Gas coal
Fat coal  (bituminous coal)
Forge coal (bituminous coal)
Nonbaking coal
Anthracite



What type of coal do you use, that will help clear things up. I made it clear I use, specifically, bituminous coal. And I mention I am familiar with other fuel types.
With you saying you use coal. I find it hard to imagine it's anything but an anthracite type of coal.
Coal types below the anthracite type produce a big amount of smoke when fired the way you describe.

I have my experiences with anthracite. Some can't get anything else but this. But I really don't like anthracite. I had 70kgs - 154lbs I ordered extra next to my bituminous coal to really try it out for research purposes. Boy..... do I wish I had not bought any of it.
It doesn't smoke, but it sure does produce clinker! I have heard this from others who use it as well.
But what bugs me the most is that anthracite doesn't give me the same hot and intense heat coked bituminous coal and coke can.

You can use it to heat stock and get it to forge welding temperatures if you put some effort in it. But it's very different in its behavior compared to coked bituminous coal and even coke.
The fire ball tends to stay in the lower portion of the fire, near the tuyere.

When heating billets to forge hammers, 2 inch - 50mm diameter stock (or larger), anthracite tends to heat the bottom.
You can try and push up the fire ball with more air, but it turns into an oxidizing fire very quickly. Antracite coal has a small surface area for the oxygen to react with.
It's not porous like coke or coked bituminous coal, so you quickly have too much oxygen.


Coke and bituminous coal can be fired in more versatile ways. I can keep the fire small for smaller stock and works. But I can enlarge it to accomodate 2 inch + stock.
And the nice thing it does, it spreads. This I very much use in my advantage. I can create a "furnace" if you will, around my stock that all glows evenly.
This provides a nice even heat that can be maintained with a neutral atmosphere. I may only have to turn once to twice for a really nice even heat in a timely manner.

All fuel types have their similarities but also still their differences.
Your argument of how much air one blows into the fire is a very important factor. But there are a lot more factors.

 

[Charles R. Stevens]

Andricite certainly works a bit different, but I find if I use nut coal, you can hear it crackle as it cokes. It dosnt stick to gether and it still goes out in about 5 min with out air, but as I use charcoal a lot, it isn't a big shift. (Exept you don't use a bellows with out a thral)

Bitamith on the other hand is a big shift for me, lol

[JHCC]

I've had some very odd experiences with anthracite. Nut coal seems to work better; I've been having a LOT of trouble getting a rice coal fire to maintain a forging heat.

[gote]

On 2016-06-29 at 4:02 AM, swedefiddle said:

Good Morning Gote,

My understanding of the little blue flames, is that is the Coal Gas burning off.

Yes of course. Town/coal-gas is produced by turning coal into coke and CO is a great part of it. It is possible to turn all the carbon into CO. That is what we ran automobiles on during the war, They had  gas generators mounted on the rear bumper or in a trolley behind that were converting charcoal into CO that was piped to the engine. Since the flame are visible also after that the coal on top has coked I think they are nearly pure CO.

I add the new Coal to the sides and slowly push in into the center. I never add new Coal to the top center. If you use a lot of air blow, you can move the Fire-Ball up higher above the Tuyere.

Absolutely. It will also grow.  I tried to express that in earlier posts

I like setting it up this way, if i am getting ready for some welding.

Greetings from Canada, my fathers family lives mostly south of Stockholm (Tystberga).

Same to you. I have three cousins and their children and grandchildren in the US - none in Canada (as far as I know).

Neil Gustafson

 

 

[gote]

Joe,

It is very difficult to find any type of coal in Scandinavia since we have no domestic coal burning tradition. Unless I buy a 20 ton lorry load I will have to take what I get and it comes with the designation "smideskol" (Smithing coal" ). It certainly is not lignite (brown) and I think the supplier would have used the word anthracite if that is what it is. .

You write above " Coke will die out rather quickly". The coal, that I put on top of the fire, turns to coke rather quickly so it is not very relevant to make a difference between coal and coke on top.

One has to take the size of the fuel in account. Burning takes place on the surface so the same amount of oxygen will support a smaller and hotter fire ball if the fuel size is small. This is something that does not get much attention in the west. Contrarily, Japanese sword smiths put great importance to the size of the charcoal they use. Obviously the size will decrease as the fuel burns but at the same time it produces clinker. 

.  

[HeMan563]

Hey guys. I'm just getting started. Made my own forge but still modifying. Trial and error. Any advise or constructive criticism welcome. Still looking for a anvil using a small one on the back of a vise for now.  Still trying to figure out proper heat so I got a regulator for my hair dryer. Works great. Still need to make tray for around pot to enlarge coal placement.  And a prop if I'm doing longer items. Got turned onto the website by a really cool,honest guy that has helped me tremendous amounts. Don't know his screen name and don't want to use real name but thanks buddy. Awesome to have people helping out the new guys. 

[ThomasPowers]

What helped me most using a brake drum forge was to install a sheet metal "fence" along the inside allowing me to pile the fire higher and get the workpiece in the hotspot *horizontally*!   I made the fence with the ends not meeting for a gap to push the workpiece in and then opposite the gap I cut a "mousehole" for longer pieces to run out the back. (Cut it with a cold chisel using a cutting plate on my anvil.)  I didn't need to weld the fence it just used the spring of the metal to hold it in place.  VERY IMPORTANT  don't use galvanized or painted sheet metal.

This setup ended up being my main billet welding forge for several years.

[SandHuf]

How many pounds of coal would say you go through in an hour?

[JHCC]

On 6/29/2016 at 0:57 PM, JHCC said:

I've had some very odd experiences with anthracite. Nut coal seems to work better; I've been having a LOT of trouble getting a rice coal fire to maintain a forging heat.

Okay, looking back over this thread, I realize that I need to modify this statement. After further experience and tweaking my setup, I've come to prefer rice coal. Why? Well, with a sufficient supply of steady air and (critically) a good, hot fire of newspaper and softwood kindling to get things going, I've been able to get good strong fires that bring stock up to forging heat quickly (the biggest I'm working is about 1-1/2" dia. round), don't oxidize the steel too much (the increased surface area of the smaller pieces helps consume extra O2), and are easy to remove the clinker from (it settles between the pieces to form a nice coherent and easy-to-remove lump at the bottom of the firepit). Because the small pieces conform themselves to the shape of whatever you put in them, it's fairly easy to heat pieces evenly, without hot spots or cool areas.

[SandHuf]

Could I start the fire with a big blow torch I have?

[Adun Clebr]

Yes. I dab a paper towel in some vegetable cooking oil, then ball it up tightly inside some heavy brown craft paper. I place this fist-sized ball over the air grate & blow torch it.

Sometimes I have used an oxy/acet flame, but it was always overkill...

[ThomasPowers]

4 hours ago, Sander Huff said:

How many pounds of coal would say you go through in an hour?

Totally depends on what I am doing and which forge I'm working with.  If I'm heating 2" sq stock in my "RR Forge" with the electric blower I'd go though 10 times as much coal as if I was working 1/4" sq stock using a small forge with a double lunged bellows.

BTAIM; for working small stock for a demo in a small forge with a hand crank blower I usually budget a 5 gallon bucket of coal for two days of Demo. (I generally bring two buckets but end up topping the second one off with breeze for the trip home.)

[SandHuf]

This is what I will be using. It's 18" in diameter and about 2-3 inches deep. How much coal would you think?

[JHCC]

4 minutes ago, Sander Huff said:

This is what I will be using. It's 18" in diameter and about 2-3 inches deep. How much coal would you think?

Impossible to say; so much depends on your work and your fire management skills and what kind of coal you have available. Get yourself a couple of sacks of coal, get good at managing your fire, and then come back here and let us know how much you use.