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I Forge Iron

Design Advise Wanted


Ajbforging

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So, I've gone through a few different designs, trying to build an efficient coal forge. I started out using a grill lid and putting a mixture of sand and plaster of Paris in it to form the bowl where my fire would be held, with a "airtight" tunnel coming from the side of the lid where I bolted the centrifuge fan I used for my air supply. This design brought me up to forge welding temperature but the "refractory" decayed. I demolished the bowl and decided to go with a firepot made of 1/4 stainless steel surrounded by patio brick. This design was a few steps back and I can't bring my heat up high enough to forge weld and begin folding metal. My question now is, is there a surefire design that can give me the heat efficiency? I am having a hard time believing a brake drum forge would give me ample amount of heat to hear up the metal to forge welding temperature. 

 

I eventually would like to attempt to make demascus steel. Which is why I stress forge welding. 

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Somewhat frustrated because you have not been able to recreate the pinnacle results of 5000 years of human endeavor by yourself in a few weekends?  Join the club.

No, really, I mean it.  JOIN A CLUB!  Post your location, find a cell of like-minded individuals, travel to a few different shops and hammer-ins if at all possible.  Get yourself a guru, go take lessons.  It will cut a few decades of self-paced learning out of the loop.  I still find something worth learning after a few decades of visiting other schools, shops and smiths.  Every time.

 

Now that is off my chest, you can easily get wood charcoal or mineral coal up to forge welding heat in a hole in the ground if (1) the shape of the bowl is correct and (2) the air supply is adequate. We need pictures to diagnose your builds so far.

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What he said.

Many students attend my class have tried to make a forge of sorts and (obviously) hammer out knives from RR Spikes. cuz that is what we all want to start with........... LOL  

When they obtain hands-on experience their eyes are opened and they advance their knowledge of the craft. I invite some of them back to "work" with me in the shop as an "apprentice" for a day. Sorta a one-on-one session to build confidence.

They can't believe how difficult it is to simply draw-out a 3/8" round rod to a three inch long taper and then round that. A beginners hammer control exercise most don't desire to learn.

A brake drum forge will destroy a 5/8" square RR Spike in short order if the air supply is adequate, such as a hair dryer set to low speed with excess air dumped to atmosphere via a gate valve. On low speed, a simple hair dryer will just about lift a bed of  coke out of the forge.

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In the picture at least it looks like your blower is directly below your fire pot.  Especially since you show a fairly large unrestricted hole, that will allow ash, clinker, molten metal, etc to run straight down into your blower.  This could damage or destroy your blower, but also you could end up with a plugged air path.  Typically you'll see a "T" fitting at the bottom of the fire pot so that the blower can be mounted off to the side more or less horizontally and an ash dump straight down from the fire pot to avoid this problem. 

I wouldn't worry about the bricks being a heat sink with either charcoal or coal.  The fire should be contained in the pot itself and the combination of ash and unburned fuel provides some insulation effect.  Regardless of whether it's open air outside the fireball area or thick rocks, that should have no noticeable impact on the fire temperature itself.  That is governed by the shape of the fire and the air blowing into the fire.  However, based on your pictures I don't see a good way for you to get stock down into the correct zone of the fire for heating once you have your fire ball established.  As long as those bricks are just a loose stack that is no problem since you can create gaps on opposite sides of the fire to feed your stock into the fire at the correct height.  It will probably be easier for you if those are vertical slots or V shapes rather than just a gap part way down though.  It might be a good idea for you to have at least one bar or some other restriction across your opening for your air gate though.  One preferred method on here is the use of a domed pipe cap with a number of holes drilled into it.  The dome shape allows the slag/clinker to run down around the cap in a donut shape and avoid plugging up your air holes.  With a wide open bottom hole anything that is heavy enough and has low enough air resistance will run into the opening and down your pipe even with the blower on.

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3 minutes ago, Buzzkill said:

In the picture at least it looks like your blower is directly below your fire pot.  Especially since you show a fairly large unrestricted hole, that will allow ash, clinker, molten metal, etc to run straight down into your blower.  This could damage or destroy your blower, but also you could end up with a plugged air path.  Typically you'll see a "T" fitting at the bottom of the fire pot so that the blower can be mounted off to the side more or less horizontally and an ash dump straight down from the fire pot to avoid this problem. 

I wouldn't worry about the bricks being a heat sink with either charcoal or coal.  The fire should be contained in the pot itself and the combination of ash and unburned fuel provides some insulation effect.  Regardless of whether it's open air outside the fireball area or thick rocks, that should have no noticeable impact on the fire temperature itself.  That is governed by the shape of the fire and the air blowing into the fire.  However, based on your pictures I don't see a good way for you to get stock down into the correct zone of the fire for heating once you have your fire ball established.  As long as those bricks are just a loose stack that is no problem since you can create gaps on opposite sides of the fire to feed your stock into the fire at the correct height.  It will probably be easier for you if those are vertical slots or V shapes rather than just a gap part way down though.  It might be a good idea for you to have at least one bar or some other restriction across your opening for your air gate though.  One preferred method on here is the use of a domed pipe cap with a number of holes drilled into it.  The dome shape allows the slag/clinker to run down around the cap in a donut shape and avoid plugging up your air holes.  With a wide open bottom hole anything that is heavy enough and has low enough air resistance will run into the opening and down your pipe even with the blower on.

I was using four pieces of expanded metal bolted together to keep coal and clinkers from falling down into my pipe, but I do get what you mean by the T shape. The only reason I didn't go with the T was because I had already welded it down at work. (I'm a welder by trade.)

The expanded metal never held up though. I'll try a domed cap to replace my expanded metal grate. 

 

Another thought I had was, what if I lined the brick with a sort of refractory fire clay mixture? Might that fix my heating issue?

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"Another thought I had was, what if I lined the brick with a sort of refractory fire clay mixture? Might that fix my heating issue? "

 

 

Not likely at all.  The only purpose of claying a fire pot (typically cast iron) is to protect the pot from the heat generated, not to increase the fire temperature - for a solid fuel forge.   A propane forge is a completely different animal in the way that heat is transferred to the stock, so refractory lining becomes an issue there.  You've probably seen this stated before on this forum, but for a solid fuel forge all you need is a hole in the ground and an air supply.  We build forges only to raise the hole in the ground up to a convenient working height.  What bigger heat sink is there than solid earth all the way around a hole?  If your pot is the right depth and somewhere near the right amount of air is blowing into the fire, it will get hot.   Either too little or way too much air can cool the fire though, but between those two extremes more air = hotter fire.  If you have so much air going into the fire that it is moving your fuel around you definitely need to back it off quite a bit.

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Two "proven" designs exist, one the good old "side blast" forge. This is a hole with the tuyere (pipe the air goes in) sticking in from the side, and a bottom blast ( the new comer) with the tuyere coming in from strait down. 

I my self prefer the traditinal side blast, as I feel it is more versital. It will effencently burn charcoal, bituminous and andricite coals as well as coke. Bottom blasts will to but they tend to burn threw charcoal at a much higher rate, as well as nesting a deeper fire with charcoal. 

So the clay in a forge is just a material, if I had sand Unser my feet I would be using it in my side blast and charcoal experiments, as I am now experimenting with coal, I must now shift to ash, sand and clinker (clinker sticks to clay like glue). The same for brake drums, not the best fire pot but many use them. 

So let's visit the basic idea of a forge. A forge is a hearth, to wich we add extra air by way of a blow pipe to increase the heat. Historically tie has been a  hole in the ground with the air coming in from the side, and burning charcoal. Typicaly we use a 6-8" ball of hot embers to heat steel to a forgeable temp. As wraught iron is welded and forged at higher temps than steel, if anyone tells you charcoal dosnt get hot enugh you know they are blowing smoke. 

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1 hour ago, SReynolds said:

"T" 

You need a fire pot with access to it to place your stock into the fire ball.

But how have you been heating your stock (which you are saying is difficult or cannot do) if you are familiar with how to make knives? 

Contemporary forge 006.jpg

lever forge 2.jpg

DPP_7062.JPG

DPP_7076.JPG

Contemporary forge 009.jpg

The ball of glam has come up from the pot and I piled on a large mound of coal to insulate and hopefully expand the heat. 

 

I think my fatal flaw was my fire pot design and the way I supplied it air. I will probably get more metal and weld up a larger firepot to forge in. Is there a way to make a large firepot into a sideblast of sorts? My orginal design had my air funneling from the side of the fire and that really seemed to create a good fire. (Also trying to get away from my air supply hole getting clogged by dust, small coal or a clinker.) 

By the way, the idea behind a solid fuel forge finally dawned on me. I think the only reason my orginal design worked was because it was in a deepish bowl shape, giving me a crude fire pot. Now it seems really simple to make a forge with the idea of a "hole in the ground with a air supply"

P.S. you guys are awesome. I'm taking so much info in, makes all my previous theories crumble

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It's a little bit hard to tell how deep your fire pot is from the pictures, but the size and shape of the pot didn't strike me as particularly troubling.  Think of a sphere roughly 6 to 8 inches in diameter.  That's roughly how big the burning portion of your fuel should be in operation.  Part of that will be down in the pot and part of that will be above the rim of your pot in the fuel you have mounded up on top.  This is needed so you can access the neutral to reducing part of the fire ball which is roughly the top third.  You want to be able to lay your stock pretty much horizontally through the fire in that region.  If it's tilting down into the fire you are potentially getting into the oxidizing area of the fire ball which can turn your project into a burnt steel mess fairly quickly.   If you are just laying the stock on the very top of the mound then you are wasting a lot of fuel and again you're not in the right area of the fire for forging.  That is why we suggest having the slots on opposite sides of the fire at the correct height.  You should be able to determine fairly quickly where the correct height is for your forge.   If you build your fire and fuel mound the same way every time then the correct spot in the fire will be pretty much the same every time as well, but this is affected by the depth of your pot, so we can't give you an exact measurement to go by.

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The forum is eating my posts, but do a Google search using the following "iforgeiron just a box of dirt" and read through that thread in its entirety.  That should answer a lot of questions you may have about side blast forge construction.  After that you'll be in a good position to ask more specific questions of someone like Charles Stevens to tweak your specific design.

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BuzzKill I have found out that it is links that cause it to eat posts mostly.

if you are doing a reply that needs a link do the text first and then do the link as a separate post, the forum will combine them if you are quick ( and for anything but a very short post I copy and paste it into notepad before submitting )

txt and link mostly eaten

txt ok

link ok

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A thought I have looking at the pic of your current forge is to take all that brick and make a table around the fire pot from it. Keep 4 bricks or so in reserve to stack around your fire pot to make the size and shape fire you need. This is close to my favorite solid fuel forge the "duck's nest." My second favorite is a side blast or maybe it is my favorite I don't burn solid fuel often enough to have a real favorite type. With experience you learn to evaluate the forge type in a short time and just adjust YOUR technique to fit the tool. It's an experience thing. ;)

Frosty The Lucky.

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Buzzkill, I'm blushing! 

 

AJ, you and anyone else is certainly welcome to IM me but for questions that some one else may benifit from in the future it would be better to either ask on the forum or copy and past our off line conversation. Some one else may be lurking, our your grand kids may come across this conversation and learn from it. 

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Also google Time Lively washtub forge.

And WHO THOUGHT THAT PLASTER OF PARIS WOULD WORK IN A FORGE !!!!!  They have poisoned the well for many new people trying to get started and  end up giving up in frustration because they follow the instructions of someone who know NOTHING about blacksmithing.

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On 8/8/2016 at 4:06 PM, the iron dwarf said:

BuzzKill I have found out that it is links that cause it to eat posts mostly.

if you are doing a reply that needs a link do the text first and then do the link as a separate post, the forum will combine them if you are quick ( and for anything but a very short post I copy and paste it into notepad before submitting )

txt and link mostly eaten

txt ok

link ok

Thanks for the tip.  I believe that is exactly what was happening.

On 8/8/2016 at 7:39 PM, Charles R. Stevens said:

Buzzkill, I'm blushing! 

You shouldn't be.  As far as I'm concerned, your box of dirt post and another rail road iron anvil thread are "must read" information for anyone starting out with solid fuel and no anvil yet.  Good stuff.

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