Plan for my first slab and brick forge

[Legendary_Sid]

Hello,

Im new here (so i hope this post is in the right place) and joined as im planning on building a (very very basic) forge in my back garden. All the materials i have sourced completely free (minus the cost of petrol to go and fetch them!). I want to know what you guys think, I did some research and watched some videos and the attached image is what i came up with. The 'V' slabs, back slab and lid are thick concrete and im not sure of the material of the other slabs but they wont be in contact with heat so im not too worried. The bricks are standard house bricks and the fuel will be good old fashioned BBQ charcoal briquettes. It isnt pictures in the drawings but the forge will be slighlty inset into soil as my garden is a hill, it will be inset to approx halfway to one third of the bricks. 

I watched a video which advised the use of concrete slabs as they are incredibly resistant to combustion and heat but then i also saw in one video that concrete can explode (?!). Can anyone adivse on that so i can change the material if needed before i make the forge.

Any help, advise or tips very welcome.

Thanks, Sid.

p.s. As you can tell im no artist or scribe so apologies for the terrible drawing and writing!

[Irondragon Forge ClayWorks]

Welcome to IFI.

In my experience concrete that is exposed to the heat of a forge will explode (called spalling) in the rapidly increasing temperature of a forge. Lining the concrete slabs with clay may help with spalling. The BBQ briquettes will  work but are not the best fuel due to the fillers and glue that holds them together. It will be better if you can find lump charcoal or make your own from scrap wood. As far as the forge you designed it looks good for a side blast design. You might look up the JABOD (Just A Box Of Dirt) forge threads. What are you planning to use as an air source?

[Legendary_Sid]

OK, i think i will be able to cover the slabs with clay, if not do you have any recomendations for replacement materials in a similar shape (bearing in mind im doing this project at 0 cost (if possible). 

I can get lump charcoal, there is a coal guy that lives in the next village that i can arange that with.

The air source will be a broken hairdryer i got for free from a colleague as the heating element is broken. It will be connected to a piece of broken hollow steel tubing (originally a piece from a broken childs slide) which will be slightly bent to enable above ground feed.

[Frosty]

Welcome aboard Sid, glad to have you.  Lose the concrete except maybe as flags to stand on and keep out of the mud. What you saw on the web is a perfect example of why it's so dangerous taking anything you see as correct, that one was not only incorrect it was dangerously BAD advice. When heated above about 240f. the water that hydrates burnt lime into Portland cement boils and because it's cement it's not porous so the steam is trapped. When steam pressure exceeds the strength of the concrete the concrete breaks and when the pressure of resistance on the steam drops it flashes over meaning ALL the water in the vicinity turns into steam. 212f water expands 1,700 x in volume when it phase shifts to 212 f. steam. 

Concrete rarely spalls chips larger than say a thumb nail but they're going REALLY FAST and it rightly smarts when a piece of 240f+ concrete embeds itself in your hide. 

You're sketches are dandy, I'll take sketches on lined or better still graph paper over 3D rendered cad drawings and either beat poor photos any day.

Your basic idea is good with a little adjusting it'll make a fine forge. The depth of your trench (V) as drawn is way deeper than you need unless you're going to do large pieces. A proven way to lay this type of forge out is to line the trench with bricks on the flat slanting lengthways out of the bottom. Giving each side of the trench 9" unbroken sides and you can lay as many as you like for length. 

If you have a broken brick or two crush it into reasonably fine gravel, say roughly 1/8" = 1/4" this stuff is "Grog."  Mix this with your garden clay say 2-3 pts. grog to 1 pt. clay. The clay only needs to hold the form and the grog allows it to expand and contract with thermal cycling and it allows moisture to escape easily so it can't spall. 

You only want this mix just barely moist enough you can ram it hard. Too wet say mud and it will shrink check like a mud puddle when it dries, a nice pattern of cracks just doesn't improve forge performance. 

You can just scoop a trench in the garden, lay bricks in the trench end in and pack the surface with your grog clay mix. Lay your air pipe and go to work. Read some of Charles Stevens's posts about side draft forges, he's a huge proponent and knows a LOT about the fine details. 

Lump charcoal vs. briquettes has been covered. It's actually the powdered limestone in briquettes that makes them poor forge fuel. It's added to make them burn cooler and last longer. If you do want to use up a big old bag you have laying around break them up to acorn size pieces. The increase in surface area will speed the burn for more heat and less oxygen travel.  You want ALL the oxygen "burned" out of the fire before the fire reaches your work or the oxy will burn the steel.

Glad you brought your ideas here, the gang will steer you straight, we LOVE helping new folk get well and thoroughly addicted to hot steel, hammers and anvils. 

Frosty The Lucky.

 

[Legendary_Sid]

Consider the concrete gone! I have plenty of bricks to replace them with, i dont have any broken ones but i have enough to break one or two with a sledgehammer. I will look into making some grogg (not heard of this before) as i have all i need for it. I can arange for lumpwood charcoal and ill save my briquettes for a cheeky BBQ whenever we get our 2 days of summer.

Is there a particular reason you advise against insetting in soil? I ask as my garden is a hill, quite steep towards the top so it would be tricky for me to do it any other way without the use of a lot more bricks to level it out above ground.

I will check out those posts you recommend now.

Thanks for the advice and tips!

[Frosty]

No reason not to . . . I'm not sure just what you mean by "insetting." I speak American English. In my last post I assumed (Yeah I know, dangerous) you meant digging into your garden hill to support your forge. If you'll explain or describe what you had in mind I can be of more help.

The thing to remember is a forge is just a fire pit modern ones may be raised to a convenient height but they're all basically just holes to hold the fuel and a place to lay the tuyere iron for the air blast. Years ago I made one by piling dirt on an old kitchen table and scooping a trench in the dirt. It was temporary but worked fine without so much as making the wood hot.  Folk on your side of the pond often call them hearths. Don't get hung up on the thought a hearth HAS to be anything specific, it's just a fire place.

About the cheeky BBQ, I see a perfect beginner project. After you make your basic fire tools: rake and maybe shovel/scoop you can forge out a couple few "squirrel" cookers. They're basically toasting forks and a stand you poke into the ground to hold them up. 

I much prefer to cook steak over an open fire one bite at a time, that way it's always done just the way I like it and always hot. Grilling the whole steak means the first couple bites are good and hot but then it starts cooling off and is cold congealed and stuck to the plate before I'm finished.

Down hearth cooking is great around a camp fire or . . . forge hearth! There are so many tools you'll need to make before you can fix dinner for the family and friends you'll be busy for a while but  talk about BBQ. Mmmmmmm.

Frosty The Lucky.

[Legendary_Sid]

Yeah, i dont know if i used the right word for it but what you described then was exactly what i had planned to. It was only because my garden is steep at the top (where the forge will be going) so i was going to dig out a bunch of soil and build the forge into it. I can do it without doing that, i would just have to use some bricks to create a level foundation to put the slabs on.

I like the sound of that project actually, i didnt really have any idea where to start but i think i can get on board with that idea. I mean i had to google what a squirrel cooker was though ...

[Dax Hewitt]

Sid if its any use to you I normally have the odd horizontal compressor Air receiver kicking about. 

I'm pretty certain that we wrote off a 90 ltr tank last week, it's about 2.5 foot long, about 1 foot diameter. Cut in half and lined with clay it could make a cracking forge. 

FOC if you can collect from Leeds. 

 

[Legendary_Sid]

Sorry for the late, reply. I appreciate the offer but i dont have to tools to achieve that plus my bricks are already laid out.

[Dax Hewitt]

Not a problem good sir. 

I always have stuff like that kicking about so if you ever want one let me know, forge, bbq, log burner etc. 

[ThomasPowers]

General advice:

When you are just getting started; don't try to build the "one forge to rule them all". Blacksmithing is an iterative craft and that includes making equipment for it.

Build what you can, cheap and easy and get to working with it and let it teach you what sort of changes you want to make for your next one. (I have a firepot that's going to go in it's 4th or 5th forge this next year, as I age I need a forge that breaks down for transport easier that the one that was fine when I was 45 years old...)

We have had a number of folks post here to the tune of "I've never done any forging before; so I designed a large complex forge based on my experience---as copying a known good design would be too likely to lead to success!"

[Frosty]

Come on now Thomas, we learn from our mistakes, copying a proven design would eliminate to many mistakes. You don't really want to retard folk's educations do you? 

Frosty The Lucky.

[ThomasPowers]

Well I perhaps mistakenly consider that people visit this site because they want to learn to smith and not that they want to re-invent the gas forge starting with a technical base slightly past neolithic.  (I'm sure there is a Rule #X for that with variants for other crafts...) I freely admit I am an elitist---when I went in for surgery I researched surgeons until I found one highly skilled in the procedure having done hundreds of them with good outcomes. I didn't say give me any surgeon he can learn as he goes... I did not try to design my own insulin pump either.

I have been forging with propane for about 20 years now and have never "designed" a propane forge as I can easily and inexpensively---in materials and time---copy a known good design. I have assisted a burner designer by testing his design at 7000 feet to see how well it worked at altitudes of a "higher" order. (I may get to run it at 10K' now I'll be back near the Observatory again.)

[Frosty]

A practicing surgeon. No?

Frosty The Lucky.

[Legendary_Sid]

On 7/22/2019 at 10:28 AM, Dax Hewitt said:

Not a problem good sir. 

I always have stuff like that kicking about so if you ever want one let me know, forge, bbq, log burner etc. 

Sorry for not responding, i ended up contracting meningitis a day or two after my first post and have been pretty much out of action since.

The brick idea didnt pan out as my landlord wasnt happy with a 'permanent' structure in the garden *sigh*. I do have a used small kettle BBQ, are these capable of handling the heat needed for smithing?

[ThomasPowers]

It's not the shell that handles the heat; it's the dirt lining.  How small is small?

[Legendary_Sid]

Its 44cm / 17 inches. Ive popped a picture on, as you can see its been sitting a while.

[Ohio]

Legendary_Sid, I'll bet you that'll work. I did something similar with a dead propane forge....here's the write-up.

The Frostman is right (don't tell him I said that): a forge is just a fire pit. You use the barbecue to hold dirt or clay in place and get it at a more convenient height. Charles R. Stevens has a ton of info about the JABOD---Just A Box of Dirt---forge that is cheap and works, I highly recommend reading those threads. Torbjorn Ahamn also has a video about building a simple forge that's just like what Charles describes.

The JABOD/JAGOD actually work. For real. I didn't think my JAGOD would work because I never expect anything to work and am always pleasantly surprised when it does. But the trick is to remember what Frosty said---a forge is just a fire pit. The challenge (and it is a challenge) is using such simple things as fire and hammer as skillfully as blacksmiths do. 

And there's a real upside to using your grill---you can move it to its hiding place easily so the landlord won't get upset.

Lump charcoal is what a lot of people use for grilling. Your local coal man may or may not have any, but there may be a bag at your local Tesco (see, I speak British) or hardware store. Or you can usually find some charcoal anywhere someone build a wood fire. You'll go through it pretty quickly, especially as you learn fire management, but charcoal is easy to find or make. Regardless, a little JAGOD you make with your own grill and dirt will get you a real taste of the craft, at least enough to know if you want to continue smithing.

And it's really fun. You heat up a piece of steel---steel!---and whack it with a hammer and it moves. Astonishing.

Good luck.

[Irondragon Forge ClayWorks]

35 minutes ago, Ohio said:

a forge is just a fire pit.

Or put another way, it's a hole in the ground brought up to a comfortable working height.

[pnut]

I have a Webber kettle grill just like that. I did something a little different with it but it worked. I filled it up with clay to even with the rim and made a one inch depression in the middle about four inches wide and eight inches long and stacked bricks on either side of the trench with a pipe underneath the bricks on one side. It worked great but I didn't have it assembled very long. It was more of a proof of concept than a permanent forge. 

Pnut

[Legendary_Sid]

Thanks for the tips and advice, very helpful. Yeah, the mobility is key for me it seems (ive even mounted my ASO to an old cable reel so i can roll it about!) and you are spot on, this will be a simple and easy set up for a complete beginner. Im looking to do it as easily and cheaply as possible (so far i have spent only about 15 pounds and have everything apart from a blower or bellows).

I do have 2 questions followed by, probably, a really stupid question.

You mention lump charcoal, i think i recall being advised not to use that as it doesnt burn hot enough? Is it good enough to start at least? I was advised coke i think.

I've seen an air blower amazon link removed do you think something like this would be ok for this style of beginner forge?

Now the stupid question ... You mention dirt. Do i need a specific type of dirt? All around these parts is mostly damp clay like soil, would that work? Ive seen the video i think you are referring to and its a very dry almost sand like dirt but we dont really have that over here, at least readily available. Pnut mentioned clay, but again, is this any clay or do i need a certain type?

Sorry for all the Q's but im a complete beginner keen to get his hands dirty and get started but there is a few things google and youtube doesnt answer, plus i prefer to speak to pros and amateurs alike in person (sorta) so i can be more specific and get a good range of opinions and answers.

If any of these questions belong anywhere else please let me know, still getting the hang of it here.

Cheers

[Charles R. Stevens]

Clay works fine, thats what bricks are made from. If yo fill a jar 1/3 wit sub soil and then fill it to the 2/3 mark with water and give it a good shake, in a day or two you will be able to see the proportions of sand, silt and clay. Realy any ratio will work but 1/3 clay and atl3ast 1/2 sand is ideal. The addition of wood ash and horse manure are improvements. Now after saying all that almost any dirt will work.

 

[Irondragon Forge ClayWorks]

The lump charcoal (not BBQ briquets) here in the states will get hot enough to burn up steel and make forge welding temps easily.

[ThomasPowers]

Lump charcoal was what was used to smelt iron ore into iron until the 1700's. (cf Abraham Darby) It's been used for forging and forge welding for 3000 years.

If someone is having trouble getting heat out of it they probably have a forge not designed for it. (Which is like saying that diesel can't make a vehicle run as I tried it in my gas engine and it didn't work!)

[Legendary_Sid]

Ah, apologies, i got confused between briquettes and lump.