Building a Charcoal forge.

[Savlaka]

so I've decided I want to build a charcoal forge to expand my options for projects. I can currently heat anything up to about 3" or so in diameter and basically any straight length I want in my propane forge, and about 85-90% of all the projects I've got planned or likely to want to do can be done in my propane forge, so this project is to do those 10-15% of things I just cannot fit in the gas forge's 4.5x4x24" interior... also I'm trying to do this for As little out of pocket as I can, using whatever I can lay my hands on around the shop.

this means I'm not aiming for everyday use efficiency, I'm after something to handle bulky or large items. And after looking through a LOT of different info on solid fuel forges this is what I've come up with:

I started with a brake hub form an old M149 water buffalo and a hunk of old metal shelving that I cut and welded together. then fitted a 2x3 frame under the edge of the shelf section. and finally welded on a 2.5 to 2.25 exhaust pipe adaptor into the bottom for the air piping to fit to. The metal was painted to prevent rusting.

next I Made a grill type air diffuser, the ring is a hunk 1/2" car spring I made into a ring to fit the bearing seat lip. Then I welded on 3/8 bars (well 13/32") spaced 3/8" apart. this lets me have a removeable grill in case I ever need to replace it.

 

next I attached wooden sides to it to extend the depth so I can form the firepot tall enough and big enough to fit the types of projects I intend to use this for.

the stacked wood is me trying to decide how I want to shape the firepot and if I've got enough depth...

 

Right now it's 8" from the grill to the top of the wood sides. and I'm looking at a firepot in the range of 9-11" x 12-14" and between 8 to 10" deep. I think that will get me a fire big enough to heat up the biggest item I need to do (a 5.5" round 2.5" thick).

I intend to add about a 2" rim to widen the sides to match the distance from center that I have at the back. I'll be filling the box in with a sand (2/3) and clay mix (1/3) to build the actual firepot. the clay will be bentonite from floor dry / cat litter, sand I have easy access to, it's Florida that's all we have for "soil", though I may buy a few bags to ensure its not limestone sand. I tried to get some fireclay but none of the possible suppliers around here carry it. One told me they could get it, but as a special order I'd have to buy 10 bags- yeah that's not happening.

I do have about 10lbs of Satenite sitting around and wonder if I could use it as a top coat over the sand/ clay base at least in and around the firepot.

I'll update things as I get to them.

 

[wirerabbit]

Savlaka, I'm glad you're branching out into charcoal forging and wish you success.

I love using charcoal in my small side draft forge. I use it when I need a short heat and use my two burner propane forge when I need to either heat up a larger mass of metal or a longer heat. I'm still learning, so take my comments with a few grains of salt. I have forged over half my current tools ( punches, chisels, tongs, hardy cut, etc) in my charcoal forge, so I know it works well. The original reason for me to buy an inexpensive propane forge was to hold me over until I could make some new modifications to my charcoal forge. HA HA, I made the modifications to the forge in less than and hour and was forging with charcoal immediately. It heated 1 inch square bar quickly.

I have read many many posts on this forum about the particular needs of charcoal as opposed to coal/coke. Many folks swear by side drafting of charcoal instead of bottom drafting, but others have had no problem with bottom drafting charcoal. Tons of suggestions on the height of the fire as well as how deep the fire pot. All are good starting points, but nothing beats performing your own experiments!

When you want to discuss the results of your forge, I'd be happy to participate. My suggestion for right now is to leave everything as alterable as you can. I have a feeling you are going to want to change some things, so don't cast your fire pot with expensive refractory until you know you have the dimensions, location, and air input the way that actually works for your fuel, your projects, and you.

I'm looking forward to seeing how things progress. I may be making some changes to my charcoal forge in the near future myself.

[Frosty]

Savlaka: You're building a REAL fuel hog of a charcoal forge there. Unlike coal the fire WILL spread to the entire load if charcoal in contact with the fire. Seriously it WILL make a fire 12" x 14" x 8" deep  that won't go out until you douse it or the fuel is gone. Just to heat something 5.5" dia. x 2.5" ? You could heat that bit of stock to welding temp in a forge maybe 8" x 8" x 4" deep that sipped air. Sure you'd have to add charcoal frequently but you wouldn't be adding it with a 5gal bucket.

Take a look at the basic JABOD and just widen the fire trench to about 8" half way down so you can nest the stock in the coals completely and go easy on the air. 

Frosty The Lucky.

[Irondragon Forge ClayWorks]

The main difference between lump charcoal (not BBQ briquets) and coal/coke is the amount of air blast needed. Charcoal needs a lot less air to get a good hot fire as opposed to coal/coke. My bottom blast forge will work well with both fuels, because I use a hand cranked blower and can control the air blast to match the fuel.

I see Frosty and I were posting at the same time, so I should note he is right about the size of the fire pot. Mine is much shallower and smaller in diameter.

I can't control the wind, all I can do is adjust my sail’s.
Semper Paratus

 

[Savlaka]

Wirerabbit- I actually started with charcoal. my first "forge" was a dug out trench in the ground with a side blast done with a small electric blower fan through a 1" pipe. me and a friend in high school  built it and tried to learn how to smith in a lot next to my house, our "anvil" was a Press block from a truck repair shop's old hydraulic press a 2.5 x 6 x 14" hunk of steel we bolted to a stump... it was a few years later when I had my own house that I built my first gas forge.

as to being alterable - the only things "fixed" in place right now is the parts I welded. I expect to need to play with things to get it all to work the way I need it to... i'm only using cat litter / floor sweep and sand at first and all the wood is "reclaimed" lumber and is only screwed together nothing fancy...

 

Frosty- Yeah, I assumed that this thing would be a charcoal pig... and I actually already read through the JABOD thread, if this was to be my main forge I'd be aiming for about 1/2 the size... I'll probably only fire this thing up once a month or so in the long run...

The exact size that I make the pot is still to be determined, but after reading through a few old papers on charcoal vs coal forge design and looking at the offerings of the (fairly few) commercially available forge designs that list as designed to use charcoal what I'd seen is that I'll need at least 1-2 inches of space wider than the largest items I want to heat - so 8-10"  is the size I'd need in the smallest dimension. I was looking at 9x12 at 8 inches deep total... the 8 inches deep was coming from many, many places where smiths built 4-5" deep (like most commercially made Coal forges are) and needed to add bricks to get the depth to heat stock over 2-3" when using charcoal.

The biggest single item I have to do is 5.5dia x 2.5" but I need to heat a 3.25dia x 3" piece (both are 1045 steel) at the same time as these are to be forge welded together, then some shaping and a simple heat treatment to harden the finished item.

Though I do hear you, and I'll aim on the smaller end of the size range I've researched.

 

IronDragon- I have a basic hand crank blower I intend to use for this, nothing great mind you but it should be sufficient for this project. that and that old brake hub is actually why I looked a bottom blast for this project since those things are just taking up space at the moment, be nice to find a use for them both.

[Savlaka]

I've gotten a bit of work done on this project. I've put on the wood rim, and legs, and moved it into place in the pole barn, I have a part to make for the front still but I'm still working out exactly how I want it to be shaped. I have a section of thin sheet metal from the casing of a water heater that I'm turning into a Heatshield / hood and smokestack. it's almost too thin for my welder to work, and after trying for way too long I finished up with sheet metal screws. this is not a full hood since I just didn't have enough of the material to do that... and I was really mostly after keeping stray rain spray out (its still under the roof, but right at the end) and giving a bit of a heatshield to the post and the fence that are close by.

I'm also working out exactly how the fill will be mixed up this tub is currently about 15lb of clay and 50lbs of all purpose sand, lightly wetted and mixed. I'm going to let it set overnight then check it's consistency, I'm looking for it to be able to be formed into a ball, and not crumble when I roll it between my hands but still be as Dry as possible. I think that will let me pack it Very hard and let it keep it's form well. I may add some ashes to the mix since I plan to smoke some meat this weekend and I'll have some to use then...

 

[Jason L]

I would leave the front just like it is. Having it lower like that will allow you to run a smaller fire and position your work further down in the pot if you want. I ran charcoal for many years and the only problem I had was the fast rate at which it burned. It got real expensive, real quick. Having said that, like Frosty said, once the fire is going it will spread throughout so make sure all the wood surfaces are sufficiently fireproofed. Another  thing to be careful of is the charcoal dust mixed with fire and air sends sparks flying everywhere so make sure to keep all combustibles clear of the forge. I'm not sure how much good your hood is going to be without a chimney to draw the air up and out. It may end up channeling all the smoke and sparks back towards you. I'd be careful with that arrangement. You may be better off without a hood at all. If you decide to keep it I would definitely look into adding a chimney.

[lary]

Savlaka Thanks for posting your progress. I built a coal forge for the same reasons, but so far have only used charcoal that I've made, or lump charcoal I've bought. Its a bottom draft with hand crank blower. Forge welding was another reason for putting it together. Unfortunately because of the fire flees its a winter time forge only.

[Savlaka]

This morning  saw me fitting the parts for the front of the forge in place and packing the clay/sand filler into shape.

I used a section of the bag the sand came in and some rounds I cut out for the shape of the firepot... I was only after a rough form and did the final packing by hand using a hunk of 2x2 as a packing stick. 

Took me about 125lbs of fill in the end, I shaped the work entryway to accept firebricks so I could adjust the depth of the fire and work piece as needed. At it's lowest I have just under 5" of depth to the grill, and with 2 bricks I can get 7.5".

[Savlaka]

Jason- I do have a chimney on there, it's not as big as I'd like, as I was running out of sheet metal. It's final size came out to 2.5 x 7.5 x 30" that gets it a bit above the roof.

Eventually I'll probably build a better hood and a 6-8" diameter chimney for it, but this is what I have on hand at the moment.

[Savlaka]

I Got the air supply and ash dump fitted up, and gave it a test burn... Heated up a 1.25" bar ok, wasn't really trying too do more than test things out and give the fill an initial baking...  in the photo It's in full daylight so it only looks a bit reddish orange.

The hood mostly works, but I'll definitely be building something better when I can find the materials to do so. It fully  works as the heat shield I wanted, less so for the dust and sparks. Though of course the wind had to start blowing directly into the chimney opening... I'm thinking an old water pressure or compressor tank would work.

 

[Frosty]

Look for a 5 gal steel bucket like you buy grease, etc. in. Stood open end down with a stove pipe jack on top and an opening in the side to draw smoke is really all it takes for a good side draft hood. I don't know what to do to make what you have there work very well. Is there a pass through so you can heat the middle of long stock, say you wanted to bend something 36" long in the middle?

Frosty The Lucky.

[Savlaka]

Yep, the "hood" is quite janky ... I've been looking for metal buckets for over a year now, nothing seems to still come in them. The shop I used to work at got their grease, specific oils and solvents in 5 gallon plastic buckets. We'd actually had to replace our air grease bucket since it didn't work with the plastic buckets... I checked at paint and auto shops and even there basically everything comes in plastics now, only a few types of solvents didn't and they were normally 1 gallon cans or 35 and 55 gal drums that they wouldn't sell or give away.

Everyone in my neighborhood is on a well system so there's a good chance someone will have a failed pressure tank around.

The biggest issue is the "chimney" is too small and not mounted in the right way, finding anything better will be a bit of a challenge, there's nothing in the way of fireplace, wood stove, or similar supplies readily available down here. I'm sure you can go into your local home center and find basic stuff for all of those kind of items, but none of that is stocked in Florida - it's all special order, at best.

As to a passthrough, Nope. If I needed to I can place work on diagonal across the forge. But realistically I'd just heat a long bar in the gas forge. I don't do the fence, window and railing type work so it's not too likely I'll have a need for anything like that.

This isn't the kind of forge many would build, it's bigger than is economic to run all the time, and it isn't configured the best for general work. But it'll do exactly what I need it to and so far out of pocket I've only spent about $20. Everything but the sand and clay was stuff I had laying around - left overs from other projects or salvage materials...

[Frosty]

Yeah, steel buckets are getting harder to find alright. Maybe a helium tank would do the job? It'd be more work but you can usually pick them up for free, I see them at the Transfer Station (dump) all the time. Maybe check with a party supply shop? 

I don't suppose you have any more wood stove type shops than we have surf shops. Yeah, water heater, well tank, etc. is probably about it. I'm not a fan of using HVAC ducting too near the fire, it's all galvy, around here anyway. 

Making it from brick is pretty traditional and makes a great theft deterrent but not my idea of desirable. Still . . . 

Frosty The Lucky.

[Jason L]

Check with old timers, farmers, roofers, etc. They sometimes hang on to old drums in the 30 gallon range that tar or other chemicals came in. If the top rusted out they might give you one. I've seen hoods made from 55 gallon drums. It looks like they were cut in half then cut on an angle towards the top to allow for plenty of working room. There's an older thread here about it, here--->   

It looks like a pretty good arrangement and I may copy it later if I ever get an inside to put it all in. 

[Nobody Special]

Good evening, I've used the 55 gallon drum cut down. It worked pretty well, but I had better luck with a 20-gallon drum set just barely over the fire pot so they more or less side drafted. Automotive places have them sometimes; the chemicals are expensive, but to them the empty drums are just trash. I got a ZEP brake flush drum from one that size once and used it outside for four years before the poor thing rusted out.

[Jason L]

Around here those drums are hard to come by but I know they're around. I live in an agricultural area so anything like that is kept and reused till it's powder. I used to sell molasses blocks for cattle which came in drums that looked like a 55 gallon drum that was only about 1 1/2 - 2 feet tall. Now they come in plastic tubs. They made great fire rings, grills, washtubs, planters, water troughs, feed troughs, etc. They had a million uses.

I once made a forge for a guy out of a 55 gallon drum that I cut a hole in the top of and put a disk blade into it for the firepot just to show him it could be done. It worked great. Drums area as handy as a shirt pocket and around here they are hard to get in any size.

[Savlaka]

I was doing some yard cleanup and rearranging of stuff, and I found I still had my old compressor. I'd replaced it when it's motor died and set it outside the fence to deal with later and it seems I promptly forgot it was there. after cutting the tank off just below the handles i have a 16" dia x about 18" tall section I can use to make a better hood... now I just have to come up with something to make the chimney from.

[Frosty]

Oh BABY will that work a treat! Lay it on it's side with the open end facing the fire and run a stack up from the back end. You can buy stovepipe jacks online, the ones with the wide flashing will bend around your new side draft hood easily and pop rivet or sheet metal screw on. Stovepipe roof flashings are different things and you can't socket stove pipe into them.

Of course you can simply roll some sheet steel so stove pipe slips in and rests on the bead and weld your jack to your new side draft hood.

Frosty The Lucky.

[wirerabbit]

I was going to suggest looking for an old water heater, but that will do just fine, won't it? 

I don't know if it is just my specific situation, but I have never needed a hood for the small charcoal forge of mine. The only time I get smoke or fire fleas is on start up and that lasts for less than a minute. Of course, you've done this before, so you know what you're doing, but I'm curious about your experiences with charcoal and hoods.

[Jason L]

Nice! I went to Tractor Supply for something the other day after I mentioned the metal drums and lo and behold, right in the front of the store they had some 5 gallon metal cans of something, probably oil of some sort. I think the price was around $125 or something. I couldn't bother to remember what it was because I was there to get something specific and the wife was with me. She is my lighthouse in troubled waters when distractions invade my space, not an easy thing to contend with.

[Scott NC]

  They used to sell part cleaner solution in metal cans.  A good member told me to ask at Fastenal for metal buckets once and the do have them!  

[Jason L]

Look around the scrapyard for stuff as well. I got a deep freezer for $20 there last year. The wife wanted something to put ice water in for a morning dunk to help with circulation or something. It wasn't big enough for her to fully submerge and I never could get it to stop leaking so I tossed it. I wish I had saved the sheet metal skin from it now. I might could have fashioned a reasonable hood from that now that I think about it. At the time I wasn't thinking about a hood though. 

[Savlaka]

I've been working on the better hood design. - Sorry Frosty not a side draft, but for my needs I think a full hood will be better for my installation. the roof is only about 4 foot above the forge table and next to a main beam, so I have to think about radiant heat management.  I've got the base frame partly assembled, and the tank cut to size. and I've started fitting the remnants of the old hood as a rain guard for the table - while it's under the roof it's right at the edge and will get spray and sometimes even direct rain depending on the wind.  I still need to cut and build the front opening, I'll start on that tomorrow most likely.

I found some metal to make the chimney from some metal table braces they are a bit under 7 foot long 6" wide made of 1/8" steel. trimmed and fitted up they will give me a solid (if a bit heavy) 6x6x37" square tube, currently I have the tube just tacked together, I'll run solid welds once I've got all the upper mounting decided on. I made a square mount on the top of the tank from some 2" 3/16" bar stock, and the chimney bolts onto that using some stainless 5/16" bolts. I still need to design and build a Rain cap for it, and finish cutting the roof panels to fit.

[Frosty]

No need to apologize to me for not using a suggestion, it's your situation and set up. I will be interested in how that hood works for you, I'm always interested in different ways to do things. 

Frosty The Lucky.