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Thread: Charcoal Forge

  1. #1
    Join Date
    Nov 2011
    Riverina NSW

    Default Charcoal Forge

    I can't really remember exactly when I decided to have a go at blacksmithing but around this time in 2013 I started clearing out the shed to reorganise, insulate and line it. As part of setting up a woodwork and metalwork area I had already had in mind a forge would go in a corner, complete with anvil and post vice, a range of hammers and tongs. If you've ever seen the Blacksmithing episode of the BBC series Mastercrafts, that's what I wanted. Never going to happen but at least I could have elements of that traditional English setting like a bricked forge, massive anvil, coal or coke and all those tools, throw some brick stencils on the gyprock walls for authenticity.
    Here's a link to that episode, well worth a watch

    As reality set in I got inspiration from what people make do with. I've already talked about anvils as I've settled for one made from rail line and although I've got the bricks and a bit of bricking under my belt to confidently pull off a satisfactory brick forge, I can't commit to a permanent place for it. An LPG forge could be a goer but part of all this is just enjoying poking a fire. Speaking of fuel types, where do you get coal? I don't care anymore really, I just don't get how so much is dug up and shipped off yet you can't buy a bag readily. Same as coke which is becoming harder to source. There's really negligible domestic demand but anyway, I saw something about charcoal ages ago, watched a couple of docos and tried heating up scrap metal in the wood heater with charcoal. Worked well and I can make it myself but how will it go in a forge with blower. So far, really well though I've only test fired and haven't tried to reach welding temps. I've read charcoal burns quicker and may not burn as hot as the other two but I'm impressed so far.

    There wasn't much online for charcoal forges specifically so I looked at different firepot designs for coke and coal users and the following's what I've come up with.

    The measurements in white are incorrect. I got them off a video I saw ages ago, wrote the measurements down and copied them. The geometry didn't work so I came up with my own of 12" x 11" top and approx 3" x 2 and a bit inches for the bottom and used common angles copied with a sliding bevel. It was pretty rough cutting with the grinder and afterwards I clamped like sides together to grind them to match. I'm using old 5mm plate and once welded the pot is only 2" in depth. Not as deep as I thought it would end up.

    Took a while to setup and tack. I'm using 0.9mm gasless mig which I'm not real good with. I much prefer stick and have never tried gmaw.

    I'm putting angle around it so it can drop into a table.

    There's bits of bar tacked to the bottom to not only act as a grate but may be rearranged at angles like fins to direct the air if need be. I do need to add another fin or add thinner sections on top at right angles because after going through half a bucket of charcoal this afternoon, too many smaller unburnt bits fell through the grate.

    For the test fire, I placed the pot on 100x4mm round pipe which rested on two rail offcuts, gapped to allow air to be forced through with a tiny hair dryer. Scrap is used to cover the gap. I didn't think it would be up to the task but it was more than adequate. Eventually I want bellows, despite the convenience of an electrically powered fan. A few coals were taken from the wood heater then charcoal on top. With the blower turned on you get sparks but negligible smoke. I placed the big pedestal fan as shown and it pushed sparks and fumes outside. Lots of circulation with two opposing doors open so no dramas re fumes in the shed.

    Despite the shallow pot it heated thin and thick pretty quickly without a huge mound of charcoal.

    I really need to make tongs.

    I'm estimating under 5 litres volume of loose charcoal was consumed in 30 mins and two cup fulls of smaller charcoal fell through the grate unburnt. No clinker either, just a bit of light ash.

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  3. #2
    Join Date
    Nov 2011
    Riverina NSW


    Some good progress yesterday and surprising results. We got to welding heat and then some. I didn't think it would be possible with so little fuel (size of fire wise), or type (ie home made charcoal) and with a tiny 60mm hair dryer fan but within 5mins, sparks are flying. I'll throw in a 4min video at the bottom. Towards the end of it you'll see a couple of rods being burnt. We weren't paying attention but when I saw the branching sparks for the first time I was excited, knowing that we were passing welding heat.

    I've yet to mount the firepot permanently but I measured up the table size and cut the hole in the plate for the firepot to sit in to get some idea of form and fit, workable height - basically whatever ergonomics come into play - and decided I'll go as high as my metal workbench which is about 900mm. The tuyere and blower was welded up and connected and with my 16yo son helping we got carried away with firing the forge and bashing metal that the next thing you know it's 9pm and too late to do much else. Further to that, I got the anvil mounted on 3 sleeper off cuts which I bolted together vertically earlier in the day. Took ages to level the wood and put 10 bolts in. Still a bit to go with that but as with the forge, everything's usable at the moment.

    You can see the cutout of course which was mostly done by oxycutting. I'm not real good with the torch but it's a hell of a lot quieter than cutting discs. I was getting sick of the noise and dust so started oxy cutting to do a few things till I ran out of O2 then changed to the grinder to finish this cutout. The dimension of the hearth is drawn out in white which has to be cut still, along with legs and everything else.

    I cut the hole for the air inlet and my son mig'd the pipes together, the hinge and ash flap, plus attached the assembly to the firepot. The whole lot can be lifted out of the hearth cutout without much trouble.

    Incredibly, this little 60mm fan from a little hairdryer we stole from my daughter, provides enough air to power the forge. It doesn't roar away and two thirds power will heat metal to forge in no time. Full power gets to welding heat and beyond. For a while now I've set aside an old squirrel cage HVAC fan from an old mercedes thinking that's how much air I need. But it draws 11amps at 13v and apart from lining up some car batteries, I didn't have a way to control the speed or power it. This hairdryer only had two speeds with heat on all the time. So I pulled it apart yesterday to try and disable the heating element. In doing so I found there was a bridge rectifier over the motor terminals which I presumed meant it was a DC motor. Some testing later revealed it pulled well under 1amp, I forget exactly, at 13vdc. So we rigged the fan and it's cage to a really old model train controller and now have variable control of airflow. The setup is in the video. I'm still amazed we ended up with this cheap and convenient low voltage solution that works. I really doubt I'll be bothered chasing the idea of bellows.

    The fan I originally was going to use. This would blow the fire out of the pot.

    Controller and fan. The power cord for the fan is reused 240v powercord from the hairdryer, removed from it's switch and 240v plug. Apart from reusing the wire it ensures there's not a one ended 240v plug and lead with exposed wires laying around the shed. I guarantee I'd accidentally plug it in. The fan cage and screen from the back of the hairdryer are taped to the pipe with reflective tape. A bit of heat conducts it's way to that pipe through conduction and radiation from not only the firepot but the base of the ash dump. I still haven't added more fins or screening to the bottom of the firepot, so as a result, burning embers just under a cm cubed will fall through and continue to slowly burn at the bottom of the ash pipe. After hours use last night and a couple this afternoon, the fan's not going to be adversely affected by heat reaching it.

    I start with wood shavings, works well.

    Although I bought some 100x100x5mm square to mount underneath the firepot so a good seal after welding was achieved, I used the 100mm round instead which has worked well. The idea being that some air escapes around the underside of the pot to keep it cooler. Despite the forge getting hot enough to burn rod, the firepot never glowed and the fins/grate, never showed signs of burning or glowing for that matter. In one of the photos and later in the video you'll see orange in the gap between the pipe and pot but it's just reflection of the light from the charcoal.

    Whilst I type this my smart alec son has been beating away at some of the rusty rod I've got to practice on and made a set of pliers. To say I'm jealous is an understatement. Their crude but damn, they work and surprisingly strong enough. Thing is I only showed him a demo video by Brian Brazeal after he got back from school a few hours ago. Geez!

    Lastly, here's the video. Earlier, my son hammered away at some rod to make a fairly well proportioned scroll, but when we decided to film, he kinda lost his way. LOL. Still did better than me. I was filming because I was sidelined with my left hand in cold water after picking up the wrong end of a hot rod. I had been wearing gloves all day, but took em off during a break. There's a walkaround the anvil stand too but it needs more work before I post about it.

  4. #3
    Join Date
    Jan 2004
    Mackay Qld


    I like your ideas. I live in one of the coal export areas, but the type of coal available is wrong I think.

    I had planned on an LPG oven /forge for some light smithing projects, but charcoal may well be a viable alternative.

    How thick is your forge plate .It looks about 10mm by the pics. You don't want to strain a foo valve handling it.



  5. #4
    Join Date
    Nov 2011
    Riverina NSW


    Hi Grahame, it's only 6mm plate. I think I said 5mm earlier but meant to edit the post after I put callipers on a clean edge. I wanted a more rectangular shape but am really happy with the area it heats which I'd estimate makes up to 5" of rod glow to forge temp in no time and the depth seems perfect to allow a piece to lay flat on the hearth and slide into the hot zone without being angled down or propped up.

    I'm just a beginner though and I think there's still a lot to appreciate and learn about charcoal size and fire maintenance. I think I got lucky with the way it's turned out, though with experience some limitations might crop up.

  6. #5
    Join Date
    Nov 2011
    Riverina NSW


    The forge is pretty well finished too and after a few afternoons using it with my son we've discovered a few things.

    Firstly, despite the shallow pot we found ourselves putting pieces in the fire on an angle to get in the hot zone, then covering pieces with hot or fresh charcoal. It needs a bed of hot coals under a piece at least 40mm deep then some charcoal on top, be alight or not didn't seem to matter so long as the piece is covered. So in building the hearth I've put angle around three sides which act as a ledge to add tools or a rack or two, plus aids in resting a piece into the hot zone and keeps the reserve of charcoal from falling off.

    As a result of the above we involuntarily migrated to the side of the forge rather than the front. The hearth is rectangular and it just seems easier and more practical to stand at the side, hold or rest the work piece in the fire with the left hand and work the fire and charcoal with the right. In doing this the blower control is around the corner and we'd quite often forget to turn the fan down or off. Even if the blower control was near where we were standing we'd forget because hands are busy picking up hot metal and reaching for the hammer. So now we've added a foot switch from a pedestal light that was in the trailer awaiting dumping. So much easier now to conserve fuel.

    Lastly, charcoal does produce clinker. Maybe not all, but during a heat I found some lumps that wouldn't burn and lying on the grate they were blocking airflow. To my surprise there was this metallic glass like brittle rubbish in the bottom of the pot. The other night I collected about a palm full of it of pieces bigger than marbles. The grate has been improved with welding rods tacked across the grate to close the gaps between the fins and I think a lot of this clinker would've dropped through in the past and is why I haven't noticed it before and it came from the redgum charcoal I've made.

    I tried some commercial charcoal, this being Indonesian hardwood lump charcoal I've had in a bag for well over a year. I don't know if it produces clinker but whilst warming up with blower on full it tends to pop occasionally but violently for up to a minute. Kind of fun waiting for it if I'm honest but once burning it behaved like the redgum.

    Adding angle to the edge and cutting the hearth to size.

    We got through one afternoon of cutting and welding and used the forge like this. There was still some rhs to go around the bottom of the legs but we also found the slightly raised forge to be a pain so far as rakes and shovels were getting caught on the lip of the firepot. So in the third shot the hole's been cut larger then flat bar tacked around the hole to form a lip for the firepot to sit on.

    Firepot flush fit and note the extra bits of rod tacked into the grate to limit the loss of usable burning charcoal dropping down to the ash dump.

    Lastly, the footswitch. Despite it being a 240vac switch, only up to 14vdc is going through it. It's been wired in line between the 12v transformer/controller and the dc fan and has been a huge benefit. It's simply on/off but the speed can still be varied by the controller if need be.

    That's the forge done really. There's a bit of tidying to be done like cleaning up weld splatter and other clean up grinding. I thought about painting it hammertone grey like the old controller but, blah, overkill. There'll be a tool rack added later and may be shelf but need will dictate what and when gets added. The only thing I haven't sorted out yet is a permanent solution for ventilation. Ideally I'd like a hood and spark arrester that will capture the sparks and ash that currently gets deposited all over the hearth but that will come when I sort out a more permanent position for the forge. I kind of like where it is, particularly that all 4 legs sit flush in just that spot, so a whirly bird on the roof may be as good as it gets in the short term.

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