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I use a oooold coal forge which is supplied with air from a foot driven blower. I think I might have a problem with the coal I use. The coal burns pretty quickly, and goes from pieces around 30x30 mm to 5x10 mm. So within 45 min of the start of forge session I need to clean out the small pieces, since it seems like they dont burn. Are this the case, and I need to treat them as ash. Or is it just not enough air to heat the coal?

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Are you burning the coke formed?  Coke is what you want to heat your piece as it's nearly pure carbon and so not contaminating it with sulfur.

(Coke is to Coal as Charcoal is to Wood).  Coke has a porous structure to it, may even float!

Coal should go from rock to tarry mess to coke to ash.  Can you tell us more about your air supply, forge and how you know you are using "good" coal?

Where are you at?  15 minutes in a smithy with someone who knows what they are doing could solve a LOT of possible issues getting started!

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3 hours ago, ThomasPowers said:

Are you burning the coke formed?

I'm living in Eastern Norway, so finding 'professional' blacksmiths are rare.

I am not totally sure if I'm burning the coal to coke. I usually have a decent amount green coal 'huddled' around my firepot, in an attempt to transform the coal to coke without too much smoke. Usually I end up with having to use some green coal, since the coal/coke in the firepot seems to burn quicker than i can 'produce' coke around the fire/firepot. SInce the forge is foot driven, I need to treadle quite fast to get enough airflow going. The coal I'm using are from somewhere in Germany, and it doesn't really produce much clinker.

 I don't have any specs on my forge, since it is from a unknown producer way back in the (mid) 20th century.  But if you've seen Make'n Create on youtube, I have a very similar 'feltesse'. They were used out in the field doing forging under construction, restoration etc.

How small can the coke pieces become before they steal more heat than they produce?

 

There is no need to quote the entire post that we all just read,  and when quoting its polite to trim the post to what is needed many members still use dial up and pay by Kb used

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They should put out more heat as they get smaller---more surface area to burn at.  Are you getting too much air?  Can we have a picture of your forge in use?  To see the fuel and air flow and heat.

I seem to remember IFI having at least one other smith from Norway.

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I don't have a picture here right now, but can post one next time I use the forge (probably this weekend). I do have some picture of it during restoration, and I haven't changed much since. If you want to see the airflow though, I will need to take some new pictures.

I know forges need more air *volume* than air *pressure*, and since I need to treadle quite fast I'm unsure which one of them I get the most of.

20190601_135037.jpg

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First, the top picture shows a round firepot and the bottom shows a rectangular one.

I'm going to assume you don't know anything and I'm not good with metrics. 

Your forge and firepot are pretty good for forging. However, the left side of your firepot is too close to the side of your forge. It looks like the pan is replaceable, or made out of plate or sheet metal, not cast. If this is the case I would modify the location of your firepot. I'd move it to the right and center the firepot on the centerline of your forge. I'm assuming you stand facing your forge in the above pic and your back to the camera. Or do you stand on the right side and pump with your left foot? In this case, I'd rotate my firepot 90* and leave it centered where it is. It's really best to be able to have most of your green coal on both sides (in about equal amounts) of firepot so you can control the height of your green coal. Note just below, you need at least 2" of coke above your work, and the green coal on the sides makes this possible. 

You want no green coal in your firepot, only coke.

You want 4" of coke underneath your work.

You want 2" of coke on top of your work. it looks like your fire pot is pretty close to this deapthwise.

Keep your green coal wet in order to control your fire. Dry coal means a loss of heat thru the spaces in the green coal and faster burn a d thus loss of heat.

The important point of air supply is you want air volume, not air velocity. If you get high flames and lots of ash going up, you have way too much velocity. Watch your coke, and pick a temp by color. Learn to see a  dull red, a full red, a bright red, a yellow and learn the proper air flow(volume) to maintain each of those temp colors.

At the same time, your coke, in the center, burns to clinker and ash. As your green coal cokes at the sides, gently use your poker or rake to move this new coke into the hollow center, then pull the outer green coal up to replace where you got your new coke. Again, keep the green coal wet.

This ought to help you get started with basic fire control. 

It takes time to get this down. As an example, when I teach a class, my students usually go from total beginner on day one to having the above pretty well under control about two weeks later. 5 days a week, about 4 hours a day in the fire.

 

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  • Glenn changed the title to Coal/forge problem

The firepot is rectangular. The top picture is a bucket. I'm standing with my back towards the camera while forging and pump with my right foot. I kinda thought the placement of the firepot wasn't the ideal, but since the drive wheel need to line up with the axle on the forgeblower, it has to be placed like that.

My firpot is 235 mm long, 205 mm wide and 40 mm deep. That's about 9 x 8 x 1 ½ inch. I've been thinking/worrying that the depth may be too shallow (even though that shouldn't interfere with the forge getting hot?)

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You say it is best to have the firepot centered, would it work if I made an extension to the left, making it centered? I could try to make a simple table with two legs on the other end, and use some kind of hooks to attach it to the main forge table? Then I could build up the green coal in equal amounts on the sides.

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That would work.

From the pic it looks like your firepot is deeper than 1-1/2" deep. It looks like the lip of your forge is about 1-1/2". If you are correct, you could use fire clay to the top of your forge lip. This would do three things. It gives more depth to your firepot, getting you closer to 4" depth. It would give you a nice flat plane at the front and back of your firepot to keep your work well supported as it wouldn't sag. The way it is now, your coal would give some support on a long piece, but coal can move. Finally it would protect your forge from burning out due to heat. It most likely wouldn't happen no matter what in your lifetime, but it is a consideration. If you clay your forge, then you could add your extension at this height. As well as legs, you could make 3-4 nice forged brackets that would hook over the forge lip and bend up at the outer edge to keep the plate secure. No fasteners needed. I see it in my mind. Lol. The forge side of the bracket would extend into your forge. Then come down say a 1/2" on the outside of the lip. Outward ~6" parallel with the forge bottom, then up 1/2". Now you have a nice secure place to put a piece of half inch plate. And made by you in your forge. ;)

I'm curious, is your forge body cast or iron/steel?

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Nice idea! That's something I will look into.

The forge frame is probably made from iron/steel. It's very old, so I'm not sure if it's steel or iron. The table/plate is sheet metal.

DennisCA, in Norway you will find many different designs/versions of the 'feltesse'. When I bought mine it had the holes drilled for mounting the blower. Earlier today I checked/confirmed that I can move the firepot so it all lines up correctly.

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I keep a couple of firebrick in dry storage to increase the depth of my firepot when needed.  I even have a set of ugly "hot firebrick tongs" that are used with them and the gas forge door bricks..

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