Joel OF Posted November 15, 2015 Share Posted November 15, 2015 Hi folks, to cut a long story short I've been forced into a horrible situation that involves changing workshop and at the same time being thrown into switching from using a bottom blast forge to a side blast forge. The real problem is I don't have any time to get used to the fire change as I have to make and design a range of Christmas market stock now in 5 days as my first market is next weekend. I'll start by saying I have trawled through lots of old threads looking for the answer but haven't had any joy. I'm sure now that I've said that someone will link me to the one thread I haven't yet found that details everything I'm asking... With regards to side blast forges, (particuarly water cooled), putting aside the depth under the tue and focusing solely on the coke level above the centre line of the tue...I can't seem to find a coherent theme or constant depth suggested. I have restored a side blast forge without any cut outs at the sides and I have followed the advice in The Blacksmith's Craft book to make the sides 3 inches above the centre line of the tue. I have saved the illustration they give in the book which shows this but to avoid any copyright infringment I won't upload that. I hope instead that John B won't mind if I upload an illustration of his (that he included in a reply to someone else on an old thread on a similar subject) that I saved a while ago, as the picture is virtually identical. (Yes, I am that sad, I save illustrations of fires for my own reference). That would suggest to me that your fire is always going to be at least 4 inches deep, (3 under the sides, 1 inch over your work on top). However I've read from some very experienced smiths on here that the centre line of the tue could be only 1 inch below the sides, or even at the same height. So if you're laying a long bar across the fire and resting it on both sides, that's a massive difference in fire depth and I'd assume that a fire only 1 inch deep would be rich in oxygen and you're work would be very scaley and hard to fire weld(?). Frustratingly I was confident at fire welding on my bottom blast forge but now with the change I'm reluctant to design any stock that includes fire welds as I can't afford the time to battle dirty welds that fail because I've got the fire depth wrong. I expect I'm overlooking something obvious, I usually do. As I say the situation I'm in is a bit nightmare-ish (feeling like I'm working in someone elses workshop too so I feel disorientated too) so if anyone can offer some words of wisdom it'd be much appreciated. Cheers Quote Link to comment Share on other sites More sharing options...
Charles R. Stevens Posted November 15, 2015 Share Posted November 15, 2015 Depends on two things, fuel type and tuyeer size. For a charcoal forge 3/4-1" is the animal, 3" below the tuyeer opening, and 4" above. Same for coal in this size but charcoal realy only likes this one size, creating a 6" fireball. Glenn posted a chart that shows deapth to the top of the tuyeer opening under a descusian of air volume needed for coal forge. http://www.iforgeiron.com/topic/29282-how-much-air-to-forge/ Note, 3/4" schedual 40 pipe is close to 7/8", wile 3/4" schedual 80 is 3/4", most of us use the less expensive pipe and go a bit deaper Quote Link to comment Share on other sites More sharing options...
Joel OF Posted November 15, 2015 Author Share Posted November 15, 2015 Cheers. I'm a coke man. Quote Link to comment Share on other sites More sharing options...
Everything Mac Posted November 15, 2015 Share Posted November 15, 2015 That's interesting - I have a PDF from Mark Aspery that says the forge pan should be 9.5-10" deep. And I'm sure I've seen it written that the centre of the blast hole should be about 4" from the bottom of the pan. Maybe it's worth contacting Mike Judd over at Greystone forge mate. - he's made one or two in his time. He should know a thing or two about it. Failing that I'm sure JohnB will be along shortly. There was a build thread on here where the guy made a side blast forge with a side draft chimney (it looked ace) but for the life of me I can't find the thread or any pictures. I'm sure it had dimensions in it. Andy Quote Link to comment Share on other sites More sharing options...
Joel OF Posted November 15, 2015 Author Share Posted November 15, 2015 The depth of the hearth on the one I've restored is 12 inches. As I fabricated the bosh and tue all in one but didn't taper the tue, I've shimmed up the back of the bosh to tilt it down. In practice that's nudging my tue air hole down to 3.5 inches from the top of the sides and 8.5 inches off the bottom. I made the tue with what I had available so it's 3 inches O/D with a 1 inch air hole. I'm going to drop in on the local ol' boy farrier/blacksmith who runs (or ran) coke forges to grab some bags of ash off him, I'm sure he'll have a pearl or two. Quote Link to comment Share on other sites More sharing options...
Everything Mac Posted November 15, 2015 Share Posted November 15, 2015 Fair enough Joel. I'd be interested to see how you get on. I've taken a fancy to fabricating a small side blast myself so I'll be interested to see how yours performs. Best of luck with it. Andy Quote Link to comment Share on other sites More sharing options...
Joel OF Posted November 16, 2015 Author Share Posted November 16, 2015 12 hours ago, Everything Mac said: I've taken a fancy to fabricating a small side blast myself so I'll be interested to see how yours performs. I typed out a long answer to this earlier but it disappeared into the ether when I hit reply. In short I'd say go for it, even though I'm bumbleing around inefficiently I can see the benefits. I suppose my main concerns are whether I'm burning coke than is necessary with the fire at this depth, and how much higher would I want to build the fire up to hit the sweet spot for fire welding? My bottom blast forge was about 4 inches deep, for fire welding I'd build that up to about 6 inches and have my metal in at 4 inches. Quote Link to comment Share on other sites More sharing options...
Everything Mac Posted November 16, 2015 Share Posted November 16, 2015 If I were you Joel I'd build it deeper/ bigger for now and if you find it's too big you can always cut it down? All the best Andy Quote Link to comment Share on other sites More sharing options...
Charles R. Stevens Posted November 16, 2015 Share Posted November 16, 2015 3" is about minimum to provide insulation for the bottom. The depth from the top is not from the top of the box, but from the side notches. Quote Link to comment Share on other sites More sharing options...
Joel OF Posted November 17, 2015 Author Share Posted November 17, 2015 15 hours ago, Charles R. Stevens said: The depth from the top is not from the top of the box, but from the side notches. I haven't got notches / cut outs in the side walls, the sides are the same height all the way along. Quote Link to comment Share on other sites More sharing options...
Everything Mac Posted November 17, 2015 Share Posted November 17, 2015 Just to really stir things up Joel a buddy of mine has a greystone forge. I'm told the pan is 8" deep with the blast hole at 3.5" from the bottom. (Though there is a firebrick insert below) That would suggest you've at least 3" for the top of the sides to the blast hole... Andy Quote Link to comment Share on other sites More sharing options...
Charles R. Stevens Posted November 17, 2015 Share Posted November 17, 2015 If you are rebuilding an existing forge, go with the original desighn, if its to shallow, a few fire bricks will dial things in for welding (or just cosintrating/conserving fuel) on can also slot the hole that the tuyere comes in so you can dial it in. Quote Link to comment Share on other sites More sharing options...
Joel OF Posted November 22, 2015 Author Share Posted November 22, 2015 I seem to be getting the hang of managing this new fire. All in all I guess the thing that's been making me scratch my head is how can side blast fires get away with being so shallow in comparrison to bottom blast fires? A couple years back when I researched how to make a bottom blast forge I constantly heard to make the pot 4" deep. I guess that extra depth is because in a bottom blast your work is placed in the path of the air, so you need more fuel to soak up some of that air, but with a side blast your work is above the path of the air meaning your work doesn't get so oxidized??? Quote Link to comment Share on other sites More sharing options...
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