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Charles R. Stevens

Anatomy and a brief history of simple side blast forges

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So I was asked to try and impart what I have learned about designing a side blast forge. So I will  give it a try. 

First, how I came by my knowledge. I started by asking members from England about their forges, and I googled commercial English forges. I went so far as to read adverts that had pictures of old forges for sale. 

Then I asked another member, our expert on Civil War blacksmithing. He shared some blueprints for traveling forges, mountain howitzer pack forges, and navy portable forges of the era. 

Then I started reading everything I could find on Iron Age and Viking-era forges, to include side trips into African, Iron-Age European, and Viking-era direct-process smelters. 

I looked at Japanese sword forges, but I didn't find much coming out of Japan.

(The rest of the world seems scarce in information on early and primitive forges. Probably because either they are not posting much archaeology on the net from Africa and the Near, Middle, and Far East, or because Google is filtering out non-English content.)

I also rooted through pre-copyright manuals and trade magazine anthologies, third world development extension resources, and other smiths' personal websites. 

Armed with this information, I built a box, and dug a hole. I lit a fire and  saw what I got. Then I modified it and tried again, and so on. This was the Mark I dirt box forge. 

Then I built the just a box of dirt (JABOD) forge and posted it for all of you. 

I have not stoped experimenting and reading and am ready to try a third version.

So let's get on to what I think I know.   

 

First we will examine the oldest design, a simple bowl. There is some speculation that after the blow pipe, a trench was dug, flat rocks went over it, and it was covered up.   

Easy enough: your 3/4" schedule 40 pipe tuyere is 3-3 1/2" from the top, so there's 1" under the tuyere to the bottom of the bowl. The bowl is 6-8" across at the top. 

You can put the tuyere coming in right at the bottom for charcoal, but it's nice to have a place for ash to collect. 

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Second up, is an Asian/African style: a trench. The same basic depth and tuyere location holds true but we have a 4" wide and 8" long trench. On each side is a wall 3-4" high to help contain the charcoal.

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The third is a Viking-era forge with a bellows stone. The historical record shows a 3/4-1" inside diameter tuyere. As 3/4" schedule 40 is 7/8" ID. So near perfect. Make sure to use a rock that won't explode when heated.

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Number 5 is essentially a cavalry traveling forge. The back is hollow; I assume it's cooling the plate and preheating the air (early regenerative forge?). 

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So these designs are suitable for up to 1" stock and either charcoal or coal. If you're burning coal and want to heat larger stock, just scale up with a deeper fire and a larger tuyere.

Now charcoal is finicky and doesn't scale up as well. With a charcoal forge, we play a different game: multiple tuyeres 5-6" apart, either in line along a trench or around the circumference of a bowl:

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Finally, here are a post-Civil War smith's recommendations for the tuyere sizes of coal forges:

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Thank you for all your hard work putting this together. I admit to being a "gadget guy". I often use the most complex, over engineered version of whatever tool I can get my hands on when I would be better served with the simplest version of the same tool. It is comforting to know that my forging could continue with minimalist equipment if events made it necessary. If I ever do get round to building one of these I'll post it but I already feel like I've benefited from your work just by having the information.

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"If events make it necessary" there will be a lot of very nice smithing stuff available at my place(s)!

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This was a team effort, I had an editor! But thank you. At some point I imagine I may have to acualy write something for instructables and a magazine article. We need to get some informations out there to compete with break drums and carving London patterns out of rails.  

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Awesome!

Thanks for the info Charles. O like the look of the one with the multiple tuyere's around the circumference of the bowl..... but i am jumping way ahead of my self I still have to build the one that you and I were discussing. Chellie saw the air mattress pumps that you directed me towards at our Walmart. I am hoping to get around to building it soon. I have been busier than a one legged man in a you know what contest haha. Have a blessed one fellas and thanks again for the post Charles!

 

Also please let me know if you write an article for a magazine!

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The multi tuyere ones are for long stock or large stock. Classics will heat 1x1x6" now if your doing long scrolls or small anvils with charcoal you should be fine. If your using coal you go with a bigger tuyere and deeper hearth. 

Is the article clear enugh? 

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I actually was reading this earlier. Thank you Mr. Stevens. I think I understand it. I'm not good with the more technical side of building a forge. Tommie understands it much better than I. But the drawings you have here give me a good visual and it seems to make more sense in my simple brain.

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Oh no, your research and explanation and drawings are excellent! I just tend to be a little thick skulled when it comes to reading or having someone explain things like this to me. Just ask Tommie;) I seem to learn by doing easier. The side blast with charcoal is something I really want us to do. We are running bottom blast right now and by reading, I have learned that it's not particularly charcoal friendly. Also by experience. I haven't done any forging in awhile now and I chalked it up to different excuses. I have had a lot of unexpected babysitting of two very young grandkids. Just me and them and fire doesn't sound like a good idea...but it was really a couple pieces I did, I was burning the steel in the fire and got a little disheartened because I thought maybe I wasn't very good at it. I am sort of a perfectionist. But after Tommie talked to you and I have read so much about side blast versus bottom blast for charcoal I have hope that maybe once we get a forge worked out I will do better. I love this craft and I find myself thinking about it a LOT. I appreciate the time you put into it to help folks like us out. I could never repay you in a lifetime.

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I get to daydreaming and burn up steel with electric blowers, lol. I am much better off with manual air. It's all learning curve.

as to dealing with little ones, I say a chain link dog kennel with a swing set in it beside a trailer set close to the interstate in Kentucky, looked like a great idea ;-) 

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Yeah the hairdryer seems intense. We have it connected with an LB conduit and even with the gate opened all the way, it seems like a lot. Mr. Powers pointed out maybe too much air and not enough fuel or maybe both. He is right but haven't figured out how to balance it. Maybe a monster pile of charcoal? But I really like your suggestion of the air mattress pumps. 9.99 at Wal Mart. I used to work there. Don't miss it, but I miss my discount card. It was awesome at Christmas time! 

The dog kennel and swing thing sounds like a plan. These little rug rats like working with you. They love hammers and nails and tools of all sorts. They wouldn't be content with playing, they want to help you work and build things! They helped Tommie build our last set of rabbit cages.

That's too funny! I didn't know you had just posted Tommie

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Yeah the hairdryer seems intense. We have it connected with an LB conduit and even with the gate opened all the way, it seems like a lot.

The thing about the conduit fitting is that it doesn't close the tuyere down to nothing; some amount of air will always get through. You might want to try a gate valve, which can taper the blast from a raging gale down to a gentle sigh. I did a thread about my homemade version ; check it out. 

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I use a 3/4 inch valve on the JABOD forge, I have added a "T" to exaust air because its quieter.  Excess air is the bain  of charcoal. 

 

I find the bed pump to be meditative and quiet. Around here I had to go to Academy sports to find the model I wanted. As it is bigger and has a bottom outlet. 

 

 

I have to get my mark III JABOD forge together for the state meeting, every one demotes with a $1000 or more in kit, I want to show up with $100 or less. Just to show the kids they don't need a bunch of money.

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JHCC

Thank you for directing me to your posts on the gate valve. It's got my brain turning. Brilliant use of on hand materials. That is right up our alley.

Mr. Stevens

I am the same way for quietness. The hairdryer is dreadfully noisy. But I think since we have this one already, we can modify it for less air flow with a gate valve and build a side blast with the manuel pump as time allows. Tommie is the builder and he is gone for work a lot. He goes full steam trying to get things done while he is home. IFI sure helps him with the blacksmithing part of things we do. It is a great thing you show people you don't have to have a lot of money to be able to smith. I had that idea coming into this myself. I bought a book called The Home Blacksmith by Ryan Ridgeway, DVM before Tommie found IFI. He conveys the same idea for the most part. Except he doesn't like RR track anvils. But you and many others here put a lot of time in TEACHING us all how to do it  and on the cheap, for free. Just have to put the studying and doing time in. You should write a book Mr. Stevens!

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When I was a kid we had an old pop-up camper in a fenced in area with a swingset....

I still have the "O.K. Corraled" sign dad made. (Ornery kids, according to my mother)

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That's a lot of good information.  I am still in the process of designing a side blast and was wondering what book that last picture came out of?

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