Maine hammer

? About side blast forge's

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From what I see and read is that the tuyere is set up off the bottom of the fire box about two to three inches and most of them look to have a id of 3/4 to 1 inch. Is this correct information or am I not reading and seeing right?

Edited by Maine hammer

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I was told to lift the centre of the tuyere to be level with the top edge of the hearth.

The reasoning being to have the centre of your fire high enough so you could heat the centre of a long bar resting on either edge. 

I filled the box with a mix of earth and ash up to 1'' below the outside edge so you could have a layer of coke drying off without it all falling over the edge. To much fuel around the fire and you can have problems preventing the fire from walking. 

The earth and ash was a bit higher around the tuyere. I scooped out a "swan's nest" directly in front of the tuyere to contain the fire. This was hemispherical in shape and about Ø200mm (Ø8").

Later on when I acquired a power hammer I laid a lump of 50mm square bar across the front to contain a longer fire, before I threw it all away and went for a flat plate bottom blast system. The flat plate with a double row of holes along it was much better for long fire / long heats 600mm (24"). I used to drop on pieces of 12mm (1/2") plate to cover up some of the blast holes if I wanted a shorter fire / isolated heat.

I now use the hearth primarily to support my small gas furnace, I don't think I have lit the fire for 15 years. Last time was to show a student what a fire weld was.

You may like to consider my heat source development and whether you might learn from my experience and cut out the coke/coal hearth altogether…go straight to a gas furnace.

Alan

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Under the tread on how much air pressure for solid fuel forges Glenn posted a good chart.

2" of insulation under the fire, offten a pair of firebricks to keep you from digging down to deep. 1" to the bottom of the tuyree opening.  Then depending on the size of your tuyeer how deep bellow the sides of the box is the top of the tuyeer. 

There is a good illistration in everything mac's post on portable side blasts. 

Now charcoal is rather limited in tuyeer choices, 3/4-1" work best (a 3/4" schedual 40 pipe is about 7/8" ID) this gives you about a 6" heat zone. Unlike coal more air dosnt help make a bigger fire, it cools the fire and wastes fuel. More tuyeers are needed. 

Lastly it helps to have a provisian to keep slag from getting under the tuyeer. Often two fire bricks with a hole notched between them form a back wall for the nest (water cooled tuyeers have a big flat nose so this isnt an issue)

 

So if you want to use both coal and charcoal, a 7-8" deap box is good. 2" from the bottom, 1" for slag, 1" for the tuyeer, 3-4" for fuel bellow the center of the fire. (Your milage may very so be prepared to notch the sides to move the long stock down to the fire center.

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I now use the hearth primarily to support my small gas furnace, I don't think I have lit the fire for 15 years. Last time was to show a student what a fire weld was.

You may like to consider my heat source development and whether you might learn from my experience and cut out the coke/coal hearth altogether…go straight to a gas furnace.

Alan

There is a great deal of wisdom in these last two sentences which I fear will be lost in the technical discussion to address the original questions.

Bottom line is not to be bound to something specific unless you are after historical accuracy rather than optimum efficiency.  I used to be very stubborn about always using a coal fire for all of my work but lo and behold, a gas forge came along and now all the coal forge does is collect dust.  Next thing on my agenda will be induction...until something better comes along.

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Building scrap is cheap, as are scrap pallats and yard waste. Propain costs $ wile scrap wood converted to charcoal costs time/labor. Furthermore often one needs a pair or three gas forges for effency. A single burner, a double and a one brick. 

Each fuel has its proes and cons, I use all three. 

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There is a great deal of wisdom in these last two sentences which I fear will be lost in the technical discussion to address the original questions.

Bottom line is not to be bound to something specific unless you are after historical accuracy rather than optimum efficiency.  I used to be very stubborn about always using a coal fire for all of my work but lo and behold, a gas forge came along and now all the coal forge does is collect dust.  Next thing on my agenda will be induction...until something better comes along.

Yes indeed. That is exactly the point.

I almost ordered an induction plant earlier this year. But the project it would have been paid for by, and perfect for, evaporated…one day…one day.

Alan

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