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I Forge Iron

Side blast vs. Bottom Blast

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My forge is currently a nice heavy brake drum set into a dry stacked hearth of firebrick. Bottom blast.

Works very well, but the wide shallow brake drum makes a BIG fire... Haven't figured out a way to really control that yet. But coal is cheap. And I save my left over coke like a miser.

(Young beginning smiths, don't ever ever let someone tell you that a brake drum forge doesn't work. there is a, seemingly, popular site that has an entire page dedicated to bashing brake drum forges. Ignore it. My brake drum in a hearth is every bit as good as the Centaur firepot in a hearth I learned on.)

But... was looking at some side blast forges that are basically stacked firebrick with the blast coming in from a gap in the side.

I am intrigued. It looks you would have a lot more control over the size of the fire, and the location of the "sweet spot."

So. Bottom Blast vs. Side Blast. Discuss.

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A favorite subject of mine...

A fire in a bottom blast pot will form to a natural size and for all practical purposes, not get any larger. It is also hard to make it smaller - large amounts of water are about the only way but it's also possible to cool the fire and/or potentially crack the pot. The fixed size can be a convenience or a hindrance, depending on the type of work being done. One advantage is a well regulated fire depth - assuming the fire is managed properly. In addition, the bottom blast pot is relatively cheap to make and maintain so it was more prevalent in America in past centuries and why it remains very popular.

A fire in the side blast can be adjusted by using fire bricks to push the blast (and the subsequent burning fuel) into different shapes. However, the typical patent style, water-cooled, cast iron tuyere is not so cheap to make and can be difficult to use in cold climates without resorting to anti-freeze in the tank. The tank also eventually rusts out or the nose burns back to a point where a leak starts. Of course, you can always simply use a piece of pipe and let it burn back over time, which is probably the most cost effective way of obtaining a side blast.

I no longer use a side blast since I have propane for long heats and my Buffalo 12x14 bottom blast works just fine when I need a coal fire - BUT - a home made side blast can be an effective and relatively cheap way for the smith to make an efficient fire and I would have no problem going back to one.

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MY forge is a large brake drum. I had the same problem of controlling the fire. I mixed a batch of fire clay and portland cement. I placed the mud in the brake drum and formed a funnel shape with my hands. The bottom of the funnel is the size of my grate(3 pieces of 3/8 round), the top is the size of the brake drum........worked for me for the last 3 yrs.......Donnie

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Hello, other than introduceing myself this is my first post, just figured I'd add to what was said about the breke drums, I made mine out of a 16" wheel and it also works really good.
Another good refractory is just fire clay and sand.


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I have a solution that works for me on the side blast that doesn't require a water tank or burning pipe. I sort of mede an extension of my pipe by placing a brick on either side and on on top with the end of the pipe about 2 inches back from the fire. I would imagine a castable refractory nipple would work better.

Another potential benefit to the side blast is the air can come in a bit above the bottom of the fire pot which can help prevent clinker and ash from blocking the air flow.


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