Need for a chimney?

[nogrodoth]

So I'm building my first coal forge, it will be outside, essentially itl be just a table with a brake drum set into it. I am in a residential area so minimal/no smoke production would be great, so I'm just wondering is, will a chimney reduce the amount of smoke in an outdoor forge? Would it have a use at all?

Thanks

[ThomasPowers]

It won't reduce the ammount of smoke, just channel where it goes.

[nogrodoth]

What made me ask was the 55 forge blueprints, how they said the 'supercharger' allowed the smoke itself to burn..

 

"The fire creates a draft up the 6 feet of 24" diameter chimney and in doing so sucks in air through the opening. This fresh air then mixes with the smoke from the fire, (I have noticed the little tornados of air and smoke being mixed at both sides of the opening), the fire burns the smoke, which creates more draft from the heat, which pulls in more air. The end result is smoke being burned, and what is not burned is diluted with fresh air. The forge was designed for outside use so the 24" diameter chimney is not a problem. Using the same coal, same blower, same fire pot, and the same tuyere as the original 55 Forge, the 55 Forge with the Supercharger (the 55 gallon drum on top) produces much less smoke."

 

Do you need a chimney/thing that big (~5'x2') in order to get that effect?

 

And thank you for the extremely quick reply:P

[Charles R. Stevens]

If you use a stack, at least 12"D it will pull a lot of air in to delute the smoke, glens "super charger" draws a bunch of air, and often the smoke will ignite and suport flames above the coal. If you light up with coke and manage your coal so that you have plenty of coke and don't dump a bunch if green coal in the fire you will have minimum smoke. Certainly les than crippling hamburgers.

[nogrodoth]

Ok. Thank you:)

[Charles R. Stevens]

Another trick. Back in the day they made a smoke hood that swiveled over the fire pot, and drew the smoke to the inlet side of the blower, that allowed the smoke to burn wile starting green coal.

[ThomasPowers]

I believe that is shown in "The Complete Modern Blacksmith", Weygers

[Glenn]

The secret is to punch a hole in the top of the coal covering the fire. This allows the flame to escape (think volcano) and it will burn a lot of the smoke. Using coke instead of green coal reduces the amount of smoke generated. Dilution of the remainder of the smoke with air reduces the appearance of the amount of smoke. Work all three and you can be almost smokeless, almost being the operative word. 

 

Drive behind a cattle truck or a pig truck going down the interstate. You can smell it for miles but never see the animal. You can always tell when something upsets a skunk, but you may never see the actual skunk. Using coke, letting the fire out the top of the coke, and then diluting the remainder of the smoke does not eliminate the flavor or characteristic aroma of smoke as the nose is much more sensitive then the eyes. But it does reduce the aroma as much as possible. 

 

All this smoke we are talking about is usually only present when you start the fire. Good fire maintenance will keep the smoke to a minimum as you forge.

 

The 55 Forge with the supercharger was developed to get the smoke up and out of the work area. It uses a minimum of materials, stuff that is usually on site anyway. I have used a side draft forge hood on the 55 forge with a 8, 10, 12, 14, 16, and 18 inch diameter chimney. The 10, 12, and 14 worked best. The height of all were close to the same and the 14 needed a bit more height to really work for me. 

[ThorsHammer82]

I don't use anything on my outdoor forge. There is only smoke when green coal is first light. after that you can't see the smoke, but you can smell it.

[VaughnT]

Using a chimney on an outside forge isn't a bad idea.  Even if you can't see the smoke, the chimney is still drawing it up and away from you.  The higher the chimney, the better the dispersal, too.

[ThorsHammer82]

I should clarify. There is only smoke when there is green coal put on the fire. But there are still fumes. I make it a point to stay out of them. Having a chimney would get them up and away from me. but that would also reduce the portablilty of my set up and I can't see myself doing that right now.

[Charles R. Stevens]

A wind shield on your portable forge will help direct the smoke up. For some reason the boundary layer of air around walls seems attracts smoke.

[ThorsHammer82]

Charles,

 

it's the eddy (sp?) effect. Think of a river and the water flowing down it is the wind. as the water goes around an obstical it creates and eddy in the slack behind the obsticle drawing things into it like floating branches leaves, ects. the same effect happens as the

wind goes around an obsticle. thats why they use water tunels for aerodynamic testing. They can use dies in the water to see the eddy effect if there is any.

 

I don't have a lot of wind, and I'm working right next to my shop which acts as a wind break so I don't have a lot of issues with the smoke/fumes not going straight up.