Hi all,

 

The forge is ready for a chimney and I've decided to try the one in the Blueprint section called a Hofi style chimney.  

'?do=embed' frameborder='0' data-embedContent>>         The instructions seem simple:  A 13in x 13in x 4ft box open at the forge end and on the other end is a 2" high collar for a 12" chimney.   Is this all there is to it?  No smoke shelf or anything, just a straight box to a 12" chimney which extends higher than the roof?

 

If so, I will find a fabricator to begin the box part as soon as he can (I can handle the chimney part).  Would any of you who have worked with a fabricator have a rough ballpark guess as to what the cost might be for something like this?

 

Thanks, I appreciate your help.

 

Larry

if you are able to weld, I'd do the table yourself. To machine a 12" disk with 8 holes I was asked for about $60. I'd say about $100 as an absolute minimium.

The chimney can be a culvert pipe or other material. The horizontal box can be fabricated from sheet metal or plate steel easily enough. Think of it is two L shaped pieces of metal connected to each other. Nothing wrong with it being round either.

I can't weld but I'm happy to see that it shouldn't cost more than a couple of hundred dollars.  I already have the chimney.  Thanks for your help guys.

no need to weld. sheet metal, and angle iron and either bolts or rivots could make that square section. than just add some high heat sealant or tape to keep the smoke/fumes in the pipe and you're good to go.

So I see this is a real old thread, but if this goes through, Thor, thankyou for that post.  Sometimes the most simple solution is the one I should have thought about long ago, before I wasted my time making two chimneys that almost worked!  What's even funnier is that I looked at the angle iron trick for a super sucker chimney but still decided to test never welded sheet metal skills... phew. Great quote to.  Glad this topic was posted.  Off to build another- hopefully functional chimney!

I was quoted $145 for the box with the end closed and the 12 inch duct ring, by a sheet metal place in San Francisco.  i think anyplace else would be somewhat cheaper.

If you figure at least $60 an hour (bet it is more) not a bad price. Tho 12" round with a "T" or a "90" has worked for others.

12 x 12 is 144 square inches.

The area of a 12 inch diameter pipe is 113 sq. inches

 

*  You could use round instead of the square. (Think HVAC for either or both)

 

* To make the box you can use angle iron and available flat metal. Just cut and screw it together.

 

* 12-ft x 26-in 31-Gauge Plain Corrugated Steel Roof Panel is $15. Fold it 90* and screw 2 pieces together to form a 12x12 inch box. One for the inside, and one for the outside chimney.

 

You do not have to make an exact copy of the project. You only need an idea from which to build YOUR project with the materials you have available in YOUR location. 

 

----------------------

 

I have made chimneys from the inside metal tank found in a hot water heater (Thank you Jerry Carroll for that idea), the outter skin from the same hot water tank, spiral pipe (HVAC), snapping two pieces of stove pipe together to form a larger diameter. corrugated steel roofing, 55 gallon drums, grease drums, 5 gallon metal buckets. a fan to blow the smoke away, and the list goes on. The idea is to get the smoke out and away from where YOU are.

 

 

QUIT LOOKING, START SEEING

Do not look for an object, see possibilities 

 

If you look for a hammer, only a hammer will work. 

If you want to hit something, most anything will work.

Or as as some one reminded me (who was that, Glenn?! Lol) a 55 gallon drum is 3x6 FEET of sheet steel. Working sheet isn't all that hard, it cuts with large snips, or a chisel a bench, clamps and a piece of 2x stock or angle iron, sheet metal pliers and a hammer and a square edged peice of hardwood or steel scrap.

I take it that I was wrong thinking that 6" black stove pipe would work for my brake drum forge? Glad I didn't spend any money on it yet. Forge is under the carport just at the edge, will take 10 feet of pipe to get it above my roof. I can't light forge while Wife is home. If she even get's a whiff of coal smoke she is on me for it. Neighbors are not too happy either, though they are all over a 200yds away at least. I was hoping that 6" black would work as it is not crazy expensive and not too ugly. Is 12" the recommended size? Will snapping two 6" together give me 12"? I could probably buy 3 sticks of 6" for the price of one stick of 12"

Will snapping two 6" together give me 12"? I could probably buy 3 sticks of 6" for the price of one stick of 12"

Yes

Two 6" diameter will give you 3x3xPi =28.28 x2 = 56.5 square inches
One 12" diameter will give you 6x6xPi=113

So to roughly equal the cross sectional area you would need four 6" diameter pipes to one 12" diameter and five or six to equal a 12" square trunking

My old Alcosa hearth had a 36" square bed and the hood had a 10" diameter (79sq. in.) upstand to take the flue sections. I increased that to 12" square (144sq.in. when I converted it from a water cooled side blast to a long slotted plate base for long heats. The 10" could not cope with the larger fires.

Alan

Circle Circumference = 2 π r
Circle Area = π r2

Circumference of 6 inch is 19 inches 

Area of 6 inch is 28 sq in.

 

Circumference of 12 inch is 38 inches 

Area of 12 inch is 113 sq in.

 

You are not running twin 6 inch pipes but are making a new pipe with 2x the 6 inch circumference.

Circumference of 6 in pipe 19 inches x 2 is 19+19 or 38 inches. 

38 inches is the circumference of a 12 inch pipe.

Ah, I read "snapping two pipes together" as just that, making a double barrelled flue.

The 6" black stove pipe over here is vitreous enamelled and therefore would be a pain in the neck to cut open and reform into a larger diameter.

I don't know why but the the orientation of images when I post them seems to be entirely at random! Is there a way to ensure that they remain in the aspect that they display on the camera and original computer.?

Stove pipe and HVAC here are shipped open and on location are fitted together and snap lock. 

I went back and re-read thread, 12'X26" corrugated roofing panel. I have a pile of barn metal just like that. Thanks for the money saving tip. As well as the math lessons. Nice builds above though I must say. If and when I enclose work area I will build a nice one of these. Thank you all for sharing.