Question about what material to use for a forge chimney. I have recently completed my new blacksmithing shop all I need to add is the forge chimney and I am stuck. Im planning on do something like this I Forge Iron*-* BP0394 Side Draft Forge. No my question is what to use for the bigger pipe that goes up through the ceiling and where to get it. None of the hardwares stores near me seems to have pipe larger than 10 inch and even if they did im not certain what I should get.

Ben, I found my 12-inch at a larger plumbing-heating contractor supply house (in Toledo), so it's out there. I wouldn't want to go smaller on the pipe, either. In another case where I wanted a short piece of 14 inch, I used two 7-inch pieces from Home Depot. It worked fine, just less convenient to have to put them together.

I use this design for my side draft hood.
Steel s-draft drawing
I didn't build the stand, mine is mounted to the forge and braced from the back wall of my shop. This thing really draws the smoke out and isn't complicated to build. I have a 12 inch galvanized chimney Ipicked up at a heating and air supply house.

I got my chimney from a store that sells woodstoves and such. 10" diameter SS double walled made for woodstoves and they had all the parts and pieces for mounting, etc, but I needed only the chimney to go through the roof. The whole thing sits in place by its own weight. Any hardware store should be able to order what you need if they don't have it in stock.

If you can't find 10" you can put two pieces of 5" together.

Frosty

I rolled my 12 " out of 16 gauge sheet metal

Mike Tanner

ide check your scrapyard i priced the double walled ss stuff for woodstoves ane it was out of my buget but scrownging at the local scrap/salvage yard i found a double wall pipe with all the stuff i needed . ( i think it was used for industrial furnace or similar) it was aluminum but shouldnt matter as there isnt as much heat as a wood stove produces and the hot part is the lower end anyway ... Good luck!

Ok so i got two pieces of 7 inch stove pipe linked together for the chimney now I just need a way to mount it. I am planing on using the method of having a ten inch pipe com off the forge an feed into the chimney so that only a few inches of the chimney extened into the structure. Now I am not sure how to instal/support it any thoughts?

use a colvert- the steel pipe they put under your driveway...12-14 inch 10 to 12 feet long or longer

Why not look at the inside of a water tank? It is fairly thick and about 5 feet long. Diameters I have found are 14 inch to 18 inch. As to support, just build a stand to rest the bottom section upon.

Why not look at the inside of a water tank? It is fairly thick and about 5 feet long. Diameters I have found are 14 inch to 18 inch. As to support, just build a stand to rest the bottom section upon.

Assuming you're talking water heater tanks, those tanks have nice 3/4 inch nipples welded into the top and might be incorporated into 3/4 inch pipe support struts if you simple turn the heater upside-down, leaving the top, now the bottom, on. I believe it would work real well for a side draft exhaust. Just an idea.

Somewhere there are some pics of Uri Hofi's chimney set up in Germany. It is braethtakingly simple and has increased my aready profound respect for that man. He uses stainless because it outlasts everything else.

The Set Up Is Not !!!!!!!!! In Germany
It Is In My Smithy And School In Israel.
Some Of My Students In Germany Did The Same But Not Those In The Photo's
Hofi

Mr Hofi,

That is a great design.

Any idea what the height and diameter of the round pipes are?

Thank you,

Don

Hello Don
The Ss Pipes Are 12'' Id
The Squer Tonel Is 13''x13'' 4 Degrees Dowen To Prevent The Rain Water To Flow Into The Fire .
The Hight Of The Chimney Is 10'
Hofi

Uri,

Is the chimney supported by the straps or by the square tunnel or both?

Rick
Dowen On The Tunnel There Is A 2'' High Coller That The Chimney Tube Is Seatting On .
And With A Coller Band Holding The Chimney With Straps Bolted To The Wall
One Can See It Very Clearly On The Foto
Hofi

When I said put two pieces of 5" stove pipe together to make a 10" piece, I didn't mean USE two 5" pieces. I meant snap the two pieces together along their locking seams to form a 10" diameter piece of pipe.

You can make odd sizes as well, a piece each of 8" and 6" will make a 14" diameter piece and so on.

Sorry for the confusion Mr. Hofi, I should've checked what I wrote before replying.

Frosty

Thank you for your sugestions all. I will look into something like what you use in your shop it looks like a really good idea!

My flu is similar to Maestro Hofi's, but I just ran the 12"dia pipe thru the wall via an elbow, and into the forge. I didn’t know if it would work because I didn’t see any others like that at the time. It does work, but probably not as good as Hofi’s, because I suspect his square tunnel provides a chamber for the gases to expand before being drawn up the chimney.

Hey Ben, did you and I speak at the Queen Cutlery show last summer?

I suspect his square tunnel provides a chamber for the gases to expand before being drawn up the chimney.

Why would it be important to expand the gases before entering the chimney?

It would create a draw like a carburetor in a car by speeding up the airflow thru the tighter spot and opening up into a larger chamber . Also the taller your chimney is the better your draw will generally be.Hope this helps

There Are Some Reasons For The ''squer Tunnel''
1 If The Tunnel Is Round The ''suction'' Of The Smoke Is Done Only In The Center And Not All The Smoke Is Been Sucked In.

2 The Tunnel Is Cut In An Angel That The Upper Part Is Almost Above The Center Of The Fire And That Increases The Suction.

3 The Tunnel Is Welded To The Coke And Tyre Steel Table In A Way That There Is Balance Between The Two Sections From Both Sides Of The Wall And There Is No Need To Fasten It Strong Or Heavy.

4 Because The Cross Cut Of The Tunnel Is A Bit Bigger Then The Chimney The Air And Smoke Slows Down And The Ash Is Falling Down On The Bottom Of The Tunnel And Every 3-4 Years I Open The Rear Cover And Clean By This Almost No Ash Is Going Into The Environment

5 The Upper Part Of The Chimney Is Used To Put A Small Gas Forge For Pree Heating One Can Not Do It With A Round Tube

6 The Connection Between The Pipe And The Chimney Is Very Simple And Stable No Need For Special Elbows Or Arrangements

7 From The Architectural Design It Is Nice And Very Impotent For Me
Hofi

Unlike a car engine where it is drawn through a small venturi then into a larger volume manifold, Hofi has a 13 x 13 tunnel is 169 sq inches to 12 inches id or 113 sq inches. That is 67% reduction in volume.

An expansion chamber in the chimney close to the fire, such as a side draft hood where the smoke is drawn in, allowed to expand, then exits out a opening equal to or about the same size as the entrance, would seem to slow the smoke down. The only advantage I can see is to drop out any heavy particulate matter at the expense of slowing the draft.