Black Maple Forge Posted March 22, 2009 Share Posted March 22, 2009 Not that I don't like my old chimney, but it when I forge, I practically have to scrub the soot out of my hair:o! I am thinking about making a side draft instead. I hear that 10" round pipe or 8" x 13" masonry works best (Coal Information). My question is, could I give or take a few inches on the brick chimney and have it work as efficiently? Like 7" x 14" or 8" x 14"... (All about getting bricks to fit well using the same size bricks) Thanks! Quote Link to comment Share on other sites More sharing options...
Glenn Posted March 22, 2009 Share Posted March 22, 2009 There is some discussion on the fluid dynamics of how the smoke moves within a particular configuration. To start the discussion, are square inches of area equal to square inches of area? For example does the smoke move/flow equally, better, or less, in a 100 square inch round opening or a 100 square inch rectangular opening? Quote Link to comment Share on other sites More sharing options...
Glenn Posted March 22, 2009 Share Posted March 22, 2009 To give some numbers to the stack sizes you mentioned: 10 inches round is 78 sq inches of area. 8 x 13 inches is 104 sq inches. 7 x 14 is 98 sq inches. 8 x 14 is 112 sq inches. Quote Link to comment Share on other sites More sharing options...
Hofi Posted March 22, 2009 Share Posted March 22, 2009 When one use a round chimney then 100% of the area is working as suction but if one use a squar or rectangle chimney one have to deduct the corners because all the 4 corners are causing big friction and the air in the corners is mooving very much slower. To calculate the righ area when useing sqar or rectangle one have to diduct aprox 15% off from the calculated area. 12x12''=144 less 15% =122.4 squar '' hofi Quote Link to comment Share on other sites More sharing options...
Hofi Posted March 22, 2009 Share Posted March 22, 2009 The suction of 12x12'' chimney will be only a bit more effective then 12'' round hofi Quote Link to comment Share on other sites More sharing options...
rokshasa Posted March 22, 2009 Share Posted March 22, 2009 you could also line the brick chimny with 12" dia. pipe if your not really sure about the mesurments, but that ristricts you to a square look. i use 12" dia pipe with a 10" square hole for the openning it works great Quote Link to comment Share on other sites More sharing options...
Black Maple Forge Posted March 22, 2009 Author Share Posted March 22, 2009 (edited) Glenn, Good point. I am curious to whether a round 10" x 10" will draw as much/as well as a square/rectangle 10" x 10". Does anyone know? Edited March 22, 2009 by Black Maple Forge This is a better response! :D Quote Link to comment Share on other sites More sharing options...
Jeff Bly Posted March 23, 2009 Share Posted March 23, 2009 When one use a round chimney then 100% of the area is working as suction but if one use a squar or rectangle chimney one have to deduct the corners because all the 4 corners are causing big friction and the air in the corners is mooving very much slower. To calculate the righ area when useing sqar or rectangle one have to diduct aprox 15% off from the calculated area. 12x12''=144 less 15% =122.4 squar '' hofi You must have just missed this. If you are refering to the opening, I am sure the same fluid dynamics should apply. Quote Link to comment Share on other sites More sharing options...
Black Maple Forge Posted March 23, 2009 Author Share Posted March 23, 2009 Oh. I didn't see that. Pretty nice to know! Thanks Hofi (and Jeff for pointing out my miss:rolleyes:)! Quote Link to comment Share on other sites More sharing options...
Black Maple Forge Posted March 23, 2009 Author Share Posted March 23, 2009 Another question. Would a rectangular brick chimney of 10" (wide) x 15" (long) work well to vent smoke? It would give a good ~127.5 sq." of area, but I am not sure if a longer and more narrow design would work well as a side draft.:confused: Has anyone ever used a chimney like I described? I see a lot of pictures where the forges are wider than long, but what about the reverse? Quote Link to comment Share on other sites More sharing options...
Ferrous Beuler Posted March 23, 2009 Share Posted March 23, 2009 beautifuliron.com covered this in depth with good supporting photography, I'm glad I printed that section awhile back because now it is under construction on the site. I hope it all comes back, lots of good stuff on beautifuliron. Quote Link to comment Share on other sites More sharing options...
blksmth Posted March 24, 2009 Share Posted March 24, 2009 My brick chimney was built around a 12" square clay flue liner. I used the liner as my building is wood and wanted the extra safety. That liner is less than 11" square inside. Normally 11" square inside might be a little small,but my chimney is 34 feet tall (2 story building) and the taller the chimney, the better it will draw. A friend liked my chimney/forge and had the same bricklayer build one for him. He was in a single story metal building, so didn't think he need the flue liner for safety. He built his chimney to go between the 24" on center roof rafters and so it was a little less than 2 and 1/2 bricks deep by 3 and 1/2 bricks wide. Therefore the inside dimensions were approx. 14" by 20". His chimney was 16 feet tall. That forge draws better than any forge I've seen. It draws better than my 34 ft. tall chimney that is only 11" square inside. I have also had a 16' tall 14" diameter metal chimney, side draft, that worked very well. I also had a 34' tall 8" diameter, side draft, metal chimney that required a fan in the wall to take out the extra smoke in the room. Quote Link to comment Share on other sites More sharing options...
blksmth Posted March 24, 2009 Share Posted March 24, 2009 Attached is a file. It shows my friends side draft chimney talked about in my last post. The chimney opening is about 14" wide right next to the fire pot. The approx. 6" long bricks around the opening taper back to a 10.5" wide opening approx. 5.5" back from the fire pot. The opening is approx. 16" high. The bricks around the opening are just hard bricks from the brickyard and seem to last well. I have seen some older softer bricks around forge chimneys deteriorate a little ( at least the bottom 2 or 3 on each side). The reason for the tapered bricks it to leave a spot for a pile of coal next to the chimney side of the fire pot, and to restrict the actual opening to approx. 10.5" by 16" as the smaller the opening the better the chimney will draw. This was typical of some well used older brick and stone forges. Quote Link to comment Share on other sites More sharing options...
Black Maple Forge Posted March 24, 2009 Author Share Posted March 24, 2009 Interesting designs. I didn't know that a smaller opening drew more smoke... :rolleyes: Quote Link to comment Share on other sites More sharing options...
Avadon Posted March 24, 2009 Share Posted March 24, 2009 That chimney is AWESOME looking blksmth! It looks like a miniature opening in some castle. I keep thinking a little troll is going to pop out of there. You do excellent brick work. Quote Link to comment Share on other sites More sharing options...
blksmth Posted March 25, 2009 Share Posted March 25, 2009 Thanks Avadon, I did not do the brick work, but I did design the forge & chimney. The same wooden form that was used for my forge opening was also used for my friends forge. That form now (with a handle) closes my opening to keep the heat in the room when I'm not using the forge. It was made of 2 pieces of plywood spaced about 4 inches apart with the back piece forming the narrow part of the opening and the front piece forming the front wider part of the opening. The bricklayer just laid the bricks around the form. Also, I will mention that both of those brick forges have a smoke shelf, but I wouldn't put one in should I build another forge. In other words I don't think they are necessary in forge chimneys. Quote Link to comment Share on other sites More sharing options...
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