OUR $100 WOOD-BURNING FURNACE SAVES US $1,200 A YEAR!
(Page 2 of 5)
November/December 1975
By the Mother Earth News editors
THE MATERIALS WE USED
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After Harvey and I had figured out what we were going to build, we began to scrounge and buy the materials we needed for the project. They included:
1 barrel stove door (used and free)
6 sheets of 20-gauge steel (mill-ends which cost 7¢ a pound)
6 sheets of 16-gauge steel (same as above)
35 running feet of 2" cast-iron pipe (scrounged)
6 2-foot sections of 6" stovepipe, one "T", and 4 elbows (bought new for $15.00)
Ductwork (made to fit installation by local tin shop for $58.00)
Nuts, bolts, welding rod, assorted hardware ($10.00)
The steel sheets listed above cost us a total of $20.00 and our labor was free. I repaid Harvey for his time by helping out with a job that he needed done.
HOW WE BUILT OUR WOOD-BURNER
The firebox in our furnace is 32 inches tall (including grate and ashpit) and 36 inches long. The combustion chamber is 28 inches wide at the top and tapers (so that the wood within will fall together as it burns) to a width of 24 inches at the bottom. This means, of course, that the top of the firebox measures 36" X 28" and the bottom, 36" X 24". We used 16-gauge steel for all surfaces that come into direct contact with the blaze.
The firebox's front face is a 36" X 36" square of 16-gauge steel. Its upper corners each extend out (4 inches) and up (4 inches) from the "real" upper corners of the furnace's combustion chamber. The lower corners of the firebox's face also extend horizontally 6 inches past the lower corners of the combustion chamber. No, this wasn't a mistake. By leaving the strip of "extra" plate across the top and down both sides of the firebox's "real" front, we were also forming the front face of the air jacket that we knew we wanted to fit around our furnace.
The rear face of the firebox was handled entirely differently than the front. It's -a piece of 16-gauge steel that measures 28 inches across the top, 25-1/2 inches along the bottom, and 20-1/2 inches down each side. This somewhat irregularly shaped slab of flat stock is set three inches forward of the rear edges of the combustion chamber's vertical sides, positioned so that its lower edge is 11-1/2 inches above the floor of the ashpit, and welded in place. (When the furnace is in use, the gap left along the bottom of this back plate allows smoke to exit from the firebox.)
Once we had the front and back of the firebox welded to its walls, we fastened our grate supports in place. These supports are two 36" lengths of scrap angle iron welded to the inside surfaces of the combustion chamber walls. The angles are 36" long, extend the entire length of the firebox, and are positioned to hold the grate horizontally and six inches above the floor of the ashpit.
The grate itself is nothing but a dozen or so cut-to-fit lengths of 2"-diameter cast-iron pipe laid crossways on the angle irons. The sections of pipe are movable so that we can jiggle them with a poker when we want to make ashes fall through to the ashpit below.
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