How to Build the Vulcan Homemade Stove

Your commercial fireplace may be pumping most of the heat it produces straight up the chimney, but that open window to the sky can be easily replaced with this inexpensive Vulcan homemade stove.
November/December 1982
http://www.motherearthnews.com/diy/vulcan-homemade-stove-zmaz82ndzgoe.aspx
The Vulcan stove should be built to a size that will allow plenty of air space between its metal sides and the fireplace. A fan can then circulate air around the box to extract warmth.


PHOTO: LAMAR TOOZE

Learn how to build the inexpensive Vulcan homemade stove. (See the Vulcan stove photos and diagrams in the image gallery.)

While a warm, crackling fire in an open hearth on a cold winter's night can be wonderfully soothing, it's also pretty danged wasteful. The fact is that most conventional fireplaces are of dubious value when it comes to keeping a home cozy. Such devices typically have efficiency ratings of only 10% to 30%, and some especially poorly designed and/or constructed models will actually cool a room by venting its warm air up the chimney.

That realization struck me one winter's evening while a group of friends and I were sitting before (and seemingly inching ever closer to) a cheery open blaze in my home's family room. We were busily discussing the state of the world when the talk spontaneously turned to how chilly we all were. And although that subject led—in its turn—to comments about the high cost of heating oil, the balance of trade, the fate of the U.S. dollar, and the social habits and ancestry of various members of the OPEC cartel (as well as to the donning of sweaters!), the central theme was clear: Roaring fire or no, it was awfully damn cold in that room ever since economy had demanded that the oil furnace be turned off. So our little group decided to take action . . . and the Vulcan Stove was the result.

Now let me say at the outset that none of us is exactly what you might call an artisan (much less an experienced stove designer) . . . nor is the Vulcan beautiful. Nevertheless, we did manage to pool our resources, imagination, and sundry talents to develop a truly functional woodburner with the Vulcan homemade stove . . . and we were able to manufacture six of the units for a total cost (in 1978) of just under $300.

A Heater is Born: The Vulcan Stove

Our design criteria were limited in number but quite firm. Every member of the group wanted a stove, but nobody wanted a freestanding model that would require a brick pad and a pipe angling off into the nearest wall. And everyone wanted a firebox that would be both efficient and easy to tend. Finally, each of us wanted a heater that would represent the epitome of woodburning elegance . . . but in deference to our abilities, that last requirement was soon quietly forgotten!

We decided that our best bet was to design a stove that would fit inside an existing fireplace. No home remodeling would be necessary to install such a heater, and the firebox would be unobtrusive. As a bonus, the surrounding brick would—we imagined—serve as a heat sink, radiating the warmth of the fire for hours after the flames had gone out.

The Vulcan Stove is basically a simple rectangular box, fabricated from 1/4 inch-thick steel plate and provided with cooling fins—constructed of 1/4 inch by 1 inch by 1 inch angle iron— welded to its outer surface. Smoke is vented through a short length of 6 inch stovepipe that extends (partially collapsed) through the fireplace's damper slot. The remainder of that opening is closed off to prevent the passage of room air up the chimney. A small, inexpensive fan provides air circulation for the mostly enclosed woodburner.

And although the design may sound too primitive to be efficient, we've found that a Vulcan is perfectly capable of keeping us comfortable. It can, for example, raise the temperature in my family room—all 1,200 cubic feet of it—from 55 degrees Fahrenheit to 85 degrees Fahrenheit in about an hour! Considering that performance, as well as the stove's durability and decidedly modest cost, I think our homemade woodburner is a real demonstration of the virtues of simplicity.

Fabricating a Finished Firebox

The Vulcan was designed to fit my fireplace, and the dimensions referred to in this article reflect that requirement. In practice, however, the stove could be sized for just about any recessed hearth . . . as long as the builder leaves sufficient free space to allow a flow of air around the heater. I engineered our prototype to have a 10-inch clearance on the side facing the fan . . . a 6-inch separation between stove and fireplace brick at the opposite side . . . another 6-inch space at the rear . . . and an 8-inch gap at the top.

The first step in building a firebox is to mark and cut the steel plate as shown in the pattern in Figure 1 (see Figure 1 in the image gallery). You'll note that a 48 inch by 96 inch sheet will produce two stoves . . . except for their baffle plates, which you should be able to fabricate from smaller scrap, since each one measures only 12 inches by 22 inches (Save yourself some money by purchasing the metal plate at a salvage yard. Most of the steel sold there is every bit as good as new, and any rust can be easily removed with a sanding disk.)

You'll find that the task of cutting the metal with precision will be a lot easier if your torch is equipped with a set of "training wheels" . . . which clamp onto the cutting tip and provide an exact offset against a straightedge guide, while allowing you to steadily maintain the proper flame contact. If the cut pieces of steel begin to warp (as they sometimes will), you can pound them flat with a sledgehammer.

Your next job will be to tackle the primary assembly, using bar clamps and tack welds to attach the steel plate to an internal angle iron framework (which will both support the walls and guarantee right angles) and following up with finishing welds. Notice that the top and bottom sheets fit inside the side and back walls. (The upper piece should not be attached at this stage, though, since you still have work to do on the interior of the firebox.)

The angle iron framing at the front of the stove must be flush with the edges of the opening. Except for a few sections of bead that can be ground flat, weld only on the back "leg" of the angle iron . . . the facing surface has to provide a flat mounting point for the doors, allowing them to seal out room air. (Remember: A woodstove is supposed to be pretty much airtight except for the draft opening and the chimney.)

When the sides, back, and floor of the Vulcan have been assembled and welded in place, it's time to attach the front plate . . . being careful not to put a bead on the angle iron that extends below the plate (remember that airtight seal). The "factory smooth" edge of the top front sheet should be placed at the bottom, where it'll form an even mating lip to match the upper extremities of the closed doors. (The rougher torch-cut rim will—of course—be at the top of the stove.)

Next, weld a length of angle iron to the bottom of the front top plate, with the "leg" facing downward and the "shelf" at the top. (The lower edge of the iron should extend about 1/2 inch below the line of the metal sheet to provide a sealing point at the top of the doors.) Follow this by welding another horizontal strip of angle iron to the firebox's rear wall, at the same height and in the same position as the piece at the front (see Figure 2 in the image gallery).

The baffle—which will be supported by the "shelves" of the twin angle iron strips—is fabricated to provide a 1-inch clearance all around, thus permitting in direct passage of smoke from the fire pit to the upper portion of the stove and then out the pipe. I positioned the obstructing device by welding two tabs on its front edge and one on the rear, and then simply slipping the baffle into place with the protrusions resting on the angle iron ledges.

Now, you can go on to lay the door plate in the position it will occupy, being sure that its smoothest edge meets with the factory (uncut) edge of the top front plate. Mark the perimeter with a piece of soapstone, trim it, and then divide the plate into two equal door sections.

I fabricated my hinges from bar steel (see the accompanying photo). To attach them, first place a sheet of some thin material—like a magazine cover—between door and frame, and one thickness of cardboard in the center gap between the portals to provide a working clearance. Holding the to-be-hinged panels in place with clamps, weld the hinges first to the firebox and then to the doors, with the 1/2 inch hinge pins already in place.

Forming the shoulder of the pivot pin on the door latch will require a little lathe work. (If you can't arrange this, a simple bolt-fastened swiveling bar—or a similar substitute—will do the job.) Place the latch plate over the tongue of the latch before welding it, and bevel the engaging edges of the fastener with a file.

You'll need a lathe to make a draft control like the one shown in the photos, too, but a simple swinging flap covering a hole in the door would work nearly as well and be much easier to construct (although it could, when open, provide an exit rift for sparks).

Follow that operation by cutting a vent in the heater's top plate to accommodate the stovepipe collar. The best method of doing so is to use a circle cutter on your torch. If that's not possible, simply cut a less-than-perfect undersized hole and rest the collar on top. Either way, weld this component securely in place. Then go on to weld the stove's top into position, enclosing the firebox.

The next task will be to attach the outer fins. I used five on each side and six on top (see the photos), and I suggest that you adhere to my formula of placing the cooling devices on 3-inch centers . . . with the "legs" pointing up. In this way, they'll serve to increase the radiating and conducting surface of the Vulcan significantly . . . and I also believe that omitting them would lead to overheating, warpage, inefficiency, and a shorter use span for the woodburner. (Don't try to improve on the stove's design by placing fins on the doors, though, because they'd tend to warp the hatches when installed and prevent easy flattening of the sheets, should that task ever be necessary.)

Hot Tips for Homemade Stove Testing

In order to test-fire the stove before installing it, move it to your tryout site (I used the back yard), and—before lighting it (remove the baffle plate, as it could warp)—pave the bottom with firebricks. Should you need to split any, the masonry can be easily severed by scoring it with a hatchet or cold chisel and then snapping it over a straightedge. You'll also want to lay a 4 inch-one-brick-high-lining along the interior walls above the base. (No mortar is required to hold the firebrick in place.)

Start with a small fire, and then add enough dry fuel to set the stove blazing. During this test you'll be running at a higher temperature than you'd likely ever want or need to use when the woodburner is in your home, but an initial hot fire is necessary as a stress-relieving procedure for the new firebox. Continue feeding the flames until the first visible red spot appears at some point on the stove's body.

When installing your new Vulcan in the fireplace, set it on bricks to provide a bottom clearance for air circulation. And don't forget to position the stove off center in its niche with the larger air space on the side where you'll place the fan.

Next, run a piece of 6 inch stovepipe-long enough to extend a few inches through the damper slot-up the chimney of the fireplace, and crimp the seam with a pair of pliers to prevent its loosening. (You may have to remove the damper bar to get the partially flattened pipe up the vent, but that's usually easy enough to do.) Then seal the remainder of the opening with completely non-flammable, high-temperature spun insulation . . . don't forget to remove any paper backing. [EDITOR'S NOTE: A preferred installation technique would be to run stovepipe all the way to the top of the chimney, and to fit a steel plate around it to prevent heat loss.] 

Now come the finishing touches. Cover the Vulcan's exterior with stove polish, and place a couple of ordinary cookie sheets in front of the doors to catch the ashes that may fall when you open the heater. Then set an inexpensive floor fan on the hearth, as shown in the photo, so that it will blow into the fireplace. This will provide for circulation of warm forced air within the room and also prevent the doors from overheating (although that isn't very likely in any case).

Since it's a remarkably efficient stove, the Vulcan can be operated with a relatively small fire (it should never be run red-hot), and the optimal draft will be significantly less than you might think necessary . . . so experiment. The largest logs or splits that can be inserted in the firebox will produce the longest and steadiest burn.

The six original Vulcans have been in satisfactory operation for a good while now. One winter they were forced to perform as primary sources of heat during an extended power outage . . . and even without the help of fan-induced air circulation, the stoves succeeded in maintaining a steady temperature of 70 degrees Fahrenheit in the rooms in which they'd been installed.

In summary, the Vulcan Stove is inexpensive, efficient, and relatively simple to build. And while it may leave something to be desired aesthetically, when I total my (reduced!) fuel oil bill, I never find myself regretting the loss of my "open window on the sky".


Homemade Vulcan Stove Tools and Materials List

Here's the equipment we used in constructing our homegrown fireplace inserts.

[1] A 225-amp AC arc welder (I don't suggest anything smaller).
[2] Lincoln Fleetweld 37 electrodes, 1/8 inch at 135 amps, and Lincoln Jetweld 3 electrodes, 1/8 inch and 5/32 inch. (I strongly recommend that you use the Jetweld a rod on all horizontal seams, because of its typically beautiful bead and ease of application.)
[3] An oxyacetylene cutting torch equipped with a circle-carving attachment and "training wheels" for making straight cuts.
[4] A commercial-duty disk grinder with coarse-grit wheels.
[5] C-clamps and Pony bar clamps mounted on 1/2 inch pipe.
[6] Miscellaneous items, such as a square, a measuring tape, soapstone marking pens . . . and 17 cases of beer (optional).

Our bill of materials was equally brief. The design for the Vulcan Stove calls for a firebox 16 inches deep, 18 inches high, and 24 inches wide. Therefore, two complete stoves (excluding the baffle plates) can be cut from one standard 4 foot by 8 foot sheet of 1/4 inch steel plate. The construction of each woodburner also requires about 42 feet of 1/4 inch by 1 inch by 1 inch angle iron for the internal framing and external fins . . . 3 feet of 1/4 inch by 1 inch flat bar steel for the hinges and latch . . . a 6 inch (outside diameter) steel pipe collar about 1-1/2 inches long . . . and the necessary length of 6 inch stovepipe.

Should you want to alter the Vulcan's dimensions to fit your own fireplace, go ahead! I do think, though, that you should be sure the space allotted to the doors is no more than two-thirds the height of the firebox (by preserving this ratio, you'll be able to keep your woodburner from smoking even when both doors are open).

EDITOR'S NOTE: For information on ordering woodburning store plans from MOTHER, see page 148 of this issue.