The following is part one of a three part series on wood fire cook stoves that you can easily make and use at home. This article is written by Hangtown Frank.
This is the first of a series of three discussions about three improvised wood-fired “rocket” cook stoves I have made for my own outdoor use. In all three types, the stove top is at a convenient elevation above floor/ground. What I have done for my own use should not be construed to be advice to you or anyone else. Seek the advice of a safety professional regarding proper safety precautions for your situation.
The wood used in these stoves includes 4-ft long pieces of broken branches, stove-wood length split fire wood for use in traditional cast iron wood-fired cook stoves, and short chunks of branch wood where chunk diameter and length are about equal. Wood diameters less than ½ inch tend to burn out too fast and diameters greater than 2½ inches tend to burn too slow.
My rocket stoves are less expensive, but heavier and less portable, than commercially available ones. My stoves utilize locally available home & patio construction materials such as fired clay bricks, concrete patio pavers, concrete building blocks and assorted pieces of scrap metals. In their simplest forms, they require no tools to build. My more “elegant” versions require ordinary hand-held home maintenance tools such as a metal cutting hacksaw, drill, and pop riveter.
Type I discusses the simplest stove – the one where the cooking utensil (kettle, pot, skillet, griddle, or grill) is supported by the stove itself and the entire stove is constructed on a roll around cart so it can be stored in one location and used in another.
Type II concerns four variations of a more complex version of improvised stoves. The common feature of these variations is that the weight the cooking utensil is supported on a separate structure that is cantilevered from a porch railing and over the stove. The stove supports none of the weight of the utensils. This feature was developed to minimize the risk of toppling the stove when heavy utensils are placed onto the stove or removed from it. This cantilever arrangement is not mobile.
In the simplest of these four variations, the sides and handles of the cooking utensils are exposed to the flames of the stove. In the second version the sides and handles of the utensils are shielded from the flames and the cantilever includes a simple temperature control device that is important for safe operation of pressure cookers/canners. The third version shows use of a Dutch oven on the cantilever over the stove. And, the fourth version shows an improvised baking oven on the cantilever.
Type III concerns a semi-permanent installation that is somewhat reminiscent of an old-fashioned wood fired cook stove but, while heavy, can be disassembled, transported from one location to another, and quickly reassembled by one person with a wheelbarrow or pickup truck.
Type I – A Basic Mobile Stove.
The simplest stove was built on the top surface of a roll around cart. The cart allows for out-of-the-way storage of the stove when it is not being used and then, depending on the weather, use of the stove in sunny or shady areas of my back porch. It could have been built on bare ground.
For this stove an 18” square concrete paver was placed on the metal top of the cart. Then 4 bricks were arranged on the paver as shown in photo 1 below. One of the bricks is a “half brick”. If a full length brick had been used it would be arranged so that the gap in bricks would remain as shown in the photo. The extra length would have projected outward from the arrangement and towards the bottom of the photo.
Photo 2 shows the stove with the second tier of bricks. Note the use of slightly smaller bricks in the upper tier. I changed brick sizes simply because I had no more of the larger bricks. Note also how the brick at the upper right spans the gap in the lower tier. When the stove is in operation this gap allows for air entry into the combustion chamber as well as for insertion of fire wood into the combustion chamber (i.e., the hollow space within the stove).
Photos 3 & 4 below show the completed stove. It is now 3 bricks high. Note the intentional difference in the arrangement of bricks in the top tier. This helps prevent collapse of the stove. See photos 31 – 33 for better views of the brick stacking arrangements.Photo 2 shows the stove with the second tier of bricks. Note the use of slightly smaller bricks in the upper tier. I changed brick sizes simply because I had no more of the larger bricks. Note also how the brick at the upper right spans the gap in the lower tier. When the stove is in operation this gap allows for air entry into the combustion chamber as well as for insertion of fire wood into the combustion chamber (i.e., the hollow space within the stove).
In photo 4, the gap in the bottom tier bricks is just large enough for insertion of the ash removal shovel.
Short pieces of 1” square steel tube are placed atop the stack of bricks for support of the coffee pot. These tubes have 2 functions: first they support whatever is being heated; and, second, they allow escape of smoke from the fire. Short lengths of 1½” angle iron could also be used. In this case, lay them so that the 2 edges of each angle are on the bricks and their corners up upwards (See photo 33). Don’t use round pieces of pipe. They can work like rollers and allow the pot to roll off.
Photos 5 & 6 show the stove in operation.
Note the emplacement of 2 pieces of 2” x 2” angle iron on either side of the wood insertion hole. These ensure that burning pieces of wood don’t fall off the sides of the cart. If the cart were placed closer to the deck railing I’d have placed a heat shield on the railing also.
The L-shaped sheet aluminum between the coffee pot and the cart handle ensure that the wood handle isn’t damaged by the hot exhaust from the stove. It may not be needed.
This stove is held together only by gravity and friction between the bricks. If desired, it could be held together more firmly by mortar or clamping devices. Thus far, in all versions of the stove I have made I’ve found no need for mortar or clamping devices. However, repeated heating cycles do cause gaps to develop between bricks. These can be closed by gentle tapping of the bricks back together. Be aware that simple stacking of the bricks without mortar or clamps does present a safety hazard. The stack could collapse if bumped vigorously. Type II of the stove (installment 2) reduces this hazard.
Long pieces of firewood can be used in this stove – just gently shove them in further as they are consumed in the stove. Pieces up to 4 feet long have been used. Installment 3 photos show how the long pieces are used.
Unless you periodically shove the wood further into the stove the fire will creep out of the stove a few inches. During subsequent use of this stove and its several variations, which are discussed later, the fire has never crept out any further than shown in photo 5.
To easily start a fire in this stove, remove the pot and its support bars from the stove top. Wad up a bit of newspaper and place it inside the stove near its air/wood access hole. Pile on some small twigs or small kindling and set the paper alight using a large wooden kitchen match. After the kindling starts burning, pile small pieces of firewood atop the kindling. After these ignite insert longer pieces of wood thru the stove’s access hole, replace the pot support bars, and then emplace the pot to be heated.
Normally, this stove in not used my wood deck during the warm dry months of the year. And, when using it any time on the deck I hose down the deck first unless it is already wet from rain or snow. I also keep of bucket of water handy.
The 18” square and 1” thick paver used in this stove did fracture into several pieces after several firings. This large paver was replaced with 12” square and 2” thick pavers. They have not cracked or broken after multiple firings in this stove and my type II and type III stoves.