This is the second 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 II – A Cantilevered Arm Supports the Cooking Utensil Over the Stove
Type II of my rocket stove differs from Type I as follows:
a) The stove is no longer mobile. It is set atop portable and variable elevation sitting bench.
b) The length of the stove has been increased from 1 brick to 2 bricks. Its width and height remain unchanged. This modification was made to provide for a longer fire box (combustion chamber) and hence – a bigger fire.
c) The cooking utensil is not supported on the brick structure. Rather, it is supported on a 1” square steel tube pop-riveted structure that is cantilevered from the deck railing. There is a 1” air gap between the cantilever and the top tier of bricks. The cantilever provides a more stable (safer) structure for holding heavy utensils than the Type I stove.
Type II – Variation A
Photos 1 & 2 show the stove and its cantilever support for heavy canning kettles. These kettles can also be used for heating water for other purposes such as doing laundry. Note that the sides and handles on the kettles are not protected from smoke and flame.
1 Heating water in a canning kettle
2 Processing bottles of apple juice
3 Bottled apple juice
Variation B – Heat shields are added to (a) protect utensil sides & handles from smoke & flame and (b) control heat input to cooking utensils
Variation B of the stove differs from Variation A in 2 ways:
a) Photo 4 shows a rectangular sheet of steel, with a central octagonal hole, which is placed atop the cantilever structure. The bottom of a pot set on the hole is exposed directly to the flame but its sides and handles are shielded from the fire. Side shielding is especially important when using pots with plastic handles that could be damaged by the fire.
Exposure of the pot bottom directly to the flame increases the rate of heat input to the pot. This is especially important when using a pot or kettle that has ridges on its bottom – ridges that prevent intimate contact of the bottom of a pot set on a solid plate.
The hole could be round. The use of an octagonal hole made for easier hole-cutting operations.
b) As can just barely seen in the photo 5, there is a small piece of sheet metal projecting out from the right of the support cantilever. This is a “heat controller”. It slides in and out under the steel sheet’s central hole to vary the area of the pot bottom that is exposed to the fire. Photos 6 – 8 show details of the temperature controller.
The heat controller is especially important when using a pressure cooker/canner on this stove. Even with it, use of a pressure cooker/canner on this stove requires constant attention to ensure that the cooker/canner doesn’t over-pressurize and “pop” (activate) its safety valve. If this were this to happen it would create a very nasty mess to clean up and, possibly, a major safety problem.
I have used a pressure cookers and pressure canners on this stove several times. This heat controller requires more development to improve its reliability and ease of use before I’d trust anyone but myself to use a pressure cooker on this stove. Even then, Do Not attempt pressure cooking or pressure canning on a rocket stove before you become thoroughly familiar with the process on a conventional electric or gas cooking range.
Note the guide rails for the temperature controller
Photos 9 & 10 show the stove with a pressure cooker and with a pressure canner.
The hole in the temperature controller is for a tool to push the controller in to decrease heating rate or pull it out to increase the heating rate.
The sheet steel heat shield on top of the cantilever (photos 8 – 10) can be removed and replaced by a rectangular griddle or grill. Beware of ugly grease spills off a griddle when using a griddle or grate over on a wood deck or a concrete patio.
In photos 4 & 5, there is a simple flat metal sheet under the paver. It has sharp corners. Later, it was replaced with a shallow metal pan with rounded edges and corners. It was purchased from an auto parts store. It is what’s used for preventing oil and grease drippings from under their automobile onto garage floors. Cooking things like pancakes on the griddle doesn’t require a grease trapping pan.
A heat shield to protect the deck railing might be required. That device remains to be developed. The trash cans in the background of photo 5 are for storage of kindling and stove-wood length fuel. They protect the dry wood from rain and snow.
Variation C – Dutch Oven Baking
Baking corn bread in a Dutch oven on a rocket stove.
Photo 11is the Dutch oven, all fired up and cooking. With “campfire” Dutch oven cooking, most of the heat is transferred into the oven thru the lid which would normally have a thick layer of coals on its lid.
On a rocket stove all the heat goes in thru the oven’s bottom and tends to burn the product being baked. To prevent this, place a trivet on the oven’s bottom (photo 12). You may even need to put some aluminum foil between the trivet and the baking pan.
Photo 13 shows the oven with trivet and baking pan. My “baking pan” is an old cast iron skillet with its handle removed. Use a pair of pliers to lift it out of the oven after baking. Photo 14 shows corn bread batter/dough in the pan and ready for baking.
In photo 15, the Dutch oven lid shown in photo 11 has been replaced by a canning kettle lid which is much lighter and easier to handle. It holds heat in the oven nicely. Photo 16 shows the pan of corn bread after baking. Photo 17 shows the baked pan of bread ready for slicing and slathering with butter and honey.
Variation D – An Improvised Baking Oven
Dutch ovens are expensive but can be inexpensively improvised for bread, muffin, or other baking. Photo 18 shows a 17” wide x 21”long x ½” thick aluminum plate setting on the cantilever on a fired up stove. I got the plate at a salvage yard (Blue Collar Supply) in Sacramento.
To begin cooking, the plate is set on the cantilever and centered over the fire. Then a trivet is then placed on the plate, and the cast iron muffin pan is set atop the trivet (photo 19). The plate could have been smaller just so long as the muffin pan cover (an inverted aluminum dish pan) will fit on it. I have used steel plates rather than aluminum. But they are much heavier (more difficult to handle) and aluminum does a better job of transferring heat into the oven than steel.
In photo 20, corn bread muffin batter/dough is added to the muffin pan. Photo 21 shows an aluminum dish washing pan inverted and set over the muffin pan. The cardboard helps raise temperature in the pan. A folded towel can also be set on the pan to raise the temperature under the pan. If you use a towel be careful that its edges don’t touch the plate. The can burn or melt of your plate temperature is too high.
In photo 21, note the thermometer near the corner of the plate. This gives an indirect measure of the temperature in the baking area. The exact temperature in the baking area isn’t important so long as it is above about 220F. That will be hot enough to evaporate the water but won’t brown the bread. Even without browning the bread will be good. A plate temperature much above 300F may cause burning of the bread’s surface.
Here are the baked muffins (photo 22). They would have raised more if I had used white flour rather than whole wheat flour and had reduced the cornmeal-to-wheat ratio.
End Installment 2