And so, in a big circle, we come back to the beginning again. The high temperature, low carbon, high oxygen and high velocity environment inside of a well tuned Rocket Stove is just about the perfect environment for destruction of metals. When a Rocket Stove is running properly, metals inside the burn chamber are eroded away in very short time. Unfortunately, metal rocket stoves are a poor choice. Cast refractory products and/or natural clay-based mixtures have the same issues as brick. Building an angled feed out of brick is annoying to do (I've done it) and since friction with brick is so high, they don't work anyway.
Angled feeds tend to work better when made out of metals, rarely do you see them made of anything else. If left alone, the stove tends NOT to put itself out, instead it is more likely than either of the others to back-fire, as fire wants to creep up (and out) while the wood stays in place. It is also difficult to be fuel-wise with the angled feed. If the wood is even a little irregularly shaped, it will simply fail to slide in friction is too great to allow smooth feeding of the fire. As an automatic feeder, it is more likely to NOT work than otherwise. After a LOT of experimentation and long term use, I am of the opinion that it fails to do ANY of the things that the L-feed and vertical J-feed can do. I assume that the idea is to save space and simplify the build. Honestly, I don't really understand the need for the angled J-feed (actually, I should say that I reject it). The vertical arrangment holds the wood in a more ideal position for efficient burning, with a lot less operator intervention as the fuel burns away, fresh wood comes down automatically to replace the old. With this method, it is not as easy to be miserly with the wood, but there is an efficiency trade-off. With the FULLY VERTICAL J-feed, the wood is automatically metered via gravity.
If it is left untended for long, the fire will smoulder and go out. The drawback to this is that the operator must constantly monitor the wood to keep the fire going. With the L, it is quite easy to meter the amount of wood used the operator can pull wood out or back very easily. The L-feed was invented specifically for environments where fuel was scarce. This keeps the smoke all going into the fire instead of into your face. Air should flow down, over the wood and into the combustion chamber. In the J design, air injected from the bottom or sides tends to smoke back, more than not. PMID 22563898.Rocket Stove Science - Rocket Stove Schematics From The German Interwebs. "Are rocket mud stoves associated with lower indoor carbon monoxide and personal exposure in rural Kenya?: Kitchen and personal CO from traditional and rocket stoves". ^ "Aprovecho Research Center and ProBEC / Efficient stoves for institutional cooking".^ "TWP and AHDESA / Fuel-efficient stoves for tortilla makers".An Encyclopędia of Domestic Economy: Comprising Such Subjects As Are Most Immediately Connected with Housekeeping. ^ "Build a rocket stove for home heating".^ "Building a rocket stove to heat up the house".In rural Kenya, a comparison of traditional three-stone stove and rocket mud stoves (RMS) showed that RMS use resulted in a 33% reduction of carbon monoxide production in the kitchen and a 42% reduction in "personal" carbon monoxide production, which was measured with data loggers placed on clothing in the study. Rocket stoves are better at combusting the fuel, thus use less fuel and produce less smoke, carbon monoxide and soot. Many developing countries use traditional wood fuel stoves without proper ventilation, which produces indoor concentrations of smoke particles "typically 10 to 100 times the long-term levels recommended by the World Health Organization." Chronic exposure to these particles are linked with disease. Aprovecho rocket stoves were sold in Lesotho, Malawi, Uganda, Mozambique, Tanzania and Zambia. Aprovecho won the same award in 2006 for their rocket stoves. A stove was designed to make tortillas based on the principles of the rocket stove and won an Ashden Award in 2005. Larry Winiarski, Technical Director of Aprovecho, began developing the rocket stove in 1980 based on a VITA stove, designed by Sam Baldwin, and rediscovered the principles of the systems developed by the Romans in hypocaust heating and cooking systems. As well as being used for lighting, this design was also used for cooking and heating water due to it "affording much the strongest heat without smoke". This was a major development of the traditional oil lamp, which introduced a glass chimney above the flame to increase air-flow. A precursor to the rocket stove was the Argand lamp, which was patented in 1780.