Note that the goal of the drafting chimney is not to soak up a lot of heat, but rather to be insulated and have low thermal mass to minimize heat loss. The higher the air exit temperature from the riser, the stronger the draft. The important thing for self-drafting is to heat the air in the riser, and only secondarily heat the riser material itself.
A good design should make startup as "idiot proof" as possible. I've seen a few builds that use a 12V case fan on the air intake. Since the goal is to heat up the air in the riser (and that heating the riser... draws hot air into the riser), all you have to do is "tip it over" into that stable equilibrium.
Imo there's a market opportunity for an inexpensive, compact, nice looking, and easy to operate rocket stove. The open source (and excellently documented) "batch rocket" design seems a good place to start. http://batchrocket.eu/en/
Smoke free startup is an important design/operational consideration. There are lots of videos demonstrating startup technique (search "rocket stove starting"). Here's a couple good ones: https://www.youtube.com/watch?v=Ls_eqNB6d0Y&t=1m23s https://www.youtube.com/watch?v=aSkUquOQt5w
Note that the goal of the drafting chimney is not to soak up a lot of heat, but rather to be insulated and have low thermal mass to minimize heat loss. The higher the air exit temperature from the riser, the stronger the draft. The important thing for self-drafting is to heat the air in the riser, and only secondarily heat the riser material itself.
A good design should make startup as "idiot proof" as possible. I've seen a few builds that use a 12V case fan on the air intake. Since the goal is to heat up the air in the riser (and that heating the riser... draws hot air into the riser), all you have to do is "tip it over" into that stable equilibrium.
Imo there's a market opportunity for an inexpensive, compact, nice looking, and easy to operate rocket stove. The open source (and excellently documented) "batch rocket" design seems a good place to start. http://batchrocket.eu/en/