OK, here are some pics of a couple of stoves I have been playing with.
This is an inverted downdraft wood gasifier made from a coffee can and a 15 oz. been can. It works best batch loaded, meaning you load it and light it and use it untill it is done and start over. I have been able to reload it during operation but it takes some practice.
And here is my latest creation, a forced air wood burner. It is like a mini-forge! The heat output is incredible, it boils water faster than my MSR PocketRocket!
It is made from a coffee can, a 14 oz sweetened condensed milk can, a small DC motor salvaged from a cheap toy, and some small scraps of sheet aluminum. It runs on two AA batteries. The fan is made from the cut out lid of the coffee can. I reverse one of the batteries in the battery box while carrying and flip it around to run the fan, or bypass it with a small piece of metal for a low speed setting using only one battery. So far my 2650 mA-hour batteries have run the fan for a total of about an hour without needing a recharge.
The forced air burner is much hotter and boils water 2 or 3 times faster, but I think that the inverted downdraft is more fuel efficient. Wood is free, so this isn't much of an issue. The fan adds a lot of complexity and is therefore more likely to fail. However, the parts could be canibalized to make a simpler stove in an emergency(don't forget your multitool!). For me the best reason to use the ID gasifier is that it is quiet. Firing up my PocketRocket, Dragonfly, or the forced air burner while in a nice quiet wilderness mood is a real buzzkill.