Bill Ryan from Waukegan, Illinois is a long time steam builder most famous for his go-karts that, when they run, or more precisely, went, go very fast.  Here he has made a frusto-conical monotube coil wood fired steam generator that is designed for 200 psi and is controlled by steam pressure. 

The Rocket stove design is very clever in that it has an opening in the top to drop fuel into and there is a down draft generated by the smoke going up the smokestack so that no heat or flame or smoke comes out of the opening.  Bill made this for another party and we do not think any further development has taken place.