[Cob] Rocket Stove

[michael montagne]

So I look at pictures and diagrams of rocket stoves and I read how they work
and where to clean what when but a question still remains.  Are these 55
gallon steel drum heat exchanger containers just upside down barrels?  In
other words, is it necessary to open the top for maintenance?  If not, why
don't more people just substitute cob for the steel barrel?  I guess that's
really more than one question.  Also, where to source the smaller barrel for
the feed tube?  I'm in Portland, Oregon.  My stove will be outside, heating
a small covered area of my deck to allow use during the cooler months.

-mjm