https://picasaweb.google.com/Jonnygms/RocketStoveKiln#
I posted this link in another thread, but it seems that you are looking for the same answer. These pictures show the build of an inexpensive kiln made with cob materials and a dual rocket stove setup. There were some problems but they address these in the photo captions.
Does anyone see any issues with building a pottery kiln of this design? I am not experienced with cob or rocket stove building, so I would like some input on this design.