[Cob] Re: Washington, DC Jackson's Rocket

[Raduazo at aol.com]

Jackson's Rocket
            Photos available upon request.
            My friend Chris Jackson lives in a trailer with his wife and 
daughter near Blackrock, VA. He has an unheated shell near his trailer that 
someday he hopes will become his home. Last week we decided to build a rocket stove 
in the shell and although we opted for a very conservative design we made two 
or three departures from the rockets in Ianto’s book that greatly simplified 
the design and speeded construction.     The first change was the use of a 
section of zero-clearance stainless steel chimney as the heat riser. ( This pipe 
replaces elements D, E, F and J on page 25 of the book. Also note the device 
shown on page 29 of Ianto’s book.) The zero-clearance pipe is normally used in a 
building when the flue gasses of a wood stove must pass through a combustible 
wall. It is a little expensive, but Chris has some scavenged from a dumpster.
            The beauty of using a zero-clearance pipe as the heat riser is 
ease of use and flexibility. To mount the pipe on the burn chamber we drove a 
metal post into the ground next to the burn chamber set the pipe on top of the 
burn chamber and used a stainless steel strap to lash the zero-clearance pipe 
on to the post. Then we used a purlite/slip mix to seal the gaps around the 
pipe and to insulate the burn chamber.
            Another advantage of the zero-clearance chimney pipe is that the 
thin layer of insulation in the pipe makes it possible to use replace the 
conventional 55-gallon drum with something a little more graceful and attractive. 
I would like to take strips of steel and bend them around a mandrel then weld 
them to form a more elegant looking drum.
            The second change we made was to use rectangular flue liners as 
the combustion chamber, and form the combustion chamber as an inverted T-shape 
instead of the conventional L-shape. This gives us a clean-out opening 
adjacent the burn tube. Eventually Chris plans to make a 4-sided ash sled with a 
handle that will sit in the burn chamber during a burn. After the burn is complete 
you will be able to grab the handle and slide the sled out the clean out 
opening in order to empty the ashes. We made connections for the rectangular flue 
liner by cutting out rectangular sections of the flu-liner with a diamond saw. 
We used one cut out section to block the end of the burn chamber and direct 
flu gasses up to the zero-clearance pipe section.
The disadvantage of using a flue liner is that they crack if heated too 
rapidly and indeed ours cracked, but it stayed in place, and it is our hope that it 
will continue to stay in place as the cracks do not affect the operation of 
our rocket.
I love working with Chris because he is a skilled stone worker and he has an 
endless supply of white quarts rock. The temperature was seldom above freezing 
while we were working, so we mixed up our clay-sand-water in a cut in half 
plastic drum using a drywall mixing paddle in a ½ inch drill. We used hot water 
of course as the sand and clay had to be melted before we could mix it.
In three days of work we finished the burn chamber, riser and barrel portion, 
and we finished nearly half of the rock/cob bench. It draws beautifully, and 
the final chimney is cool to rest your bare hand upon it.