Re: Lanny's Rocket Wok Cooking Stove

["Lanny Henson" <lanny@roman.net>]

Dean,
I was not expecting 28%  efficiency with our first prototype. I under
estimated your design skills.
I was waiting to see if the stove worked before I was willing to take
credit/blame. If the stove failed I was going to say that it was your design
and I was just the tin man. If the stove worked the I was going to say that
it was our design. So it looks like its our codesign.
The field test is a good idea to see if the stove is practical.
Lanny
----- Original Message -----
From: Dean Still <dstill@epud.net>
To: Lanny Henson <lanny@roman.net>; <stoves@crest.org>; Hanna Still
<hannastill@earthlink.net>; brad <bvanappel@yahoo.com>; Christopher Schmidt
<schmidty2020@yahoo.com>; Cousins, Ananda <ACousins@seattleu.edu>; Daniel M.
Kammen <kammen@Princeton.EDU>; David Pennise
<dpennise@uclink4.berkeley.edu>; Delacie Barney <delaciebarney@yahoo.com>;
Derick Calderon <entre16@intelnet.net.gt>; Don O'Neal <dononeal@fni.com>;
Elizabeth Bates <elizabethb@itdg.org.uk>; Frank Vignola
<fev@darkwing.uoregon.edu>; George Rudy <rudy@wehi.EDU.AU>; Grant
Ballard-Tremeer <grant@ecoharmony.com>; horizon
<horizon@engr.colostate.edu>; Jeff Conant <jeff@hesperian.org>; Jonathan E.
Sinton <jesldc@dante.lbl.gov>; Karissa Ansell-Bell
<krisab@OREGON.UOREGON.EDU>; Ken Goyer <goyen@efn.org>; Kenmore, Peter
(AGPP) <Peter.Kenmore@fao.org>; kenneth mark bryden <kmbryden@iastate.edu>;
kevin hallinan <Kevin.
Sent: Thursday, January 24, 2002 4:50 PM
Subject: Lanny's Rocket Wok Cooking Stove


> Dear Friends,
>
> I received Lanny's beautifully made stainless steel stove a couple of
weeks
> ago and have really enjoyed playing with it. The stove features a ceramic
> well insulated Rocket combustion chamber with a eight inch tall internal
> chimney below the partially sunken wok (three inches below the top of the
> stove). A horizontal twelve inch long, five inch in diameter tube makes
the
> feed magazine and connects to the bottom of the internal chimney below the
> wok. The wok seals at a circular rim so flue gases exit from a six inch in
> diameter stove pipe installed in the side of the stove body. If the stove
is
> lit without troubles no smoke enters the room since the seal is well made.
A
> shelf, one third up from the bottom the tube, holds seven one inch in
> diameter sticks that are pushed into the fire as they are burnt. Air
enters
> under the shelf, especially when sticks fill the space on top.
>
> First, a couple of remarks about the wok as a great example of evolution
in
> cooking design. Folks at Aprovecho hate one thing most about using wood
for
> cooking, soot on the pots make them impossible to clean in a sink without
> sooting up the sink, hands, towels, etc. So staff have forced the A.T.
> builders to make griddle stoves where soot does not touch pots. But, as we
> all know, passing heat through steel into pots is not a most efficient use
> of wood. (As a rule of thumb, the griddle halves efficiency.)
>
> The wok solves this problem because it is cleaned in place using a brush
and
> water available at the stove. The waste water is dumped onto the inclined
> top of the stove and drains into a trough that funnels waste down a tube.
> The soot does not contaminate the cleanliness of the kitchen. Marvelous
> idea! Also the wok can be used for boiling, steaming and frying, even
> baking. The steel is thin for good heat transfer and the bowl shape is
also
> helpful in this regard. Tools to make use of the wok have evolved over
time
> and are equally ingenious. And cheap because so many are made. Woks are a
> great reminder to me that looking for human evolved answers to A.T.
problems
> is probably a lot more effective than other more removed approaches; i.e.,
> white guys like me who haven't cooked much with wood coming up with
> "inventions".
>
> The 150,000,000 improved wok stoves recently made in China use a box like
> combustion chamber under the wok formed from cast iron surrounded by
> insulation. I wondered if a Rocket combustion chamber might help the stove
> to be a bit more fuel efficient and less polluting. So Lanny and I worked
up
> a prototype that I'm now testing and tweaking.
>
> Today, I put about 11 pounds of water, (5,000 grams), in the wok. The
water
> was brought to a rolling boil in 11 minutes. I then kept the water close
to
> 212F (100C) for 1/2 an hour and used 960 grams of wood. Two to three
sticks
> were needed to keep the water at temperature. I use 8,600 BTU's per pound
of
> wood. Adding up sensible heat and figuring 1,005 BTU per pound of water
> boiled off, the stove was 28% fuel efficient. My son and a friend need a
> school project and we will work together to improve the heat transfer by
> finding the best gap between the wok and the skirt that forces hot flue
> gases to scrape against the wok surface under the stove top. We also will
> try reducing the one inch distance between the top of the internal chimney
> and the bottom of the wok. Having a external chimney (6' high in the
> experimental model) gives us a lot of draft allowing gaps to shrink.
>
> After we get done, the stove goes to a family of 6 who will use the stove
> for a month and report back. I'll put a picture on the ETHOS page when
it's
> up and write again if we improve efficiency. So far my only major
> improvement would be to try lowering more of the wok under the top of the
> stove. A six inch feed magazine would give more power but I'm going to
wait
> and see if the family thinks it necessary.
>
> Best,
>
> Dean
>
>
>
>
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