VITA TECHNICAL BULLETIN
51029-BK
Double-Drum Sawdust Stove
JEFFREY L. WARTLUFT
This bulletin
describes an inexpensive home-made stove for burning loose
sawdust.
Constructed from empty oil drums, the stove
can heat a room 20
feet square
for 6 to 8 hours without tending.
Jeffrey
Wartluft is a VITA Volunteer who is a forest products technologist
with the
United States Forest Service. While
working on the design for the
sawdust
stove, he researched old VITA plans from Afghanistan and compared
them with
stoves he had seen while in Chile as a Peace Corps Volunteer.
The
result has
been published as Forest Service Research Note NE-208, 1975,
from which
this bulletin was taken.
Please send
testing results, comments, suggestions and requests for further
information
to:
Technical Bulletins
VITA Publications Service
1600 Wilson Boulevard, Suite
500
Arlington, VA 22209 USA
ISBN 0-86619-109-7
Volunteers In
Technical Assistance
1600 Wilson
Boulevard, Suite 500
Arlington, VA
22209, USA
VITA TECHNICAL BULLETINS
This
Technical Bulletin is one of a series of
publications
that offer do-it-yourself technology
information
on a wide variety of subjects.
Technical
Bulletins are idea generators, intended
not so much
to provide a definitive answer as to
guide the
user's thinking and planning. Premises
are sound and
testing results are provided, if
available.
Users of the
information are asked to send us their
evaluations
and comments based on their experiences.
Results are
incorporated into subsequent
editions,
thus providing additional guidelines for
adaptation
and use in a greater variety of conditions.
In the United
States, sawdust traditionally has been burned in large furnaces
for
industrial heating, in smaller furnaces for home heating, and in fireplaces
in the form
of compressed logs. In other parts of
the world, loose sawdust has
been burned
for years in inexpensive double-drum stoves.
These stoves are well
suited for
heating cabins or workshop areas.
The
double-drum sawdust stove has other advantages.
It is inexpensive to
fabricate; it
uses recycled components; it burns inexpensive fuel; and it heats
a long time
with minimum tending.
After seeing
these stoves heating homes in Chile and reviewing plans(1) for the
types used in
Afghanistan and England, I fabricated an experimental stove
(Figure 1) at
the Forest Products Marketing Laboratory in Princeton, West
02p01a.gif (486x486)
Virginia.
Then I learned how to use the stove by
firing it with several kinds
of fuel
having different moisture contents.
(1) Wood
Waste as a Fuel,
Forest
Products Research
Lab.
Research
Leaflet
41. Princes
Risborough,
England.
11 pp. 1956.
Fabrication
The
experimental double-drum stove was made from a 55-gallon steel drum and a
30-gallon
drum, plus about $25 worth of other materials, including stovepipe.
Tools needed
for fabrication are tin snips, hammer and anvil, rivet tool, drill
and bit,
metal-cutting saber saw, and equipment for brazing with bronze.
The stove
(Figure 2) consists of two drums, one inside the other.
A false
02p01b.gif (600x600)
floor inside
the outer barrel supports the inner barrel.
A drawer opening
below the
false floor provides draft, and the drawer catches dropping ashes,
which are
then easily
removed.
Three-inch
holes in the
center
of the false
floor
and the inner
barrel
bottom let
air pass
up to the
fuel and
let ashes
fall into
the drawer.
A tightly
fitting lid covers the outer barrel.
Under this lid are about
3 inches of
clearance to the top of the inner barrel.
Two 6-inch diameter
stovepipes
exit from the outer barrel, allowing smoke to exhaust.
The outer
barrel is
supported by three legs to keep excess heat from the floor and
prevent
rocking.
The false
floor and drawer were fashioned from 20-gage sheet metal.
Drawer
tabs and
curved front were fastened with rivets.
The false floor rests on
two parallel
1/2-inch steel rods, which were run through holes on opposite
sides of the
outer barrel, and were brazed to it.
Two handles
of the lid and one on the drawer were made of 1/2-inch steel
rod, bent to
shape, and attached by brazing.
The two
joints of stovepipe were brazed to the outer barrel, one near the
top of the
stove and the other directly beneath it.
These two horizontal
pipes join
into a common vertical pipe. The upper
horizontal pipe is
fitted with a
damper. The vertical pipe is fitted
with elbows, straight
lengths, wall
or ceiling thimble, and a vent cap to suit the individual
installation.
Smaller or
larger stoves can be fabricated with heavy-gage sheet metal
(about 14
gage). The relative sizes of the
components should be roughly
proportional
to the dimensions of our experimental stove.
Installation
The stove
should be placed at least 24 inches away from any combustible
wall or floor
material.(2) It should be set on a
fireproof floor pad that
extends at
least 18 inches in front of the drawer opening.
A wall thimble
or triple
wall pipe should be used where the pipe goes through the wall or
ceiling and
roof. The flue pipe should not have
long horizontal sections,
as they favor
condensation of flue gas. The
condensates leak at the joints
and cause
pipe corrosion.
(2) Using
Coal and Wood Stoves Safely. National
Fire Protection Association
NFPA
HS-8. 12 p. Boston. 1974.
Fuels
In addition
to sawdust, bark residue from sawmills and planer shavings from
planing mills
can be burned in the stove. The
limiting factor for fuels is
their
moisture content. Though fuel having
more than 100 percent moisture
content
(oven-dry basis)(3) will burn, most of the heat is used in evaporating
fuel
moisture. Fuel below 60 percent
moisture contents works well. Fresh
sawdust,
shavings, and bark typically have moisture contents ranging from 50
to 110
percent. The best source of fuel is
sawdust or shavings from dried
lumber.
(3) The water
in the material weighs as much as the dry material itself.
Fuel can be
stored in a bin or in plastic garbage bags.
If a bin is used,
the inner
barrel is either removed and taken to the bin for filling, or a
large bucket
is used to transfer the fuel from bin to stove.
How to Use
the Stove
A round
wooden mold, 3 feet long, tapering from 5 inches to 2 7/8 inches, is
used to shape
the fuel charge.
To fill the
stove, place the small end of the wooden mold in the hole at the
bottom of the
inner barrel. Then tamp sawdust or bark
around it until the
inner barrel
is full. Wet fuel should not be tamped
as much as dry fuel.
Carefully
remove the mold, leaving a vertical hole in the center of the fuel
charge
(Figure 3).
02p03y.gif (600x600)
Before
lighting the fire, open the drawer and damper.
Then crumple waste
paper, drop
it down the hole in the fuel, and place the lid on the outer
barrel.
Place additional crumpled paper in the
drawer and light it; move
the drawer in
so the flames will ignite the paper in the hole.
Once the fuel
is burning, adjust the drawer and damper to obtain the desirable
rate of
burning and output of heat. Closing the
damper forces hot air
to circulate
lower in the stove before leaving through the bottom stovepipe.
Thus more
heat is transferred to the room and less is lost through the pipe.
CAUTION:
Do not open the lid while the fuel is burning.
Oxygen thus mixed
with flammable gases can cause a
flare-up.
With dry
sawdust and a good draft, one charge of this stove can heat a room
20 feet
square for 6 to 8 hours with no tending.
Wetter fuel heats less but
lasts
longer. During the first 2 hours of
burning, there is enough heat at
the center of
the lid to boil water or cook with. As
burning progresses,
the heat on
the lid is distributed more toward the rim.
VITA
VOLUNTEERS
IN TECHNICAL
ASSISTANCE
ABOUT VITA
Volunteers in
Technical Assistance (VITA) is
a private,
nonprofit, international development
organization.
Started in 1959 by a
group of
concerned scientists and engineers,
VITA
maintains an extensive documentation
center and
worldwide roster of volunteer
technical
experts. VITA makes available to
individuals
and groups in developing countries
a variety of
information and technical
resources
aimed at fostering self-sufficiency--needs
assessment and
program development
support;
by-mail and on-site consulting
services;
information systems training. It
also
publishes a quarterly newsletter and a
variety of
technical manuals and bulletins.
For more information, contact:
VITA
1600 Wilson Boulevard, Suite 500
Arlington, VA 22209 USA
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