Truncated cone basket grates

["Crispin" <crispin@newdawn.sz>]

Dear Stovers

The nomenclature problem for the grate is recognized.  I have no real
opinion on it.  What is clear to you?

If you want to make a basket grate and try it out, make a truncated cone
with a large diameter (the top) of about 135-140mm and a bottom of about
115mm. The height should be about 250-275mm.  Space the holes in it so that
the are approximately evenly distributed. Make 60-80 holes with a diameter
of 7.5mm (a-la-Hancock) or 10.5 (a-la-New Dawn).  The bottom is completely
open with just enough wire or grate or expanded steel sheet to hold the fuel
while it is burning.

It has to sit inside a secondary air tube that is very loose, about 145mm in
diameter and similar height.  Hold it as you will, fill with about 150-250
grams of small wood and bottom light!  Once it is heated up, it should boil
a litre of water in under 3 minutes depending on the pot's mass
size/colour/finish.

You can create a charcoaling grate by placing a large washer cut from sheet
metal so the bottom hole is reduced to 25-40 in diameter and then drop in a
sleeve made from a rolled up sheet so that it blocks half or more of the
holes.

Paul, you might try this so you can block secondary air in portions of the
grate in an experimental fashion.  The fuel at the bottom, though
bottom-burning not top-burning, is starved of air and smokes excessively.
This smoke is burned in the upper section of the grate when mixed with
pre-heated secondary air.  Substantial charcoal is produced because of a
lack of primary air.  I do not find this useful.

You can continue to add fuel from the top as long as you only add it up to
the top of the inner sleeve.  More charcoal can be made in this way.
Removing the sleeve and washer turns it into a regular stove again.  The
washer will block the ash from falling out so it will not clear itself like
a Tsotso or Basintuthu.

One problem I have had with the choked stoves is that if the primary air is
preheated it is difficult to turn the power down without continuing to
generate so much wood gas that it lights up when it has left the stove/pot
area and flames off like an oil rig.  It is impressive but it is not very
efficient when doing that.  The immediate cause appears to be that heat
stored in the steel work drives the gassing and as the temperature of the
incoming air rises significantly due to its decreased velocity, the process
may even accelerate!  Not what I have in mind.  My cure is to limit the fuel
content as the main power control mechanism on that layout.

Regards
Crispin


-
Stoves List Archives and Website:
http://www.crest.org/discussion/stoves/current/
http://www.ikweb.com/enuff/public_html/Stoves.html

Stoves List Moderators:
Ron Larson, ronallarson@qwest.net
Alex English, english@adan.kingston.net
Elsen L. Karstad, elk@wananchi.com www.chardust.com

List-Post: <mailto:stoves@crest.org>
List-Help: <mailto:stoves-help@crest.org>
List-Unsubscribe: <mailto:stoves-unsubscribe@crest.org>
List-Subscribe: <mailto:stoves-subscribe@crest.org>

Sponsor the Stoves List: http://www.crest.org/discuss3.html
-
Other Biomass Stoves Events and Information:
http://www.bioenergy2002.org
http://solstice.crest.org/renewables/biomass-info/
http://solstice.crest.org/renewables/biomass-info/carbon.shtml

For information about CHAMBERS STOVES
http://www.ikweb.com/enuff/public_html/Chamber.htm