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Tom,<br>
<br>
Thanks for hunting down and posting the photos for me.<br>
<br>
Crispin,<br>
<br>
Thanks once more for the advice. I am weighing up whether to cut
away some more material from the bricks at either side of the throat
to give space to modify the grate angle and/or height once the stove
is complete or if I should modify the grate (quite possibly make a
new one from bar as you suggested) so that it can be lifted higher.
I'm thinking it would be best not to cut the bricks. <br>
<br>
I was just looking at pricing for refractory board to make the
sloping sides in the upper part of the combustion chamber. I'm
planning to have three boards on all sides except where the door
is. <br>
<br>
I'm looking at 300mm x 200mm x 10mm - prices for soldering boards on
ebay, about £10 each). My father rang me and I told him what I'm up
to and he said he thought he had a sheet of fireproof roofing sheet
(asbestos replacement), which his brother had given him, in his shed
which should be big enough for what I need....<br>
<br>
I've decided to add a second secondary air inlet on the front of the
burner, if for no other reason than to have it inputting some hot
air up by the window in the door to keep it clean. Also means I can
play about with the opening of primary air, flue damper, both
secondary air inlets and see what effect each has on the burn in the
combustion chamber.<br>
<br>
Best<br>
<br>
Darren<br>
<br>
<br>
<br>
On 25/11/2011 22:20, Crispin Pemberton-Pigott wrote:
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<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">Dear
Darren<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">This
is coming along well.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">></span><span
lang="EN-US">Some photos are attached.<span
style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">Got
them, thanks.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><br>
<span style="color:#1F497D">></span>The door and hatch
are made and have fire rope seals. <span
style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">Good
move. The hopper should have no air passing through it.
There is a pyrolysis zone above and near the primary air
entrance, then a burning zone further to the left (back of
the grate) then a gas burning zone above the rear of the
grate ascending into the vertical chimney.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">></span><span
lang="EN-US">I've used a cast iron grate from an old coal
stove that was the perfect size.<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">It
looks really. I think you should expect to make two changes
once you get going. One is to decrease the gap between the
grate and the ceramic bridge (we found 75mm is perfect for
the fuel we are burning) and to increase the 10 degree angle
as a means for achieving this. That means lifting up the
front or near end of the grate. What would make you want to
try that would be excessive smoke caused by too much fuel
burning at once. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">We
ran quite a number of tests with different spacings like 65,
70, 75 and 85 and 90mm but all having 10 degrees of slope.
The 75 mm straight line distance was perfect. It gave an
excess air ratio of 80-120% and extraordinarily low PM
values for much of the time. Because your fuel is different
you are going to have to do some hit and miss too until you
get a really clean flame about 15 minutes after ignition and
thereafter, no smoke. Hopefully it will perform as expected.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><br>
*At the moment all the secondary air is going in through
some square section pipe with an internal diameter of
20x20mm that enters at the rear of the combustion chamber
above the ceramic blocks. (shown as blue square in
stove2-7.jpg). Is this going to supply enough air or should
I put a similar sized secondary air inlet on the front of
the stove also?<br>
<br>
<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">This
si going to be a very difficult question to answer without
equipment. Suppose you have enough air but your 100mm grate
gap is too big. It might incline you to provide more
secondary air when you really needed to reduce the burn
rate. At some point, you have enough power, so the air to
match it is ‘X’ value. At a higher or lower burn rate, you
need a different amount. You are gonna tell us what you
need! I think the 20 x 20 may be too much but the fuel is
different. The easy test is to open and close it when there
is only a little smoke. It should make very little as it
transitions from one firepower to another as it lights up.
Somehow the feedback from you hand closing it will tell you
which way to take things.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">If
you can’t see any need for it, close it totally. It just add
air with no effect other than to cool the output gases. If
you need it, leave it open. We have not found any need to
adjust the secondary volume when it is running. Most of the
secondary air enters through the far end (back) of the grate
where there is less fuel.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><br>
*Crispins GIZ design has an area where the combustion
chamber tapers wider (an expansion chamber?). I've drawn
this in green in stove2-7.jpg . How important is this? <span
style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">The
expansion is important but not critical. If you can, do it.
Professor Lodoysamba found that filling the combustion
chamber with wood and top-lighting it provided immediate
heat for cooking, very low emissions and easy ignition
(automatic) of the fuel under the hopper. Very clever.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">When
the fire reaches under the hopper, he had to shake the grate
to move fuel down onto the grate. That is all in terms of
attention.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">></span><span
lang="EN-US">What effect does it have on combustion? what
would happen if I leave them out?<br>
<br>
<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">The
effect of the bricks/ceramic is to improve the combustion by
having hot walls. If you can’t get real refractory bricks
second hand, use the hardest clay face bring you can find.
It will last the longers in terms of off the shelf material.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><br>
<span style="color:#1F497D">>…</span>Hopefully I should
finish and test fire it in the coming week.<br>
<br>
<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">Looking
forward to more pictures and your comments.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">></span><span
lang="EN-US">I've attached a diagram of how I'm now planning
to build the grate and throat area. (I took the liberty of
modifying the GIZ diagram Crispin kindly sent to explain an
appropriate layout) <br>
<br>
<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">You
construction matches the drawing.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><br>
As I'm only going to be burning wood and in my experience of
wood stoves all the wood burns to a light ash which would
easily fall through the grate I am planning to have a
stationary grate. Am I making the wrong decision here? <br>
<br>
<span style="color:#1F497D"><o:p></o:p></span></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">The
grate gaps look large which will create extra charcoal that
might get snuffed in the ashes. Other than that it is fine.
If the grate turns out to be too ‘coarse’ you can drop in a
set of 12mm steel reinforcing bars welded into a grid. Works
fine.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><br>
<span style="color:#1F497D">></span>Hoping to get it
finished soon. Considering the number of people I've been
describing it to all year it would be good to also let them
know how it works!!! I've never seen anything like this in
action - I'm thoroughly intrigued. <br>
<br>
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">You
are going to have to try it with charcoal briquettes, wood
pellets, wood, chopped up wood, coal and switchgrass cubes
if you want us all to be happy! Good luck.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">Crispin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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