<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><br class=""></div><div class="">Dear Crispin,</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div>Does it set in a metal bucket make a big difference? Its the same stove just placed into a bucket -right?<div class=""><br class=""></div><div class="">Thanks</div><div class=""><br class=""></div><div class="">Frank</div><div class=""><br class=""></div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Dec 13, 2015, at 6:14 PM, Crispin Pemberton-Pigott <<a href="mailto:crispinpigott@outlook.com" class="">crispinpigott@outlook.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; font-family: Helvetica; font-size: 18px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Dear Francesco<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">This device was discussed earlier this year (late last year?) on this list. Perhaps you did not see those messages.<span class="Apple-converted-space"> </span><o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">In terms of function, it is very similar to the grate added to the traditional Keren Stove from Java which is produced in the millions each year by artisans.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">The Keren was improved significantly, particularly in terms of fuel efficiency, by adding a sloped grate under the fire and admitting air at the back instead of all coming from the front. Another change was increasing the height of the cylindrical portion of the body above the fuel entrance which had the effect of lowering the fuel door height. Another modification was reducing the pot rest height from 25 to 7mm in order to cap t he total gas flow rate past the pot. This is the poor man’s alternative to controlling air entry.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Here is the original:<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class=""><span id="cid:image003.jpg@01D13658.49560090"><image003.jpg></span></span><span style="color: rgb(31, 73, 125);" class=""><o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">And here is the Keren Super<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class=""><span id="cid:image005.jpg@01D13658.49560090"><image005.jpg></span></span><span style="color: rgb(31, 73, 125);" class=""><o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">And here is the Keren Super 2 which is in an insulated metal bucket:<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class=""><span id="cid:image007.jpg@01D13658.49560090"><image007.jpg></span></span><span style="color: rgb(31, 73, 125);" class=""><o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">The other air entry holes (which were random, really) are all removed, with air entering only with the fuel and under the rear of the grate.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">The grate bar gap is important. It should be 4 to 5 mm (only) and the bars should be 12mm round or reinforcing bars. It is cheaper to use a smaller diameter but there is a difference in performance in that the air flow through the grate is spread over a larger area and the effectiveness at burning the charcoal is reduced.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">The stoves look almost exactly the same at a glance, but the performance is very different. The energy efficiency (fuel consumed energy to pot energy) for the traditional layout is about 16-17%. The Keren Super is 27-28%. The main contributor is the taller top and lower pot rests. The CO is reduced by the grate and air supply.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">The fuel saving is pretty large (1-old %/new %)*100% = 40% for such a simple set of changes.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Anything that produces the same result will work, including the metal grate inserted under the fire.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Here is a cast iron version of the Keren Super grate.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class=""><span id="cid:image010.jpg@01D13658.49560090"><image010.jpg></span></span><span style="color: rgb(31, 73, 125);" class=""><o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Note that the legs on the left are taller than the right. The left side goes at the back and the short ones at the front. The casting pattern has all the legs the same length. The two sides are identical and the legs shortened afterwards. It is in two parts so it can fit through the hole.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Care should be taken with the shape of the top of the stove so the different pot profiles all sit in such a way that the gap is 7mm. The gap is related to the circumference and the firepower. It does not scale linearly. If you change the pot and fire size a lot, check each gap 1mm at a time until you fine that it is optimised. If the gas flow rate is too low, smoke will emerge from the fuel door. It should<span class="Apple-converted-space"> </span><i class="">almost</i><span class="Apple-converted-space"> </span>do that.<span class="Apple-converted-space"> </span><o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">The Indian Chula can be improved by applying theses three adaptions: check the pot rest height, increase the cylinder height (reducing the door height as much as you an depending on the fuel that must get into it), add a grate with air enter at the back (to push the fire towards the centre, not against the back wall).<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">The orientation of the grate bars should be front to back, not left to right. This allows the air entry to do a better job of pushing the fire and when fuel it fed in, it is more likely to push the ash through the grate and the charcoal to the back where the rear air will burn it cleanly.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Have fun!<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class="">Crispin<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;" class="" type="cite"><blockquote style="margin-top: 5pt; margin-bottom: 5pt;" class="" type="cite"><pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class=""><o:p class=""> </o:p></pre><pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class="">Has anyone seen this addition to a traditional stone heart? It is has been<o:p class=""></o:p></pre><pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class="">developed in collaboration with the University of Iowa.<o:p class=""></o:p></pre><pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class=""><o:p class=""> </o:p></pre><pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class=""><a href="http://www.thesolutionsjournal.com/node/237379" style="color: rgb(149, 79, 114); text-decoration: underline;" class="">http://www.thesolutionsjournal.com/node/237379</a><o:p class=""></o:p></pre><pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class=""><o:p class=""> </o:p></pre><pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class="">Francesco<o:p class=""></o:p></pre></blockquote><pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class=""><o:p class=""> </o:p></pre></blockquote></div><span style="font-family: Helvetica; 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