<html><head><base href="x-msg://53/"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">So there you have it Vincent and Crispin<div> </div><div>Seems that a compromise would be for a smaller surface contact area to optimize char production but still one which tapers to the bottom of the stove to limit bridging would be the ideal. </div><div>viz;</div><blockquote class="webkit-indent-blockquote" style="margin: 0 0 0 40px; border: none; padding: 0px;"><blockquote class="webkit-indent-blockquote" style="margin: 0 0 0 40px; border: none; padding: 0px;"><blockquote class="webkit-indent-blockquote" style="margin: 0 0 0 40px; border: none; padding: 0px;"><blockquote class="webkit-indent-blockquote" style="margin: 0 0 0 40px; border: none; padding: 0px;"><blockquote class="webkit-indent-blockquote" style="margin: 0 0 0 40px; border: none; padding: 0px;"><div><img id="0a3924d2-aba5-44a0-b2b0-b085f51b0097" height="480" width="530" apple-width="yes" apple-height="yes" src="cid:D178F707-3D79-4765-9F53-EA2439D6FF60"></div><div><br></div></blockquote></blockquote></blockquote></blockquote></blockquote><div>Richard </div><div><br></div><div><br></div><div><br></div><div><div><div>On Jan 22, 2014, at 4:51 PM, Crispin Pemberton-Pigott wrote:</div><br class="Apple-interchange-newline"><div lang="EN-CA" link="blue" vlink="purple"><div class="WordSection1" style="page: WordSection1; "><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Dear Richard and Vincent<o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Jambo.<o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">I see just about everyone found that adding a grate to a flat-bottomed stove improves the performance.<o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><b><span lang="EN-US" style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">RS>…</span></b>I would advise use of round bars as Crispin but I would suggest you grind any round bars down to result in effectively a series of had cylinders along their length with the flat side up.<span style="color: rgb(31, 73, 125); "><o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">I would advise the opposite and the metric to use in evaluating the difference is the mass fraction of charcoal produced by the fire. We found (for reasons that are not yet known) having a flat top definitely produces more char thus losing more heat. It may have something to do with the thermal contact the char piece makes with the metal, conducting the heat away. This lowers the temperature of the ‘coal’ and causes it to burn poorly or go out. There was a large mass difference for flat and round bars – more than double. The thermal contact between a coal and the round bar is much smaller.<o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">That is the only ‘guess’ I have so far. We will look into this further at YDD this year. The two things tried were round bars from mild steel (multiple welded pieces) and cast iron with a flat top (single piece). Cast iron conducts less heat than mild steel but it still consistently produced much more char. That is not useful as fuel in most homes and it is tossed with the ash. Indar reported the round bar grate produced virtually no char at all, finishing its burn at virtually the same time as the wood. That was amazing.<o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">You may need to restrict the air entry area to limit the air level below the combustion chamber. If it is ‘right’ you will see large flames wandering around in a low velocity environment below the pot – no flapping arms of flame. You should limit the pot gap (by shaping those tongues of clay) to about 7mm for all pot sizes. This means trimming the slanted ones and lowering the top ones (in most stoves).<o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">The combination gives you the right balance of primary and secondary air.<o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Nzuri kuhusu<o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Crispin<o:p></o:p></span></div><div style="margin-top: 0mm; margin-right: 0mm; margin-bottom: 0.0001pt; margin-left: 0mm; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div></div></div>_______________________________________________<br>Stoves mailing list<br><br>to Send a Message to the list, use the email address<br><a href="mailto:stoves@lists.bioenergylists.org" style="color: blue; text-decoration: underline; ">stoves@lists.bioenergylists.org</a><br><br>to UNSUBSCRIBE or Change your List Settings use the web page<br><a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" style="color: blue; text-decoration: underline; ">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br><br>for more Biomass Cooking Stoves, News and Information see our web site:<br><a href="http://stoves.bioenergylists.org/" style="color: blue; text-decoration: underline; ">http://stoves.bioenergylists.org/</a><br><br></div></div><br></div></body></html>