<html><head></head><body data-blackberry-caret-color="#00a8df" style="background-color: rgb(255, 255, 255); line-height: initial;"><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><span style="font-size: initial; line-height: initial; text-align: initial;"><br name="BB10" caretmarkerset="INVALID" class="markedForCaretMarkerRemoval"></span></div> Dear David the Experimenter<div><br></div><div>Well done. You have reproduced the effects including the breaking of the edges of the material. </div><div><br></div><div>Notes:</div><div><br name="BB10" caretmarkerset="INVALID" class="markedForCaretMarkerRemoval"></div><div>Hot rolled steel is less prone to cracking than cold rolled steel. They are marked CRS and HRS. CRS lasts slightly longer in a fire because it is smoother. Corrodes slower. </div><div><br></div><div>Galvanised sheets are available in two types: suitable for rolling into tanks and hammering into products, then a higher carbon version for making roofing. The higher carbon means its ductility is lower and it cracks more easily. </div><div><br></div><div>If the punch has a rounded end (it is just a forming tool) it cracks less. Oiling it helps. I use a 45 deg bevel on it and a 'lead' the diameter of the hole because I can make the tool myself. After a counterbore, the die can have a guide hole the same diameter as the initial hole to guide the punch and material keeping everything centred. </div><div><br></div><div>Thanks for reporting the result. </div><div><br></div><div>Regards </div><div>Crispin making diluter parts on the lathe today</div><div><br><div style=""><meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<div class="PlainText">On Wed, Apr 30, 2014 at 07:26:31AM +0800, Crispin Pembert-Pigott wrote:<br>
> To get better penetration into the rising column of gas, make holes as<br>
> follows:<br>
<br>
I have tried this out. I can see a difference: judging by the shape of<br>
the flames, the secondary air penetrates further into the rising wood<br>
gas in narrower jets.<br>
<br>
It's difficult to punch inlets that do not have cracks in them, but I'm<br>
having better luck in my latest attempts than when I began. Oiling both<br>
the homemade punch and die seems to help.<br>
<br>
I can induce a swirl by tilting the secondary air inlets. I have found<br>
that reinserting the punch and using it to bend the inlets in the<br>
direction I desire is easier than punching with punch and die offset.<br>
Bending the inlets lengthen any cracks in the sheet metal.<br>
<br>
My previous burner used 48 secondary inlets with sharp edges. My<br>
current burner uses 32 inlets with radiused edges. I'm not getting<br>
complete combustion (soot builds up on my kettle), so I'm going to try<br>
concentrating rings (both inner and outer) above the secondary air<br>
supply, since that is a simple and nondestructive experiment. Then I<br>
may add more inlets.<br>
<br>
Dave<br>
<br>
-- <br>
David Young<br>
dyoung@pobox.com Urbana, IL (217) 721-9981<br>
<br>
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