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Post by Donkey on Oct 21, 2011 12:58:46 GMT -8
So I pulled out the piece, cooled it and ground it down to a 3/8 inch gap. Was just out inspecting the thing and realized that I've completely forgotten to shorten the tab hanging down into the burn tunnel. It still protrudes about 1/2 inch down. Next time, I'll NOT grind it straight down to 3/8 inch (air gap width) right away.. Each tank of hot water needs two fills of the feed, one load from a dead start and one with a fully heated stove core. It's a bit hare-brained but I've been running back and forth to the grinder and seeing differences thus far.. |
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Post by peterberg on Oct 23, 2011 1:09:27 GMT -8
(I think i got that right, Peter?) Thank you, Donkey! Your description of the trip wire is very comprehensive, even I was able to understand it first time. endrunner, The phenomenon was first discovered by Ludwig Prandtl, one of the founders of modern aerodynamics. A crash course on aerodynamics and turbulence you'll find here all about boundary layers, trip wires, vortex generators and whatnot. |
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Post by peterberg on Oct 23, 2011 2:37:49 GMT -8
...As a last ditch observational exercise, I sniffed at the flue opening.. Now, at this point it's ENTIRELY subjective but it seems as though the odor was a little.... Lighter is the word that comes to mind. This stove tends to have a slight wet charcoal, sweaty socks kind of smell. Yesterday it smelled like the socks had dried somewhat Here at home, the Testo sniffed at the exhaust, which is less subjective. But, this apparatus did come to the same conclusion. Namely, less residue in the exhaust gases. According to the Good Info by Erica, your stove is a little bit closer to complete combustion. The 9-methyl ketone she mentions can still be smelled in a very low concentration, even down to a couple of molecules. When you only THINK it's lighter, it definitely is. Consequently, more of the fuel has been reacting with oxygen and providing more heat in the process. Not a lot, but also tiny steps forward are still forward... P.S., May I suggest to leave the tab overhang as it is for the moment? The exact measurement of this is not as important as the gap. |
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hpmer
Full Member
Posts: 240
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Post by hpmer on Oct 23, 2011 15:11:49 GMT -8
Could one use a simple copper pipe to provide the secondary air? Perhaps a 3/4" pipe (or two)?
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Post by endrunner on Oct 23, 2011 16:07:11 GMT -8
thanks for the explanation and links!
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Post by Donkey on Oct 23, 2011 17:04:33 GMT -8
May I suggest to leave the tab overhang as it is for the moment? The exact measurement of this is not as important as the gap. Oops.. Too late. It's ground to it's final 3/8 of an inch. I ran it today and it appears to work perfectly. No slow start problem and it appears to burn quite well. There's no way really to tell what it's doing, good bad or indifferent... It appears to help, by the nose, but at this point it's all subjective. I suppose I'll need to run the stove with it and compare to running without to see if a REAL difference can be discerned. |
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Post by Donkey on Oct 23, 2011 18:25:41 GMT -8
Could one use a simple copper pipe to provide the secondary air? Perhaps a 3/4" pipe (or two)? Perhaps.. Seems to me that the simple plate spacer is elegant and (probably) solves AT LEAST 3 problems simultaneously. The first, it may clean up the burn a bit. The second, it may keep the fire from creeping up and out of the firebox. The third, which occurred to me just yesterday, it may cool the first brick just enough to keep it from cracking. Using pipes may help clean up the fire a bit, but it probably won't solve the other issues as cleanly or simply. |
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Post by peterberg on Oct 24, 2011 11:33:39 GMT -8
Seems to me that the simple plate spacer is elegant and (probably) solves AT LEAST 3 problems simultaneously. Another problem is solved for sure: with the plate in place it is impossible to let the fuel lean to the burn tunnel and create a dirty burn. Not even by accident. I've seen it happen last Saturday, running an unaltered 8" system. I've brought the Testo equipment along and was able to show the effect with a live graphic. Exactly the same reaction as with the 4" system, albeit not as pronounced. |
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Post by Donkey on Oct 27, 2011 18:20:12 GMT -8
Well, I'm pretty convinced that my shower house stove is GREATLY improved with the new addition.
I've run it several times now, sometimes with and sometimes without the air channel. I've started the stove and pulled the thing in and out and watched the difference.
Pretty much without a doubt, this thing's a winner with my stove!
I'm sold and now looking for excuses to try it in other stoves.. I've got a six incher down in the guest hut that needs a little repair, I think I'll build an air plate for it too.
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Post by peterberg on Oct 28, 2011 10:07:17 GMT -8
@donkey, Thanks! I'm very glad you're able to confirm my findings. Maybe the repairs in the guest hut is involving the bridge over the burn tunnel? If that's the case, you could consider to modify a brick, say the second one from the feed.  Something like the one in the picture. It will form a usable trip wire, although not with a smaller than 90 degrees angle to the air stream, that will be a tad more complicated. So, the "bluff body" itself is quite small but adequate, a 1/4" or even smaller will be all you need. It will perturb the boundary layer without too much friction in the air path. |
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Post by pinhead on Oct 28, 2011 12:20:53 GMT -8
One question: What percentage of the feed tube cross-sectional area comprises the secondary air inlet?
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Post by peterberg on Oct 28, 2011 13:19:55 GMT -8
One question: What percentage of the feed tube cross-sectional area comprises the secondary air inlet? When total opening is 100%, the 2nd inlet is 5%. A tiny proportion of the opening is occupied by the metal plate, not calculated. |
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Post by Donkey on Oct 28, 2011 21:30:10 GMT -8
Maybe the repairs in the guest hut is involving the bridge over the burn tunnel? If that's the case, you could consider to modify a brick, say the second one from the feed. That's funny.. I was thinking the EXACT same thing. No, I had no intention of doing surgery on the burn tunnel, though now that you've seconded the thought I might try it. The way I put the barrel on was weak and the connection broke too easily. I'll be re-setting the barrel in a better configuration, etc. Unfortunately, the thing has been finish plastered already which complicates things.. That is if I don't want to just re-plaster the whole thing, which I don't.  Anyhow.. Here are some pictures of the air channel plate in my shower house.  As I said before, it was made from a piece of an old water tank, beat to shape over an anvil, then ground to size and fit. You can see there's some kind of baked on enamel that coated the inside of the tank. It's quite resilient stuff, only really comes off when it's banged HARD between sledge and anvil. It bubbled a bit on the bottom from exposure to the fire.. I think it would be best to get the stuff off, I'll try burning it off on my charcoal forge soon.  Notice how the wings are bent? The way they set, makes it fall tight against the face of the brick and keep it there. I'll accentuate the effect by notching out the underside of the wings a little at their "arm-pits".  |
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Post by ringoism on Nov 2, 2011 0:04:07 GMT -8
Hey, just jumped over here from the heating section where you'd replied to my earlier post. Your work is amazing - thanks so much for your efforts, I'm sure they'll prove useful for countless people in the days / years to come. The self-destruction of your burn tunnel from heat is not something I'd read about much elsewhere in my research. I'm slightly concerned about that in my case since the unit I'm building is not likely to be very easily dismantled. Refractory castings / bricks / mortar would certainly be available in the "big city" but that's minimum 9-hrs on bad roads through the mountains from here by bus/car and I'm sort of looking for a more simply constructed (not messing with forms, etc) and completely self-contained unit anyway. I mentioned in another post about the supposed heat-cracking problems of 304-grade stainless in boiler applications, which I actually found photos of online. Do you have any specific experience with this or other grades of stainless in high-heat applications? I understand that 409 is better? Also, is there some reason that nobody seems to be using glass-fiber insulation in these units? That's really the only thing (besides wood-ash, which is said to be inferior) I have available - again, without going to the big city and searching endlessly in dusty, nasty third-world industrial markets for something like "vermiculite" which they may very well call by some other name...
Never would have known from reading your posts that English was not your first language - excellent communications / descriptions. BTW, I had the pleasure of visiting the Netherlands some years ago while doing volunteer welding work on a hospital ship used for charity - that was in Rotterdam, but traveled with my roommate north to his home in Kroningen, then later by motorcycle down through the southern hills towards Belgium. Lovely experience re: the time I spent with your countrymen. The countryside / farmland was wonderful, as well.
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Post by Donkey on Nov 10, 2011 13:55:19 GMT -8
@donkey, Thanks! I'm very glad you're able to confirm my findings. Maybe the repairs in the guest hut is involving the bridge over the burn tunnel? If that's the case, you could consider to modify a brick, say the second one from the feed. Something like the one in the picture. It will form a usable trip wire, although not with a smaller than 90 degrees angle to the air stream, that will be a tad more complicated. So, the "bluff body" itself is quite small but adequate, a 1/4" or even smaller will be all you need. It will perturb the boundary layer without too much friction in the air path. OK, The mud hut's rocket stove is only one brick deep, best not to mess with it. Peter, do you think that the down-hanging plate can be (made into) a trip-wire of sorts too? I am currently helping to build a rocket stove not too far from here, I've included your idea with the brick in an 8 inch rocket stove. It's placed 3rd in a 4 and-a-half brick burn tunnel (counting from the feed box). I'd like to see the plate in it as well. Hopefully, it'll only be a week or so before we start seeing results with it. |
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