THE KIWI STOVE

Contributed byJim Rogers, 1/08/02


Here's a new stove design that burns just like the Photon/Pepsi can stove, but is as easy to make as the Cat stove. I call it the "Kiwi Stove." I do not have a web site, so I'm just posting the instructions here. It's so simple, however, that no pictures are needed if you are at all familiar with the Photon stove.

I believe this to be a new design as I searched the web and found nothing like it. However, if this design has already been used by someone, I apologize profusely and will gladly give the correct credit.

Instructions:

1.) Read and understand the Photon Stove instruction page ( http://www.members.home.net/d.h.j/index.html), especially the disclaimer. While my design is very similar in principle to the Photon stove and I have been using it for several months with no problem, I'm no stove engineer and, for all I know, there might be some condition that could cause it to explode and kill you.

2.) Purchase a can of Kiwi shoe polish (hence the name of the stove!) and empty its contents. (If you get the neutral color, there is less chance of making a huge mess.) Warning-- I don't know why, but about half of the Kiwi cans on the store shelves have a hole punctured in the top with a small disk of clear tape covering it. Don't get one of those. Get one where the top has no holes in it.

3.) The bottom of the Kiwi can will be the top of the stove. Make the pin holes in the bottom of the can just like for the Photon stove (i.e., get the size right-- I use the recommended needle and a hammer). There is even a little rim around the edge of the can bottom so that you can have 8 holes facing at an angle toward the center and eight pointing straight up from the peak of the ridge, just as in the Photon. While it works fine this way, I didn't like that orientation of holes because the flames were spaced out to the edges of my kettle and they tended to ride up the sides too much for my liking. (However, with flames at both the bottom and sides of the kettle, boil times were really fast! I'm just afraid to have that tall of flames when I cook in my vestibule.) Thus, I make 18 pin holes in a lattice pattern with about inch spacing. The holes are thus in an area about the size a half dollar right in the center. It burns just like a Bunsen burner with one nice large blue flame in the middle. However you do it, make sure you have 17-18 holes rather than the 20 of the Photon stove. Warning-- see the P.S. below on experimenting with burner holes!

4.) 2-3 more holes must be added to the top (same size as the others), but these are put into the side of the top, facing straight out sideways. The little twisty thing used to separate the halves will be another side hole (it's not air-tight), so put the 2-3 aditional holes in a symmetric pattern, e.g., one pin hole directly opposite the twisty thing and two more at 3 and 9 o'clock, or, with the twisty thing at 12 o'clock, put one pinhole at 4 o'clock and one at 8 o'clock. As far as up/down orientation, put them at a slightly higher level than the twisty thing.

5.) Make the base out of the 10 oz. chicken can just like for the Photon stove, but make it a bittaller-- so that the side of the base is just a smidgen taller than the assembled Kiwi can when it sits in the base. Also make the pot support the same way out of the metal cloth (however, mine worked better when it was a half inch taller). Finally, make the same windscreen-- I used oven liner aluminum, but whatever you use make sure it is tall enough to overlap the kettle by at least an inch.

6.) You're done! To use the stove:

i) Separate the halves of the Kiwi can (using the little twisty thing provided on the side) and put the desired amount of alcohol into the bottom half (which was originally the top of the polish can). Two 20 oz. soda bottle capfuls is plenty to boil 16 oz. of 50* water. Put the top back on (i.e., put the halves back together), making sure that in snaps together tightly. Warning-- read the Photon page about fuels. Use only alcohol!!!!

ii) Place the fuel-filled Kiwi can in the base (centered) with the pot support and windscreen in place. Have the water in the kettle and ready to go. (You can leave out the windscreen initially while you are testing so that you can see how the stove is performing.)

iii) Put a little less than of a capful of alcohol in the base to get it started. Because the base is deeper than it was for the Photon stove, it is difficult to light if all of the starter alcohol is down in the base, so be sure to drip some right on the top of the Kiwi can.

iv) Light the starter fuel on top of the Kiwi can. In less than a second, the rest in the base will ignite. Put the water on the stove. After about 30-60 seconds, you should hear the hissing sound characteristic of the main fuel supply (in the Kiwi can) being induced to boil by the starter fuel (in the base). (The fuel burning in the base will light the fuel coming out of the Kiwi can.) If you left out the windscreen for testing, you'll see the main burners ignite and eventually shoot out a strong blue flame. When the stove is really going, you won't see the individual side flames, just flame generally in the base. After it has been burning for awhile, you will see individual side flames.

7.) The principle: Like the Photon stove, the burner holes are at just the right diameter so as to create a small amount of pressure in the system. Unlike the Photon stove where the outside flames heat the lip of the bottom half to boil the fuel contained below, the Kiwi stove uses a few jets shooting sideways to heat the base which subsequently heats the fuel in the Kiwi can. At first I feared that these side jets might "waste" some of the fuel inasmuch as they are not directly pointing at the kettle, but the performance figures (see below) seem to indicate that this is not a problem.

8.) Performance: The performance of the Kiwi stove appears to at least the same as the Photon stove. I have accurately measured out 16 oz. of water, put it at 50* and timed the boil. The elevation of my town is 996 feet. The times are always in the range of 3:15-3:45 to get a furious, roiling boil (with steam shooting vigourously out of the spout). My kettle is aluminum (the Photon was tested with a titanium kettle), so the better conductance of the aluminum probably accounts for the slightly faster time, but my kettle also has an open spout (which loses some heat), so I don't know for sure. Anyway, it's no slower and it weighs almost exactly the same. The Kiwi can is aluminum, and while my base is a bit heavier (since it is taller), there is no JB weld in the burner so it's a wash.

9.) Troubleshooting: The main thing is to get the holes right. If the main fuel is lighting initially but losing its urgency after the starter fuel is gone, make sure the side jets are working. There should be flames shooting out sideways from them right on to the base can. If the flame is going over the top of the base, make a taller base. If the base looks OK, add a third side hole (if you were using two). If it still does not work, there is something wrong with the top burner holes. You need to make them a bit smaller if the flames have no urgency and a bit larger if they are going like a blowtorch and trying to blow themselves out by rising above the surface of the Kiwi can. One of the benefits of this design is that you can easily play around with hole sizes, numbers, and patterns since all you have to do is buy and empty another inexpensive can of shoe polish. With the Photon stove, you would have to do a fair amount of cutting, three-hole punching, fitting and gluing of the cans only to find out the holes are no good. Warning-- see the P.S. below for a hole experiment NOT to try!

10.) My impression of the Kiwi stove vs. the Photon stove:

i) Weight, compactness (packing), and performance are virtually identical.

ii) The Kiwi stove is much easier to make. No cutting, punching, and gluing of the burner. Also, there are no filler hole issues since the two halves just come apart. Just punch the burner holes, make the base and pot support and it's done. As stated above, the ease of assembly makes the idea of experimenting with different hole designs much more appealing.

iii) The fuel heating mechanism of the Photon stove is, IMHO, a more elegant design than the Kiwi stove's side jets. However, the side jet design does seem to work as well. One potential issue is that the base of the Kiwi stove (heated by the side jets) heats the fuel in the Kiwi can. Therefore, it may get hotter than the Photon stove base (although I do not know this for a fact). I suppose there are some conditions (dry grass under the stove?) where this could be an issue. However, if you set up on a rock or dirt there is no potential for problems. After all, the Photon base would be just as hot during the lighting phase.

iv) The fuel capacity of the Kiwi stove is limited, so if you want to bring something to a boil and then let it simmer for a really long time, the Kiwi stove may not hold enough fuel. About 4-5 capfuls (from a 20 oz. soda bottle) is the limit. Capacity is not an issue for me since I only boil water and 3-4 capfuls of alcohol will easily bring a full quart of cold water to a furious roiling boil (usually with some fuel to spare, but, of course, it depends on the starting temp of the water). The Photon stove looks like it could hold much more fuel. Speaking of simmering, I have not designed a simmering ring (I never simmer), but I would do it by making a ring that would encircle the Kiwi can close enough to snuff the side jets. I know for a fact that without side jets (or too few side jets), it will still burn, just not very hard.

That's my stove design. Give it a try, and let me know how it works out. I am very pleased with mine-- In the last five months since I worked out this design, I've probably boiled 10 gallons of water (16 oz. at a time-- my wife thought I was going nuts!) under various circumstances with no problems at all.

Good Luck!

P.S. A dangerous attempt at a hole design for the Kiwi Stove:

Since it is so easy to make this stove, I played around with about 10 different hole designs. As stated above, I wanted more of a Bunsen burner type flame so, looking at the Cat stove design with that huge hole in the center, I thought I might try making a single burner hole in the center of the burner that would have the same area as the sum of the 20 pin holes of the Photon stove. I calculated that my smallest drill bit would be about right, so I tried it. I lit the starter fuel and it worked, but the flame was coming out too hard-- like a blow torch. So I decided to make the hole bigger. However, the next smallest drill bit I had was 3/32 (very small, but about twice as large as the first hole), but I decided to give it a shot anyway. Big mistake. The hole was big enough for the fire from the starter fuel to instantly ignite the fuel vapors in the Kiwi can-- a possibility I had not considered. The whole thing exploded the second I lighted it, spewing flaming alcohol all over my shirt and the hand I used to light it. Luckily, un-pressurized ethanol burns very gently and I put myself out before I was burned. Also, because the stove readily separates into two halves, the force of the explosion was not as great as it might have been had the stove been a sealed unit with a tight filler cap. Lord only knows what might of happened in that case. The moral of the story is to BE CAREFUL WHEN EXPERIMENTING WITH STOVE DESIGNS!!!!!!!!!! These things have the potential to be very dangerous if a poor design is used!

Now, with pin holes, I've never had any problems. They are just too small for the fire to get into the main fuel holder-- the experience of the many people who use the Photon stove confirms this. I'm very confident that if you stick to experimenting with different layouts of about 18 pinholes, you will have no trouble at all and may come up with a better design than the one I describe in the instructions!


 
 
Jim Rogers, 1/08/02
jrogers@unmc.edu


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