DOSIP Stove
Name of stove: DOSIP (DOuble-wall, SemI-Pressurized, based on the original Pepsi-can stove).
Type of stove: Try guessing this, using only the name.
URL of original instructions: Based on Scott Henderson’s original Pepsi Can stove. This was later refined to two stoves: the Pepsi-G Stove and Scott’s Mini Stove, a smaller version. (See archived instructions at http://bit.ly/Khbsze and http://bit.ly/Jl6ty4 and for general info on light weight do-it-yourself stoves, see the Zenstoves links page at http://bit.ly/9fZe6O)
Description of difficulty: Higher than the previous stoves, but a little more fun to make, if you like to play with tiny intricate parts having insanely sharp edges. Can be maddening to fit together because the parts just don’t want to go. Sometimes. And you need to take extra special care not to cut your fingers to pieces. It’s by no means impossible or even hard, but can be a little bit slow the first time through especially if you want to do it without getting cut.
Overview: This is a light, hot-burning, nicely-finished type of stove, very similar to the commercially-made Swedish Trangia, but free, and shinier. It is much more complicated to make than the other alcohol stoves listed here, and really no more or less effective but if made carefully enough the result looks professional.
The higher the operating pressure of a stove, the faster and hotter it burns, and the sooner the fuel is gone. Too much pressure, too big a flame, too small a pot, and you’ve wasted a lot of your fuel — the flame just laps up around the outside of the pot and the heat is lost. Generally speaking, the slower-burning stoves are more frugal than the fast and hot ones, but a stove that’s too feeble just won’t work either — heat will leak away just as fast as it goes into the pot. A stove for the ultralight backpacker must be in the sweet spot between cool efficiency and hot waste.
Technical details:
Height: 1" (25 mm)
Diameter: 2.1" (53 mm)
Weight: 0.35 ounce (10 g)
Volume: 1 ounce (30 ml)
Composition: Aluminum cans and aluminized tape.
Materials list:
Two empty 5.5 ounce (163 ml) aluminum juice cans
Foil tape (dryer vent tape, aluminum with adhesive on the back)
Hammer
Ruler
Magazines
Marking pen
Pushpin, heavy safety pin or heavy needle
Sandpaper (100 grit, or thereabouts)
Scissors (beaters that you can cut aluminum with)
Scribe (Pushpin, heavy safety pin or heavy needle)
Sheet of paper
Tape
Utility knife
Work gloves
Overview of construction process: You’ll cut the bottom off two juice cans, and squeeze them together with another, flat sheet of aluminum forming an open vertical cylinder in between. This cylinder forms the stove’s double wall where the fuel boils.
Step-by-step construction:
1: Get two 5.5-ounce juice cans.
These are the ones that V-8 juice or various fruit juices come in. It’s a lot easier working with the larger 12 fluid ounce cans because they’re bigger, but using the smaller cans will give you the smallest, lightest stove. Empty, rinse and dry two cans.
2: Punch burner holes.
A pushpin is the easiest and safest way to get burner holes formed. Watch your fingers, though.
Work with the bottom of one can. There is a ridge on the bottom of the can. Between this ridge and the can wall is a shallow depression, a sort of shoulder. Place the pin on this shoulder and push it through. Tapping it ever so gently with a light hammer works well for this.
Start by placing one hole, then put another one on the opposite side. Punch the third hole on the rim halfway between the first two holes, and put the fourth one opposite that.
Now you’ll have four holes equally spaced around the rim on the bottom of the can. Place each of the next four holes right in between those holes. When done, you’ll have eight holes pretty evenly spaced around the rim of the can.
Go ahead and keep this up until you’ve got either 32 holes, or you get tired, or you’ve go as many holes as you can stand to punch, as evenly spaced as you can get them. Having “too many” holes is better than having “too few”, so don’t get upset if you end up with closer to 40 holes than 32. After the first few, it gets harder and harder to keep them exactly spaced, or at least it gets easier to see that they aren’t exactly spaced, so you’ll probably have to stick in a few extra holes to fill in ugly-looking gaps.
Think of your result as having that “authentic” hand-made look rather than being a failed attempt at achieving perfection. Some holes will always be too far apart, too close to each other, or a little high or low on the rim. Too bad. That’s life. Enjoy it.
If you are impossibly tidy and incapable of enjoying a little randomness, then you can make a template from paper, calculate exactly where each hole should be, use this template to mark the can, and then punch the holes. And they will be absolutely perfect. Happy now?
3: Cut central vent hole.
For this stove, the vent hole is a big one, right in the middle.
Put on your gloves. Still working with the same can, use the utility knife, and put its point inside the can bottom’s central concavity. Keep the point of the knife there with a medium amount of pressure and turn the can around and around. You want to score the aluminum until you can pop out the whole bottom in one disk.
This will take a while, so be patient, and try to make things more efficient by keeping the knife point running in one track, like a phonograph needle in the record groove (for any of you old enough to remember records). OK, I’m repeating this paragraph in all instruction sets, I know. Chill out.
Go around and around and around and around , until you’ve cut deeply enough that you can tap the bottom of the can and it breaks loose. Don’t be in a hurry. This will take like what seems forever. You may have to keep scoring the can for 50 or 100 revolutions. Going slowly is not only safer, but it will give you a better result. Let it happen in its own time.
The bottom of the can will first break through in just one spot — the whole thing won’t suddenly pop out cleanly, but you can keep working at it until you’ve got it all removed.
Some tapping with the blunt end of the utility knife will help. Tap lightly and see if anything happens. If not, then keep scoring. Eventually you’ll get a section of the can’s bottom to break free. Make it wiggle. It will take some wiggling until the metal fatigues and lets go. Work with it. Work your way around until the whole disk pops free.
You will end up with a pretty clean cut that needs a minimum of dressing to make it smooth and safe.
4: Cut away the top of the can.
We’re still working with the first can here. Stand the can up next to a stack of magazines. Be sure your work gloves are on. Leather ones are best. Be sure your utility knife has a sharp, new blade in it.
Lay the utility knife on its side on top of the magazines and put the blade’s point up to the can. At this point you’ll have the can sitting upright, with the burner holes on the bottom, on your work surface.
Adjust the blade’s height by adding or removing magazines (or pieces of cardboard or sheets of paper, for fine tuning) until the knife point is 0.8" (20 mm) above the work surface.
The point of the blade should be just touching the side of the can. Hold the knife down solidly, on its side, with one hand and rotate the can with the other hand, scoring the side of the can. Keep some pressure on the side of the can, but not enough to dent it.
Keep turning the can carefully for several revolutions. You want to make a deeper and deeper score line in the side of the can, and you want to keep the knife in the same groove on each pass. This is impossible to do perfectly, but get as close as you can.
When you think you’ve cut most of the way through the side wall of the can you need to stress it. Use the back side of your knife’s blade (the dull side) or your thumb. Press hard enough to flex the side of the can a little without denting it, and move back and forth along the score line.
Stress a short section of the the can wall this way over and over again. What you’re doing here is trying to fatigue the metal of the can until it breaks apart. This will give you a cleaner result than if you cut through the can with the knife.
This part of the process is trial and error, so just keep at it until you find a scored part of the can’s wall that just lets go. You can go back to scoring the side again for awhile, to deepen the cut if this doesn’t seem to be working. It takes a while to start working.
Once part of the scored line breaks through you can keep working along it, turning the can and breaking it apart along your scored line until the top part separates from the bottom part. Once you get the process started, it will be a give and take between stressing the metal and gently pulling the two halves of the can away from each other.
Work very gently. The two main things to keep in mind are not to damage the can and not to get cut. The can will separate when it’s ready.
When done with this step you’ll have the bottom 0.8" (20 mm) of the can separated from the top.
5: Cut the bottom off the second can.
Repeat what you just did, but with the bottom of the second can. When you’ve removed it, you will have a can bottom that’s intact (no holes or cuts). It will be 0.8" (20 mm) high.
6: Make stove’s inner wall.
Take one of the cans that you’ve removed the bottom from and hack off the top, saving the middle part. You want to end up with a rectangle of sheet metal from the side of the can. The can’s bottom is already off, and now you want to remove its top.
Put on your gloves first. This is a part that’s tricky to do without getting sliced to bits. Seriously. This stuff has razor sharp edges as I’ve said elsewhere. The easiest way to do this is with a scissors. You won’t want to use the scissors for anything else after you cut metal with it, so get an old pair, or buy a pair to use just for making stoves. Shorter scissors really help in tight places like this. Coleman sells a pair of folding camp scissors for about three bucks. They’re about the right size and price, and they work well.
OK, this can still has a top. Cut from the end of the can where the bottom used to be (you’ve just removed it, remember?). Cut up toward the top of the can until you get to the can’s shoulder, then gently turn the scissors and begin cutting around the circumference of the can until you’ve cut off the top too.
What you’ll have left is the piece of the can that used to form the can’s side wall. It’s a sheet of aluminum that wants to stay curled up into a cylinder.
Gently flatten it out and tape it shiny side up to a sheet of cardboard (the thin, solid stuff from a tablet of paper or the side of a breakfast cereal box works pretty well). You want this sheet of metal to be flat, and you don’t want it to suddenly lunge at you, so tape it down well.
With a scribe and a ruler, mark off a rectangular piece measuring 1" by 6.5" or 25 by 166 mm. (You can use the point of a pin or needle as a scribe.) Cut this piece out. You can either use the ruler and the utility knife to keep scoring the metal and flexing it until it breaks free, or use the scissors on it. The scissors method is easier, but is harder to cut a straight line with.
Find the midpoint of the long side and mark it, then measure 2.75" (70 mm) to each side, and make a mark at each of those points. You are going to cut a slit in each end, but in opposite sides of the strip. To make these slits, cut a little more than half way through the strip, one cut from the left side and the other cut from the right side. (Or from the “top” and “bottom”, if you prefer to think of it that way.) You ought to have about 0.5" (13 mm) extra material at each end of the strip.
Now make three marks. Start at one of the slits you just cut, and stay on one long side of the strip. Let’s say we’re working from left to right. So make the first mark 1" (25 mm) from the slit. Then make the second mark 2.75" (70 mm) to the right of the slit, and make the third mark 4.5" (115 mm) to the right of the slit.
Now use the paper punch and punch a hole at each of these new marks, cutting through the edge of the aluminum sheet (the hole should lap over the edge a little bit — in other words, the hole won’t be fully round, more like an archway). You’ll have three notches in one edge of the sheet.
An alternate way to do this is to use your scissors and cut a triangular notch at each of these points. The shape of the notches doesn’t really matter.
Now gently bend this sheet of aluminum into a cylinder and hook one slit over the other. The excess “ears” of sheet metal will be on the outside of the cylinder. This cylinder will hold itself together because the two slits will have locked together.
This cylinder will go inside the stove and form its inside wall. The three notches you cut in one edge will be fuel entry ports. They will let fuel flow into the hollow space between the walls of the stove.
You can put a bit of tape over the two ears of excess sheet metal to hold them flat. If you have too much overlap you can trim this down a little, but the shorter the ears get the harder it is to make them lie flat, so a little extra metal is a non-issue.
7: Prepare top for joining.
With the scissors, cut eight slits into the top of the stove (the piece with the burner holes punched into it). The slits should stop about 2 mm short of the shoulder (where the metal curves). In inches, this is between 1/16" and 1/8". These slits will allow the top of the stove to fit over the bottom. Since both the top and the bottom are made from the same size of juice can bottoms, they’re the same diameter, and are hard to fit together, so you’ll create some slack by cutting these slits.
Deems Burton (Pika Stoves — see “more info” section) manages to stretch the metal in one can and fits two cans together that way. Check it out.
8: Join top, bottom, and inner wall.
This step will test your manual dexterity and your patience.
Place the inner wall (the cylinder of sheet metal you just made) into the bottom of the stove, with the notches down. The can bottom has a groove in it, and this wall should fit just about perfectly into that groove. If the wall is the wrong size — too big or too small in diameter to fit — then you’ll have to cut another one. But you should be OK.
This piece (the inner wall) can be held in place by a tiny bit of tape or glue (or even a couple of drops of honey, which will burn away), but you probably won’t need to do this.
Now for the tricky part. You have three pieces to juggle.
Carefully fit the top of the stove over the bottom while keeping the inner wall in place. The top has the burner vents in it, the bottom is an intact can bottom, and the strip you cut is the inner wall, and will fit snugly in between the stove’s top and bottom.
You may need a thin knife blade, jeweler’s screwdriver, or maybe a scrap of leftover sheet metal (with dulled edges) to help with this. The stove’s top half has those slits around its side and they form eight little flaps, like pleats in a skirt. (Or pleats in a kilt, for us manly men.)
You want to ease the top down over the bottom so all of those flaps are on the outside of the stove’s bottom, which has no slits in it. The trick is to get all the flaps started and then push the top and bottom together. You may need to get one flap started and then work your way around until they’re all overlapping the bottom part of the stove a little bit.
This is where the knife blade, etcetera. can come in handy. You will need at least three hands to do this, if not more. Tentacles, if you have them, are great. Human hands never seem to have quite enough fingers for this part, but it is possible, so keep at it. The magic seems to happen about the time you get dizzy and everything begins to blur. Then, suddenly, it all fits perfectly. You never quite know exactly how though.
You might need to add a little tape to hold things in place as you work. One problem is that you’ll get a flap or two from the top of the stove in place, and the top will be sitting there at an angle, and you go to the other side and try to wiggle those flaps into position, and while you’re doing that, the first flaps slip off, and so on. Arrr.
Yes, this part can be maddening, but if you’re careful you can do it. Just keep trying. Be sure not to bend anything out of place or the stove will leak flames (and maybe fuel) when you use it. On the other hand, sometimes things just seem to slip into place. Partly it depends on the size of the slits you’ve cut. But cut them too long and you’ll have to build another stove top (the burner part) from the beginning.
When you have the top of the stove overlapping the bottom, set the stove down on a solid, flat surface, check to see that the inner wall is in place and lined up properly, be sure that everything is level, then gently lay a thin book, small piece of wood, or something else flat and stiff over the top of the stove. Now gently push it down into place. Gently.
When you’ve got this done right, the top and bottom should end up fitting together snug and level, and the inner wall should be tight. The inner wall will be holding the top and bottom apart by a millimeter or so.
You have to be really careful not to crush the stove or bend anything during this process. Again as always, work slowly.
The inner wall (the rectangular piece you cut and bent into a cylinder) fits into the grooves that the cans came with. As far as your stove is concerned, one of these is in the top of the stove and the other is in the bottom of the stove. This third piece, the strip you cut, gives the stove a hollow side wall and allows fuel to flow between the inner and outer walls, where it heats, vaporizes, and shoots out the burner holes in the top.
Once again, you don’t need a stove this complicated, but it is cool to make, and even cooler to see in operation.
9: Tape stove together.
Unroll an inch or so of the dryer vent tape and cut it off so you have a clean edge to work with. Throw that first piece away. Then unroll a little more than 6.5" (166 mm), and cut it lengthwise to get a piece that will fit around the stove. The outer wall of the stove should be 18 mm to 20 mm high (0.7" to 0.8"), and that’s how wide you should cut the tape. Remove the backing and carefully apply the sticky side of the tape to the stove and trim the free end so that you have a clean seam where the two ends meet.
Gently smooth it out with the flat side of a fingernail so you have a wrinkle-free surface. You’ll end up with a silver stove covered with silver tape. Looking down through the central vent hole at the inside of the stove you’ll see a clean joint where the inner wall overlaps with itself, where it’s hooked together, and three equally-spaced notches (not perfectly equally-spaced, but no one will be able to tell. (Heh, heh.)
The more carefully you’ve measured and cut, the more professional your stove will look. When you show it off, there will be people who won’t believe that you made it (especially if you can get the burner holes more evenly spaced than I can).
10: Burning in.
The stove needs to be fired before using it to cook with.
The original cans were covered with printing. This will stink and smoke until you get that burned off.
Choose a safe, fireproof area such as a fire grate at a local park, add a small amount of denatured alcohol fuel to the stove, and burn it. About a quarter ounce will do. Check it out afterward and repeat as many times as you need to until you don’t get any smoke or burning smells coming off the stove.
Don’t set the stove on a wood fire to burn it in or you will melt it (it’s pretty thin), and you will burn the tape you put around the outside. Take your time. Relax. Keep it fun.
Keep a pot of water nearby in case you need to quench any flames, or the stove gets knocked over while it’s burning. Watch for problems.
If you used any tape or glue to hold the various parts together, or there is any juice residue inside the stove, you’ll want to be sure you get that burned out before cooking on the stove. And of course there is that aluminized tape you wrapped around the outside of the stove. That needs to burn in too. Surprisingly, although the stove gets hot when it runs, this tape seems to hold up pretty well.
This type of stove is more elegant than the other alcohol stoves described here, but it also is more complex and has more parts that must fit together properly. Don’t be scared though. If you got the parts to slip together without destroying anything you’re probably home free. Just be sure to thoroughly check out the stove before you take it backpacking as your only source of heat.
To use, put down a sheet of aluminum foil (either from a roll or cut out of an oven liner) put fuel in the cup, set it on the foil, and light it. A pot stand (described later) will serve to support your cooking pot over this stove.
When you light the stove, you may not see flames if working in bright daylight, and the stove will need a minute or two to get up to working temperature.
When it does get up to working temperature, you’ll see a burner that looks like a miniature gas range. Eager blue flames will shoot out of the burner holes. The flames look cool but they’re seriously hot, so be careful. Seriously. If you use an alcohol stove with a hardware cloth pot support, you may see the support glowing bright red. That means it’s hot, more than hot enough to bite you hard enough to hurt. Once again, be careful.
The only sound you should hear while the stove is running is fuel boiling inside it after the stove reaches working temperature.
One can bottom is the top of the stove and another is the bottom. A flat band bent into a hoop forms the inner wall. Fuel runs through notches at the bottom of that wall, and as the stove burns it gets hot and vaporizes fuel there. The hot vapor shoots out the pinholes in the top of the stove where it burns. Some flame also comes out the large center hole.