Beverage-can stove

File:Pepsi can stove lit.JPG

Pepsi can stove (pot stand omitted for clarity).

A beverage can stove is a homemade, ultra-light backpacking stove. The simple design is made entirely from cans (typically soft drink or beer cans) and burns denatured alcohol. Countless variations on the basic design exist. Pepsi cans are often used because they have a bottom shape that lends itself to securing the stove's inner wall, and because of this the stoves are sometimes called Pepsi can stoves. The stove weighs 0.4 oz (10 g) and will boil two cups of water in five minutes with two tablespoons of fuel. Total weight, including a windscreen/stand can be less than one ounce (30 g). Due to the low weight compared to commercial stoves and their fuel canisters, backpackers can save about one pound (450 g) of pack weight with this stove. This advantage may be lost on long hiking trips however, because the stove is less efficient and requires more fuel, especially when cooking for more than one person.

History and design

The basic design dates back more than one hundred years². It consists of a double wall gas generator, a perforated burner ring, and an inner pre-heat chamber. A similar design was patented in 1904 by New York coppersmith J. Heinrichs³. Trangia has been selling a commercial version of the design since the 1950s, Safesport marketed a stainless steel stove in the 1990s. Interestingly the Trangia stove burner is made from brass, even though all the other associated parts that come with it are aluminum. A plastic bag is provided for the burner so that when packed away the two dissimilar metals do not develop corrosion.

The double wall acts as a gas generator, transferring heat from the flame to the fuel. This effect enhances combustion, producing more heat than other passive designs. The inner wall also creates a convenient preheat chamber for starting the stove. Once the fuel has warmed up, its vapor will travel up the hollow wall, pass through the perforations, and form a ring of flame. Vapor also rises from the center of the stove, but will pass through the ring of flame for efficient combustion, as long as a pot is over the stove.

Fuel is poured into the stove and ignited, burning in the center.

The flame heats the fuel and interior of the stove, causing the fuel to vaporize.

When hot enough, vapor pressure causes fuel jets and a ring of flame.

Aluminum can construction

Three piece Pepsi can stove, exploded view.

The stove is made from two aluminum can bottoms. An inner wall is cut and rolled from can material. A ring of holes is pierced into the top with a pin. Parts are glued with high temperature epoxy, or sealed with thermal foil tape. Total height is less than two inches (50 mm), though dimensions can be increased to hold more fuel or decreased to take up even less space.

The choice of aluminum has several advantages; light weight, low cost, and good thermal conductivity to aid vaporization of fuel. Alternative construction materials have been used, including stoves made of tin cans such as cat food tins, tuna cans, and juice cans - the basic design is very similar [1][2].

Windscreens/stands can be fabricated from tin cans, cut to size and with ventilation holes added.

Operation and performance

The stove is designed for one or two people. When used to cook larger meals (greater than 2 cups (0.5 l), it is less efficient than a more powerful stove that delivers more heat to a pot. This is because a longer cooking time is required, during which more heat is lost to the surroundings. A more powerful, pressurized version is shown below.

Operation

To use the stove, a small amount of fuel is poured into the stove and ignited. The pot is then placed above the stove, on a windscreen or stand. The flame is small at first, only burning from the inner chamber. Once the fuel has warmed up, requiring about one minute, its vapor will pass through the perforations and form a ring of flame. Enough heat from the flame is passed to the fuel to maintain full combustion until fuel runs out.

The stove should not be re-lit unless it is fully cooled, otherwise flare-ups or explosive combustion (in the case of a pressurized design) may occur.

Ratings

• Heat output: ~4800 BTU/hour (1400 W)
• Time to boil 2 cups (500 ml): ~5 minutes (<2 tablespoons (30 ml) of fuel)
• Time to boil 4 cups (1 l): ~12 minutes (<3 tablespoons (45 ml) of fuel)
• Burn time: ~9 minutes with 2 tablespoons (30 ml) of fuel
• Burn time (full): ~30 minutes with 5-6 tablespoons (75-90 ml) of fuel

Comparison to other stoves

The stove can outperform some commercial models in cold environments, where propane and butane canisters fail. Ronald Mueser, in Long-Distance Hiking, surveyed hikers on the Appalachian Trail and found that this stove was the only design with a zero percent failure rate⁴.

Fuel usage (by weight) is about fifty percent greater than a Peak I or MSR Pocket Rocket although these stoves use gasoline and the can stove uses alcohol⁵. The can stove saves about one pound (0.45 kg) of weight over these models for an overnight hike. The weight savings is lost for hikes greater than one week due to the additional fuel usage.

Other attributes of the beverage can stove are its nearly silent operation and suitability as an emergency backup. Denatured alcohol is a relatively environmentally friendly fuel that doesn't leave soot, though it is toxic to drink. (Pure ethanol is rarely used as stove fuel, since being drinkable, it is usually subject to liquor tax.) Denatured alcohol is commonly available at camping outfitters and hardware stores. These stoves operate well on 90% isopropyl alcohol, marginally on 70% and not at all with 50%.

Unsealed alcohol stoves can be inherently dangerous, since spilling is possible and the fuel burns with a nearly invisible flame. Trangia offers an anti-flashback fuel bottle with auto shutoff pourer.

Variations

Pepsi can stove variations with cross sections in yellow: from left to right, Standard design, Inverted two piece, Side burner, Pressurized.

A side burner stove built from a single can as part of a scouting project.

Standard

The classic ultra light weight backpacking stove. Designed for one person, lighter than commercial models of the same design.

Inverted two piece

Smaller and lighter than the standard version, difficult to fill.

Side burner

Doubles as its own pot stand (holes are in the side). A tight fitting pot can increase fuel pressure.

Pressurized

A more powerful version, but heavier and more difficult to make. The stove is sealed with a thumbnut after filling with fuel. An additional base is used to hold fuel for preheating.

References

1. Stove and Fuel comparisons, (Bushwalking.org)
2. US Patent 560319: W.J.D. Mast (1895) Patent image
3. US Patent 766618: J Heinrichs (1904) Patent image
4. Mueser, Roland Long-Distance Hiking: Lessons from the Appalachian Trail (1997)
5. Weight comparison of beverage can stoves vs. some commercial stoves (Hikinghq.net)
6. Berger, Karen: Hiking Light Handbook (2004)

See also

• Portable stove
• Hiking
• Camping
• Cooking on a campfire
• Sterno
• Buddy Burner

External links

• Zen Seeker's Backpacking Stoves
• Pepsi Can Stove
• Convex Top Coke stove
• Wings homemade stoves
• Tinman's Stove
• Pritchard's Stove
• Zen and the Art of the Alcohol Stove