Light-Weight Alcohol Stove Information

SECTION I – CONSTRUCTION TECHNIQUES

There is a lot of good information regarding the construction of Alcohol stoves. Please see www.zenstoves.com for information.

However, there is one thing I can bring to the stove-building party: Use ice. I like to add water to the cans I'm going to cut, to a level of 1/2” higher than where the cut will be. Then, I place the can into the freezer until it is throughly frozen. Once frozen, it's a lot easier to get a good, clean cut because the sides of the can have support, and don't crumple if you push too hard. The quality and appearance of my stoves improved dramatically once I started doing this.

18 June 2007 Update: In section IV, various versions of Penny Stoves were built using Heineken cans. I discovered that not every can in a 24-can case had numbers pressed into them. The ones without numbers are ideal for making burner assemblies.

SECTION II – USING ALCOHOL STOVES SAFELY

Safety First

Before using or testing your stove, there are several steps you should take to ensure your safety and get optimal results

You are, quite literally, playing with fire. Fortunately, alcohol is less volatile than other fuels, but you must still take care. Please be sure to follow common-sense safety precautions when testing your stove. Here are some things I like to do.

• Make sure my test area is well ventilated. I'm not interested in kicking off from carbon monoxide poisoning.

• Have a good fire extinguisher handy. Lots of folks recommend using water to put out your stove in a pinch.

• Make sure I have a fireproof work surface. My own personal surface has a piece of ceramic tile covered by aluminum foil. The foil has up-turned edges to catch any spilled alcohol.

• Control the lighting. If your test area has too much light, you won't be able to see the flames. If it has too little, you'll fumble and spill alcohol. Subdued, not dark, lighting works best for me.

• Make sure the alcohol can is capped and moved to a safe place before attempting a test. I like to pour the alcohol into a one-ounce container (to measure) then from that container into the stove.

• Never pour from the can directly into the stove.

• Listen for noise, and s-l-o-w-l-y feel for heat coming from the stove, to be sure the flame is extinguished before attempting to do anything with the stove once a test has started.

SECTION III – ALCOHOL STOVE TESTING AND RESULTS

Introduction and Purpose

I had been working with several different stove designs. I had several ideas on how to change the stove or related environment, but was frustrated by not being able to get consistent test results. Part of the problem is the generally accepted performance measurement was how long it took for water to reach the boiling point. I knew there were too many variations with this measurement. I suspected one of the primary factors was the initial, or starting, temperature of the water. Also, I was not sure about the affect, if any, of the ambient air temperature. Finally, most of the evaluations on the 'net were related to the time it takes to reach boiling. However, it was never clear as to what, exactly, people mean by 'boiling'. That is, as what point do you look at a pot of water and say, “Now it's boiling.”?

I set up a series of tests where each variable could be better controlled, or, at least, recorded. After researching the various stove designs, and trying several of them myself, I settled on two designs for the initial tests: the Pepsi Stove and the Penny Stove. While the “Photon” stove is similar to the Penny Stove, its lack of a pressure release/control mechanism makes it too risky to use. I have one, and it works, but quite frankly it's scary.

My plan is to work on improving the designs (a difficult task, as these are pretty good), or improving the ability of the heat to get into the pot.

Tools Used

• All tests were conducted with the same aluminum coffeepot. It measured 5 1/2” tall, and the diameter is 5 9/16”.

• The pot was placed on a pot stand as described by Mark Jurey at www.csun.edu/~mjurey/penny.html.

• The Pepsi Stove used was a standard Pepsi, but with fewer, larger holes. The model used had 16 holes, each 1/16” of an inch, evenly distributed.

• Two variants of Penny Stoves were used. Both made out of “pop”, or soda, cans only.

• The first variant used the 'nip/tuck' method of constructing the burner.

• The second variant used the standard crimp method as described by Mark Jurey.

• A digital thermometer was used for measuring water temperature.

• A Seiko digital watch was used for measuring time.

Procedures

• Each test was conducted with 2 ½ cups of water.

• We used approximately 25ml. of denatured alcohol (ethanol) for each test.

• We recorded the ambient air temperature, and the initial temperature of the water.

• Each test was conducted in an enclosed location (my garage) to eliminate the need for a wind screen.

• Altitude is (approximately) 975 feet above sea level.

• For each test, we started the timer as soon as the stove was lit. We then kept track of two separate values:

1. The time it took for the stove to become fully functional. That is, for the jets to reach full, proper height. Note this variable is somewhat subjective.

2. The time it took for the temperature of the water to raise by 100 degrees Fahrenheit. Note: is was from time 0.

• We then let the pot reach full boil. The water was used to brew tea and not wasted.

Test Runs

Baseline (Pepsi Stove)

I used the Pepsi Stove to get the initial baseline. My experience with the Penny Stove is it does not always prime correctly on the first attempt. The Pepsi Stove worked correctly every time.

There was a 1 3/8” gap between the top of the Pepsi Stove and the bottom of the pot.

Average time to target: 289 seconds.

Addition of a 1/4” collar around the bottom of the pot (Pepsi Stove)

The purpose of this these tests was to see if a collar, or lip, around the bottom of the pot would aid in heat transfer from the stove to the pot.

After a couple of tests, it was clear this had little, if any, effect and we did no more of these.

Addition of a lid (Pepsi Stove)

The purpose of these tests was to see if a lid on the pot would improve (reduce) the time needed to heat the water 100º F.

Average time to target: 261 seconds.

Raising the height of the Pepsi Stove

These tests were conducted with the Pepsi Stove position closer to the port. The new gap was 1 1/8” between the top of the stove and the bottom of the pot. The pot had a lid.

Average time to target: 265 seconds.

Use of the Penny Stove (nip/tuck construction)

For these tests, we switched to the Penny Stove. There was 1 1/2” between the top of the stove and the bottom of the pot. The pot had a lid.

Our initial attempts to get measurements were hampered by the failure of the stove to properly light during the priming phase. We began using an external priming pan, and placed several drops of fuel in this pan.

Average time to target: 191 seconds.

Use of the Penny Stove (standard construction)

For these tests, we used the Penny Stove with the burner made with the crimp technique. There was 1 1/2” between the top of the stove and the bottom of the pot. The pot had a lid.

We did several runs using this stove, but only kept the data for the runs were the stove primed correctly on the first attempt.

Note 1: This run reached full jets faster than expected (faster than any of the nip/tuck runs), and I missed the time.

Rejected Tests

One idea was to increase the effectiveness of getting the heat into the water. To do this, we tried a couple of tests whereby a large pot was placed inverted over the smaller pot, with enough clearance to allow suitable oxygen to reach the stove. We called this the Dome of Heat Retention (DOHR). A couple of tests were all that was needed to determine this was 1) very inconvenient and awkward, and 2) No better than putting a lid on the pot.

Test Summary

Observations

These observation are supported by the data and/or experience:

1. Use a lid. In our tests, it provided a 9% reduction in the time it took to reach the desired temperature.

2. The Penny Stove reaches temperature 29% faster than the Pepsi stove.

3. If you are using a Penny Stove, consider the use of a priming ring.
   
   18 May 2007 Update: The problems we had with priming are likely due to an incomplete seal between the penny and the burner. After working on this a bit, I got more consistent results. The flue tape technique described on Mark Jurey's site works well. However, I still recommend the use of the priming pan. The priming pan will cause the stove to prime faster, and this is when it is most efficient. This, too, can be verified with testing.

These observations are a bit more subjective.

1. The Pepsi Stove was the more convenient stove to use. It worked every time without having to monkey around with the stove after it was started.

2. However, even if we had to repeat the priming process, the Penny Stove was still faster than the Pepsi Stove at reaching temperature. That is, the overall time, start to finish, was shorter with the Penny Stove.

3. We rejected the data from the runs where the Penny Stove did not properly prime on the first attempt. I did notice the temperature of the water increased by about 10º F before the flames went out.

4. When you really need that first 'cuppa' in the morning, use the Penny Stove.

5. Each test use 'about' the same amount of fuel. I was a little loose with the amounts. Having said that, it seemed to me that both stoves got the pot to boiling, then had just a bit of fuel left. That is, both stoves seemed to have about the same efficiency, but the Penny Stove was faster. This could be determined with additional testing.

6. If you accidentally drop your Pepsi Stove onto your concrete garage floor, it bounces and takes little damage. If you drop your Penny Stove on the same floor and it hits at the upper edge of the stove, you'll be unhappy with the results.

SECTION IV – PENNY STOVE TESTING AND RESULTS

Introduction and Purpose

This series of tests was intended to determine what, if any, difference in performance we might find in the various ways that a Penny Stove could be constructed. For this, the procedures were slightly modified:

• Each test was conducted with a precise amount of fuel. We used 24ml. of alcohol in the burner, and 1ml. of alcohol to prime the stove.

• Yes, we primed every run. In normal operation, if a stove fails to prime, it's no big deal and recovery is easy. When you are doing a controlled test, if a stove fails to prime, the entire run is worthless

• We kept track of the total burn time of the stove. Tests were run under low-light conditions, and the burn was considered completed when the last, tiny flame was out.

In hindsight, there was one other variable we should have measured: Relative Humidity. The tests runs as part of Section III (above) were all run during relatively cool, dry conditions. This was a lucky accident. As we progressed into May and June, the humidity became much more variable. The longest, slowest run we had (5/20/07 08:30) was very humid; so much so that I was wondering why on earth I was making tea. It's an important point, because I subsequently only did a test when I felt the need for a hot drink. This was never on a hot or humid day, so own behavior may have skewed the data. On the other hand, I now have a probable explanation for the variation in the data.

Test Data

Penny Stove (No-Crimp)

For these tests, we used a Penny Stove where the burner was wrapped with several turns of teflon tape to create the seal between the burner and the cup. The cup was made from a Heineken can, the burner was made from the bottom of a Guinness can.

Penny Stove (Nip-Tuck)

For these tests, we used a Penny Stove where the burner was made using the Nip-Tuck method (my own creation). The cup was made from a Heineken can, the burner was made from the bottom of a pop can.

Penny Stove (Original Design)

For these tests, we used a Penny Stove where the stove was made according to Mark Jurey's original design..

Conclusions

1. Because of the aforementioned issue with humidity, I didn't summarize the data. Just looking at the data, I believe the no-crimp-teflon-tape method to be slightly less effective than the other two designs.

2. There seems to be no reason to deviate from the original design of the stove. The original design, by the way, is also probably the easiest to make. The biggest problem is in finding the Heineken cans for construction.

3. Pennies made after 1982 are not made of copper. These do not seal as well. Neither do they hold up to the heat. Stick with copper pennies if they are available.

4. The shape of the bottom of a Heineken can is most suited for the burner. Pop (soda) cans are slightly narrower and steeper. I had a harder time getting a good seal with them.

WARNINGS!

Information on this site is provided for educational purposes only.

Neither the webmaster nor anyone else whose information may be included on, or linked to, this web site can attest to or endorse the safety of using any techniques, equipment, supplies or services evaluated or referred to therein. Any endorsement or recommendation is limited solely to the evaluator's opinion about their effectiveness when used for their intended purpose in accordance with safe operating procedures, and if available, in accordance with any instructions provided by the inventor or manufacturer. Some survival and outdoors equipment and supplies are inherently unsafe and can injure, maim or kill even when used appropriately.

Endorsement or recommendation of any equipment, supplies, services or techniques does not constitute a guaranty or warranty the equipment, supplies, services or techniques will function when needed.

In daylight you may not be able to see a flame or hear an audible sound from an alcohol stove.

A windscreen wrapped partially around the stove may aid in seeing a flame more easily.

DO NOT OVERFILL STOVE. A space above the fuel inside stove is necessary for proper operation and overfilled liquid fuel may be ejected instead of alcohol vapor, creating a potentially hazardous fire.

Do not attempt anything you see here if you do not have the proper training and experienced with the tools you will be using.

Use Eye and Hand protection when working with tools or sharp metal. Use ear protection when using loud motorized tools.

Follow all safety procedures. These stoves use fire. Don't try to use them in areas at risk for fire.

Do not use any other fuel besides alcohol in these stoves! It may result in severe burns and/or death.