Wednesday, June 13, 2007

Making my stove...

I didn't know much anything about gearing up for backpacking on last year's hike of the John Muir Trail.

The gear I took for cooking was no exception. I packed the newly-introduced Jet Boil "Personal Cooking System." It wasn't clear at the time, but now I'm under the impression that anything labeled as fancily as a "Cooking System":
  • Will be heavy,
  • Will be complicated, and,
  • Will be expensive.
The stove won a best-of award from Backpacker Magazine, but I think it was on the criterion that it could bring a cup of water to rolling boil inside of 4 minutes. Granted, it wasn't really that complicated, but the weight was just under a pound at 15.25 ounces (432 g), and the price tag was just shy of $100. This, of course, is before you add fuel into the equation. You have to use special cannisters to fuel this thing. The fuel adds weight and cost, though the Jet Boil is fortunately rather efficient as far as cooking goes, mitigating these factors somewhat.

Nonetheless, when I encountered Nano (and Valerie) 100 miles into the JMT, I was jealous of their cooking equipment. They were both traveling with Brasslite alcohol stoves. They both took an extra two minutes to boil their water, and simmering was a pain in the ass -- but on a long distance through hike, you're happy to sit down for 6 minutes at the end of an 18-mile day. And complicated food was one of the reasons I nearly starved myself last year (more on this in a separate blog).

I will summarize the main benefits of an alcohol stove for you:
  • Lightweight (the Brasslite Turbo II-F weighs in at 1.4 oz / 40 g)
  • Fuel Availability (These stoves burn ethyl and methyl alcohol which are widely available in the most remote of stores as Everclear, denatured alcohol, HEET fuel additive, etc.)
  • Size (The volume of a JetBoil is about half a gallon. The volume of the Brasslite is about half a pint)
  • Simplicity (Just pour the alcohol in a Brasslite and ignite. A Brasslite doesn't have threaded connectors or machined valves, so there isn't much to fix. Try repairing a Jet Boil outside of town).
  • Price (Alcohol stoves can be purchased for well under $50, and plans are freely available on the internets to make them for even less money. Alcohol is also an inexpensive fuel.)
Of course, my argument (let's call it a "point," we're not fighting, are we?) is predicated on the assumption that one likes small, simple, light, cheap and easy-to-fuel cooking devices. This is not always such a high priority for 3-day, 16-mile weekend backpacking trip (and almost never for car camping). But for a hundred-mile trek with infrequent resupplies where you're a day and a half or more from civilization -- well, I would assert that it's indispensable.

When I started looking around for stoves this year, alcohol burners were at the top of my list. I am amazed at just how many options there are. Particularly fascinating to me are the Popcan stoves -- just as they sound, stoves made from spent pop cans. There are a staggering variety of designs available, each with their own benefits and drawbacks.

I quickly became interested in the pressurized design variant. Primarily because of its fuel efficiency. After searching, I located a design that had a few safety and ease-of-construction modifications.

Striving to make the stove even smaller and lighter, I settled on using an energy drink can for the casing. (Also, I haven't been drinking much caffeine lately and have had half a case of Bing! energy drink laying around from a sponsorship meeting I had with them over a month ago for Geeks Who Drink).

Now, I present to you, my energy drink can alcohol stove:

The first item I had to procure, of course, was the energy drink can in question. It is a "standard" energy drink can size. To the left you can see some acetaminophen I was taking since I was a jackass earlier in the day and went on a 26-mile bike ride without any sunscreen on my arms. Behind, you'll see some origami Sonobe module pieces I made -- it's how I pass the time when I'm procastinatng. And finally, to the right, you'll see a printout I made that has 24 radii pointing out to the edges of a circle the diameter of the can. This is the template for making evenly-spaced fuel jet holes.

To make the holes in the bottom of the can (well, not the bottom, but the side of the lip on the bottom) I just used a pushpin. A lot of the instructions on the web use sewing needles held in X-acto knives and other complications. I found that he pushpins were cheaper, stronger, and generally sharper. Also, because of the way you have to hold the pushpin, I think you have a greater amount of control in just barely puncturing the aluminum without greatly enlarging the hole.

Next came the cutting of the can. The directions I linked to above use a box cutter blade screwed to a block of wood. I had just as easy a time using a razor blade I held to the top of the book. the process was the same: I twisted the can against the blade, gently applying pressure until I got through it. You can tell rather easily if you're pressing too hard before you actually dent the can.

To tap the fuel fill hole, I set the can piece on top of the acetaminophen bottle and drove a screw through. To the right of the can halves, you'll see the large bag of perlite generously donated to me by my friend Kat. An inert filler is generally accepted as a way to increase vapor pressure (at the expense of preheating time) while providing a measure of safety in the event the stove is tipped over.

I had some trouble getting the top of the stove to fit around the bottom part. In the original instructions, they more or less assemble the stove before poking holes in it. To encourage a smooth fit, they jam an unopened can into the lower part to enlarge it. Next time, I will give this a go. Nonetheless I got my top on with only minor denting.

This design is one that is likely tight enough to not have any leaks between the two cans, but just to be sure, I applied a bead of JB Weld metal epoxy around the seam of the two cans. This stuff is easy to use and heat-resistant to 600 degrees Fahrenheit. I think I'm going to use it to attach a pilot light base to the stove and maybe a pot stand at some point.

And finally, here's a video the stove's test firing.

I'm pleased with the performance overall. Using pop can tabs as a pot stand (which hold the pot about 2mm above the rim of the stove) I was able to get a cup of water to a gentle boil in 7 minutes using Everclear. This performance is acceptable for my uses, though I'm going to see if I can tune it a little and improve things with a better pot stand and a windscreen. I'm also going to make a stove out of a regularly-sized pop can and see how it performs.

Weight: 13g (0.459 oz.)
Approximate materials cost: $1.00

1 comment:

katty said...

I love the big stove specially because i like to cook all kind of recipe, how ever i prefer to have a reasonable place. Actually i saw a beautiful stove in a house that was published in costa rica homes for sale it was big and beautiful, i think i will go there because it catched my attention.