Philmont: The Photon Alcohol Stove


Date: Tue, 15 May 2001 08:48:04 -0700
From: Jim <pinewood@magicnet.net>
Subject: [Philmont] "Photon" (Alcohol) Stove...Eureka!
March, 2001:

After hearing so much about this alternative stove I just had to try one, as if I didn't have enough stoves already (12 and counting, including a recently purchased Trangia« that I got just for comparison purposes). Actually, we built three - one prototype last weekend and two with my son this weekend. Thought y'all might like to read what we discovered. (I'd put pictures up on a website, but I don't have one. So if someone wants to contact me, I'd be happy to forward some pictures with a summary for posting...somewhere. I understand you filter attachments here.)

First, my hat's off to Don Johnson for an ingenious piece of ultralite engineering. Never having used an alcohol stove before, I used the directions on Don's website as a basis to start.

I adapted some of Bill Jones's recommendations as well, like the hole pattern, "tee-nut" filler hole, and combo wind screen/pot stand. I had to make one innovation myself: as an avid Coke« drinker, I couldn't bring myself to use Pepsi« cans. I truly believe that Coke« cans are easier to work with, will give you better performance, and longer burn times...and are lighter too! :-))

We made several discoveries in the process of making these stoves:

PROTOTYPE:

The first stove was cut using the recommended wood block wood spacer/box cutter technique. Although this worked OK for the soda cans, cutting the heavier gauge steel tuna can was a bear and took forever. Next time, out came the Dremel« tool and drill press stand...worked like a charm. I cut the tuna can with only about a 1/4" raised lip. This seemed to work fine for holding what little pre-heat fuel is needed. Trying the Dremel« tool on the soda cans don't really work all that well, it tears them up, too much power here. You still have to be careful with the box cutter blade though as to much pressure and impatience can make a rough cut here that will make assembly difficult. The trick with the soda cans seems to be a slower and steady hand, constant but not too much pressure, and a new blade with every can!

I used a #8 tee-nut« which I substituted a #6 for in the other two stoves. Also used stainless steel wing nut and machine screw arrangement. Proved very easy to use, undo/tighten. In reality, there is little difference in weight or bulk in these two sizes should the #6's prove hard to come by. I like the easy install and usage of this filler hole design. The tee-nut« proved much easier to install without the problem of getting epoxy on the threads of the nut in the "standard" filler hole design.

I used a 24 hole pattern on the prototype, similar to Bill Jones's description, all on the outside of the bottom of soda can ring. Although the burn pattern seems good, this attempt had two flaws. First, I used a 3/0 harness needle to punch the holes, thinking this was a sturdy needle size I wouldn't have to worry about breaking. As it turned out, the hole size ended up too big which caused the stove to burn too hot initially, and burn it's fuel too quickly. The flame pattern was HOT, with high mostly yellow flames that shot up 8+" and burned thru 1 oz. of fuel in 5 or less minutes. The second "problem" was I thought I might have too many holes. The rate of burn seems to be proportional to the total area available for escaping evaporated fuel (ie: size and # of holes) and the temperature the fuel is heated to, that is, the hotter the fuel, the more pressure, the quicker fuel escapes. Solution: make holes smaller and fewer of them. So, in the other two stoves, we used a 1/0 harness needle (0 needle size would probably work too) and varied the hole pattern to 16 on one and 18 on the other. Both these adjustments made a big difference in performance (see "performance" below). BTW, harness needles are used in leather work and saddle making, and should be available thru any leather store or tack shop.

16 HOLE STOVE:

This stove was put together similar to the prototype with some minor adjustments to correct mostly performance problems. We were more careful in the assembly, with only a 1/16" lip on the outer can (above the inner "burner" can), just enough for an epoxy bead seal that sat flush with the cut lip of the can. This made for a cleaner looking finished product, although I don't think it affects performance. That was significantly improved with the smaller burner holes and the 16 hole pattern, which consisted of skipping every third hole in the 24 hole layout.

18 HOLE STOVE:

My son built an 18 hole pattern stove almost identical to the 16 hole one I built, except for one other variable: his was 1/4" higher, which meant it had more volume in the fuel chamber. This seemed to have only a slight effect in the difference of the two stoves performance, mainly it seemed to burn "hot" (higher) a little longer, probably due to the higher volume which allowed for more evaporation and consequent pressure inside, and burned out a little sooner. This could have also been due to two extra holes. His 18 hole pattern consisted of skipping every fourth hole in the 24 hole layout.

Performance:

We did (4) burn tests on each stove in a kitchen sink w/o windscreen (didn't think we needed it :-)). Each was run with .5 oz. of fuel plus a little for the pre-heat tray. Each was adequate to boil (or nearly boil) 2 cups of water (16 oz.) in a titanium tea pot (.85 ltr. capacity). In order to appreciate this discussion of the results, let me attempt to describe the characteristics of the burning cycle I noticed that were pretty typical of all the tests. Each burn cycle seemed to go thru 3 stages: initial high (hot) stage, a long medium (steady burning) stage and a relatively short final simmer (low output) stage.

For the 16 & 18 hole stoves the results were similar. An initial "hot" stage took place 10-12 seconds after lighting. This stage burned for 60-90 seconds with high flames (4-5") that consisted of more yellow in color than blue. This stage was very hot, seemed to put out more heat than could efficiently be absorbed by the pot and therefore, a lot of wasted heat. The prototype had the longest "hot" burn time, sometimes exceeding 90 seconds with flames that shot up in excess of 8-9". This also resulted in a shortened "medium" stage for the prototype (equal or less time), since it seemed to burn so much fuel in this initial stage (remember - larger/more holes). The medium stage was were the bulk of the burn time and subsequent heating took place. It varied form 3.0 -3.5 minutes and had a nice steady burn with flames more blue in color and about 1"▒ in height. The only exception was the prototype, which burned thru this stage in 90 seconds or less. The final stage, about 40-60 seconds, was a lower to very low burn while it burned itself out. There was considerably less heat, although adequate to take a nearly boiling pot to boil. For the prototype, this stage was closer to 30 seconds.

The prototype burned thru its fuel in 3.0-3.5 minutes and really never brought a pot to boil. The other two burned for 5.0-6.0 minutes with very good results, boiling the pot almost every time. The 18 hole version tended to burn hotter longer, and go out a little quicker (10-15 seconds).

Having used mostly white gas and canister type stoves most of my life, and coming into this experiment with such a bias, I am very impressed with the results. I am anxious to try this stove out on my next outing. Although not as convenient as canister stoves, as hot as either, and with less (no?) control over the temperature, this stove definitely has potential. It would seem to have an advantage over a long trek where the amount of fuel you carry becomes a factor. Who wooda thunk a littl' denatured alcohol could be harnessed so effectively.
--
YiS,

James Ball
Central Florida Council (Orlando), BSA


Date: Tue, 15 May 2001 08:49:07 -0700
From: Jim <pinewood@magicnet.net>
Subject: [Philmont] Reflections on the "Photon" (Alcohol) Stove
For John, Karl, et al,

April 30, 2001:

> "DavidA Burroughs" wrote:
> > I was able to make the requisite holes with a thumbtack. You have to
> > be careful,

> "Wildgoose" wrote:
> On this thread,...i have found that using a drywall screw, or deck
> screw works well to get the penetration of the can started.... Just
> get the hole started, then size the hole with the needle holding it
> in a pair of pliers.
After several attempts using both push pins and needles, I was always frustrated (a little) with the lack of precision, and the corresponding lack of predictability in the burn time, that these methods produced. On the aesthetics side, no two flame patterns where exactly the same and even between the holes on a single stove the pattern varies greatly. This was due to the lack of precision you are able to obtain by "punching" thru the can's thin wall. Now don't get me wrong, this stove is good, very good, even with "punched" holes. But if you want to take your stove to the next performance level, read on.

It was only when I went to making the holes (stoves # 5 & 6) with a Dremel drill using a .025" dia. drill bit (also in a drill press accessory) that I achieved a level of precision in the holes and a level of predictability in the burn time of the stove's operation. I now have two stoves that are every bit as good as any commercially manufactured product. They also run circles around my Trangia« in both the weight and performance arenas.

The reason all this discussion is relevant is due to the way in which this stove works. The genius of Photon's design is in the fact that his creates a "sealed" chamber for the expanding heated fuel vapors, which in turn forces these vapors out the burner holes under pressure, thus creating the "gas stove" like flame patterns that are so desired for optimum heating. If you put enough fuel in the "burner cup" ring to preheat the stove's fuel thru out the burn cycle, you can actually create a high pressure, high heat, high power stove approaching that found in your noisy white gas stoves, but I'm not recommending this for obvious reasons. Controlling the pressure and optimizing the flame pattern is what makes this stove different than almost any other alcohol stove design I've seen. It is simply more efficient than an open flame in a "cup" type alcohol stove (which produces very little pressure).

Photon's design goes a long way in making up for the fact that alcohol puts out only about 60% of the BTU's (per equal amount of fuel) that white gas does. Your tools to control its output are the size, number, and precision of your holes. The goal is to balance the TOTAL AREA+PATTERN of the HOLES with the the amount of HEATING, and subsequent PRESSURIZATION, you are able to generate during its burning cycle thru the heat convected from the burner ring to the fuel in the fuel chamber. The fewer and smaller the holes - the more pressure (to a point), the more and the larger the holes - the LESS the pressure you are able to achieve in the fuel chamber. There is a point at which the number of hole and their size gets too small to be effective, either for a flame or to produce heat for heating the fuel still in the chamber. I suspect that this point is a hole size not too much smaller than the .025" advocated by Photon. I have had good luck with a .024" hole size as well, but have not tried anything smaller.

As a footnote, my hat's off to Photon for his pioneering work in this stove concept!

> "oodle_oodle" wrote:
> There was one idea experimented with in my trials:
> Integral pre-heat ring glued to the base of the stove.
> Makes for one less part to the assembly.
> ...heating water in a tit. cup has a virtue in that the
> wind shroud is smaller, and therefore it saves on space
> in the pack....
Two points here, both relating to weight and bulk. In Bill Jones' refinements of Photon's stove, he uses a custom cut pattern of aluminum flashing for both a windscreen and a pot holder. The pot is actually supported by wire or stakes on the windscreen. This works great for a couple of reasons. One, you can roll it around your fuel bottle, with a bungie "hair band" and it takes up almost no bulk in your pack, its always were you want it when you want it, and it weighs almost nothing - 1.0 oz (without the stakes). I also made mine about 1" higher so it covers up part of the side of the pot, channeling the heat up the sides and giving additional wind protection for at least some of the pot's surface. Two, it has allowed me to reduce the size of the tuna can base on Photon's stove from the 10 oz size can (needed for Photon's pot stand design) to the 6 oz size which is just enough to use for a burner cup to preheat the fuel chamber. I also cut the lip down to less than 1/4" in height. This cuts down on both bulk and weight. The tuna can base (along with the steel screw filler hole plug) represent the bulk of the weight of this stove. My prototype stove weight went from 1.6 oz to 1.2 oz in weight with this change. I now have a stove/windscreen/pot stand system that weighs only 2.2 oz.

For those of you who are still with this thread, I'm sure there is a point at which all this discussion of shaving grams becomes somewhat academic. At 2, or even 4 oz, most of you are probably reaching a point of "good enough", beyond which you enter the land of "diminishing returns aren't worth the effort", which is OK. But for Photon, Bill, et al - ain't it great to be a perfectionist?? Without that drive to be or do the best, we'd never have a "Hennessy Hammock", a "G4 pack", silnylon tarps, or SWA filters. Thank you to all you perfectionists out there and all your unsung efforts, both successful and unsuccessful, and those of you yet to be discovered. --
YiS,

James Ball


Date: Tue, 15 May 2001 09:41:38 -0700
From: "Keith T. Hooks" <KeithHooks@kilgore.net>
Subject: RE: [Philmont] "Photon" (Alcohol) Stove...Eureka!
Jim,

For the ultimate in lightweight performance, use DIET Coke cans - and not the decaf kind, either. The caffein gives it that little extra kick.

With tongue firmly in cheek,

Keith
KeithHooks@kilgore.net
ASM, Troop 252
Kilgore, TX
Philmont Advisor
811-F2 (1997)
810-D2 (1999)
812-F2 (2001)


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