Donald - I echo your comments to Roger, especially regarding the fundamental equivalence between "gas" and "petrol" (ok, I'll admit it:I am a nerdy chemical engineer by training, and have spent more time than I will admit going through the energy calculations Roger has clearly laid out.....). I am replying to you because it seems to me that the "real" difference between the gas and petrol stoves is the restriction on the use of a windscreen around the gas stoves. I am interested in your comments regarding "always" using a windscreen. I have experimented with this only once - and decided the windscreen worked...but had no reference for how warm is "too warm" regarding how hot to let the cannister get. Understanding the manufacturers dire warnings about this, and admitting (and warning other readers) that Bad Things can happen when you let a cannister get to warm - might I implore you to relate to us your experience on just how you decide that a cannister is getting too warm?????

1. Here's a common comment one reads in this regard (i.e. "how warm is too warm"): if you can't keep your finger on the the canister, it is too warm. Now, I don't really know how valid that "test" really is. Certainly, I would agree with it as stated, but does that mean that if one can keep their finger on a can, that it is 'ok'? That I don't know. I believe that Dr. Caffin has earlier written 105 deg F as a max. temp. I can keep my finger on 105 deg F however. In fact, a quick websearch showed that Californians, amongst others, immerse their entire body in 105 deg F hot tubs - and that's "moist" heat. However, I think that this is perhaps the absolute max temp anyone should use for a hot tub and that "stays" in the tub are of very short duration, but I don't know. 105 seems very high to me for water immersion - core temp will rise quickly, I would imagine. Maybe 101-103 is better??? I would think even core body temp (37C or 98.6F)would feel nice to the skin, but then I've never even dipped a toe in a hot tub, so what do I know?!!! [Hot Tub owners help out here.] So, 105 deg F might be the right number, but most people aren't going to be able to determine 105 deg F with their fingers alone, IMHO.

2. At the risk of allowing the can to cool too much from use, one can use the DrJ "under burner" pie plate, or some similar heavy duty Al shield. This will shield the canister from radiant heat from the burning gas and keep it from getting too hot. But, will it allow it to cool too much for best operation in colder weather since it will not be warmed any by the burning fuel?

Just some thoughts. Anyone have any opinions about these two points?

I'd like to invite comments or critiques of my canister stove windscreen set up. With a couple of inches of space on the bottom, a reflector, and 3/4 wraparound it's designed more for safety than efficiency but I've found to to be fairly efficient. I run the stove for a few minutes at a time. Am I being too cautious or not cautious enough?

Probably a bit cautious: my setup has a windscreen to the same height and a similar, but not so wide, opening, but it goes to ground level (attached to a closed-cell foam pad with an aluminium foil layer on), and no reflector.
I tend to cook 'real' food, rather than just boiling water, and the cannister has never become more than warm (ie: comfortable to press fingers on for a long period).
This set-up improves the cold weather performance, but if I'm expecting anything below freezing I switch to a hose-fed stove and invert the cannister.

Edited by nsjohnstone on 03/12/2006 12:42:01 MST.

>> This makes me wonder why manufacturers aren't making a canister with a dip tube which pulls liquid fuel from the bottom of the cannister. Seems like this would solve many of the cold weather performance problems.

>Think about this one for a moment. Imagine taking an upright stove like the Snow Peak GS100, or any other stove like that, and tipping it upside down. You will get liquid fuel coming out the jet, and a huge fireball! Because it does NOT have the preheat tube so utterly essential to using a liquid feed.

>A TERRIFYING thought for those who have seen such things before.

>Cheers

Thanks for the insight on the necessity of the preheat tube. seems like maybe the modified windpro would be a good model for and improved canister stove. I like the coleman powermax stove, but it seems like a stove with a preaheat tube which screwed directly onto a canister with a dip tube to take up liquid fuel would be a good design.

Edited by iancrae on 03/12/2006 12:46:32 MST.

I've had canisters in my car trunk in summertime without its exploding into a ball of flame, and it surely gets into the 130-140 range in there, but prudence prevails anyway. Perhaps the important point is that a system heating the canister to feel warm to the touch could well continue to increase the temperature further, to the danger point. Intervention might be warranted before that can happen.

I agree that it's impossible to compare dry metal surface temperatures to water temperatures. We've all picked up items far warmer than 105 without burning our hands (if briefly!). I can't handle a hot tub over 105, but have sauna'd much hotter than that.

Could one "over-shield" the cartridge for cold conditions? Probably.

Rick, Does your trunk really get that hot? I wonder. The interior of a car gets much warmer than a trunk, typically. It's the sunlight that penetrates the glass in the interior (passenger compartment) that causes the 140deg temps. The trunk is generally cooler. Check it out sometime after your car has been standing still in the sun. You will notice that it is much cooler in the trunk than in the passenger compartment. A simple test which many reading this may have done is to transport their old LP records ( not that they played them in a car) in the trunk of a car. Had either been stored in the passenger compartment, in the sunlight, they would probably be ruined. But this doesn't happen in the trunk - to my knowledge. I did however, as a teen, transport a stack of LPs on the floor of the backseat. Left the car in the sun for an afternoon and the LPs were ruined/warped. Subsequent to that, I transported several times LPs in the trunk of my car and left them there throughout an afternoon in the sun with no damage to them.

Please don't misunderstand me. I'm NOT saying that a trunk can't get hotter than the OAT. I'm only saying that it generally doesn't reach the same temp as the passenger compartment.

My point of this is I don't think that the trunk test is a valid test if we're trying to get to 140deg canister temp. Maybe we're getting to 115 or 125 at most - frankly, I don't know.

You know...I hate to say this, but the question here could be tested. (I hereby issue the required "do not try this at home...it could be dangerous" warning, and that by saying what I am about to, I in no way encourage anyone to actually do this....it is just an intellectual exercise. What we are REALLY interested in is what pressure can one of these cylinders support without rupturing. As the cylinder heats, the liquid gas inside will be shifted to a higer vapor pressure (that pressure being dependent on temperature). This suggests the following experiment: Take a cannister, run it until it is almost empty (say 1/2 oz of fuel or so), attach a thermocouple to it, run the wire a sufficient distance away (preferably behind a tree), attach to an appropriate meter, light the stove, arrange a windscreen around it, return back to the safety of said tree (making sure nobody else is or can go anywhere near the thing....then track the temperature and see if/when the thing lets loose. Again...take this as a thought only - not a direct suggestion....undoubtedly with more thought a safer method of doing this experiment will come to light.....

"safer method" - Nah..., testing is often done to destruction/failure. Please report back your findings. I would suggest multiple samples, so that any manufacturing "defects" in one particular canister can be somewhat statistically eliminated. Go for it! Can't wait to see your test results.

You know, if a max. safe canister temp is determined, then it might be an easy matter for someone to manufacture a small light weight thermo-chromatic "Go No-Go" temperature indicator that can be stuck/afixed to the canister via an adhesive backing. When the temperature indicator changes from black or dark-green to red, the canister must be shielded or the burning halted. Not sure of the safety margin we would want before maximum safe temp is reached?

Paul, Oh I agree - testing to failure is a necessity....by "safer" I was referring more to safety of life-and-limb.. :-)

Thanks for the feedback, Neil. I may tighten up the windscreen and ditch the reflector, at least for cooler weather. In cold weather, say below the mid-twenties, I carry the effective, but much heavier, Coleman Xtreme. I've been paying attention to Bill Fornshell's threads and am curious to see what Roger Caffin has come up with. Which hose-feed stove do you use and how do you support the inverted canister? Thanks.

Dondo

Understood. Your suggestion is always a good idea, especially if it is your life and limb on the line!!

I use a Windpro, because it uses 'standard' cannisters. Regardless of what Coleman may say, Xtreme cannisters are not readily available in UK/Northern Europe, while the 'standard' versions are available in remote areas. As cannisters cannot be taken by air, it makes a lot more sense to use what is locally available!

The inverted cannister is held up by three pegs and a thick rubber band - total weight less than 25g.

Hi Paul,

Hard telling actual temps reached in there, but based on how hot items are when I retrieve them, I've got no doubt that under the "right" conditions, my trunk gets very, very hot (e.g., on a 110-degree day in an open asphalt parking lot). Given sufficient time the temps will tend to equalize throughout.

To follow your point, it may well be that one of my previous rides could get hotter in back than my present one because they were hatchbacks (even more glass!).

(Come to think of it, since more than half of passenger vehicles sold are "light trucks," trunks aren't terribly common anyway--everything is technically the passenger compartment.)

One of many lessons I've learned the hard way is get the wine home quickly in the summer. It's remarkable how much liquid will force its way past the cork. Doesn't smell as good as one might think, either.

To bring my tangent back to planet earth, I'll wager that some percentage of fuel canisters inadvertantly get very hot during routine handling and transportation without spectacular failure (e.g., freight car parked on a siding for a few days in Timbuktu). I further speculate that it's more likely that one would melt the melty bits on a stove well before they'd achieve the temps necessary to burst the canister.

[All standard disclaimers about this being an uninformed opinion in no way reflecting the opinions of the staff and management of BPL.com should be applied here, and should be consumed along with a grain of Dean and Deluca sea salt.]

FWIW the spectacular stove failures I've been privy to have all been safety valve releases on Primus, Svea and Optimus self-pressurizing white gas models. Wahoo!

Rick, You got me doin' the "Ropa-Dopa" - Good points. BTW, never owned a hatchback. I'll keep your advice about rear storage area temps in mind if I ever get one.

English translation with Computer Translator:


ikaros



Yukio-san's Stove Site

Hi guys,

Any possibility of an ETA on part 2? I do look forward to it!

Brian

Tonight!

My pan and stove are like the picture from Donald B, but my shield is simply one flat sheet of double foil that sits on the ground. As Neil says, over heating is not a problem for me. I never let the can get more than slightly warm to the touch. After all, the stoves work fine at room temperature.

I ALWAYS use the shield because it takes
almost no effort, shortens the time to heat my water, and saves a lot of fuel. It is almost like a Jetboil, but a lot lighter. :-)

Re water temperatures, I am a hot springs fan and usually carry a thermometer. For those of you familiar with Iva Bell/Fish Creek near Mammoth CA, the water at the top of the upper meadow comes out into a little pool that stays about 110. I have seen someone dunk in that pool for 10 or 20 seconds, but it is not for me. The immediately adjacent pool is usually kept at 105 - 107. At 105, I can be comfortable for 5 - 10 minutes at a time. At 107, it feels very hot getting in, and I cool off for a couple of minutes after about 4 minutes in the water.

Note that time to scald is nowhere close to linear with temp. At 120, it takes several minutes to do real tissue damage. At 130, skin damage is almost instant. That is why some people now recommend 120 for water heaters.

Edited by donhorst on 03/16/2006 08:33:36 MST.

> 1. Here's a common comment one reads in this regard (i.e. "how warm is too warm"): if you can't keep your finger on the the canister, it is too warm. Now, I don't really know how valid that "test" really is. Certainly, I would agree with it as stated, but does that mean that if one can keep their finger on a can, that it is 'ok'?

The standard physiology rule of thumb is that a normal person can keep their hand on something at 40 C (104 F) but over that there is an 'ouch' response. This temperature IS SAFE for a canister.

OK: at some stage in the future I will be writing an article on canister safety and maximum temperatures. I do have some info from manufacturers on the safety testing procedures, and I can confirm that they all routinely test at temperatures higher than 40 C.

But I'll leave the details of the article until later. Sorry!