tbeasley wrote:

>Ti is an amazing material that solves many problems; weight, strength, corrosiveness, durability, heat weakening. But poor heat conductivity makes it a poor choice for a cooking pot. Thin aluminum pots easily outperform Ti pots when you weigh in the extra time and fuel consumed

I thought the same before I did some tests, I could not make Al pots perform better than my Ti pot, this was true with alcohol and canister gas. Below is a graph of my results and the points are boiling time for different flame settings. SS even performed better than Al.

Tony

Pot Efficiencr graph

If the graph came through, the small study shows that if you want minimum fuel consumption, use of a four minute boil or so is much more important than the choice of pot material -- at least between Stainless Steel, Aluminum and Titanium.

This conclusion probably doesn't encompass the inclusion of heat exchanger devices attached between the burner flame and the pot. It makes sense that heat exchangers would increase the efficiency, and someone (JetBoil)has probably done tests to demonstrate this.

i haven't used a remote canister stove in the winter yet, but i do know that i can stop my stove (primus micron) from performing poorly in cold weather by holding the canister. obviously this warms the canister (and freezes my hands) and i get dinner in a reasonable amount of time.

my question is why wouldn't you be able to put a longer hose on the adapter and throw the canister in your sleeping bag. the temp in there would be way above freezing.
is there something i'm missing about the whole thing?
sorry if it was explained before.

If you're in the sleeping bag with the canister it would keep it warm and maintain fuel pressure. I don't know how much the vapor would cool in its path through the long hose, however. I also don't konw how much fuel you'd lose in a long hose, between uses.

In an unoccupied sleeping bag the effect would eventually be the opposite, as the bag would insulate it while it naturally cooled and it would freeze up. You'd be better off stuffing it into your jacket.

I have to agree. The material in titanium pots is so thin that conductivity differences have a minimal affect on heat efficiency. Ti pots do exhibit hot spots, which makes cooking on them trickier than aluminum, but for boiling water there's no effective difference.

Same thing for plain metal versus black-painted--no appreciable difference.

> I don't know how much the vapor would cool in its path through the long hose, however.
Actually, the temperature of the hose does not matter at all. As long as there is pressure in the canister to drive the gas out of the jet, that is enough.

> I also don't konw how much fuel you'd lose in a long hose, between uses.
Yeah, a problem in principle, but most hoses are actually filled up with something to reduce the volume down to a reasonable level. Think of the heavy SS cable in the big fuel lines of some MSR white gas stoves. The effect is there, but it is not quite that great.

Cheers

I thought it was an interesting fact that Roger Caffin posted:
-20 C is the cutoff for 30/70 canisters. Much weight, time and effort has been dedicated to keeping the canister off the snow, but if air temps are much below freezing and snow is (ideally) 0 degrees, might it make sense to make contact between cylinder and snow?
Snow surface temps are usually below zero in reality due to radiative and evaporative cooling, so may not work in real life, but made me curious...

Looks like there is some orange in the flame. It it is on pretty high (sorry, not very scientific) with about 3 MPH wind. Some orange flame is normal if run on high, but this seems just a bit more. As long as the gas gets out of the canister to the hot stove, it shouldn't be actually wasting any power, right? Although you'd be burning a higher percent of propane. Maybe just propane?


"Propane is more suited to colder environments since it evaporates at -44oF (-42oC) at atmospheric pressure. Butane evaporates at 33oF (-0.5 oC) at atmospheric pressure."

Doh.

Edited by Paul_Tree on 11/23/2008 16:14:38 MST.

I LOVE IT!

May I ask for permission to use this photo (somewhere, with acknowledgement), PLEASE!

Now to the question of why this works. Several steps.

The MSR red canister contains iso-butane, which has a boiling point of (roughly) -11 C, and propane, with a boiling point of about -42 C. This canister will work to about -24 C in liquid feed mode.

In the photo the stove is chugging along happily while the canister is embedded in ICE! I am going to guess that you froze the lot in an ice-cream tub in the freezer? So what temperature is the ice at in the photo? My guess is that it might be somewhere between 0 C and -4 C, what with the warmth of the sun etc. Note: this is well above the boiling point of iso-butane!

Finally, let's look at what the block of ice is doing. It is in GOOD thermal contact with the canister. The fuel inside is boiling away and would be cooling down, except that the huge mass of ice is busy pumping energy into the canister. I would guess that the stove is burning both propane and iso-butane (but I am not sure at what ratio).

This is (one reason) why MSR puts iso-butane rather than n-butane in this canister: it will function at temperatures slightly below freezing, and for many walkers that is as cold as they get. The downside is that the canisters are dearer than commodity 70% n-butane ones. Well, you pay your money and take your choice.

Cheers

Edited by rcaffin on 11/23/2008 23:10:36 MST.

Glad you like it Roger, it seemed like a true BPL pic.
If you want, I have a few more full size photos and maybe they are better. PM me an email address if you like, use them as you wish.

I had been assuming it would be at zero so I didn't even measure! There was just a smidge of unfrozen water in the ice, and once the stove started, it could be spun around freely and did not refreeze when extinguished. Also missing is testing of boiling times. I boiled a cup of water outside and timed it, but realized two of the same stoves were needed at the same time, one frozen and one not, to get the clearest results.
As well as 2 of the same pot and lids in good shape.
As well as a ventilated yet more wind-sheltered test area, eg garage with door open.

It would also be good to run it through a whole canister and see if there is degraded performance towards the end.
Couldn't bring myself to just let it keep burning though.

In snow, you could take off the top coldest layer of snow and get to some -2C snow. If anyone does this, try embedding an led light in the ice as well to illuminate the night shot.

Edited by Paul_Tree on 11/26/2008 20:08:14 MST.

Over-arching question - how will using the stove stand affect stove efficiency i.e. how will it affect the amount of fuel used per pint of water boiled/snow melted?

Testing of the PocketRocket, and other can stoves, was done by BPL in this thread: http://www.backpackinglight.com/cgi-bin/backpackinglight/lightweight_canister_stoves_test_report.html. Note that the gas cans and the stove were cooled to 10F before testing. The curious thing about this is that the PR was run at max flame, but fuel consumption decreased because the stove was running at a slower pace. "Under cold conditions (column 4), fuel consumption decreased because the stoves burned more slowly (equivalent to a moderate flame), even though they were set at full throttle." (under Table 2). Given that, is it advisable to run the stove at full throttle? If so, at what temps?

Second: If isobutane has a boiling point of 10F, do I need to turn the canister upside when temps are above 10F? In testing in approximately 30 degree weather, the flame increased dramatically when I turned the canister right-side up.

Third: Also, how does temperature and canister position affect which fuel (isobutane or propane) is burned?

Thanks as always.

> how will using the stove stand affect stove efficiency
Complex.
If you have the pot at the optimum height you will get 'good' efficiency. Raising the pot a foot is obviously going to seriously reduce the efficiency (out the window in fact!). Lowering the pot right onto the burner is going to quench the flame a fair bit and this too will reduce the efficiency a bit - but not as much.
But then questions of wind speed come in, as Will's article shows.
Far more important is the fact (imho) that when the pot is too close the amount of CO generated rises significantly. This was discussed at huge length in the CO series of articles.

> fuel consumption decreased because the stove was running at a slower pace
Absolutely. Running a stove flat out wastes a whole lot of heat up the side of the pot. Running it at about half power is far more efficient and heats the water almost as fast. I never run my stoves flat out, under any conditions (except for lab stove testing!).

> If isobutane has a boiling point of 10F, do I need to turn the canister upside when temps are above 10F?
By and large, it makes sense to use the canister upside down. Otherwise the propane tends to preferentially evaporate. OK, if its 60 F there's no problem, but if you are using the Brunton Stand in cold weather it makes sense to invert.

> In testing in approximately 30 degree weather, the flame increased dramatically when I turned the canister right-side up.
I don't understand this. Usually the flame increases when the canister is inverted. I suspect a blockage or the valve was knocked.

> how does temperature and canister position affect which fuel (isobutane or propane) is burned?
Read through the other articles on canister stoves I have written: it is all there in great detail. The Series on Winter Stoves will be most helpful:
Selecting a Canister Stove for Cold Weather Backpacking
Part I: Stove and Fuel Fundamentals
http://www.backpackinglight.com/cgi-bin/backpackinglight/selecting_stoves_for_cold_weather_part_1.html

Selecting a Canister Stove for Cold Weather Backpacking
Part II: Commercially Available Canister Stove Systems
http://www.backpackinglight.com/cgi-bin/backpackinglight/selecting_stoves_for_cold_weather_part_2.html

Cheers

> fuel consumption decreased because the stove was running at a slower pace
Absolutely. Running a stove flat out wastes a whole lot of heat up the side of the pot. Running it at about half power is far more efficient and heats the water almost as fast. I never run my stoves flat out, under any conditions (except for lab stove testing!).

Here's what I don't get. On the testing, a PR in cold conditions at full flame used less gas to bring 1 qt of water to a boil than a PR in optimal conditions at moderate flame did. Can you explain?

I assume I would save even more fuel if I operated the stove in cold conditions at a moderate flame.

I'm going to go test things out tonight in about 10F and report back.

Roger or anybody, has anyone had any experience with a MSR Pocket Rocket using the Brunton Stove Stand?

i took a pocket rocket apart and found that the threads in the bottom of the mixing tube are the same as the threads on the brunton stove stand. i took the jet out of the PR valve and mounted it in the brunton base, and mounted the PR directly on the base. a spacer was required to get the proper hieght. then i got rid of the brunton legs and built a new set out of aluminum. it turned out to be a nice little stove.

Daren....

Hi Daren

I think I understand, but we want a good photo of it!
And welcome to the world of MYOG canister stoves. :-)


Tad - I haven't, but it seems Daren has.

Cheers

Edited by rcaffin on 02/20/2009 22:22:53 MST.

Daren do you have any pictures of the "new" stove?

Roger; with some help from Tony B i've been building canister stoves for quite a while now. they get lighter and smaller as i learn more.

Tad; let's see if i can figure out how to post a pic here.

Daren......

Hi Daren

Ah, well, you are in good hands with Tony.

OK, I am much impressed. So much so that I want to ask some questions and make some suggestions.

What's the bit clipped to the top of the burner? A wind-deflector? If so, did you make it yourself? What metal? And does it contribute anything if you use a windshield?

The legs you have made fascinate me. I was wondering how best to reduce the weight of the originals. Aluminium angle?

The pot supports: what metal? It looks like aluminium wire, which would worry me badly. Titanium wire would be fine of course. How are they anchored into the legs - just by press-fit? I admit I would worry about them working loose over time, especially after a bit of rough treatment.

The hose connection: are you planning on adding a heat shunt to this for inverted canister use? If so you may need to look very carefully at how the hose is kept on the fitting: when it gets warm the hose could blow off (maybe). Actually, I would worry about the hose connection anyhow: I have had them leak - at which stage there are little growing flames in the wrong places.

Fun!
Cheers
Roger

Roger;
thank you for your input.
the three-sided part on top of the burner is purported to be a windscreen by the company selling the stove in this part of the world. MSR. i take it the Kovea version doesn't have this feature?

the base legs are made from 14gauge 5052 aluminum sheet. all cutting and drilling was done "on the flat" and they were formed afterwards. (i'm a metal-worker by trade)

the pot supports are in fact aluminum welding rod. 1/8" diameter, 7000 series (i forget exactly which). the rods are threaded and the base legs are tapped with a #5 machine screw thread. i appreciate, and understand, your concerns about the potstand legs being aluminum. i was concerned as well; at first. after a half dozen stoves and many pots of water boiled, none of my potstands have collapsed due to heat. i had one tip over with a heavey kitchen pot on it with four liters of water. no damage, just a soggy kitchen. :D .
i hadn't planned on any future additions to this particular stove. if i did add a heat shunt i would completely change the fuel input line to a copper line, and run it up through the edge of the fire. but, i have two other stoves with this feature, so i doubt this will ever happen.
i've had fuel leaks as well. they aren't fun, but are easily avoidable.

when i did the modifications to the stand and stove i had not yet started building my own stoves. it was a stepping stone on the road to actually machining my own stuff. i've got a lot of commercial stoves and the only ones i won't mess with, (besides antiques), are the Optimus Nova, and the Snow Peak GS100.

Daren........

Edited by DarenN on 02/21/2009 17:40:33 MST.

Hi Daren

The Kovea stove I was referring to is rather like the Vargo Jet-Ti and the Snow Peak GS100. These two are my idea of a Gold Standard for uprights.

That the 1/8" Al rod supports are surviving the heat so well is very interesting. Hum ... That the rods were threaded into the angle was not visible in the pics.

> i had one tip over with a heavy kitchen pot
The solution to this problem, in my experience, is to switch from 3 pot supports to 4. The extra support really does make a lot of difference to the stability. But, of course, it is extra weight.

We want to see more MYOG canister stoves! If you want to make even more of the stove, remember that the thread on the Lindal valve is 7/16" 28 tpi UNEF (UNEF). Taps and dies are available from e-taps.

Cheers

Edited by rcaffin on 02/21/2009 20:47:58 MST.

here's a pic of my latest stove. it boils two cups of water in 6 minutes using 6 grams of fuel, or 3 minutes using 9 grams of fuel. i'm using a Brunton valve for now as i havn't gotten into machining my own yet. the stove weighs 27 grams (not including valve).