Remote Canister stove Recommendations
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Hikin' Jim
(hikin_jim) - MLife

Locale: Orange County, CA, USA
power for melting snow. on 04/10/2013 15:48:44 MDT Print View

Walter,

Interesting numbers, and if I may, let me paint a bigger picture:

Total power is determined by fuel type, jet aperture size, and fuel pressure (either direct from the canister or by phase change expansion in the generator/preheat loop), but how much of that power gets transferred to the pot has a lot to do with how efficient your set up is. Your numbers describe the first half (power) of the equation of snow melting. Efficiency describes the remainder.

Ways to more efficiently melt snow (i.e. transfer more of that heat to the pot):
-Use a windscreen
-Use a lid
-Use a moderate flame (may not be practical when melting snow, but it is more efficient)
-Use a wider pot
-Use a heat exchanger pot
-Use a darker colored pot (probably less important than the other items on the efficiency list)

On the efficiency side:
One of the big arguments in my mind in favor of an inverted canister stove (like the Optimus Vega, MSR Windpro, Kovea Spider, etc.) is that you can use a better, i.e. full 360 degree, windscreen.

On the power side:
Another argument in favor of an inverted canister stove in the case where a lot of power is desireable (e.g. snow melting) is the issue of canister pressure vs. pressure due to phase change (going from liquid to gas). In an upright canister, the phase change happens in the canister, and your pressure at the burner is basically determined by the pressure in the canister. However, in an inverted canister stove, the fuel is still liquid when it leaves the canister. The phase change happens at the burner (i.e. in the pre-heat loop). The fuel expands some 200+ times its original volume when it goes from liquid to vapor. A 200 fold expansion gives you a lot of pressure at the burner even if your canister has a fairly low temperature -- and low canister temperature is just what you might have when you're melting snow.


An MSR Whisperlite Universal cranking out big time BTU's. Yes, it's running in inverted canister mode

So, the power of a stove matters and thank you for those numbers. In addition, one has to consider how best to make sure that power winds up as heat in the pot. That's why you might get a person with a lower powered stove (but with a heat exchanger pot) who can melt snow more efficiently than a person with a higher powered stove.

Anyway! Just a few thoughts about power and efficiency. Hopefully it will stimulate some thinking.

HJ
Adventures In Stoving

Edited by hikin_jim on 04/10/2013 15:57:08 MDT.

Walter Carrington
(Snowleopard) - M

Locale: Mass.
Power output with inverted canister? on 04/10/2013 17:14:04 MDT Print View

Actually, Jim, I wonder if the remote canister stoves give their power ratings with the canister upright. Do all these invertable canister stoves increase output considerably when you invert the canister? Perhaps Optimus Vega is just the only one that gives both ratings. That would be consistent with your info on fuel pressure with a liquid feed. I have a Primus Eta Power that I'll have to test this with when I get a chance. The Primus specs are 7000BTU/hour, 2000W.

The other factor to consider is how cold will it be? On local hikes it can get to -10F at night and, in NH, -30F or colder. In mid-winter I would probably carry my liquid fuel stove, an Optimus Nova. I won't be able to compare the very cold weather performance of the Opt. Nova and the Primus Eta till next winter.

Finally, if the temps are in the 20s or even teens it is often possible to find some liquid water which saves lots of fuel and time.

Chris Pund
(chrispund)
Re: Re: Re: Re: Re: fire-maple/kovea on 04/10/2013 22:02:56 MDT Print View

I used a MSR Windpro for a number of years and really like the stove.

I'm now using a Kovea Spider and havent had any issues. I havent had it out in anything too cold yet (not below freezing). Lots of goods reviews on it from Adventures in Stoving and Wood Trekker blogs.

6 ounces and $60.

http://www.thegearhouse.com/Camping-Hiking/Camp-Kitchen-Cooking/Stoves/Backpacking-Stoves/Kovea-Spider-Remote-Canister-Stove.html


Full disclosure: I'm partial to the Kovea stoves because I sell them in my online store and am the first in the US to be offering them - no more waiting two weeks from Korea, you'll have it in a couple days.

Hikin' Jim
(hikin_jim) - MLife

Locale: Orange County, CA, USA
Re: Power output with inverted canister? on 04/11/2013 00:44:31 MDT Print View

Actually, Jim, I wonder if the remote canister stoves give their power ratings with the canister upright. Do all these invertable canister stoves increase output considerably when you invert the canister? Perhaps Optimus Vega is just the only one that gives both ratings. That would be consistent with your info on fuel pressure with a liquid feed. I have a Primus Eta Power that I'll have to test this with when I get a chance. The Primus specs are 7000BTU/hour, 2000W.
Walter, I'm not sure how stove companies derive their specs. I assume they're for upright operation, but I haven't corroborated that.

Generally though, stoves increase power when you switch them to inverted canister mode. You get a lot more power but typically less fine control. Try it some time. Turn your stove down fairly low after it's had a chance to warm up a bit, and then invert the canister. You should see a marked increase in output, particularly on a cold day.

The other factor to consider is how cold will it be? On local hikes it can get to -10F at night and, in NH, -30F or colder. In mid-winter I would probably carry my liquid fuel stove, an Optimus Nova. I won't be able to compare the very cold weather performance of the Opt. Nova and the Primus Eta till next winter.
I usually think of a remote canister stove as good down to 0F with good fuel (no regular butane). Below 0F, you either have to warm the canister or switch to liquid fuel. Even liquid fueled stoves have problems in really cold weather -20F and below. Parts on pumps hard, seals don't work properly, etc. Personally, for a group, I'd bring a gas stove capable of inverted operation AND a liquid fueled stove. The gas stove will be more mechanically reliable but the liquid fueled stove will work if for some reason you can't find a way to warm the canister. Remember that in cold weather you can do things that might be stupid dangerous in hot weather -- but always be careful and test the canister by hand when employing warming techniques. All you have to do is to heat the canister to say freezing, and you'll have all the power you'll need.

Finally, if the temps are in the 20s or even teens it is often possible to find some liquid water which saves lots of fuel and time.
Yes, by all means. Avoid melting snow whenever there's liquid water available. That's an even better fuel savings than a heat exchanger pot. :)

HJ
Adventures in Stoving

Stuart R
(Scunnered) - F

Locale: Scotland
Re: Power output with inverted canister on 04/11/2013 02:16:30 MDT Print View

Hi Jim
"However, in an inverted canister stove, the fuel is still liquid when it leaves the canister. The phase change happens at the burner (i.e. in the pre-heat loop). The fuel expands some 200+ times its original volume when it goes from liquid to vapor. A 200 fold expansion gives you a lot of pressure at the burner even if your canister has a fairly low temperature"

Think about this for a moment. The liquid fuel is boiling in the pre-heat tube and therefore there is a ~200x increase in volume. That volume wants to go somewhere - where? The fuel line has restrictions at both ends - the jet at one end and the valve at the other. So, if the boiling fuel in the pre-heat tube were to increase the pressure in the fuel line, that increase in pressure would be evident at both ends of the fuel line - the jet and the valve. That would create a 'back pressure' at the valve, forcing fuel back into the canister. Obviously that can't happen!

So, what does happen? The highest pressure in the system is in the canister. After passing thru' the valve, the pressure in the fuel line is lower. And after passing thru' the jet the pressure in the burner tube is lower still (lower than atmospheric, that's why air gets sucked in thru' those air holes). The boiling fuel in the pre-heat tube does not increase the pressure in the fuel line at all.

"But", you say, "when I invert the canister I see the flame increase, so there must be more pressure!"
Yes there is, but for a different reason. The fuel valve is restricting the flow of fuel, but it is restricting the (approximate) volume flow rate, not the mass flow rate. So, if a particular valve position and canister presure were to give say 1ml per minute of fuel, then with the canister upright that will be 1ml per minute of gas, but with the canister inverted what will be 1ml per minute of liquid, or would be if there was no jet - there is not enough pressure to force 200ml per minute of gas (from the expanded liquid) thru the jet. Nonetheless, when the canister is inverted there is an increase in the mass flow rate of fuel and so a bigger flame.
HTH, cheers.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Power output with inverted canister on 04/11/2013 02:53:58 MDT Print View

> The boiling fuel in the pre-heat tube does not increase the pressure in the fuel line at all.
Stuart is right of course about the valve restricting the volume flow, at least in the average.

> That would create a 'back pressure' at the valve, forcing fuel back into the
> canister. Obviously that can't happen!
Ah well, not so fast. It is quite possible to get an oscillation in the hose, with the fuel pulsing back and forward as the pressure oscillates. It can oscillate if the fuel boils in 'lumps', which is possible if the fuel can surge into a hot region. That is why hoses have filler cords and the Coleman Xtreme stove has that long brass rod inside the fuel line at the stove end. The filler cord damps the flow and the brass rod gives a smoother boiling process.

You don't normally see this oscillation, because the hose is usually opaque and covered in mesh (and it can be very fast). However, I have seen in many times on some of my test rigs. Also, quite a few remote canister stoves make a bit of a chug-chug noise at times. That is the oscillation. It is also fairly common with white gas stoves, which is why they are often called 'chooffers' (or chuffers).

> Do all these invertable canister stoves increase output considerably when you
> invert the canister?
The pressure behind the jet drives the flow, and that is about the same as the pressure inside the canister. The size of the jet hole does not change, so the flow rate of fuel out the jet is usually about the same, all things being equal. So there should be very little difference in peak power between inverted and non-inverted canister operation, as long as the canister is warm enough.

Cheers

Edited by rcaffin on 04/11/2013 02:58:48 MDT.

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: Re: Power output with inverted canister on 04/11/2013 04:52:14 MDT Print View

Roger is correct. Also, around the jet we have this thing called Bernoulli's principle. Basically this says we are trading pressure for speed. This is what mixes air with the fuel, even though the fuel is at a higher pressure and velocity as it leaves the jet, it draws air INTO the "mixing chamber". Ignoring friction, this means it has a higher volume at lower presure at the flame spreader. Even though the gas is at a higher pressure than the air, Bernoulli's principle insures that air, at a lower pressure, is drawn in and not pushed out.

Note that Pressure/temperature can be considered as one in a closed system. Applying back pressure as Roger is describing, will also supply heat to the canister. This is NOT direct thermal feedback as in the recent article he wrote. "Chuffing" is not all bad.

Stuart R
(Scunnered) - F

Locale: Scotland
Re: Re: Re: Power output with inverted canister on 04/11/2013 06:13:08 MDT Print View

Hi Roger

Yes, I know that there can be short pulses in pressure as the fuel boils and I have seen how the bubbles in a clear PFA fuel hose can sometimes oscillate or move in steps. I have eliminated this effect by inserting stainless wire into my pre-heat tube.
However, I was trying hard not to over-complicate my original explanation...

Ryan Bressler
(ryanbressler) - F
Re: Re: Re: fire-maple/kovea on 04/11/2013 10:37:07 MDT Print View

>I don't know what Ryan's problems were, but we suspect a partially blocked jet. Both the FMS-118 and the Kovea Spider work >perfectly well on my bench. I would trust both of them in the cold.

My testing was done with a new stove so if the jet is blocked it is indicative of poor QC. Additionally it was done in real world mountain conditions. IE with partially exhausted canisters at 3800' with temperatures between 0 and 20 F and blustery-gusty winds. The windpro II performed admirably in the same conditions.

I respectfully request that you seek out similar test conditions before offering advice to people who will be depending on such gear in winter; bench testing is not a substitute.

Further I was able to reduce the issue by inserting a bit of wire into the preheat tube as Stuart R suggested. Further testing (and more cold weather to do it in) is needed but this suggests that the issue is in fact with the preheat tube:

http://blog.hillmap.com/2013/02/fixing-fire-maple-fms-118-inverted.html

Hikin' Jim
(hikin_jim) - MLife

Locale: Orange County, CA, USA
Re: Re: Re: Re: Power output with inverted canister on 04/11/2013 10:51:03 MDT Print View

Ah! Very interesting. So it's about the relative amount of mass flowing through the jet vs. the valve not the actual pressure. And of course a gas has much less mass than a liquid. That makes sense. I knew that if there were more pressure in the generator than in the canister things wouldn't flow (flows occur from high to low after all), but I could see the obvious and marked increase in output at the burner. I tried to explain the observed increase in terms of pressure, but I had a niggling feeling in the back of my mind that I was missing some technical nuance.

HJ
Adventures in Stoving

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
re: Express Spider on 04/11/2013 10:52:24 MDT Print View

A bit late to the party but I'll add a data point.

I've been using a Primus Express Spider for 16 months now and am quite pleased with it. Beyond the obvious benefits in cold weather, the remote canister is nice for using a windscreen, and because being able to invert the canister helps wring out every little bit of fuel. I used it for many trips all last summer because the 3-4 oz weight penalty over an upright canister stove was paid back in efficiency.

The only functional difference between this and a Windpro seems to be the orientation of the control knob. The Windpro wins there, but having to adjust the Spider before I invert the canister isn't really a big deal.

A month ago I noticed that performance was a bit degraded and pulled apart the canister end valve and cleaned out a bit of gunk. That returned it to full power functioning.

I'm content with just the Spider and an alcohol stove for summer solo use as my stove quiver.

Hikin' Jim
(hikin_jim) - MLife

Locale: Orange County, CA, USA
Re: Re: Re: Re: Re: Power output with inverted canister on 04/11/2013 10:59:45 MDT Print View

> Do all these invertable canister stoves increase output considerably when you
> invert the canister?
The pressure behind the jet drives the flow, and that is about the same as the pressure inside the canister. The size of the jet hole does not change, so the flow rate of fuel out the jet is usually about the same, all things being equal. So there should be very little difference in peak power between inverted and non-inverted canister operation, as long as the canister is warm enough.
That doesn't seem to square with my observations. I notice a marked increase in output when I invert the canister. Marked. In the photo I posted, above, I've seen no higher output in a Whisperlite Universal than in inverted canister mode.

What am I missing here? You're saying that all I need to do is just open up the valve further, and I'll get the same kind of high output? That doesn't seem to square with my memory, but maybe I need to burn some more fuel. :)

HJ
Adventures in Stoving

Roger B
(rogerb) - MLife

Locale: Here and there
Re: re: Express Spider on 04/11/2013 13:05:25 MDT Print View

@DaveC I am just wondering what you use for an alcohol stove? Caldera, Clickstand, MYOG or ... I am guessing you use 1 pot for all occasions.

Stuart R
(Scunnered) - F

Locale: Scotland
Re: Re: Re: Re: Re: Re: Power output with inverted canister on 04/11/2013 14:19:44 MDT Print View

Jim - I would expect to see the same initial flame size with inverted and non-inverted canster when the valve is fully open. Initial flame size only because the evaporative cooling in the non-inverted canister will quickly reduce the pressure within. When the valve is partially open then the degree of restriction is different for gas than for liquid so I would expect this to give a different flame size. cheers.

David Chenault
(DaveC) - BPL Staff - F

Locale: Crown of the Continent
re: alc stove on 04/11/2013 15:44:08 MDT Print View

I use a cat can stove a la Skurka, with a BPL 900ml pot. Slow and not much good below 40F or so, but I like how simple and quiet and clean (v. esbit) it is, and in summer am willing to wait a bit longer for water to boil.

Hikin' Jim
(hikin_jim) - MLife

Locale: Orange County, CA, USA
Re: Power output with inverted canister on 04/11/2013 15:55:07 MDT Print View

Jim - I would expect to see the same initial flame size with inverted and non-inverted canster when the valve is fully open. Initial flame size only because the evaporative cooling in the non-inverted canister will quickly reduce the pressure within. When the valve is partially open then the degree of restriction is different for gas than for liquid so I would expect this to give a different flame size. cheers.
Interesting. Thank you for that, Stuart.

So they start out at the same flame size, but as the internal pressure drops in upright mode due to evaporative cooling, the internal canister pressure will fall and the flame size will in turn decrease. In inverted mode, their isn't the same degreee of evaporative cooling, therefore the internal canister pressure doesn't fall as much, and flame size stays larger. All this with the valve open fully.

What I've observed is that flame size makes a sudden and dramatic increase when I invert a canister, but I don't know that I've ever inverted a canister with the valve fully open (standard advice is to turn the stove down precisely because flame size does tend to surge when the canister is inverted).

And the reason that the flame size increases when the canister is inverted but the valve is not fully open lies in the fact that liquid fuel exists at the valve whereas gaseous fuel exists at the jet, yes? Can you say more about the particulars? I understand that more mass (a greater number of molecules) will travel through the valve since the fuel flow here will be liquid whereas less mass will travel through the jet since the fuel there will be in gaseous form, but I don't quite understand the mechanism whereby the flame size increases upon inversion. Is it simply one of impedence? That is, is it harder for the liquid to flow back through the valve than it is for gas to exit the jet and therefore effective pressure is created in the direction of the jet? I'm just having trouble visualizing what's going on here.

I'm sure the fact that it was a friend's birthday last night and that the vodka was flowing freely has nothing to do with my current lack of comprehension. ;) Please pardon my slowness.

HJ
Adventures In Stoving

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: Re: Power output with inverted canister on 04/11/2013 15:57:23 MDT Print View

> I was trying hard not to over-complicate my original explanation...
Stuart, Stuart - we THRIVE on complications!
:-) :-)

Cheers
PS: Al wire might work even better?

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: Re: Re: Re: Power output with inverted canister on 04/11/2013 16:05:43 MDT Print View

Hi Jim

> > So there should be very little difference in peak power between inverted and
> > non-inverted canister operation, as long as the canister is warm enough.
> You're saying that all I need to do is just open up the valve further, and I'll get
> the same kind of high output?

I should have added emphasis to the phrase 'peak power'. But since you probably never run at absolute peak power, you may not have seen this.

Yes, when you invert a canister under typical conditions you will get a change in flame. That's because the mass flow rate through the needle valve changed when it switched from gas flow to liquid flow. Remember the 250:1 expansion from liquid to gas!

If the hose presents a significant obstruction to the flow, then you may also get a difference due to that. Obviously you can get more mass down a partially blocked hose in liquid form than in gas form. Yeah, tricky.

That SOTO video shows a flame decreasing as the canister cools. Any walker would simply open the valve a little more when this happens. Dead simple. The SOTO regulator does that for you. Well, big deal of course.

Cheers

Edited by rcaffin on 04/11/2013 16:09:26 MDT.

Hikin' Jim
(hikin_jim) - MLife

Locale: Orange County, CA, USA
Re: Re: Re: Re: Re: Re: Re: Power output with inverted canister on 04/11/2013 20:00:06 MDT Print View

I still don't understand the interplay between the internal pressure within the canister, the pressure from expansion in the generator, and the higher mass flow through the valve. Perhaps a decent night's sleep will allow me to conceptualize it, but if anyone has a good illustrative analogy, I am all ears.

HJ
Adventures In Stoving

Jim W.
(jimqpublic) - MLife

Locale: So-Cal
Canister stove jet vs. valve limiting flow? on 04/16/2013 13:16:01 MDT Print View

Obviously you want vapor going out the jet, not liquid, whether the canister is upright or inverted. The valve though will see liquid when the canister is inverted.

I played around with a JetBoil Helios in the snow last weekend. It seems that the stove output increased quite a bit when inverting the canister, but that was at low valve openings. I presume that if we were at full throttle then the jet would be the limiting factor and the flow wouldn't change when inverting.

Jim W.