Bushwalk Australia

A little lateral thinking... How Much Gas Do I Have Left?

That's an old trick. The MSR canisters even have those lines printed on the side now.

It seems inconvenient though. I wonder if anyone's canister has floated away in a lake while doing this?

I experimented a while back with using a thin elastic cord along with a second inelastic cord that I'd calibrated with markings. The elastic I was using stretched about 1mm/g and I found I could discriminate 10g changes in weight fairly reliably. At least at home. In the cold the elastic constant would change so I would have had to adjust for temperature. I never took it outside to play with. I just estimate the fuel contents by shaking the canister. But that takes some practice to get a good feel for it.

For trekking pole users there is another way of doing it :
http://www.backpackinglight.com/cgi-bin ... _id=104621

Thanks, Franco.
I don't know why I didn't think of that (hits self on head).

An adjustable pole makes this a little trickier to get right. It might affect consistency of measurement.
And then of course if you use your poles as part of your shelter the technique isn't always available.

Still, I'm sure it's more accurate than my shake method. And so simple.

I read somewhere that u can pour some boiling water on it and it shows the line were its up to. But ive Never tried it.

Orion wrote:It seems inconvenient though. I wonder if anyone's canister has floated away in a lake while doing this?

Seriously? I have my cooking pot in front of me, filled with water ready to heat - what is inconvenient about floating a canister in it?

"Seriously? I have my cooking pot in front of me, filled with water ready to heat - what is inconvenient about floating a canister in it?"
That came to mind reading about canisters floating down the river but as it is for me with a couple of pots I can't put a 230g canister inside them.
The canister is wider than those pots.

Franco wrote:That came to mind reading about canisters floating down the river but as it is for me with a couple of pots I can't put a 230g canister inside them.
The canister is wider than those pots.

In the bush, just dig a dirt hole and fill it with water. Then float the canister. Otherwise, fill a waterproof compression sack with water... So many options.

I thought that it would be impossible to fully burp the bottom of the canister and also difficult to read the level while it was in my 2 liter pot. But when I tried it just now it worked fine. I think there was one last small bubble of air stuck underneath but it wasn't enough to affect the level. Of course a canister wouldn't fit in a small pot.

On the large MSR cans it's about 1mm per 10 grams of fuel. I'm not sure I could consistently discriminate a 1mm difference in the level. So maybe I could only tell to +/-10g. That's not bad. There's also a small temperature effect. For example, if the canister level indicated 150g at 25°C it would read 6g low at 5°C. Still pretty good.

Usually a shake is good enough for me. But there have been occasions where I've wished I could know more precisely. Maybe I'll use this trick sometime -- if I happen to have an MSR canister.

walkerchris77 wrote:I read somewhere that u can pour some boiling water on it and it shows the line were its up to. But ive Never tried it.

I'm not sure about boiling water but often you can see a line of condensation on the side of the canister when it's in use. There used to be little fuel gauge stickers you could buy that were basically linear thermometers. I think Primus sold them.

Shake shake shake -- I think we can have another pot of tea!

I think the real value is in monitoring, knowing the rate of use on a multi-day trip. Thereby allowing one to plan for the remaining days.

I don't have a precise measure of the amount of gas I need to cook different meals. In fact it varies with conditions. So accurately knowing the fuel remaining is only half of the problem in planning. If it were really predictable you could figure it all out at home.

Orion wrote:I don't have a precise measure of the amount of gas I need to cook different meals. In fact it varies with conditions. So accurately knowing the fuel remaining is only half of the problem in planning. If it were really predictable you could figure it all out at home.

Yes, hence the rate of usage. One that allows one to adjust to the condition.

If I take a scale I can accurately calculate the rate of gas usage. But I still won't know how much fuel a particular meal will require in a particular set of conditions. Each meal is different in terms of cooking requirements. And the environmental conditions are often unpredictable.

I usually take a little extra for these reasons. So it's rare that I'm trying to squeeze a canister because if I'm in that mode it means I screwed up the packing at home. I should have taken more fuel. But sometimes it does happen and I wish I could measure what's in there. Sometimes. When I've screwed up at home. My partner makes me remember those times, yes she does.

GPS Guided,
Take a look at this 2010 thread , it might amuse you :
http://www.backpackinglight.com/cgi-bin ... d_id=30461

Don't tell the UL crowd that I do but I usually have a 5L kitchen sink with me.

Thanks Franco for the link. Yes, there are few truly original discoveries out there. I also carry a fold up 8.4L capacity 'water bag' that I bought cheap off Aliexpress. For 74g, carrying and storing wash and cooking water around camp is so much easier as a result.

Nice, Franco. I didn't know that anyone had sold an actual spring scale for this purpose. I've actually thought about carrying my 500x0.01g pocket scale, just to actually see the numbers on a real trip. The scale weighs 136g, probably not much heavier than your sink.

I've never carried a water bucket but always have enough capacity (usually in the form of 2L platys) so that we only need to make one trip to get water at the end of the day and then we're good until after breakfast the next morning. I think those water bags weigh about 40g and we usually have two or three of them. Sometimes four.