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Accurately weight the fuel left in a canister — using your hiking pole


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Home Forums Gear Forums Make Your Own Gear Accurately weight the fuel left in a canister — using your hiking pole

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  • #1330247
    Jan Miksovsky
    Spectator

    @jan_miksovsky

    Locale: Seattle

    Here’s a way to quickly and accurately measure how much gas is left in a metal fuel canister when you’re on the trail, within a tolerance of about ±1g.

    At home, you can quickly measure the fuel in a canister by weighing it on a kitchen scale. A full small fuel canister weighs 200g, and that same canister weighs 100g when empty. But on the trail, you can’t guess the weight of something in that range very accurately just from its heft in your hand.

    It turns out that you make some simple marks on a hiking/trekking pole to create an ancient kind of balance scale called a bismar scale (http://www.isasc.org/Tutorial/Scale-Types.html#Bismar). In such a scale, the pivot moves along a balance arm, while the weight and counterweight stay fixed. The moving pivot makes such a scale harder to read, and less useful, in general life but can still be accurate enough for our purposes.

    Here, your hiking pole acts as both the balance arm and the counterweight against the canister you want to weigh. All you’ll need to do is scratch some marks on your pole at home beforehand:

    Marks on hiking pole

    This hiking pole has been etched with 11 crosswise marks. The tiny knife is pointing to the leftmost mark, which represents a weight of 100g. The rightmost mark represents 200g, with other marks at 10g intervals between. The 150g mark in the middle, as well as the 100g and 200g marks on the ends are slightly longer than the other marks.

    In a bismar balance, the relationship between the marks and weight is NOT constant — you can notice a bigger gap exists between the 100g and 110g marks on the left than between the 190g and 200g marks on the right.

    Suppose you’re on the trail, and want to know how much fuel remains in a canister. First, knock any dirt off your pole. Then, slip the canister into your pole’s strap. Conveniently, you can tighten the pole strap to ensure the canister won’t slip out.

    Fuel canister hangs in the balance

    The fact that the strap hangs off your pole at a fixed location means that the load you want to weigh is always in a known position. You then just balance the pole on your finger or — if you want better accuracy — the blade of a knife:

    Weighing the fuel canister on the edge of a knife

    Once you’ve balanced the pole, you look down to see to read the canister’s weight:

    Reading the scale

    Here the knife blade is just about at the 110g mark, maybe a hair to the left, so somewhere between 109g–110g. (As noted above, the distance between weights on this scale gets smaller the heavier you go, so you need to keep that in mind when reading the scale.) This result means you’re nearly done with this canister, but still have a bit left for a boil or two.

    I happened to take the above pictures on the last morning of a recent hike. Now back at home, let’s check the actual result on a kitchen scale:

    Weighing the fuel canister on a kitchen scale

    The kitchen scale reads 109g, so the hiking pole balance was pretty accurate! Each time I’ve tested this hiking pole scale against a kitchen scale, the weight given by the hiking pole has been within a gram of the weight given by the kitchen scale. That precision gives you a very good sense of how many meals or hot beverages you can prepare with what remains in your canister.

    How to mark your hiking pole for use as a scale:

    Making the markings at home is simply a matter of measuring a series of known reference weights, and scratching marks at the balancing points. I found that a small, sealable TupperWare container that could be filled with water worked as an adjustable reference weight.

    1. Clean any loose dirt off your pole.
    2. Start by checking that your pole can accommodate marks at the heaviest end of the range you want to cover. If you have a short pole, the heavier balancing points might end up on your handle. (The collapsible 48” pole shown in these photos is very light, so the balancing marks ended up near the top of the pole, just below the handle, making such a scale just barely possible.) So begin with the heaviest weight you want to be able to measure (e.g., 200g) first. Put the container on your kitchen scale, with its lid next to it. Then slowly fill the container with water until it weighs exactly 200g.
    3. Once you’ve got the container of water weighing exactly what you want, seal the container with the lid. Slip it into the hiking pole strap and tighten the strap.
    4. Balance the pole on the edge of a knife blade. Take your time. You may have to make very slight adjustments back and forth until the pole holds fairly still.
    5. When the pole is balanced, mark the pole at that position: press the pole down into the knife blade, and rotate it back and forth a bit to score the underside of the pole.
    6. Repeat steps 2–5 for the remaining weights: 190g, 180g, …, down to 100g.
    7. Grab a fuel canister, give the scale a test, then weigh the canister on the kitchen scale to see how well the scale works.

    Since you’re calibrating your scale for future use, it pays to make the reference weights as accurate as possible. I found it useful to remove the container of water from the kitchen scale, then re-weigh it to double-check that I really had the weight correct.

    You could add numbers (e.g., with a dremel) if you wanted, but I didn’t feel the need for those; I’m the only one who has to know what these marks mean. I’d originally tried writing marks on a sticker or tape on the pole, but the handle on this collapsible pole needs to cover that portion of the pole when the pole is collapsed, and a sticker or tape was too thick to slide under the pole’s handle. Scratches work well enough, and are easy enough to make.

    I find that carrying this balance scale with me is reassuring. I like the convenience of gas canister stoves, but have wished there were a way to know how much fuel is left in a canister. This is part vague anxiety, and part practical consideration. If I’m near the end of my last canister, I’d like to know if I have enough fuel for both a hot morning beverage, while still leaving enough for a hot meal at the end of a day. On a longer trip, I may want to check my fuel consumption as I go for peace of mind. Using a hiking pole as a balance can answer those questions, and is just fun to be able to do!

    #2210565
    Hiking Malto
    BPL Member

    @gg-man

    I never ceases to amaze me how creative some folk can be. So simple and doesn't require an expensive backer packer magazine recommended gizmo.

    #2210618
    Colin Krusor
    BPL Member

    @ckrusor

    Locale: Northwest US

    If BPL had a MYOG innovation hall of fame (and maybe it should), ranked by merit, this would have to be near the top. Your tool weighs literally nothing and solves an old and perennial problem. Also, your explanation is excellent.

    Beautiful. Thanks for posting this.

    #2210640
    Dale Wambaugh
    BPL Member

    @dwambaugh

    Locale: Pacific Northwest

    Very clever! I would refrain from etching the pole and use some other method of marking. Scratching some materials like that can create a breaking point, especially carbon fiber. Thin tape, paint, or ink might be better.

    #2210676
    Valerie E
    BPL Member

    @wildtowner

    Locale: Grand Canyon State

    Great idea, and really creative, out-of-the-box thinking!

    I'd suggest using nail polish for marking the pole — it wears like iron.

    #2210677
    Jerry Adams
    BPL Member

    @retiredjerry

    Locale: Oregon and Washington

    does nail polish stick to plastic?

    #2210697
    Chad B
    BPL Member

    @cenazwalker

    Locale: Southwest

    That's one of the coolest things I've seen on here in a long time. Thanks for posting.

    #2210699
    Gary Dunckel
    BPL Member

    @zia-grill-guy

    Locale: Boulder

    That is very impressive!

    #2210705
    Greg Mihalik
    BPL Member

    @greg23

    Locale: Colorado

    "does nail polish stick to plastic?"

    Sally Hansen's Hard As Nails sticks to carbon fiber just fine.
    (I use it to modify my 98% CF tenkara rods.)

    #2210710
    Valerie E
    BPL Member

    @wildtowner

    Locale: Grand Canyon State

    "does nail polish stick to plastic?"

    LOL, I think you'd have a harder time finding things nail polish DOESN'T stick to…

    #2210833
    Nick Smolinske
    BPL Member

    @smo

    Locale: Rogue Panda Designs

    Nail polish does a pretty impressive job marking climbing gear – some of my markings on carabiners are 4 years old and still going strong. So I think it would do just fine for this.

    #2210894
    Dan Yeruski
    BPL Member

    @zelph

    Locale: www.bplite.com

    Thanks for sharing :-)

    #2210911
    Garrett McLarty
    BPL Member

    @gmac

    Locale: New England, PNW, Northern India

    Thanks so much for sharing. Beats taking a scale:)

    #2211207
    Kevin Beeden
    BPL Member

    @captain_paranoia

    Locale: UK

    I wonder if the length markings on 2 or 3-piece adjustable poles could be exploited for this; rather than mark balance points, you'd have a single balance point, and then use the extension markings to measure the weight.

    One difficulty with the method is that different manufacturers canisters often weigh different amounts, we'd need a 'tare function' of some sort…

    I confess that as soon as I saw the thread title, I knew how it would work. It's cunning, and I like it…

    #2211211
    Greg Mihalik
    BPL Member

    @greg23

    Locale: Colorado

    ^^^

    There's a reason the marks shown are so close to the grip …

    #2214171
    george carr
    BPL Member

    @hammer-one

    Locale: Loco Libre Gear

    I'm like a little kid – the simplest solutions are the ones that get me the most excited (and it's free). I'm gonna mark one pole for the smallest canisters and the other for the next bigger since I use both. Thanks for the tip!

    #2214256
    monkey
    Spectator

    @monkeysee

    Locale: Up a tree

    What I love about this is the natural simplicity standing its ground against technological sophistication. In our age with computers, GPS navigators and the like – we often forget about original and in many cases equally efficient solutions! Its really nice to be able to understand and get back to the basics, which is what hiking is often about after all. Thanks so much for sharing.

    #2215026
    Rich K.
    Spectator

    @scrabbler

    Most excellent Jan, thanks for such a clever idea!

    #2215031
    Franco Darioli
    Spectator

    @franco

    Locale: Gauche, CU.

    Great!
    I have posted about putting "water marks" on the canister (drop the canister into water and see how far it sinks) but you either need a largish pot or still water nearby to do it and then of course mark every cartridge you use.
    The peculiar part here is that I grew up seeing my father using a balance scale* as , well into the 60', did the local vendors at the fresh produce market.
    In fact even today the word for a scale in Italian is balance (bilancia).
    *This was the type :
    Balance scale

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