Auto shutoff stove

I suspect that switching off a gas or alcohol stove could be a bit more complicated  than doing it with an electric heating element.

A gas-fired water heater does this every time it’s come to temperature. But the thermostatically-controlled gas valve is about the size of a small paperback book and weighs about a pound. Of course, if there was a market, it could be made smaller, but all the ways I’m imagining would require the burner and pot to be one unit, like the water heater is one unit.

I hate it when I get distracted, the pot comes to a boil, it continues boiling creating clouds of steam,…

If you use an alcohol stove for a while you get pretty good at knowing almost exactly how much fuel to put in the stove for a given size boil (and temperature).  I’ve found that my Caldera Cone setup did exactly what you said…I’d put 16 ml of alcohol in the 12-10 stove, light it, put my pot on, and walk away.  If I were watching I’d see some steam escaping right before the burner went out, but often I’d come back to a nice pot of boiled water (6-8 minutes later) and would prepare dinner.

I’ve switched to one of Zelph’s Starlyte stoves (which can hold more fuel than you need and you can snuff it out and save the unused fuel) and I’m still trying to figure out if I like the “snuff & save” feature or if I want to go back to putting a measured amount in and just letting it burn itself out.

As I hinted in my first post, with an electric kettle there is a switch that is triggered by steam hitting a thermostat.

With gas and alcohol you need a mechanical switch off valve . I don’t know how that could be done in a light portable device and in any case you would still need some electrical circuit to trigger it.

Anyway, if you make a hot drink you don’t need boiling water (unless the boil is to purifying it) so you save fuel by turning it off when you start to see some babbles rising. When re-hydrating on the other hand the water should be as hot as it can be so you need to be there to transfer the boiling water into whatever as it is boiling.

just my take …..

Hmm, with a thermoelectric generator and an Arduino plus Anniken Andee U for Bluetooth and a couple of support chips and a tiny solenoid-driven valve and a good application framework and a custom smartphone app to control the temperature and sound an alarm when the water’s hot enough and …

Or maybe just small mechanical thermostat that closes a spring-loaded valve or pinches a tube?

— Rex

Trying to get a portable, small and  light “mechanical thermostat that closes a spring-loaded valve or pinches a tube” made and then  approved for sale could be a bit more difficult that it may sound .

I am not saying that it can be done, just that it could be a bit harder to do than to think about it.

Then there is the problem that the thermostat sensor would need to be in the (boiling) water, while the gas supply valve is ‘elsewhere’.

An awful lot of electric motors in Australia have a ‘thermal cutout’: a bi-metal switch which open-circuits when the motor gets too hot. These switches are not physically big.

I had to replace the thermal cutout in an important motor some years ago – or buy a whole new motor. So I asked around, and found that most (Oz) motors use a simple thermal overload switch from one company here in Sydney. It simply senses the temperature of the motor housing. OK, buy a replacement from the company.

I rang the company, and got chatting to the owner. The whole factory seems to be two very elderly guys running a 50+ year custom old stamping and riveting machine plus 3 very elderly ladies who do the calibration on a temperature cycling box. My understanding was that most of them were over 65 years old …

The switches were quite cheap, so I bought several. You never know when the staff might all drop dead. But they are snap-action electrical switches – no use for gas.

Cheers
PS: safety note: you should never leave a fuel stove running without someone to monitor it.

As already stated, using alcohol  or Esbit stoves allows this facility.

One reason why I primarily choose them over gas for backpacking. And it’s easier than gas to predict fuel needed for any one trip. And of course, always lighter overall.

(Gas might be lighter at the start for a few days on a longer trip, but in terms of weight carried per day, it’s always the heavier option over more of the days than alcohol or Esbit)

20ml of alcohol in my cone setups boils 500ml of water consistently.  Vary fuel amount to required water.

A 14g block of Esbit will usually boil 750-800ml of water.

If rolling boil  not quite reached, no big deal, the water will always be hot enough for coffee/tea/breakfast.

For most of the stoves we use, a simple spring will supply the off powr, similar to a rollover safety switch on a kerosene heater (I use these in my shop.) It isn’t real heavy and the wind-up occurs with turning it on. Or, you could wind it separately.

There are two methodes for temperature selection. The thermostatic control could simply release a trigger, but this would require heat conductance to the thermal mechanism.
This gets complicated in a hurry and would likely not be very accurate.

The second methode would be a simple timer, similar to a normal kitchen “bell” timer. These weigh in at 3-4oz, but, most of the weight is the housing, bell and clapper.

I would guess that the whole arrangement could be done for around an ounce or so. The mechanism would include: Larger disk actuater, pin trigger, spring, escapement, maybe a gear or two, housing. Hell, they make alarm wrist watches at a lot less weight.

On the topic of some sort of notification, how difficult would it be to add a “whistle” to the lid, like typical stove top kettles or some vented pot lids? Wouldn’t turn the stove off of course, but generally these are pretty loud so would alert you to turn stove off/down from anywhere within prob 50’ maybe more. Should be very light and the notification is triggered by actual boiling, not theoretical boiling based on typical timing, which is how measured fuel or a stop watch work.

maybe the mechanics of a regulator valve would be easier to actuate than a needle valve

maybe the mechanics of a regulator valve would be easier to actuate than a needle valve
Nope.
Anyhow, a ‘regulator valve’ IS a needle valve.

Cheers

Could be a good challenge for someone here to come up with the solution.

In the meantime I agree with Mole that there already is (in a round about way) a solution for alcohol and Esbit as well as Roger’s comment that you should never leave a flame unattended.

When water boils, you generate steam.  At one time there was a thought that you could pipe the steam down to blow out the alcohol flames.  That was probably discussed after several beers.

Jon’s post makes me think:

Just let your pot boil over. That could stop an esbit or alcohol stove. Sometimes it extinguishes my kitchen stove (but, alas, it doesn’t stop the gas flow)

If you had a gas or liquid butane mini-canister, fed from your main canister, you could fill the mini-canister with, say, 8 grams of fuel, close the filling valve, and then be limited to those 8 grams for a burn.

Like an alcohol fuel bottle (or their origin: an oil bottle for a two-stroke, pre-mix engine), each fill from the main fuel container to the “day tank” could be selected to be exactly the right amount.

“If you had a gas or liquid butane mini-canister, fed from your main canister, you could fill the mini-canister with, say, 8 grams of fuel, close the filling valve, and then be limited to those 8 grams for a burn”

yes that is VERY practical.

i’ll patiently wait for the exact details on how to do that.

I mean in the real world, not fantasy land.

Franco, “…in the real world…”
Ha, ha, ha, ha…

Unfortunately, it is the bane of modern society to make things complicated.

Canister fuels all require some sort of gas flow regulator. A simple needle valve works well. Instead, we have regulators with complicated flow mechanisms that operate the valve at a more consistent setting for us. Don’t even need to think about it.

They have complicated pieces of crystal, wires, springs, and mounts in the interests of something you can do with a couple thousand year old flint and steel as effectively.

And, now we are talking about saving a gram, maybe two, of fuel because we don’t have the patience to wait for the end of a five minute burn while boiling water. And, to save that 1-2gm of fuel, we would entertain suggestions of carrying an extra ounce or two (28-60gm) of additional weight to do it. IT DON’T MAKE SENSE! Sort’a like carrying a 1 pound pack is easier if you try it with a 2 pound pack.

Yup, we are indeed all light hikers, but I will not describe the lightness…Ha, hey, although I ascribe to my share of this lightness…in the real world.

Fun gadget to ponder.

Last year some one posted a nitinol wire temp indicator that pops up when your water reaches a target temp.  In theory, you could couple that mechanical actuation to a fuel shut off.  You might want to arrange it to clip to the edge of the pot for a fulcrum of some sort.  It probably has enough force to snuff an alky/esbit burner.  Might be able to trip a rollover valve.

https://backpackinglight.com/forums/topic/nitinol-wire-wapi-to-save-25-on-fuel/

Hmm… take something like a cut off soda can, invert it, put it in your cold pot and flood it.  As the water temp rises, the vapor pressure rises, and eventually it starts to fill with water vapor and floats.  That motion could be captured to actuate a shut off, and it would have more force than a little nitinol wire.

I am filled with something like admiration at the novel ideas being expressed.

How about a very thin silicone rubber seal under the edge of the pot lid, so that when the water starts to boil the lid starts to clank? It won’t turn the stove off – and indeed one might not want it to turn right off, but it might make a noise to alert the user. Total weight in the order of 1 – 2 grams.

Or even a steam whistle? This might have been mentioned already.

Cheers

I knew if I posted this that someone would tell me it wasn’t necessary, and that the geeks would work on figuring out a way to do it anyway! BPL is quite entertaining at times. I knew there’d be a fair bit of ingenuity here. Maybe you all should become the R&D for MSR.

On the comment about hot but not boiling, I like boiling water for drinks, even at home. Water that is only hot seems so unsatisfying. Not that I’d turn down a hot cuppa when I’m out hiking, if it were offered to me. But holding that beverage that is too hot to drink, and waiting until it’s just right, is part of the ritual of a hot beverage. It is one reason I carry a separate mug that isn’t my eating bowl, just so I can sit there and hold it, that’s my chief luxury item! I also use untreated water much of the time, if I know I’m going to boil it.

I can sit there and watch the stove, and most of the time I do. I would certainly not be very far away if I were alone in camp. But when trying to get moving for the day, it would be convenient to start it, and get something else done, even if it’s only a few minutes. If it’s raining, even nicer to be getting going quickly.

Really it isn’t a big deal. Nothing is, except the essentials. It’s just a “would be nice” thing.

Karen ,

just for fun…

if you indeed like your water to be HOT and have and auto cut off, you will also need with it an audible warning otherwise your water is not going to be that hot by the time you have a look .

I agree that such a device likely weighs, costs, and complicates things too much, but it’s fun to brainstorm.

I find one advantage of an HX pot is that it heats water faster at given setting AND I can run the stove on a higher setting without wasting as much fuel/heat. Therefore, with it taking only 40-50% as long to boil, I just sit and wait for it. Lots of water quantities I’m boiling are done in under a minute.