Coke Can (Stove) Capers

[Bishop]

Things to do on a rainy afternoon... because there is only so much string knitting I can do before the screaming starts. Besides my coffee had gone cold in the shed.



From right to left: Classical , Well Fire , Hades Hockey Puck


The classic in action. Simple, quiet, dependable and relatively safe in operation.


Hades Hockey Puck [Mk01]: A tad lively during the pre-heat and flare stage. Think I need to reduce the flow rate to the jets.



Thankfully it settles down with a pot in place. The flame dipping down into the pan is a result of the jets interacting not fuel leakage as I first thought. Noisy little thing, you can hear the meths boiling.


The six jets are formed by three pieces from disposable vape coils secured in place with £land superglue. Not the best adhesive for the job I grant you.


NB: there are no pics for the "Well Fire" yet, the first run was scarier than expected for an indoor test and was more concerned about putting it out than taking pictures.

 

[Toddy]

Now that looks like a good way to spend a wet day

 

[Hammock_man]

and was more concerned about putting it out than taking pictures.

THAT is a good day, bonus points for making me laugh.

 

[crosslandkelly]

I love making and using coke can stoves. look forward to seeing the well fire running.

 

[Insel Affen]

How do you stop the "cold drain" when you put the pan on top?

I've tried a couple of different stoves, which all burn well, but then when you put the pan on it leeches all the heat from the stove before it starts to heat the water.

 

[ScottE]

I love to play about with stoves, I've found the "fancee feast" style the fastest for a boil.

 

[Bishop]

How do you stop the "cold drain" when you put the pan on top?

I've tried a couple of different stoves, which all burn well, but then when you put the pan on it leeches all the heat from the stove before it starts to heat the water.

Good question... I'll do my best to answer but it has been a while since I had Physics lessons at school and Google could not find any scholarly articles about the Thermodynamics of Pop-Can stoves that I could crib from so here goes...

Almost all the stove designs intended to function as a burner & pot stand combined have this quirk. However provided the stove does not go out this is a feature not a bug. When only the side jets are burning the stove effectively becomes self-regulating system and should settle down into a state of happy equilibrium of blue flames licking the edges of the pot.

Adding a cold pot temporarily reduces the energy available to vapourise the fuel, pressure drops and the flame moves closer to the stove. Though the flame is more feeble the increased proximity means more of that heat reaches the fuel. As the stove gets hotter then the increased pressure of fuel vapor pushes the base of the flame further from the stove so less energy reaches the metal of the stove and hence the fuel despite it being bigger. Evaporating fuel is also contributing to this cooling process.

In the case of the classic self priming stove with its double wall design then adding something to reduce the amount of fuel in the void space or improve the thermal transfer from the outer wall is worth experimenting with. This will speed up the time it takes for the stove to bloom and reach equilibrium once the cooking pot goes down. Fibreglass or Pumice can be used to do this so the volume of fuel to be initially heated is smaller and less energy is required to get the feedback loop going. Alternatively steel-wool or a metal pot scrubber also reduces the fuel volume a little but more importantly conducts heat into the fuel quicker. Sand may be worth a try being both porous & a good conductor. Some also claim good results with certain types of cat litter and gardening vermiculite.

A windshield/ reflector also improves performance especially in cold weather, conversely in warmer weather running a pop-can burner inside a hobo or woodgas stove can produce an impressive column of flame.

There are other things going on such as the diameter, position and number of jet holes, the amount of energy reflected by base of the pot and the Coanda effect of air flowing around the pot & stove but that's beyond me. One day somebody will get their PHD figuring all this out lol

 

[Insel Affen]

Good question... I'll do my best to answer but it has been a while since I had Physics lessons at school and Google could not find any scholarly articles about the Thermodynamics of Pop-Can stoves that I could crib from so here goes...

Almost all the stove designs intended to function as a burner & pot stand combined have this quirk. However provided the stove does not go out this is a feature not a bug. When only the side jets are burning the stove effectively becomes self-regulating system and should settle down into a state of happy equilibrium of blue flames licking the edges of the pot.

Adding a cold pot temporarily reduces the energy available to vapourise the fuel, pressure drops and the flame moves closer to the stove. Though the flame is more feeble the increased proximity means more of that heat reaches the fuel. As the stove gets hotter then the increased pressure of fuel vapor pushes the base of the flame further from the stove so less energy reaches the metal of the stove and hence the fuel despite it being bigger. Evaporating fuel is also contributing to this cooling process.

In the case of the classic self priming stove with its double wall design then adding something to reduce the amount of fuel in the void space or improve the thermal transfer from the outer wall is worth experimenting with. This will speed up the time it takes for the stove to bloom and reach equilibrium once the cooking pot goes down. Fibreglass or Pumice can be used to do this so the volume of fuel to be initially heated is smaller and less energy is required to get the feedback loop going. Alternatively steel-wool or a metal pot scrubber also reduces the fuel volume a little but more importantly conducts heat into the fuel quicker. Sand may be worth a try being both porous & a good conductor. Some also claim good results with certain types of cat litter and gardening vermiculite.

A windshield/ reflector also improves performance especially in cold weather, conversely in warmer weather running a pop-can burner inside a hobo or woodgas stove can produce an impressive column of flame.

There are other things going on such as the diameter, position and number of jet holes, the amount of energy reflected by base of the pot and the Coanda effect of air flowing around the pot & stove but that's beyond me. One day somebody will get their PHD figuring all this out lol

Great answer!! I was thinking of making a smaller pot stand to give the can some stand-off on the top (effectively creating an air gap which the heat can pass through, but not the cold). But now I have a few ideas to change a few things and add things into the cans before sealing - therefore adding mass which is heated and then transfers at a slower rate than the cold being drawn from it. I suppose it's the same principle as the old Benghazi burner which is effectively a bucket of sand and petrol burning.