Jank builds — The cooker turned incinerator
So, the first article went great. 🤭So, here I am at it again, but this time, I’ll try to explain technical things in a much friendlier way, so by the time you read this piece, you’d come out a little bit smarter than you were. 😝
Alright, let’s get started!
This is a homemade stove:
It’s capable of burning wood so hot that it doesn’t create any smoke in the process, and eventually, it gets so hot that its stainless steel body begins to change colors and you cannot touch it for hours after the fire has stopped.
So, to understand why we made this project in an age of modern technologies like gas pipelines and induction cooktops, we have to travel back to…
The summer of 2015, when a devastating earthquake hit Nepal; it killed thousands and left millions homeless, and if that wasn’t enough, we managed to find ourselves stuck in a political mumbo jumbo which made our neighbor India blockade us — unofficially.
This meant that the tiny landlocked nation couldn’t import anything, and things were running out fast. Everything was getting more expensive by the day and cooking gas was one of them.
So, here we are, in trouble. We practically only had a week or so worth of gas left. So what do we do? 😨
Start problem-solving!
Well, move to the classical wooden fire!
But, wood and fire aren’t enough, we also need a platform
- to keep the fire in check and prevent spreading it everywhere,
- to keep the utensil in place
Just throwing utensils on the fire, would mean that we wouldn’t be able to stir nor go anywhere near the utensil once the food is ready.
Now, if you have the slightest of experience with burning wood, you would know that fire is sentient and will somehow find a way to always hit you in your face.
This can happen due to one of two reasons, either the heat isn’t enough to burn the wood completely, or there isn’t enough oxygen in the mixture. This means that we need a “cooker” which:
- keeps the fire within its limits
- has a platform to safely put on utensils
- doesn’t give out a lot of smoke
- creates a lot of heat
- and is cheap.
So, let’s come up with an initial design that follows all these constraints.
It’s just a steel table that is surrounded by bricks and has fire beneath it, we can put the utensil over it and 💥, we now have a cooking surface.
But this comes with two major flaws,
1. where will you buy such a table
2. what about the ground?
It’ll leave burn marks on the floor, and since we’d be using this on our roof, we don’t want that to happen.
So, we do the most sensible thing, we compromise, we try to find the cheapest body of steel that money can buy, such that it can be lifted off the ground easily and still follows the above constraints. So, we can use a salvaged filter body…, this steel body filter can withstand both the temperatures that we are going to expose it to and can be easily lifted off the ground, and it’s easily available, we don’t have to build anything ourselves!
I would strongly recommend against buying a new one for the project, stuff like this is always found in junkyards. Make sure you get the cap as well, otherwise, we won’t have a platform to put our utensil on.
Now, that we’ve got the filter; if we simply start to dunk wood inside and start a fire, cover it up with the cap, and hope it will work…, it wouldn’t. The reason behind that is simple, you’ve run out of oxygen. Fire needs oxygen to keep going and once you cover up your container, the fire consumes it quickly and nothing is left.
This is what we call an “optimization problem” in engineering. If you try to get it done quickly, cheaply, or, make significant compromises, you end up with a product that doesn’t work.
In our case, we just tried to use what was available to us, while hoping that we don’t have to lift a finger before it starts working, and that’s where we got it wrong. So, back to the problem at hand, there isn’t enough oxygen in the system.
So, we can fix the problem by drilling some extra holes into the container. But, how does that solve the problem?
Well, hot air rises upwards, so, the hottest air is in the flame, which tries to move up into the utensil where we are cooking. This means that there is less air at the base of the flame, and the atmosphere tries to push air into it, and adding the holes at the bottom, makes it easier for the air to be drawn in from the outside. Congratulations! You created your own low-pressure zone.
Cool… are we done?
Technically, yes, you can stop right here, the steel container itself begins to get hot on its own, which makes the flames even hotter ( because it’s surrounding is getting hotter ) ensuring a good flame, and a pretty smokeless cooking experience, but, we can still improve the performance of the system.
This is what we call “fine-tuning” in engineering, sure, the system works perfectly, but, if you add a little bit more effort, it would get a significant boost to the system.
If we add an additional hollow steel cylinder on the surface of the main cooker, the hottest of hot air will move to the center and warm up the utensil. However, the warmer air on the sides of the flame will move up along the wall of the new cylinder and the main container, giving it more time to circulate and come out even hotter, making the combustion even more efficient.
More hot air means that we create an even bigger low-pressure zone at the bottom of the flame, which then tries to suck air in, creating a positive feedback loop.
And just for the sake of completion, here is one more look at the device that you should have at the end of the build:
As you can see, it got so ridiculously hot that it changed the silver-ish color of the stainless steel body to that brownish color. We added few pieces of marble on top, to raise the utensil a little bit higher than the flame, both for easier access and increased airflow.
We used this device throughout the whole fiasco of the blockade, and then we later re-purposed it to become our trash incinerator, it now burns our vegetable trash ( like skins and leaves after they have dried out) and that ash is used for providing nutrients to the rest of the plants that we have growing.
Thank you so much for reading till the end. This is my first attempt to tell something technical, explain how and why I did it, while still trying to maintain some type of story to it. It might feel that I went a little back and forth with the design and the workings, but that’s just how real builds works, i.e., things never work out on the first try, and I wanted to share the same experience with everyone.
Let me know what you think 😁 And if you ever want to build one, I’ll let you in on all the nitty-gritty details that I’ve skipped over.
— Samridh Tuladhar ( @tsamridh86 )
