Log Idea 5: HHO Generator.
Ok kids this one is going to be a bit short. I only took a few chemistry courses in college before I dropped out and found out how much better it was to get into the trades. That's right your pop was a plumber in his last world so I am not that great with rockets or electricity but I have picked up quite a bit through osmosis. Jones would be so proud
This concept uses the process of electrolysis, sending a current of electricity through water to split its molecular bonds to create oxyhydrogen gas. This gas is important because the molecular ratio is stoichiometry. I don't believe I have ever explained this to you nor do I know if Konoha has this written down but this is important because it makes a strong fire.
All fires need three things: Oxygen, Fuel, and Heat. The ratio of water to every 2 H2O molecules, when split, creates 2 H2 molecules and 1 O2 molecule. This creates a hydrogen gas this fuel was used in my world to send people to space as well as a perfect oxidizer so all you need is a spark.
The benefit of creating these gases is they can be made while not in battle and sealed to be released later to enhance any fire jutsu. If you require money after I pass away you can buy sealing talismans that you can fill with gas to create a better explosion talismans.
If you worry that as a ninja that fire is too flashy like your dad, Oxyhydrogen gas is considered the invisible flame. Hydrogen's light emissions fall primarily in the ultraviolet so the greatest color you will see is a pale blue and a low radiant heat emission.
NASA, the Space agency in my original world, had issues with leaks when fueling their space rockets due to the fact hydrogen is the smallest molecule thus having an easier time escaping even the smallest micropore. Hydrogen is also odorless and colorless so they wouldn't know if there was any leak till it caught fire.
But when it did catch fire the agency employed the broom method where when walking around they would wave a broom about to see if it would catch fire wherever they would go. The flame was so invisible outside and radiated so little heat they would know they caught fire till they walked into the fire.
Back to the uses of these gasses. Limiting the flow of these two gases you can create an Oxyhydrogen torch. Maximum of 5,100 freedom units the hottest flame achievable using common fuel sources. Due to the dangers of not separating the gases and channeling them together as a stoichiometry, run the gas through an arrester to prevent your torch's flame from channeling back to your reservoir and combusting all at once.
Now to maximize your flame you need to match the rate of flow out of your nozzle to the rate the flame burns. This is difficult as the reaction of burning is supersonic. Your nozzlel needs to absorb enough heat to slow the reaction while the movement of the gas wicks away the heat aluminum is a great metal. I don't know if chakra could be used as a nozzle till more testing. It's a dangerous balancing act and is the point of the arrester.
Production
A glass or stainless steel water bottle. You need an anode and cathode in the bottle for your current to run through. Basic water isn't the most conductive so adding an electrolyte can help. Having the gas travel through a tube into the bottom of another jar of water. The gas will bubble through the water running out of the top of this jar is your torch. If the fire in your torch travels down your hose it will run into the water preventing the flame from reaching the reaction chamber filled with explosive HHO gas.
If you are looking to split the output safely separate the anode and cathode away from one another in the reaction chamber and surround them in domes with tubes coming out of the top of the domes. This will catch the separate gases produced over each reaction chamber now you just need to store the gases in a reservoir.
Training
Step one you can create a physical distillation setup and train on creating and channeling controlled levels of current to output a reasonable rate of flow to run a torch. You can also train on producing a greater rate of flow with a larger torch nozzle.
Step two One can engineer this into a blade and practice moving and swinging this burning blade while producing current and filling the water reservoir.
Step three you can use the pressure manipulation of water walking to control the motion of water and create a hydrolysis chamber and gas nozzle out of chakra so no tools are needed to produce a cutting torch with purely chakra and nature manipulation and change.
Footnote
Speaking about being a plumber you know that the water heater has a T&P valve to release a build-up of hot water at 210-degree Freedom units. Water boils and turns to steam at 212 if steam builds up in the water heater and pipes the expansion causes it to explode. I am going to write about the dangers of steam and steam explosions.