1742 The Rocket Stove - Explained and Demystified  

Another point that is often missed: An ordinary wood stove, once the burn is established and going, burns its wood on the entire surface of the firewood. The rate of burning is mainly controlled by the reduction of the airflow to the burn chamber. This leads inevitable to a less efficient burn. The Rocket Stove on the other hand burns its fuel (if done/loaded right) always with the maximum amount of air it can possibly get - but only at the tip of the firewood. As I said, a small detail often missed out concerning Rocket Stoves/Heaters and their efficiency. Greeting from Germany - love your channel!

Working as a welder in stainless steel a while back I made a small rocket stove, 2x2inch sq tube. I then put the stove inside a box, intake and exhaust flush welded to two sides. I added a spout to one end, and a handle to the other making a tank that holds about a gallon of water that can be poured easily. Great camping stove, I can boil tomorrows water while I cook tonights dinner, with only a few handfulls of twigs.

We have a Slow Combustion (pyrolysis) stove for heating, and a bloody great hub off a harvester outside as a "fire-pit" for enjoyment, because when its all said and done, there's something cathartic about staring into the dying embers of a mallee root open fire! Greetings from rural South Australia from a fan of your channel; thanks for such interesting content.

I do blacksmithing as a hobby, and to make charcoal for my forge (I’ve since switched to propane), I settled on a method which involved a large pipe, about 3 feet (1m) long, 2 feet (65cm) in diameter, and 1/4 inch (7mm) thick, resting on 3 inch (8cm) metal spacers to allow airflow. I’d build a small fire in the bottom, and once it got going I could throw in bigger and bigger pieces of wood, filling the pipe right up. The heat from below would bake the wood on top and release gas, which would burn as long as the bottom wasn’t clogged with ash and debris. The flame from the burning gas could get up to 4 or 5 feet (over 1m) above the top of the pipe. And large spots of the pipe (which is quite thick, remember) would actually glow cherry red. To stop the process I’d remove the spacers (easier said than done) and place an oil drum with its’ top removed upside down over top of it to smother the fire. It was quite interesting, and I did my best to use some of the principles of a rocket stove.

Another GREAT Conversation! Thank you for sharing :) Regards.

A rocket heater (without a mass) is good for a woodshop. A rocket mass heater is good for a home. A typical rocket mass heater puts out 70% as immediate heat and the rest into the mass.

The best explanation I’ve heard for a stove…. Thanks

The Fin oven is a kind of rocketstove with downdraft. Very popular in Scandinavia. With downdraft section the hottest gases will stay in the upper chamber, while colder gases that did their job, leave through the chimney. In the eighties I visited a monastery in Kyiv, they had a HUGE wood fire oven in the cellar. The heat was trapped in a second "stove" consisting of just a hollow structure. Heat was dissipated in the walls, somewhere on the low side of this chamber was the escape for the gases. This construction continued for six floors. They started heating in August and only beginning of October the walls started radiating heat on all floors. Very huge stove, very huge monastery, very impressive! In March they stopped heating, the monastery kept warm until the beginning of May. The monk who designed the stove was Kuznetsov, so they called it the Kuznetsov stove. Built somewhere in 17th century. Apparently the system to preserve thermal energy by downdraft was known when they built the monastery.

I was looking for someone to explain in great detail why its better how it works and the history behind it. You sir are amazing for this

The issue of balancing different contrary demands is the essence of engineering. Very nicely presented!

The barrel part in your Mass Rocket Heater example releases heat right away - no waiting for the "Mass" part to capture, hold and release heat later over longer periods of time. That's the way I understand the system anyway. Terrific channel!

Best explanation ever! Thank you!

YOUR VIDEOS ARE THE BEST THANK YOU

The age old question, efficiency, coal/nuclear power stations are 35-40% efficient, so any process, burning wood, wind turbines etc don’t need to be super efficient. I’ve seen lots of comments saying why bother, it’s the fun of doing that makes it worth while.

Great class 👏 Thanks!

Hold on.... mass heaters still exist in 2022??? I remember in the 1990s helping a family heating business, one of the things we often did was rip out the myriad of mass heaters put in houses in the 1950s and 1960s, when electricity was indeed cheaper overnight. I dont know of anyone installing a 'night rate' meter in a house from the 1970s or beyond!

Excellent video and very informative. Thanks also for responding to the message I posted on yesterday's video, regarding 100% carbon felt; I'll be sending you an order in a few days.

If I only could send you a small video from. 2 years ago..a ramshorn in a so called pizza oven.. super insolated control of slow fire and adding a lot of stones around.. later introduced a heat transfusion with a water spiral to feed the CV. I left the guy with whom. I shared my suggestions and support because he had1000 things else to do. This is a hell of a product. I stil love this hell of a fire stove so easy burning..you can open the heart and the oven without danger or distirbance. Ideal Too hot for a single simple home.. You ll have to share with neighbours. I wish I could send you a video.. Thanks for your concerns and information. I love it, Fredy

O no Robert, you missed out on this one. because the rocket stove generates a hotter flame in the tube everything is burnt better/cleaner. a mass heater does generate heat immediately throuhg the barrel that's on top of the j-tube.

The Rocket stove or "J" stove was invented by a French inventor (whose name has mysteriously disappeared from Wikipedia) in the 1700s to reduce the amount of fuel to cook with, in the 1980s it was rediscovered and used to heat houses. House fires work on a 7:1 ratio the fireplace is 7 times bigger than the chimney but often it was temporarily converted to a rocket stove by draping a newspaper over the fireplace to reduce the ratio. The rocket stove is designed as a 1:1 stove but putting firewood into the inlet can reduce that further to 0.5:1 giving it the classic roar. I use storage heater bricks for my stoves as they hold the heat better and are easy to build.

Watching your videos helped me refine my tire burning heater, so it doesn't give off black smoke anymore. It burns clean and since used tire are nearly free, I can heat my garage for a lot less and tires don't need to be seasoned to do the job like wood does. And there is a benefit of keeping tires out of landfills and free scrap metal to cash in at the metal recycler.

Well explained, nice one Robert, thanks for your knowledge, really needed in meany countries, small rural areas.

Concerning rocket mass heaters, it's incorrect to say you don't feel the heat for several hours. That's true of the mass component, but the rocket core runs inside a radiant bell. And that radiant bell gives off huge amounts of instant heat. The mass then absorbs most of the remaining heat, and releases it over days. The mass extracts more heat from the fuel, essentially bonus heat. This effect absolutely does make it more efficient, and absolutely does get more usable heat from the fuel.

Rocket mass heaters usually incorporate a very hot radiating section (often the end of a 200l drum) before the gasses move on to heat up the mass. Flue losses are minimised as a result. A rocket stove gets hot for sure but flue gas in a room is undesirable so a flue is then required. One needs to harvest that heat before it's all lost to the outside world. For what it's worth a operated a solid fuel heater laboratory for many years and I can guarantee that the highest efficiencies were at the slowest burn rate where the mass flow of gas had a greater chance of contributing to a rooms temperature.

Rocket mass heaters have the advantage of giving a portion of instant heat, at least the ones with the steel drum in the build and storing the excess heat in the mass thereby utilizing the most efficient fast hot complete burn. A lot of the energy in wood burnt in woodstoves that are damped for the evening goes up the chimney as smoke and soot. If it didn't loose that energy you'd not have the phenomenon of a chimney fire. Exhaust from an RMH is also often at about 40C (100F), significantly lower than a wood stove so retained heat efficiency is also improved. Thus a few of your comments were just a bit off the mark.

A big advantage of mass heaters is that they produce radiant heat not so much convecting hot air which can be lost easily, when doors open and to the ceiling. They transform, fast high temperatures (as you say) into much lower temperatures for long periods, that are more amenable to body comfort and health....a problem with metal box, high surface temperature wood burners is that dust burns on the hot surfaces and is convected into the air resulting potential respiratory issues, also the fierce heat drys the air causing further problems. The Roman Hypocaust and the ubiquitous northern European masonary or tile stove have much to recommend them for space heating purposes, albeit they take time....

I like the idea of capturing and radiating as much heat as possible so I intend to experiment with those stacked 240 litre steel drum wood burners I've seen other pyromaniac youtubers build. I think they're referred to as 'double barrel wood stoves' but I'd like to continue stacking.

Amazing video on the topic!!

Robert, as you say, the key attribute of a Rocket heater is the efficiency and the clean burn of the gasses given off by wood in the initial fire. I assumed that it would be beneficial (necessary ?) to insulate the chimney to encourage that secondary burn to reach the temps of 600-1200 you mention. That then leaves you with some pretty hot gases coming out of the top and, by enclosing the chimney with an inverted can, you retain the heat to help keep the chimney hot but also radiate into the room and (for a rocket Mass heater) exhaust into a further heat recovery and storage area viz. the "mass", extracting most of the heat from the exhaust before it leaves the building.

EXCELLENT ! !

DEF: rocket stove - "a tube, to contain the pyrolysis gas, to give that gas a chance to burn, before the wind blows it away." 😊

Using a lot less wood to whatever end is something. Personally, I want to make a turbine Stirling engine based on hurricane forces and a jet engine turbine. Good luck you say, but I'd need a miracle!

What do you think about doing a series on home made lab glassware for chemestry and expirments? I feel as thought it would be useful to many students out there that can't afford the premium stuff and are only doing some of the basic exercises. Just been doing some self study in this area lately and have been collecting jars for some time for this purpose. I know you'd be an amazing practical chemistry teacher for noobs like me. Much love from the states

Hi from Spain Very interestiing video I made a belt batch box one year ago and in my opinión you are right on some points but you forget others It is true you must think about what do you want to warm and how quick If you want quick Heat The belt batch box solution is better than others because you have direct Heat as a conventional wood STOVE and in about 15 minutes you can have a clay máss Heat just above and radiate this heat On the other hand you forget that the clay dry and clean the room and you can fell a Very confortable Heat Finaly you forget that if you dont have a lot of money the batch box can use cheap wood like rest of wood cuts or even wood fron old fornitures because the pyrolisis burn the smoke Thanks and Buenos Días !!

We had our masonry Mass oven built in 1995. Of course it needs a little bit of maintenance once in a while but it still functions perfectly. It was expensive, and of course these heaters still are, but very efficient. We have outdoor temps around 15 dgr C at the moment, and using about 15 kgs of wood we have heat for two days. The disadvantage as you mention is that it takes hours before heat comes out of the 2.3 tonnes of mass , so if we are away for several days it takes time to get some heat. But anyway, best investment ever. The upper chamber where the gasses burn acts as a cooking oven when the fire is out. A rocket mass heater can be built much cheaper and may be just as efficient.

I wonder if you could come up with an idea for a simple 'flu box' that one can sit atop a standard commercial gas heater that catches the bad smell that the burning of gas emits and lead it through a flu to the outside but not without first extracting as much heat as possible.

Actually a mass stove also give instant heat. Usually it has a glass door and this will give instant heat...

💜💜💜💜👍👍👍👍 clever stuff👍👍👍👍

My home is from the 1930s in Northern England and it has 6 air bricks, and as seen in your video about the Roman room heaters, I now need to find a way to get hit air in those bricks because it just blast's cold air through my wall sockets.

Robert. Love the Tardis on the shelf behind you.. Have you any experiments on time you can kick us off with?

Agreed on most of the points, except for one. You don't have to get really exotic and expensive to contain a hotter and more efficient rocket stove. Modified cob over stainless steel or glass works pretty good. By modified, I mean something like, instead of sand, you use a combo of fumed silica and diatamaceous earth to up insulation. And you still use some perlite and straw (or better yet, fiberglass cloth or strands for the structural part of things). Good clay can take quite a good amount of heat and over longer periods of time than steel, especially non stainless steels. I guess clay can be kind of expensive for some folks, but not really that expensive and especially not exotic for most people. The beauty is, just use some cheap steel or glass and protect these with a layer of well insulated clay (modified cob), and then you don't need much clay (rather modified cob). It's a type of composite's approach. Composites are a beautiful thing, balancing the weaknesses of different materials with the strengths of others and vice versa, so that you get a higher functioning synthesis material. Or, the whole is greater than the sum of the parts. (This connection/integration/synthesis is a material reflection of what I call spiritual truth--that of unity and connectedness [which, is really, the consciousness of Love], which I think is the heart/core of the so called "spooky action" of quantum physics. Newer physics strongly suggest what mystics from all over the world and various faiths have been saying for a very long time--everything is interconnected on a fundamental level. How else can things like quantum entanglement and Bell's theorem exist? It's really almost a "duh" if you think about it objectively and logically). And ultimately, the reason to up efficiency through things like better and well placed insulation, is so that you need less fuel to burn to get the same amount of energy out. Why not maximize this, so you can just run it on sticks and debris, rather than split logs and the like? In my yard, we have A LOT of the dreaded "gumballs". The bane of my spouse's existence apparently (she likes walking around barefoot etc), but, a potential fuel with its own aeration design built in.

You just defended your use of glass as the primary with your temperature argument. Glass doesn't start to melt well beyond the burning point of anything a rocket stove can produce. Question: Would adding a small turning vane at the base improve the rate of combustion with improved gas mix and vortex generation?

yes about the mass, good rocket stove mass heaters radiate heat now from the barrel section, then the exhaust is directed through the mass to warm it up for slow radiating. it does take a lot more space to make the mass, but once warmed it may only take 2-3 small fires a day to keep a place warm. a chimney over a kerosene heater, that collected+pushed heat through a mass could work similarly, bright white flame is pretty efficient, same burn as a decent kerosene oil lamp gives but using a much smaller wick.

Great vid, and your comments were bang on the money. Rocket stoves can be built from many types of materials for all sorts of reasons, all giving differing outputs and all working on the same basic principle as you discussed in your vid.. It's not always, however, the hotter it gets the more robust and thicker materials you need. It's sometimes how fast you can dissipate the heat from the device to stop it melting.. in my experiments (using tin cans) when I insulated the fire tube part of the rocket stove, it started to melt the tins, but the un isulated version did not as it was able to dissipate the heat to its surroundings, saving the tins from melting (great radiant heater, not quite so good for cooking on) but like you also said it burnt hot and fast, and when the fire went out it also got cool very quickly.. (my reasons to build a rocket stove were to make a greenhouse heater on the cheap. My experiments led me down the hot and fast burns with vortexes etc etc which were not appropriate for my needs and i ended up going down the route of a slower burning mass storage heater type rocket stove, using wood kitty litter pellets as a replenishable fuel source (a heat battery if you wish .. lol)) that slowly but surely kept my plants warm over winter without overheating and drying out the air. Also in my experiments, I found you need to get the air fuel ratio right as you can end up not getting your secondary burn to work well and end up filling your garden with smoke - stinking the place out with unburnt wood gas. Not ideal! Thanks for sharing your views and I agree with your comments. Great work! Looking forward to your next vid as always.

Rob, as an air control for the Rocket stove, add a flap or damper on the air inlet tube and extend the tube for the fuel (so you dont keep loading) and put a flap or door on that so the combustion air is sucked in from the front, this will be fully controllable after the stove gets up to temp. Try it and see what happens.. it is all about the air...! All the best.

I'm experimenting with some fused glass refractory material which seems to wick quite well, but it's a fine powder and splutters and pops when it starts to get hot so I suspect its a bit damp. I'll dry it out over an open flame and give it another go or I might add some water glass to it as a binder and fire it to make a ceramic.

I think cardboard fire logs could be made using a shop press and bailing wire, and without soaking in water, blending, and pressing in molds. Where I live, getting free cardboard is fairly easy, and I like the idea of cost-free fuel for a rocket stove. There are large machines in a lot of stores like Walmart that compress scrap cardboard into large bails. I think the same thing can be done on a smaller scale by cutting cardboard into strips, stacking those strips in a shop press, then compressing and securing them with bailing wire. That should give a fairly dense "log" to burn that would last a good while during the burn. Could even accidently on purpose spill some WMO or used veggie oil on the logs for added heat and longevity. Cheapest shop press I found was at Harbor Freight for $135.00 or so. I already have an electric saw to cut the cardboard. Haven't seen anyone do it this way, but it seems like it should work.

Well said! 60k-90k BTUs per log. Use it in an hour or 24 hours Their is something to be said about being able to burn almost all the fuel, but as you stated at the cost of a shorter life of the stove or complexity and/ or expensive. However, creativity and knowledge is what we're all about and being able to discover the hidden art of making materials that will extend the life of the stove, mass heater at those higher temps increasing the effective usable BTUs is just plain fun and exciting!!! I personally would love to see a mixture with relatively easy to make materials (the secret recipe) to make one that will not only last but utilize that extra 40-85% BTUs. At the same time I have no problem with those who could care less. Lol

Hello Robert, the steel rockets you've been building may be fine for making a cooker in your garden but there are some things you need to consider when plumbing them indoors. If you add a chimney and/or insulate the secondary burn area you can increase the draft which in turn will increase the efficiency and temperature of the burn, this can quickly get to temperatures where the steel will corrode and spall. A complete internal collapse of internal structure is not entirely uncommon in less than 1 full heating season even with pretty heavy steel construction. If you add systems to harvest more heat downstream of the burn chamber and don't have a complete burn of gassified wood you are creating condensation point for creosotes and a chimney fire risk or collection of CO and oxygen mixture which can set off with enough force to blow the system apart. I hope you can beg, borrow or steal an exhaust analyzer like a Testo so you can assess this yourself.

May I suggest a design that burns as hot as possible and uses replaceable fire bricks to contain the heat before diluting it with cold air before it is used or goes up the chimney? By controlling the mix ratio, you can adjust the temperature instantaneously.

Well mass heaters also do something else, which explains why we still see people making videos about the plant pot/tea light heaters. It traps the heat as a certain level in the room. So in the tea light heater, build a tea light plant pot heater and next to it put a single tea light. Both tea lights put out the same ammount of heat. But the one by itself puts all its heat up straight away. Up and typically above peoples heads and out of their line of senses. The cant feel it and since heat rises, it stays there warming up the ceiling. The plant pot gives a visua focus and as you said lengthens the time over which the heat is released, but it puts it where it can be sensed. They make nice hand warmers but not much more. If someone wants to make a really good plant pot heater for a small space then get you one plant pot. Put a small piece of screen or a small broken piece of plant pot on the drainage hole and then fill the pot with plain bargain basement unfooled around with kitty litter, or vermiculite, and set up bricks or pavers such that they will hold the pot off the ground and hold it stable so it doesnt fall over. Get you some sterno heaters or chafing dish heaters and use two or three of them to heat the pot and the litter. This will also heat the bricks or the pavers but less so. This will put out some residual heat immediately, near the device, but like he said you are just charging a heat battery. Once its hot, a small electric fan will help it heat more air more quickly buy blowing air over it. You can get this quite hot as chafing dish heaters can last 4 to 6 hours or more depending on size and type. So maybe set up something to keep people from bumping into it and burning themselves on it.

Brilliant as normal

Absolutely wonderful Rob, I honestly can't think of a good reason not to fit a rocket stove, instead of an open fire or even regular wood burner, that secondary combustion is a no brainer

I just found a channel that has a " No welding no casting DIY rocket stove" the stove is made from "Vermiculite board" and has a double vortex. You might want to look at that. I was grumpy because the steel for making the stove was costing more than I liked and found this. He has a follow up video " Make it roar rocket stove upgrades".

Hello Robert. I've been enjoying working through your very educational vids so thank you for taking the time to create and upload them. I've left a message before to see if it is possible to adapt and expand little camping stoves into heaters e.g. the Trangia, or more interestingly, a 'woodgas' camping stove? What are your thoughts?

Early on you talk about the heat going into the bottom of the pan or pot but missed one of the key points of the rocket style stoves. The gasses, soot, creosote & solids a fire pushes into the space or out the chimney. Importantly in developing parts where these were invented for those gasses were killing the folks who had to cook indoors slowly by causing cancers, black lung & in extreme cases CO2 poisoning. The more complete burn reduced these compounds dramatically. 8:00 The catch here is the barrel style of mass heaters. The quick radiant heat comes off the barrel top & sides but just after the exhaust you can push the cooling gasses into a bell or mass. This stretches out the warming time.

Well explained and perhaps it’s just as well to create a hybrid version that one can adapt for various scenarios. This could easily be achieved by adding a sleeve of insulation in the form of welding mats, that could easily be removed. Likewise, a sleeve of old storage heater bricks that could easily be added and removed depending on the circumstances. Thanks for the inspiration 👍

i like to call it a harnessed chimney fire.

*Wish* I had found your channel years ago (sigh...)

From my understanding, to give the stove the maximum live span, special fire bricks that can withstand temperatures up to 1700 degrees Celsius can be used. Based on aluminium oxide it will last longer than steel at the generated temperatures, these are readily available and do not cost much either. I would argue that the rocket mass heater shown at 8:28 is better in a way. It has a bell with the same function as the rocket stove shown a few seconds later. The second stove goes straight to the chimney after the bell, while not all energy has been extracted from the hot gasses. The first one extracts more energy from the gases by guiding it through a thermal mass (disguised as a coach) after the bell, before going into the chminey. So while they both have the same combustion efficiency and thus produce the same energy, the rocket mass heater extracts more energy from the gasses before releasing it into the chimney. With regards to energy efficiency it's better than the second stove, at the cost of added weight, bulk and complexity. Just my 2 cents ;)

Okay folks. Here's a twist. What about recommendations for a rocket stove for a maple syrup evaporator? My big question at this stage is wondering if I should put the rocket stove in front of the evaporator and have it exhaust under the pans or is some other configuration appropriate? One thing to keep in mind is that you want as fast of a boil as you can get. Slow heating isn't very useful as you're trying to keep the sap boiling and the more vigorous the boil the more efficient it seems to be.

Good video - as usual! Thought your description of the best use of the mass heater was poor though. Hear this - they normally have a more extensive chimney system inside the room - properly done they look to have a cool stack outside the house (virtually all heat left inside) and zero smoke (all fuel burnt). Now - regards the mass part. They're mostly set up in northern climes with long cold winters (Russia, Alaska etc.). So you're heating the house for months on end - continuously - day and night, to a varying degree - but always somewhat. Feeding the fire all the time is a pain - especially at night - so the idea of the mass is you run a furious fire 3/4 times a day (it goes out in-between) but it's evened out to a fairly continuous room temperature is the main idea of the mass. They use around a third to a half the amount of wood of an ordinary fire too - which save much work/money. So it's not so much a set up for Kent or Cornwall - perhaps Scotland.

A Question Of Balance.... Ah yes, wonderful Moody Blues album. :)

I think of the rocket stove as kind of mini fireplace. There is the firebox at the bottom, and a tall chimney.

I'm curious... if you're looking to make a rocket stove for winter heating... what if you capped the tube inside the building, then on top of the cap, you install another tube to exhaust outside and then you bend a bunch of copper tubes to go from the capped section to the exhaust section? Would you get more heat out of it? I think copper is a bit better at radiating heat than iron or steel... Put a small fan behind the tubes to help pull the heat off of the tubes and into the air... I dunno... thoughts?

In my opinion after having tried and built a large mass heater and being very disappointed With the amount of heat that was coming off the mass I feel the best use would be to use the rocket stove to heat water and then heat a radiant slab perhaps but the best thing is to just get the room hot and then shut the thing down you’re much better off spending your time sealing up your home and insulating then you are screwing around with a mass that just ends up looking ugly

Problem with storage heaters is you have to know what the following day will be like, which I found was an issue so great that they had to go (I never got it right). Gas central heating replaced them as soon as I could afford it. Cold turn it on, hot turn it down 🙂 is there a design which has an ash pan?

I want you to go back to your water jacket design and try and make it more effcient, I like the idea of being able to have the fire and gases burning outside but transfering the heat into a central heating system or something like that inside the house, most modern houses dont have a chimney.

Having a lot of thermal mass like the size of a house means you have more control over the temperature inside. Like not having to burn to 40 degrees in the evening to still have above 15 in the morning. Less thermal gradient = less heat loss.

There never is a best solution for all situations. Anything designed to do 2 things or more never does any of those things very well. Think using a helicopter search light to change a car tire at night. Blinding yourself extravagantly is not useful for that application. Extra physics points (for the cool geeks): You made me realize that a mass heater simply slows down the heat like a Bose-Einstein condensate slows down light and releases it slowly. Heat IS infra-red light, so man has been slowing down light since before the measurement of the "constant" speed of light! A-HA!

My understanding is if a rocket stove is shaped correctly it will burn/reburn the flammable smoke, gaining efficiency & heat..(commonly called wood gas, that is lost in the normal process)

Nice instructive video! Something to ponder over. I have been working on a design to further improve cooking vessel efficiency. Patent is the plan, though provisional is on hold for government usage right now(ie... military would be my guess for field cooking). Probably will not get the full patent within my lifetime. Since I can get no benefit from it and it has no benefit for other than cooking. I will share the basics here. Just take a cone shaped cowl(must be a metal that can handle a lot of heat) larger in diameter than the cooking vessel that is open at the bottom and is slightly shorter than the vessel. Hence, top is wider than the bottom. Attach a heavier rim(rim must be of a heavier metal than the vessel) to the cowl to then attach that to the vessel. A short metal fin attached to the rim pointing down inside the cowl to direct airflow back down to the bottom of the vessel(roughly center). The idea is that hot air will rise and be constrained up the entirety of the vessel exterior. The fin pushes the air back down in the center space. The inward cupping of the cowl bottom recirculates the hot air inside of the inner sides of the cowl. Basically gives the vessel a hot air coat that circulates around the vessel trapping heat that would otherwise be lost. In doing so the heavy rim and cowl itself will be heated and transfer more heat to vessel. Less heat losses and more efficient that way. Where efficiency is concerned it most times pays to consider working both sides of a problem from not just gains but also cutting losses. Keep the videos coming Rob! I really appreciate them, thanks!

Could you use an open flame gas heater with cooking oil with some adjustments

You should check out the batch box vortex rocket stoves, theyre a hybrid between a normal stove and a rocket, very cool!

Good one. I always thought the early experiments resembled an Indian tandoor stove, even older than the Roman hypercaust.

Hay, i am new to this channel and did not really know where to write a question to you, and sorry for my spelling! For some time, i wanted to make electricity from fire. At the top of a rocket stove, there is a lot of "wind" power. I have played around with Thermoelectric Peltier Element, but it is not that good! steam is not an option, where i want to use it. Is it possible to combine those to, your wind generator and the rocket stow? my problem is the heat at the top. it will make the coils, magnets and Berrings to hot, even when i put Berrings outside the chimney, the fan inside gets so hot, it takes the heat out to the coil and magnets outside! can it be solved or should i just give up the idea?

The rocket mass heater is more efficient because the flue gases cool in the flue pipes heating up the mass before exiting as the flue gases cool it shrinks causing a vacuum pulling in more air. There is less heat lost up the flue pipe to the outside.

have you ever tried putting a heat exchanger on or even just a water jacket so you can heat water with excess radian heat?

I wonder if one can be built with both heater and forge in mind? Turn it into a forge with the opening of an air valve or something...

Get the best of both. A rocket mass heater with a contraflow drum. Instant heat from the drum and slow heat via the mass. I wouldn't built a J tube version i would go with a box mass heater with a contraflow as you can load it and forget it.

Hi Robert, This video inspired me to formulate a challenge for you. Currently there are 2 types of stoves used in bikepacking: propane and alcohol stoves. Alcohol is not as energy dense and can be dangerous in case of a spill near the fire. But the stoves (see DIY alcohol stove) are very light (20 g?) and small, thus portable on long journeys. Fuel can be carried in different size and shape bottles. Propane needs a certain volume and it's harder to check amount left in the bottle. Access is also limited to some specialized shops that one can find or not in his/her way. Advantage: it's instant, no spilling, it's energy dense. Now, my question: Can you come up with a different type of small, easy to carry and to assemble stove design that uses some other fuel that might be cheaper and easy to find, with acceptable energy density? My next year's plan is pointing to Greece where I can find Lidl supermarkets. Stove will be used to cook food, not just tea. Trip will take 2-4 weeks, so we're talking about a lot of cooking. Thank you!

Have a watch of the last season of Moonshiners. One of them made a still with a rocket stove and a wooden barrel. Very interesting idea.

ude think these ideas would be part of building regs but these days theres that flakey thing called insurance around.

Thank you for making the concepts inherent in the "rocket stove" much simpler to understand. There are one or two points you make, however, that do not seem consistent. first, you say that the mass heater does not provide more efficiency, it just shifts the time frame of receiving the heat. Do you mean that in comparison only to a rocket stove or any wood stove, such as a cast-iron airtight stove. Isn't there loss of efficiency if there is no mass to absorb all the heat produced through a long run of pipe through a thermal mass ? At a hot enough burn to consume all the gases, most of the heat will be lost up the chimney since conduction and convection are insufficient to move all the heat produced out through the walls of the stove. The other point you make, about the rate of burn not having any effect on the total amount of energy produced, similarly seems to contradict what you explained at the beginning about the stages of wood burning. When lowering the rate of burn, one must reduce the flow of air into the stove (again, I am referring to an airtight stove). At that slower rate of burn, the gases given off cannot burn and escape up the chimney, thus reducing the total amount of energy captured by combustion (and releasing air pollution). Only a faster/hotter fire can burn those gases completely and thus gain all the energy from the fuel. If I am missing something, please explain where I am mistaken. I am certain you know a lot more about this subject than I do. Thank you !

What if, inside the chimney there is a sort of bell shape (or upside down pan), maybe with holes in, to further catch/slow the gases as they rise? Placed at the point where the temperature is best for them to burn. Perhaps it would allow for shorter chimneys. [edit: or mesh baffles around the outside edge of the chimney, and a cyclone airflow to throw the unburned gasses out to the side and keep them in the hot zone longer - maybe even a catalysed mesh, like in your flameless heater vid).

Can you guess where these lyrics come from mr. smith?"... And all this science I don't understand It's just my job five days a week A rocket man A rocket man

I wonder if It makes sense to install a rocket stove, even a brick rocket stove, outside and make two holes in my wall, high and low or left or right, and make a 20cm metal pipe go out of the house with a computer fan past the flame and back into the house and let it heat up the air in a closed system and keep the fire and fumes outside for a house without a chimney. I wonder if I could easily plug those holes back up if it would not work well. Would love it to work well tho. Thanks for making these videos.

It's not rocket science. It's rocket stove science.

how about the relatively recent improvement to Archimedes screw? instead of turning the screw you turn the housing and its *better*!

i thought the major difference in a rocket stove was the air does not go past the fuel, only through the embers allowing for much higher air flow, hence rocket.

I've seen cinderblock rocket stoves will those work as well as store bought?

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Great video again, thank you. Is it possible to capture the combustible gases to burn later or in a different device? Or is that just a silly idea?

Hey Rob seen as though you have got your rocket stoves to burn so clean... I was thinking 🤔 how about a heat reflector, like you see on the top of patio heaters???

I've been thinking about putting a wood stove in my shop. I also have lots of used engine oil from the cars I work on. I've been thinking about combining the mass rocket stove idea with an oil burner to heat the shop and get rid of waste. Any input about burning oil in a rocket stove would be appreciated.

mass heater does prevent heat loss like in a chimney large percentage of heat goes up flue

”What people tend to forget is that energy and power are two different things” Haven’t heard anything more true in a while

Still confused Rob can't make my mind up wether to go for a log burner/ multi burner .Or go for a Gamera rocket stove from Bulgaria. What confusing me is would the rocket stove give out enough heat on its own 9kw . without turning it into a mass heater . Your advice would be very grateful . keep the video,s coming 👍👍

I'm wondering if it would be helped by additional air ingestion, like the re-burn in a smokeless firepit

I have a question, Mr. Robert, Can you increase, by a homemade method, the radiation of the stove bodies? A building material, a paint job, something else ? Is it possible to achieve a significant difference? Thanks!