Len Ovens

Andy Bank wrote:I have experience with manual cameras. Kodak film boxes had exposure suggestions printed on the inside surface of the box that pertained to that specific film speed. Older films had a removable info sheet. The info still applies today no matter how old the film. ASA film speeds are what I'm familiar with. Read about film speeds here:  https://en.wikipedia.org/wiki/Film_speed     The chart will compare ASA to DIN. From this point forward I will use ASA film speeds. A good general use film speed is ASA 400. Set your camera shutter speed to 1/500 (whatever shutter speed is closest to the film speed). Corresponding lens openings (f-stop) go like this: full sun f16, light hazy sun f11, hazy sun f8, bright cloudy sky f5.6, cloudy sky f4.5, dark cloudy sky f3.2 maybe f2.8. If you change the film speed for creative applications for example (shutter speed 1/250 which doubles the exposure time) you need to decrease the light reaching the film by double f11 is used instead of f8, f8 instead of f5.6 etc.. Every time you change the shutter speed you are either doubling the amount of light reaching the film or cutting it in half. If you double it at the shutter you have to cut it in half at the lens opening. Example: 1/500 and f16, 1/250 and f11, 1/125 and f8, 1/60 and f5.4 etc. will all give you the same exposure on the film. The amount of in focus subject matter (depth of field) (what's in focus, what's not) will change. f16 large depth of field, f5.4 not as much in focus and so on. Fast shutter speeds (1/500) stop action, slower shutter speeds 1/60 moving subjects might be blurry. A camera with a built-in light meter is great if you know how to use it, they can be fooled. A light meter is assuming the exposure is 50% white and 50% black. Any variance fools the meter and you into recording the wrong exposure. To much dark area = over exposure, to much light = under exposure. Take notes for every picture, film speed, shutter speed, lens opening, lighting conditions. When you receive your prints you can see if your camera settings were correct or needed adjusting. Most of all practice, practice practice. Using your digital for exposure recommendations will work but why? You won't learn anything that way.

Very good summary. I would add only one thing. Most cameras have "flash" shutter speed for use when taking pictures using the flash. This is the fastest shutter speed where the shutter is fully open for at least some time. This is mostly SLRs that use a "slot shutter" where the slot moves across the film face and the width of the slot determines the shutter speed. The flash speed has the leading door fully cross the film before the trailing door starts moving and so the flash has a point it can expose the full film. Any speed slower can work as well and in fact the shutter can be left open (bulb setting) and the flash strobed more than once for effect. However, any higher speed will have one side of the picture dark banded.

Julie Reed wrote:Len Ovens: “Some people however, would feel a line has been crossed and the heater is now a masonry heater even though it uses the same principles in it's operation.“
Are you meaning same principles as RMH, or same as masonry heater?
I’m barely at novice level for knowledge about either of these, but from the masonry heaters I’ve seen (Russian Fireplace, etc) the principles don’t seem to be the same, aside from heating a mass. The masonry heaters appear to be a firebox beneath a zigzag flue which eventually exits a vertical stack as cool gasses (co2, h2o). The mass has time to absorb the heat, but is there a high temp and/or secondary burn such as occurs in the RMH? The one I knew the most about was built by an ‘old country’ German couple, and they ran a hot fire for about 3 days, then the entire mass was warm and they built daily small fires to maintain that level. After the initial burn it didn’t use much wood to heat their large chalet style house, but the heater was probably 6’ square and occupied the center of both levels. I did various work for them in my late teens, and learned early the value of thermal mass.

Yes I would say that any masonry heater builder today uses the same principles as the RMH. First set aside the the bench or other heat storage part of things as that is not what makes a "rocket" mass heater. What makes the rocket is the first stage to the bottom of the barrel. There are many batch box RMH designs these days and that seems to be the direction things are going. But both RMH and the masonry wood heater have the next portion, the riser where the flue gases are squeezed through a tube with a cross section similar to the exit flue to increase the velocity of the gases and finish burning the unburnt gases at a high temperature. In both cases this part of the rocket is fully enclosed and so not visible from the outside of the heater. Then the gas is redirected down around the rocket to almost the bottom of the heater in both cases and as the gases cool, they shrink and are pulled through partly by gravity (we think... at least that is the most common explanation in the RMH community that I have heard). After that comes heat removal by running the flue gases through mass. Both RMHs and masonry wood heaters do the same thing. Quite often these gases are run through a mass in the shape of a bench for heated seating. In the case of the RMH the bench is always used, probably because cob provides the best structural properties when used horizontally and because RMH are often built by amateurs who would like to avoid rebuilding the foundation to support the weight. Masonry wood heaters are most often installed by professionals who are going to add to the foundation anyway and their concern is how would the client like their stove to be. The clients on the other hand may want a more compact design with no bench or of lower price (10k CAD gets the cheapest build, but most even low end heaters are 20k and up) and so the mass is more vertical. But the thing that makes a rocket anything is the heat riser inside which acts as an internal chimney to both create draft and finish the burn. Both types add preheated air to the riser though not always intentionally. In my experience, intentionally works better. Most masons seem to agree from what I have seen.

Do note that not all  masonry wood heaters follow the exact same principals as the RMH, some are more like fireplaces in operation. However the particular model I showed in the message you quoted has pretty much the exact same flue gas flow as the RMH and even uses very similar kinds of dimensions all the way through. If you look through some of the rest of the threads here about RMHs, you will find some here that are even less like the original RMH than the one I showed. Look at the Walker style for example where the "riser" is horizontal   To some people The RMH has a barrel or it is not a RMH and you will not change their mind. I am ok with that too. In my case functionally the same is what is important.

r ranson wrote:Here's the photo taken with the argus:


and here is the photo taken with the digital camera (ISO 100, f8, 1/200)

(both photos not included again)

There are so many things one could say... every film type has a look... a set colour to it. It does not matter if one is using film or digital card, the first rule of photography is take 10 pictures, keep 1. The second thing to know is that digital cameras do a massive amount of manipulation before they even save the "raw" image. This is cheaper than a really good lens. In a digital camera there will be corner correction, for colour, brightness and shape because the lens is not perfect (even when they weight 5 times more than the camera does). The digital camera also will add sharpening, dynamic exposure control and other bits of stuff. With film, "you get what you get". The negatives are all processed the same way (as someone else has stated) with the exception that the developer can be asked to "push" the film. I can remember using iso400 film and having it pushed to 1600 so I could use the camera for taking candid photos in dimly lit places without a flash. They were of course grainier than normal, but that is true even when not pushed iso400 film is grainier than iso100.

The edges are not important, shoot for the centre of the picture, do the settings for the centre, focus for the centre. Most professionals will frame their pictures so they can crop them to show exactly what they want which will tend to remove the corners anyway.

Shooting with film is expensive... having someone else manipulate and print them even more so. Having said that, my son took all my film stuff and has been having lots of fun with it. Taking photos is an art both film and digital... but to really be artistic one has to turn all the auto features off. This is why the Pentax K1000 was the standard camera for teaching photography for 30 or 40 years. All it had was an internal meter. To tell a story with a photo, do not  record reality. Use the faults and failings of the medium to tell a story. Use monochrome film to show things colour gets in the way of. Use Fuji film for nature, kodac for people... (I am not even sure what is available these days) or the reverse if it suits.

I would not take a lens apart with out a "clean room" and an optical bench. Use the digital for sharp, hard, clean recording of a scene. Use the film to tell a story.

Photography is not something learned from a book or from one roll of film. I played around with film stuff a bit in the late 70s and early 80s but never took it far. In the end I think I did not really do much I couldn't do now digitally. I am not really that kind of artist I guess.

Victor Skaggs wrote:

Len Ovens wrote:

What not to do about climate change:

Don't: Lobby for government action. First off, it is unlikely any government action will have the desired effect as the government is guided by rich companies and single minded emotional groups. The other thing is that any action the government can take will hurt the poor... while still doing nothing to change things.

Here again is the notion that govt is inevitably wrong and evil. Really? Should we then not bother voting?

The USA govt has done a number of things which have benefited this society. TVA. Medicare. WPA. NASA. Civil Rights Bill. Environmental regs.

There are many places where the "government" (and I am not speaking US gov. in particular... I don't live there) does good things. This is not one of them. The international community that most of the first world governments subscribe too has in my opinion "got it wrong" as to the best ways of dealing with climate change. It is broad brushed across the world and does not take into account each country's climate, or population density or many other things. This means that a small land area country that happens to have geothermal energy, even in a cooler climate, can keep their citizens warm in the winter with no fossil fuel easily. However, a vast, lightly populated country in a cool or cold climate such as Canada or Russia, end up only being able to tax their citizens with a carbon tax... which does nothing towards reducing pollution at all but does mostly affect the poor (and even the not so poor). The problem is more complex than just CO2 or even CH4. Yet there is an urgency to "do something" which seems to be causing solutions to be proposed that lack good judgement and are based (from what I can see) more on "will I get voted in again" or "who will pay for my next re-election campaign".

As a small example: Because there are so many people who do not know how to use wood heat... the thought is to ban any wood burning appliance. Rather than actually study the problem thoroughly and see if the stoves themselves might be the problem. (they are) It is possible to burn wood in a clean manner. What does a ban of wood burning appliances do? it means people who depend on wood to stay warm in the winter, wood which they gather at little cost (transport and processing) would have to pay either for a higher amperage power connection or a natural gas connection as well as heating equipment. There is no financial help available for this install after which the cost of heating their own home goes up 100 times or so. For some people this is not a problem, they just look at it as an upgrade they can recupe when they sell their home. For others it may be the difference between owning their own home and selling it to rent from someone else... and still pay more than they can afford to stay warm in the winter. As I said, a band aid solution in preparation for the next election that hurts the poor (who would in no way support anyone financially anyway).

As for voting in an election being worth while or not, I would point to the last election in the US where the choice was a loud mouth, jump first then study on one hand and a secretive person who does most things behind the public's back on the other... not much choice. I do think the US got the better of the two.... As for the young fool we hope will go away next election in our country... I will not comment except that it is disheartening to know that by the time the polls close in Ontario... the choice has already been made. Not much representation for the rest of the country. Not much incentive to vote west of Ontario either. Oh, we will anyway, just in case things are close enough it makes a difference...

In the end, in fact you are part of a large global population as well as national, state and local communities. Nobody is an independent actor. Nobody makes decisions which are not affected by the possibilities and restrictions instituted by governments, corporations, and other structural forces.

If govt does nothing, then the other powers, which mostly means corporations, will be making the decisions and taking all the action, and so do we really think we can trust the Koch Bros. more than the USA govt? The mythical "free market" should control everything?

Weak central govts are a hallmark of feudalism and other great ills.

A government that knows when not to interfere is not weak. The world is full of weak governments in my opinion, "The mythical free market" really large corporations, does tend to control the governments around the world much more than is healthy. The world of democracy has become, in my opinion, a practical anarchy where the one with the biggest stick rules... and that is not generally the government or "the people". As for feudalism, I am not to sure how far away from that most people are or perhaps outright slavery but this is all my opinion and not really relevant to this discussion.

Anyway, that was not my point. My point is that waiting for someone up there to "do something" is not a great way to live life. Rather it is better to look at what I can do personally to: A) survive the inevitable changes, good or bad, and  B) Do what I can to make things better at least for my family but also for the world around me. If it is changing how I do things by living a less polluting life style, moving to live somewhere else, or inventing something that can help others to live in the new world we find ourselves in. And yes even taking time to make an informed vote and being active in our government's decisions can be a part of that.

Tyler Ludens wrote:

Len Ovens wrote: Climate change is not the end of the world, it will change our world for sure but we are better to figure out how to live in this new world rather than change the world.

I believe permaculture can rapidly and dramatically change the world for the better.  Wide-scale implementation of regenerative techniques could diminish many of the bad effects of climate change, especially at the local level, but also in the larger climate picture.

I for one don't intend to sit around waiting for my land to turn to eroded desert, but instead I am implementing regenerative techniques for a water-retentive landscape.  My neighbors might notice the difference and choose to implement these techniques as well.

Yes, exactly. There is a lot each person can do for their own situation. Example can be a strong motivator as well. I certainly hope all of your neighbours follow your example and the example of other permies. I still don't think I will be buying land in Florida... or even much closer to shore on Vancouver Island. I am within walking distance of the shoreline here, but also a good way up the hill from the highest high tide plus any sea level change likely in my lifetime. (there is only so much ice to melt) I have seen people end up with a sailboat in their backyard in a storm... I don't think I would buy there. The property is still worth more than I could afford anyway.

Take an ice cube, raise the temperature to 10C (50F-ish) the ice starts melting. Now fix the melting situation bring the temperature down to 4C (38F-ish). The ice will not stop melting, rather the whole cube will still melt even if slower. In the same way, even though there are many great things we can do to lower the earth's temperature, we are beyond the point where we can save our shorelines. In fact we might be closer to cooling by more pollution till it blocks the sun... but lets not go there. I am sure with time we can get back to the -1C needed to start refreezing the ice that gets lost but the "with time" is important. During that time the ice will continue to melt and our shorelines will change. (not that they wouldn't change in any case) Therefore, we need to stop thinking about that and move on to the things we can change such as the method we grow our food. Lets make the best of whatever situation we continue to find ourselves in. Personally, I would like to see our governments stay out of it rather than create more poverty and ban all wood burning and all IC powered cars. Some of us can't afford a new Tesla or a new house. Some people can't afford to learn to read or access to the inet so they can't learn about rocket stoves for cooking and build a camp fire in the middle of their hut. Until those people are no longer in poverty, I question  the idea that first world nations can do very much about climate change. Perhaps moving to one of these places and starting there would have more effect. I don't know.

Yes , climate change is real, and yes humans have been the cause of at least some of that. In the past, human caused climate change has kept us from freezing and now it is helping to cause warming. Is this bad? Is this good? I don't know, but it is happening. No matter what happens, even if we somehow manage to reverse this trend (I don't think so), our sea level will rise and our shorelines will change. No amount of money spent or taxation will change that. So if you live close to the ocean in a place that is likely to flood due to storms or the ocean rising, move. Move now while you might get reasonable money for your property because right now you can move at your own pace with the least disruption to your life.

What not to do about climate change:

Don't: Lobby for government action. First off, it is unlikely any government action will have the desired effect as the government is guided by rich companies and single minded emotional groups. The other thing is that any action the government can take will hurt the poor... while still doing nothing to change things.

Don't: Expect renewables to take the place fossil fuels. renewables are powered by fossil fuels and besides that they can't produce enough anyway.

Don't: Suggest the world needs to use less energy. This seems counter to things but the truth is, anything that does not help the third world countries out of poverty will fail. There is a greater percentage of the world population that needs more power than could do with less and they and their governments will get that power one way or another.

Things that could help:

Anything you can do personally to use less energy. Make your own food, build your own home, etc. Any action or change an individual can do is worth while. Do use renewables when you can.

Don't expect things to remain as they are. Prepare for change. Move if needed... and be prepared to move again in the future.

Don't expect a collapse or SHTF kind of event but be reasonably prepared should that happen. In other words, if things start to "go south" don't immediately go into SHTF mode as that could push things over the edge.

Don't stand in the way of things that could help (next gen nuclear power for example).

The take home of this is that the best things we can do about climate change are personal in our own lives. Climate change is not the end of the world, it will change our world for sure but we are better to figure out how to live in this new world rather than change the world. In the end I am responsible for me and need to deal with my own decisions. Others have to make their own. Anything our government can do will be wrong and misguided and will hurt us and others. Best if they do nothing.

Andreas Kaubisch wrote:"And finally, not a battery at all, are projects like the Kilowatt. A 1 to 10K thermonuclear generator being developed by NASA for use off world. They last 10 years... at full output, but can be throttled. Probably safer than any of the batteries discussed above. Capturing the waste heat rather than radiating it would probably double it's effective output. Sunshine or rain not a problem, no snow removal needed. I suspect the liquid salt reactor would be too big for the average homestead, but probably ideal for a small community. (it would also be an ideal place to get rid of spent fuel from kilopower generators used on local homesteads."

'thermonuclear generator' - what are the waste products of this process? Something radiocative?
Also not sure about the wisdom of putting thermonuclear devices in the hands of homesteaders all over the world.... maybe I am not clear on the technology you are referring to?

Thermonuclear power production has gotten off to an unfortunate start. Research in this area is costly. The only reason it got that funding is because of wartime needs (like the bomb) Further funding was done to get nuclear powered submarines. There was other development ongoing into molten salt reactors but that was shutdown once there were nuclear powered sub in place and it was obvious the same process could be used in civilian power production. This was a political decision and in my opinion a bad one. Using water based cooling in the middle of the ocean in a sub or even a surface vessel makes lots of sense but all three major nuclear power plant accidents have been steam explosions. Water cooled nuclear power plants absolutely must have outside power at all times to be run in a safe manner... as we have seen in Japan there can never be a guarantee of that outside power. Both the kilopower and the molten salt reactors mentioned above do not have this problem. They have a gravity based (or in the case of a microgravity kilopower unit, spring based) method of safe shutdown that will happen all on it's own with no human intervention. Heat opens a valve and the fuel or moderator drains or falls away, completely shutting the plant down safely. The generator can sit in this emergency shutdown mode without any attention and no radioactive emissions for years. So in a case like Japan, the energy spent evacuating away from the power plant (this evacuation cased more deaths than the powerplant failure) could be spent on more important emergencies. I have covered emergencies and harm that could be done first because that is the area the fearmongers spend most of their time on.

Waste disposal in the case of the kilopower is similar to lead acid batteries. The unit is sealed and after 10 to 20 years the whole unit is recycled in the same way as lead acid batteries.... they are taken back where they came from. I would imagine a deposit would be large enough to make it worth while for the user to do so. I don't know about other countries, but lead acid batteries can be returned to anyplace that sells them where I live. Liquid salt reactors, as I said, are a bit too big for the average homestead at 500kw, but they do have the advantage that they truly use up all the fuel they are given and in fact are quite happy to use the waste product of other nuclear processes as fuel. So they would be quite happy to eat up all the "spent" fuel from our current inefficient water based nuclear power plants. They would be quite happy taking the fuel  from decommissioned weapons as well. As output, they can provide medically important materials at a fraction of the cost of current processing. The remainder after all is finished is much smaller than current generation plants... in fact the radiation from the byproducts is less than the radiation from smoke emitted from coal burning power plants we have now. So in the same way that all off grid power supplies have waste be it wind generators, solar panels, batteries or whatever, they all have a life time and a waste cycle but in the case of a kilopower type of generator the energy to recycle would be less and the spent fuel would be fuel for another process that is environmentally "friendly". I think that when properly compared to all the other homestead power solutions, taking into account the whole life cycle, small nuclear power generation is no worse and possibly better than most other methods. I would add to that nuclear power generation is in its infancy. work had stopped up until only a few years ago because government funding stopped and even as development has restarted in many parts of the world (the US is behind these days) the biggest problem is not the technology, but regulations based on light water power plants. (ok, politics)

Some other advantages of some of the new nuclear processes: North America has stopped mining rare earth materials because of the byproducts. These same byproducts happen to be the needed starting point for these nuclear processes. In case it has been missed, rare earth materials are used in almost all small and large electric motors that make the best replacements for internal combustion engines.

The truth is, if there is electricity on any homestead, that homestead is reliant on modern technology and modern waste products that require off homestead disposal as well as production. One of the things that scares me about lithium based home power is that there is the assumption the end product is benign and is safe to just leave lying around.... In the end, the question very quickly starts to become, do any of us really know what we are talking about?

Thanks for a great question. The answer for the most part is that the technology is not yet ready for use off world use (where money is no object) and probably a long way off before terrestrial use is happening at all let alone common place. However, I firmly believe that if we wish to keep our shorelines sort of close to where they are, it is going to take nuclear power, particularly in the third world countries where the difference between poverty and not, is readily available power. This is not about human caused climate change, climate will change if we are here or not and it will take technology of some sort to keep our world livable.

Took a look at this from the daily post. The first question that pops into my mind is: What is Ethical? Honestly, for many people Ethical means "anything we can get away with." I worked for a (government owned) company for years who called themselves "Ethical" but I saw things that I would not class that way. One small example: Hire a company to build some plant infrastructure then delay paying until the company they hired went bankrupt... get the cheque back in the mail and go "Oh well." Ethics is an interesting subject, but so poorly defined that use of the word is almost meaningless.

Two types of batteries I would like to see mentioned, one new and one older. The new one is liquid metal with two dissimilar metals, one floating on top of the other. The case does have to be able to stand heat as the metals used have a higher melting point. However, heat input is not required as both charging and discharging create the heat required. Only of use for stationary applications, but still interesting. Lifetime not known really, time will tell

The old? Flooded NiCad. I know the "Cad" is a problem, but they have a life similar to NiFe, can take abuse similar to NiFe, can provide much higher instantaneous output current. May be had used from either the air industry or the mass transportation industry as they are used in trolley buses and and light rail transit. I would suggest that with attention to charging with a similar to what is required for LIon batteries, even sealed NiCad could last a long time.

We are of course all waiting for small high storage supercaps (ultrasupercaps?) for which I am keeping my fingers crossed...

Another thought, not really efficient either, is energy storage as heat. Not water thank you, but something with a higher boiling point (oil has been used). Insulation is a problem, but in a stationary use, 10 feet of insulation is not troubling. Recharge can be either from solar or dead solar (aka trees). Some of the highest energy use is heat anyway, especially in cooler climates. In warmer climates it is interesting that many chillers can be run with heat directly.

And finally, not a battery at all, are projects like the Kilowatt. A 1 to 10K thermonuclear generator being developed by NASA for use off world. They last 10 years... at full output, but can be throttled. Probably safer than any of the batteries discussed above. Capturing the waste heat rather than radiating it would probably double it's effective output. Sunshine or rain not a problem, no snow removal needed. I suspect the liquid salt reactor would be too big for the average homestead, but probably ideal for a small community. (it would also be an ideal place to get rid of spent fuel from kilopower generators used on local homesteads.

Shawn Klassen-Koop wrote:Interesting. I'm wondering, would a stratification chamber bench for inside a house be heavier or lighter than a pebble-style bench?

Mass is mass... but, there are a number of other factors that affect things. I don't think comparing to a pebble bench is the best comparison. While a pebble bench is better than a sand bench, I think it is less good than a cob or brick bench.

So the factors that matter are:

how much of the generated heat the mass soaks up.

how thick the mass is, as this determines the surface temperature

How well the mass conducts heat, this affects both of the above

how well the mass is insulated

how well the room is insulated

how well the room contents absorb the heat

However, a stratification chamber does not in and of itself indicate what kind of mass there is. So it would be possible to use one with gravel as a mass. In both the long pipe and the stratification chamber heat collectors, it matters how well the mass absorbs the heat from the flue gas. Then, once the heat has been transferred to the mass the next question is how fast does it travel through the mass. This determines how fast it will heat and how long it will hold it's heat. It also determines what the outside surface temperature will be. In general we want this temperature to be  as low as it can be and still be useful. There are two reasons for this. First is not getting burned by just touching the mass. The second is that hotter surfaces will radiate through walls and windows faster than a lower surface temperature. And of course, the hotter the surface is the faster the heat is used up and the sooner new fuel will need to be burned. The disadvantage to the cooler (but still hot) surface is that it does take longer to heat the living space initially but that is really a heating management problem that can be managed and has been managed for years where high mass heaters are common. (the RMH over comes this to an extent with the exposed barrel for quick heat).

The whole area of room contents and construction are a whole different topic. Any radiating heat source like you mass will radiate right through a window. It may even depend on what is outside the window (a white fence might reflect heat back into the home for example, while a sky view may allow the heat to escape to space) Massive objects in the room can absorb and re-release that heat later. Even the colour of the walls may affect things. Insulation in itself is not always the answer. In the mass heater world, the idea is not to heat the air in the room, but the objects and people instead.

In all the area of heating and how it works really is not well understood. Those who build houses for a living have figured out that if they keep the air at about 21C, their customers will not complain about it feeling cold and the building codes seem to have encapsulated that. However, what the long term healthiest way of both being comfortable and having good air to breath (air tight, one air exchange per hour is not it in my opinion) while not spending an armload of cash or sweat for fuel... is a long way from solved. I think the RMH or other masonry heater is a good start as a heating appliance but to find out the rest will take more research (AKA trial and error). I don't think I can say with any hope of being right that we know how to build good houses. I do think there have been accidental house builds that have turned out well but why they have turn out well is not understood in full. Two people build similar house, one is happy the other not so much. Some of that is what each finds comfortable, but some of it is the many small details that are different from one to the other that anyone examining the houses would not find. Anyway, I am babbling on...

Grant Holle wrote:

Len Ovens wrote:

Grant Holle wrote:Didn't know where to put this idea, and this thread seems as good as any.

Would it be possible to take Walker's half barrel design and turn it into a pit roast alternative?

tilt the barrel slightly down towards the door as the bottom may collect water from your cooking and the flue gas as it will take longer for the mass around the chamber to warm up if it is warming up the food mass as well.

I really appreciate your advice and design modifications.

No problem.

One thing I did think of when I was reading this, The door to the barrel should not be in a gully. When you open it to unload (maybe for loading too), this chamber will not have any breathable air in it. it will rather be filled with mostly water and CO2. Even though they may be quite warm, the CO2 may still be heavier than the surrounding air and not rise. having the land tilt away downwards and allowing a short time for the gas inside to be replaced with breathable air would be a good idea. Being able to deal with the food remotely would be better.

I suppose going farther, if you have a chamber with unknown air quality, you should put a lock on it when not in use for cooking. You do not want a child to decide it is a great place to explore. Normal RMH do not have this problem as there are no man doors in them, so you are treading new territory with something like this underground and open-able.

It would be less of a problem if the whole barrel was above ground if more dirt to move. Having the door at around waist height would make (un)loading a lot easier too. Also look at some of the rocket powered barrel ovens around too. It would make one's butt warming surface a bit high... but having a bed on top of the oven used to be quite popular in Russia, even 5 feet off the ground.