Category: rocket stoves

New ebook: The Rocket Powered Oven by Tim Barker, Illustrations by Joel Meadows

Cover: The Rocket Powered Oven: How to Build Your Own Super-Efficient CookerWe’re incredibly proud to be publishing this!

It’s a  step-by-step guide to building your own super-efficient rocket powered oven. The most comprehensive build-your-own project of it’s type by our very own: leading Australian alternative technology innovators, Tim Barker and Joel Meadows.

ebook available for $9 via our friends at Permaculture Principles
Price in Aussie $ — that’s something like $US6

Learn the fundamentals of rocket stove design that powers the oven, and choose between one of two designs to build. A Black Oven, which reuses an existing gas or electric oven and a White Oven, which can be made using 2 x 200lt (44 gal) drums.

Most materials required for the build are cheap and can be easily found. In fact, you may have some of them laying around your home, just crying out to be used.

A great do-it-yourself project or get together with a small group for even more fun.

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Here’s the foreword written by Adam Grubb.

Foreword: the future of fire

Around a million years ago our ancestors learnt to control the mysterious and powerful force of fire. So significant was this moment, that by the time we would retrospectively come to be known as Homo sapiens, our whole digestive system had come to expect its food cooked, and our lungs had adapted to air pollution.

It’s somewhat humbling therefore to learn that for those last one million years – and let’s not mince words here – we’ve been doing it wrong.

Three billion people continue to cook on biomass each day. The smoke caused by this (despite our genetic adaptations) is a major health concern, and the excessive use of fuel is a major environmental one. Smoke however, is nothing but unburnt fuel, and more efficient combustion offers both more heat, and an end to the cancer and coughing.

Enter the rocket stove. First conceived by Dr. Larry Winiarski in 1982, the rocket stove is so subtly simple a technology that it could have been around for all one million of those smoky years. Talk about missed opportunity. But at least it is known now. In retrospect it’s an almost obvious concept: burn the fuel first and fully, and then, and only after complete combustion, extract the heat. At the crudest end of the spectrum, you can build them with nothing more than a few bricks and some mud. It’s perhaps this simplicity – it’s not a Tesla sports car after all – that explains why the Wikipedia ‘rocket stoves’ entry at time of writing sits at a measly 150 words. But trust us, this is a much more revolutionary technology than any over-hyped sports car.

Tim Barker and Joel Meadows

Tim Barker and Joel Meadows

No one I’ve met has as much enthusiasm, knowledge, and hands on experience in rocket stoves as Tim Barker. Tim is a perennially ash and grease-stained appropriate technology tinkerer with a professional mechanical background, combined with years of experience in permaculture. He also admits to something of a pyromaniac tendency. Thank the stars he’s harnessing it for our good. You’re helping keep him on the narrow good path by downloading this booklet. Seriously, with a dearth of good, cheap, accessible information about rocket stoves, a better person could not be found to produce this booklet. Our illustrator, Joel Meadows, is a himself an appropriate technologist, craftsperson, metal worker and permaculture practitioner par excellence. When Tim and Joel get together the ideas flow and sparks always soon literally fly. They are always pushing themselves, always learning, and we’re extremely proud to have them together in this much needed publication that can help you avoid the pitfalls, and make a great rocket stove powered oven to call your own.

Adam Grubb is Co-director (with Dan Palmer) of Very Edible Gardens PTY LTD in Melbourne, Australia, and co-author of The Weed Forager’s Handbook and The Art of Frugal Hedonism.

Read the rest of the book: permacultureprinciples.com

A Rocket Oven to Call my Own

Ever since our first rocket stove workshop with Tim Barker in Victoria I’ve been secretly coveting a rocket oven to call my own.

So you simply cannot imagine my excitement when in a NZ tipshop (the famous seagull centre in Thames) I came across an old, rusty, yet solidly constructed rocket oven core that had been build almost exactly (yet seemingly independently) to the specs of Tim’s design. Right down to the two sets of baffles to force the exhaust gases to conduct an S path up each side of the oven core, slowing the transit time and allowing more heat transfer (though Tim tells me he’s gone off baffles these days, a story for another time…).

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This oven core would have taken me at least three days of material sourcing and fabricating. So to pick it up, along with some bits of flue, for $10, I was rather stoked. The only obvious issue was the abrupt reduction in the cross-sectional surface area of where the flue exited the top of the oven – an easy fix. The cavity gap or the distance between the two skins through which the flue gasses would travel was also quite small – about 25-30mm, so I wasn’t sure how well the gasses would actually flow, but it certainly seemed like there was scope for a scone or two. I loved that it looked like a bit of rusty junk but that thanks to Tim I had the eyes to see it for the precious jewel that it was.

The thing kept rusting for the next 10 months or so until we found ourselves relatively settled in our new housebus park up. Relatively settled yet ovenless. The time had come to pull it out and get it working.

After another visit to the tip shop I returned with a stand made for working on outboard motors. My mate Pete and I soon grinded (me & Pete’s son Toby) and arc welded (him) this into a perfect little stand for the core. A quick visit to my dad’s shed yielded a length of stainless steel flue pipe long enough to make up the heat riser and the flue out the top of the oven. I even got his permission before nicking off with it.

Within a day we had ourselves a stand and I had riveted on the flue top and bottom. About ten minutes later I’d put it outside and fitted into into a perfectly sized bit of concrete block (which I’ve found falls to bits after a few months – fire bricks or old red bricks much better).

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First pass (before insulation). Note the awesome home-made charcoal kiln in background (for my mate Pete’s home-made forge).

I lit it expecting it to fail dismally, or to barely work, and for us to start a long process of tweaking it to get it operational. Imagine my surprise when it started drawing straight away, and within ten minutes was hot enough to bake a tray of scones in no time at all!

The next day we took it to our house bus site and set it up again. I fitted a thermometer (again from the trusty tip shop – from an old bbq lid) in order test it out without any insulation and then to keep testing it as we gradually insulated different bits.

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The fist thing I insulated was the oven core by wrangling & riveting an old hot water cylinder shroud. Two finger cuts later we filled it up with pumice and fired it up again (thanks Ciela & Nikka!).

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Next we insulated the riser with a pumice-filled larger flue section which we squished into an oval profile for easier dismantling when we come to move the unit (thanks Brad!).

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Then the burn tunnel and base of the riser which was shedding much heat (Thanks Manda!).

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Meantime whilst I was collecting data it was obvious that what the thermometer on the door said was very different to the actual temperature inside, which was obviously a lot hotter. I estimated by about 50 degreed celsius. So in the name of science I ordered a couple more thermometers, one magnetic one for the outside and one that sits inside the oven exactly where the actual food goes, and both measuring up to a very uncool 400 degrees celsius. The pizzas kept coming and often we’d do several loaves of bread, enough pizzas for ten people, and some sort of desert in one go.

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The most impressive timed session I got out of it so far was getting to 180 degrees celsius in 6 minutes, 225 degrees C in 7 minutes, then maxing out at 365 degrees C after 13 minutes. By this point the base of the oven inside was glowing red hot. We were cooking pizzas start to finish in 3 minutes 50 seconds and the only smoke was when we left them in too long. All on a handful of twigs I tell you, a handful of twigs! The thing I really love is that is faster to heat up than a conventional electric or gas oven. So in that sense, twigs aside, it is actually more convenient than its conventional, expense, non-renewable energy gobbling alternative.

Shortly thereafter Tim visited. Things were going quite well till the moment of truth and it came time to light the oven and I got a bit nervous and overloaded it and there was smoke everywhere and flames going the wrong way, and, oh gosh it was not ideal. The student humiliating himself in front of the sensei. Only for a few minutes though – luckily the rocket then started rocketing, the awkward silence broke, and on a few willow twigs we took it up to 355 degrees c at which point the thermometer appeared to jam up. As for the pizzas – oh gosh – delicious.

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The apprentice and the sensei enjoying rocket pizza.

And that’s it. I’m done here. What, you want some kind of wrap up? Fine – here you are: Then, dear readers, me, my family, and our brand new rocket oven lived happily ever after. If you would like a similarly happy ending and a much better built oven get yourself along to our next rocket stove/efficient combustion workshop. The end.

Tim Barker explains what rocket combustion is

A short edited clip from our last rocket stove / efficient combustion workshop run by Tim (at Joel’s place).

 

Rocket Stoves Workshop Report – Part Three – Megan’s mini Rocket Cooker

So this article builds on Parts One and Two and focuses on workshop participant Megan’s construction of a little rocket-stove-powered-cooker she built during our recent The Power of Rocket Stoves workshop with Tim Barker.

Here’s the style of stove Megan was after (from this page)

 

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Ze raw ingredients

 

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Marking out a hole in a 20-litre tin

 

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Tim is the ultimate tinkerer (not to mention self-confessed pyromaniac) and knows all the tricks!

 

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Fitting the lid and flue (insulated with a subsoil/vermiculite mix)…

 

the insulation

Which looks like this

 

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Lovely…

 

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Light it up and BOOM! Actually as good as this looks it is not how rocket stoves actually work (the combustion and flames are supposed to be down inside the insulated burn chamber). But the flue Megan used was from an old fish and chip shop so this is about 20 years of fat and grease going up!

 

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Cooking up a storm a few days later at the Brunswick Tool Library

 

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So there you have it, all and all a great workshop. Tim’ll be back for another one, don’t worry about that, where we’re keen to try a rocket stove mass heater – any volunteers? Find our next rocket stove workshop here.

Our First-Ever Rocket Stoves Workshop Report – Part Two – The Water heater

So this article builds on the last and shares some photos of our construction of the rocket-stove-powered-hot-water-heater we (mostly) built during our first ever Rocket Stoves workshop with Tim Barker. This unit went up at Yandoit Farm, Victoria, and continues to work beautiful several years later…

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Breille & friend getting the base unit in place…

 

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Lovely!…

 

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Michael and Tim looking pretty stoked…

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See Part Three- Megan’s Mini Rocket Cooker here. Find our next rocket stove workshop here.

Our First-Ever Rocket Stove Workshop Report – Part One – The Oven

Back in May 2014  Tim led our first ever rocket stove workshop on how to build simple rocket stove combustion units for such uses as water heating, ovens, and mass heating. It was a fantastic workshop, hosted by the wonderful Michael and Lisa Jackson at Yandoit Farm, and we wanted to share a few photos and a bit of know-how, here on the oven, with further reports to come on the hot water unit and Megan’s mini-rocket cooker.

Now rocket stoves are super exciting for a few reasons. As noted by Tim:

  1. They offer complete combustion of the wood
  2. They can reach very high temperatures
  3. They can use wood typically considered too small to bother with
  4. They are easily built from common materials.

In other words you can knock these suckers up in a day or two, and they turn twigs into heat way more efficiently than most wood stoves and with way less cost to set up. If you are good at scavenging bits they can cost virtually nothing to build, and when you prune your fruit trees you can get the fuel you need to cook dinner, heat your home, and enjoy a nice hot shower.

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Tim kicking off in the Yandoit Farm hayshed.

We started with a little bit of theory (the workshop was about 95% hands-on) with Tim, who got across the key points of difference between rocket combustion and normal combustion. This is all Dan’s possibly muddled recollection, but the main difference is that rocket combustion is complete. Because the compounds released from the wood heated when added to the rocket stove are sucked into the flames, unlike a normal fire, combustion is complete, meaning no smoke. That’s right – smoke mean incomplete combustion, or wasted energy. It was really weird looking down the flue of our first rocket unit at the workshop and feeling the hot air but seeing zero smoke. For we are culturally trained to associate smoke with fire, but with rocket stoves it is true that sometimes when there is no smoke, there is still fire! The second difference is that rocket stoves focus on ensuring complete combustion and only then use the resultant heat. Conventional wood stoves and often use the heat before combustion is complete. The combustion chamber of the rocket stove is heavily insulated to prevent premature heat loss.

Anyway, enough theory, let’s jump to practice, as we did on the Saturday morning.

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Whilst Tim showed us how to make the base rocket stove unit from old bricks…

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VEG’s Carey and friends (Chris, Brielle & Paul) constituted the poo collection crew. 20 minutes into the workshop and they were shovelling shit!

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Which we mixed with subsoil to make a cob mix

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With some relatively clean feet..

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But not for long!

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Work that cob!

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Consider it worked.

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Relatively unclean feet..

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Beautiful cob blobs

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And such fun to make!

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Securing the base layer

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Reshaping the base unit (feeder tube, burn tunnel, and riser)

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Flue fitted

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Praise to the rocket gods

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Blob on the cob

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Coming up beautifully!

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Here’s one I prepared earlier 🙂

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Frame was attached…

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A quick chat about the immanent fate of these nice blue barrels…

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Measuring…

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Revving up the grinder (nice one Megan!)

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Brielle aka The Permaculture Terminator

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Sparks fly!

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Fitting the outer to the inner skin.

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Sitting on the frame.

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“I am Geoffrey, the badger hunter. Let me tell you the story of my people” – a comment from sculptor Dean.

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Pyromaniac Tim getting ready to fire the rocket!

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The puff that turns it from a normal fire into a rocket

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Ladies and gentlemen, we have lift off…

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This is what complete combustion looks like – look mum – no smoke!

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Go Team!!!

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Tim going for the giant-bong look…

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Yandoit farm resident and exceptionally wonderful human being Chris who finished off the stove all by herself in the two weeks after the workshop…

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And who would have thought something so rough and ready and functional could be so beauuutiful!

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Recycled old supermarket shelves

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Finishing off dinner in the oven which we can say lives up to its rep and cooked about seven pizzas and finished off these pies effortlessly and quickly on bugger all wood.

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Yeah baby!

See Part Two – the water heater here. Find our next rocket stove workshop here.

Tim’s Creation at 2015 Missoula Rocket Stove Workshop

Twice now www.AppropriateTechnology.com.au‘s Tim Barker has been invited over to the Mecca of Rocket Stoves – Paul Wheaton’s Rocket Stove Lab over in Missoula, USA. Here during his most recent visit he talks us through what he’s been up to – a portable rocket combustion powered field kitchen with a rocket hotplate, oven and water heater all in the one unit.

Building first white, low mass insulated barrel rocket oven

IMG_0438Some may remember I did an article a while ago on white ovens. If you haven’t read that, now might be a good time as this article follows on from it. Those that did read the article may remember I foolishly made a prediction on how hot I thought the oven I proposed to design and build would get. The magic number was 300degC, as the oven would at times be used for cooking pizza and also large amounts of food for catering purposes.

So lets go through the building and testing process and see how it all went. One of my main design parameters (apart from the hoping it would work) was that the oven could be built using fairly simple tools and without much engineering skill -so no welding at all in the construction. A much modified 200L barrel forms the heart of the oven. These are easy to come by and if you follow a few simple steps are easy to open up and clean.

Car workshops are a good place to get the barrels, as they will usually only have had clean oil in them. I then usually tip them upside down over a container and let them drain for 1/2 an hour and then give them a couple of washes with hot water and dishwashing liquid. Whatever you do, don’t use a drum unless you are absolutely certain you know what was in it prior. I once was invited to give an oven workshop and when I turned up all the barrels  that had been collected were ex-herbicide and pesticide barrels. Big no no!

The next thing to do is remove the ends. For this you only need a small angle grinder. Firstly use all the appropriate safety gear when using any power tools (You have been warned!). Simply grind evenly all the way round on the very end of the barrel and eventually you will see a line appear, stop grinding on this spot and move along till the line continues all the way round the drum. Then just tap around on the inside of the end of the drum with a mallet and the end should fall into the barrel where it can be retrieved. If the end is a bit stuck then note where its not moving down and give it a bit more of a grind. Do this with  both ends and save them.
Next put one of those thin steel cutting blades on the angle grinder (I love those things, they are so handy) and cut the drum in half so you basically have two round steel tubes. Each will have a thick lip on one end that corresponds with the top and bottom of the barrel.
Next take one of your steel tubes and fit what was originally the lid of the drum into the end without the thick lip and drill and pop rivet it in place. It should be a neat fit. Oh, by the way, the lid of the drum will usually have two screw-in bungs, one big, one small,  remove these and take the black “O” rings off and refit the bungs. This way when the oven heats up you won’t be getting smoked out from melting “O” rings.You now should have a half height barrel.

Next take what was the bottom of the barrel and cut it as shown in the photo, add two hinges and pop rivet the smaller piece into the end of the barrel. You now have your inner cooking chamber with door.
We then take the remaining steel “tube” and cut it vertically from top to bottom and stretch this and place it around the inner chamber. A picture is worth a thousand words so have a close look at the next  couple of photos and you will see that I have drilled through both the outer and inner chambers and installed bolts and nuts in three places on each end so that the outer cover is held in place and a gap of approx 50mm is maintained between the two steel tubes. This is where our hot gasses will flow.
Next step is to make a base. In this case a heavy but cheap plywood bench was made and a hole cut to take the oven assembly.
Being in NZ we have heaps of pumice lying round everywhere so I filed some pieces flat and used them to space the barrels away from the ply so that the base was well insulated from the oven.

We had some insulation batts made from recycled glass left over from another project so we used this to insulate the outer steel tube. You could use some perlite mixed with clay or even a clay sawdust mix as an insulating layer but we had the batts handy and they make a very big difference to the performance of the oven. Over this we put an outer cover of some thin aluminum sheet and pushed cob into the gap. Again we had the sheets lying around but you could use the skin of another barrel. Note that the extra metal layer is to stop the outer cob layer squashing the insulation flat. If you use the perlite or sawdust mix mentioned earlier the you don’t need the metal layer just cob straight over the top.

In this shot you can see the cob being pushed into the gap in the insulating layer.

This shot is from the back of the oven and you can see I have also plugged the gap between the inner barrel and the outer barrel leaving an exit hole for the exhaust gasses at the top.

A shot from the front showing the gaps between all layers filled.

Here we see the combustion gas inlet from below. It’s just a hole cut in the outermost skin of the insulating layer. You can see the inner barrel through the hole.

I then built an insulated heat riser for the rocket stove using crushed pumice rammed down between two different sized flue pipes and capped in place with cob. Next I cut slots in the ends of the outer flue and bent the tabs over to lock everything permanently in place.

I then built up a rocket stove body out of old bricks.

I wanted to have a test run with and without baffels to measure what effect having baffles in the outer chamber would make to the oven performance. So without cobing in anymore of the exterior we fired up the oven and took some temperature readings.  Fifteen minutes after lighting the oven with no baffles installed it hit  217degC and in the next 15 minutes went up to around 265degC and stabilised there.  Pretty good for a first run.

The next day we removed the cob mix from the rear of the oven where it seals between the inner and outer barrels. Baffles were made from some of the scrap fiberglass insulation wrapped in aluminum foil and then inserted into the gap between the barrels so that the combustion gasses had to follow a convoluted path to get out, hopefully giving up more heat to the inner barrel in the process.

We then reassembled everything and fired her up again.

It’s here that I have to digress a little and set the scene. I had been working with the Koanga Institute on site for nearly a year and the day in question was to be my last full day, I was due to fly out very early the next day. As you can imagine things were pretty hectic. Cleverly a week earlier Kay had said we were going to have a pizza night for my sendoff so guess what? First I had to make the oven! So there we are at 4pm in the afternoon and we haven’t hit our target of 300degC and we’re supposed to be cooking with the oven in a couple of hours. Anyway in the first 15 minutes we passed 265degC and in the next 15  we passed 400degC. The highest temperature later in the night with all the cooking done reached over 500degC. To say I was stoked would be an understatement. Of course there are lots of things I could have done better, as it was a bit of a rushed job.

On my return to teach at the institute’s next PDC some six months later the oven has had some major improvements, most notably a new experimental coat of paperdobe (paper and silt/clay) and some improvements to the baffles which were found to have slipped. Brad who did the work had found that the old baffles had slipped down, probably from heat distortion and so had constructed permanent steel ones instead. The modifications make the oven much more durable and the Paperdobe is proving to be quite a good insulating outer layer.
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All in all the oven is proving very fuel efficient and easy to use and is in near daily use at the institute cooking up lots of yummy food.

Tim is a qualified diesel fitter who has been learning and experimenting with permaculture for over 30 years.  Over the years he has run a farm, environmental adventure tourism businesses, and contracted for the Environmental Protection Agency on large projects, all the while continuing to create his own projects from a hovercraft to a home aquaponics system. His current big project is designing and building a rammed earth home for his family in Morten Bay.

This article is reproduced here with Tim’s permission from his original February 24, 2014 post for NZ’s Koanga Institute here.

Introducing white, low mass insulated barrel rocket ovens

Some may have read my earlier articles on constructing simple efficient wood fired ovens and water heaters. To date the ovens I have described are what are commonly known as “Black” ovens , now the mental image that  the description “black oven” conjures up may not be particularly appealing but the reality is I assure you far from it. Basically a black oven is one where the food being cooked is exposed to the combustion gasses of the wood so technically a wood fired pizza oven is considered a black oven. Now most i’m sure will agree that a good wood fired pizza is a beautiful thing. Having almost exclusively used a black oven these last three years for all my families roasting and baking i can attest to how tasty food from one of these ovens can be.

There are a number of broad differences between white and black ovens and i’m going to generalize here so professional pyromaniacs and oven builders please remain calm. Generally black ovens are stored heat ovens ,that is you burn wood in them and the mass of the oven stores the heat of the fire. You then clean the ash out and put your food in, be it pizza, roast or bread (again i’m glossing over a vast body of information here) and it cooks, all the while slowly losing heat. Now we’ve all seen wood fired pizza ovens where there is a fire going in the chamber. This is merely an adaption to the need in a commercial situation to cook for extended times or for ovens without adequate mass to store enough heat in the first place. Where my black ovens differ is that there is no attempt to store heat. You cook while the fire is burning with little or no need for preheating.

http://permaculturenews.org/2012/10/16/rocket-oven-a-permanent-wall-mounted-kitchen-oven/

http://permaculturenews.org/2012/11/08/rocket-oven-nitty-gritty/

Funnily enough though one of the most commonly asked questions is “doesn’t the smoke taint the food “ well to be honest i like the flavor it imparts to the food but by and large if the oven is well designed and tended then there is very little “added” flavor.

As i mentioned earlier we bake in ours, cakes, scones, biscuits lots of things with delicate flavors that wouldn’t benefit from a smoky flavor. You’ll notice i added the caveat “if well designed and tended”.  If its not well designed and smokes then it will taint the food ,ditto for wet or green wood or of particular horror if the wood is treated or painted. This cannot be overstated  Use Only Untreated Wood. And of course some people simple don’t know how to start or tend a fire (i would hazard to say most) so if the fire is poorly tended again it will smoke.

Now if your with me on this you’ve probably already guessed there is such a thing as a white oven and yes a white oven simply keeps the food and the combustion gasses separated. Now compared to the black ovens i’ve designed using old electric or gas ovens the white oven is a slightly more complex beast to construct. Firstly we have to have a gas tight inner chamber where the food cooks, this is then surrounded by a chamber where combustion gasses flow and heat the inner chamber through conduction, convection and radiation. In the interests of efficiency we also can have an outer insulating layer to trap and make better use of our heat.

So to recap we have black ovens where food is in contact with combustion gasses and these fall into two main categories and one sub category, those that cook with stored heat(mass ovens) those that cook with direct heat(Insulated ovens) and the third category being those that combine a bit of both (mass ovens with a ongoing fire).

Guess what ? White ovens fall into two main categories with a third sub category. Those that cook with stored heat, those that cook with direct heat, and those that do a little of both. Now when i talk about mass ovens and insulated ovens i don’t mean that mass ovens have no insulation, in fact the best most efficient ones do. However the insulation goes outside the mass and keeps the captured heat from escaping to the environment thereby staying hotter longer. By contrast an insulated oven has comparatively little mass and uses the heat of combustion as its produced.

White ovens that use mass to cook use ….well a lot of mass ! This can make them quite an undertaking to construct and because of the long preheat time removes a lot of the spontaneity that is the spice of life. As previously argued http://permaculturenews.org/2012/11/23/so-where-does-the-appropriate-in-appropriate-technology-come-from/ they are also very inefficient when used in the wrong context. So setting this type aside for a future date i want to concentrate on low mass insulated ovens.

But first a quick look at our sub category of mixed white ovens (some mass and ongoing heat).

Mixed white ovens have been around for some time and seem to often incorporate 200l barrels (44 gallon in old speak and 55 gallon if your from the US). I think that this is purely because they lend themselves so well to the concept and are cheap and easy to get.

Above we see a more recent design by Max and Eva Edleson of www.firespeaking.com adapted from similar ovens they saw in South America which use some mass and ongoing heat.

Interestingly enough the ovens don’t appear to use any insulation as such and so must lose a fair amount of heat to the environment. However because of the slow heat transfer rate of the Adobe bricks around the barrel  and the large fire chamber, more than enough is soaking into the barrel. Also of interest is that the fire is a traditional sort in that logs are piled in, a fire lit and off you go. As a person who has spent a fair amount of time over the last few years mucking about with rocket stoves the design cries out for a big dose of efficiency in the shape of a rocket combustion chamber, less mass and better insulation.

This Photo is of one of the oldest barrel ovens i know it dates from the 1940’s and is at Moreton Telegraph station in Far North Queensland Australia. Note the similarities to the much later design above. These were know as Ant bed ovens as they utilized the material from termite mounds broken up and mixed with water to form the outer shell. You can clearly see a layer of ant bed (think cob) packed in between the inner and outer drum to create a space for the hot combustion gasses to flow around. It was probably this oven that really sparked my initial interest in wood combustion back in the mid 90’s.

This leads us by a long and tortured path to the brief for my latest design which is a white oven with as little mass as possible using a rocket stove as the heat source. Combining these two features should i hope produce an oven that is very quick to heat up and is very frugal in its use of wood. Its always a mistake to pre-empt a design but i’m guessing this oven should hit 300 deg c (great for Pizza) on very little wood. Stay tuned.

This article is reproduced here with Tim’s permission from his original August 27, 2013 post for NZ’s Koanga Institute there titled “A Whiter shade of pale.”