In this post I’ll explain how I built my Mk II ammo can rocket stove. This is a small, inexpensive homemade wood stove which burns wood, without smoke, thanks to it’s secondary burn system. In this post and video I break the stove down and talk about how I made each component.
If you want to see this stove burning wood, without smoke, then check out this blog post.
Thanks to the feedback and comments from viewers (As well as the touching comment posted on this blog post by Tommy Cruz about him and his son Nicholas building an Ammo Can Stove together) I prioritised the build video for my Mk II Ammo Can Rocket Stove. I uploaded it as soon as I could and it is now live on YouTube.
The video details the following:
- The flue I explain how the flue is constructed and how I found a really easy way to attach it to the top of the ammo can. I then talk about options for the larger diameter flue section above the stove.
- The cooking surface / hot plate This prototype stove doesn’t have a cooking surface but I explain how you can create one really easily by simply removing the handle brackets. (Each bracket is retained by 4 small spot welds, so they are easily removed)
- The lid seal The stove rope seal around the interface of the stove lid and body.
- Turnbuckle door locks These enable the door to be locked shut extremely tightly by turning them 1/4 turn with a metal rod.
- The steel baffle This is an essential part of the stove as it directs the flow of gases during operation, reflects and retains heat within the burn chamber and creates the conditions necessary for secondary burn to take place.
- The secondary air system I explain how this draws in cold air from outside, pre-heats this air in the burn chamber, and then releases super-heated secondary air into the stove in the area just below the steel baffle. This secondary air reignites what would be smoke, eliminating this smoke via complete combustion. I explain how I made the secondary air system out of simple and cheap steel water pipes and fittings.
- The three insulated sides of the stove I used fibreglass insulation sandwiched between inner steel liners and the external skin of the ammo can. I insulated three sides and left the side with the door uninsulated. This provides enough insulation for a clean burn but also allows for great heat transfer out of the ‘front’ of the stove where the door is located.
- The stainless steel heat shield adjacent to the end of the baffle This is something I added to protect what I considered to be one of the most vulnerable parts of the stove. This area is where the flame and combustion gases change direction before heading across towards the flue. I thought that it would be prudent to add this spare stainless stell I had to protect this area. I also believe that it improves the stove by acting as a heat store, retaining and reflecting some of the heat back into the burn chamber.
- The stove door I explain how I made the stove door using stainless steel and a hinge, with mica for the viewing window. The mica is loosely held in position which allows for differential thermal expansion and contraction. As well as the previously mentioned turnbuckle door locks, the stove door also has a quarter turn door latch which I made by filing off a portion of a large headed screw and positioning it precisely below the opening I cut into the front face of the stove.
- The fuel raising grate This is simply made from some chicken wire but is essential as it allows all-round burning of the fuel.
- The insulated lower section of the stove This is where the fibreglass insulation is at its thickest (around 1/2″ or 12 mm). On top of this is a stainless steel plate to protect the bottom of the stove from glowing hot embers.
- The primary air intake / rocket stove intake This is a stainless steel 90 degree elbow I found lying around in the garage. It is where the primary air is drawn into the stove and can also be used to add fuel once the stove is up to temperature, without having open the door. This is a useful feature and I will be looking to improve it further on the Mk III.
I then talk about how you can help by making suggestions for improvements that I may go on to incorporate in the Mk III. I also mention a secret, much smaller, homemade stove that will be coming one day…
Anyway, back to the present: Watch my video ‘How I built my Ammo Can Rocket Stove – a small homemade wood stove (Mk II)‘ below:
You can buy these ammo cans here: https://amzn.to/2BkRDLl
These homemade wood stoves are very useful. I’ve had messages from people who want to use them for all kinds of purposes: A workshop in Northern Minnesota where winter temperatures of -36 degrees Celcius, refugee camps, preppers, hikers, tiny home dwellers… These little stoves seem to me to be very useful at plugging a gap in the market for a small, inexpensive, easy to build wood stove that anyone can build at home, without technical experience. I aim to help out as much as I can by making the Mk III really special.
Do you have any suggestions for the Mk III? Let me know what features you would add and anything you can think of to improve the stove. Your idea could be incorporated in to the Mk III (which I hope will become a very popular DIY stove!)
Please leave your comments below.
If you enjoyed this post, share it on social media to help me put food on our dinner table.
Adrian Tyler says
Could the secondary burn inlet be made to be part of the flue and run up the side? That way air is drawn in from outside thereby not increasing CO2 levels if used in a small tent. Plus the air will be preheated. If the inlet stopped short of the top of the chimney it would also ensure it only drew in clean air and prevent it from drawing in the spent gasses. Might be too complicated though.
I do love the secondary air part though! This is what separates it from all the others….and done so simply too.
My only other attention to detail would be extra effort in sealing it from CO escaping into the air space occupied by people. Particularly in light of the tragedy in Bavaria on Monday.
Hi Adrian, thank you for your comment.
I have thought about using a twin-walled flue with the secondary air being drawn from between the two skins of the flue. I have worked out how to do physically do it but I have some question marks about how well it would work, given that hot air rises, and the draw of the stove would be working against this in order to draw in the secondary air. It could work very well though – I need to go and spend some time tinkering and testing out different ideas to see how they work.
Regarding the CO poisoning, I have a couple of points to make. Firstly, I belive my stove design is very safe. The air intake surface areas exceed the flue surface area, and there are no dampers anywhere (On my burn video I restricted the airflow with a pice of aluminium foil purely to ‘mess with’ the flame and try to get a better shot of the flames with the camera. When the stove is in use there is no damping at all). Because the fire has plenty of oxygen, CO production should be absolutely minimal ***as long as the space that the stove is contained in has adequate airflow in order to replace the volume of gas going up out of the flue.*** Many other stoves have dampers to increase the amount of time a load of fuel lasts. I believe that reducing the airflow into a stove via dampers massively increases the chance of CO being produced… Secondly, I always talk about using CO detectors if using any open flame device in an enclosed space. They cost less than 20 USD and completely eliminate the danger posed by CO.
I have just read about the tragedy in Bavaria. What a terrible shame. Every year people die from CO poisoning. If everyone using an open flame in an enclosed space also used a CO detector then nobody would fall victim to this silent killer. Small wood burners (especially smokeless ones) are a fantastic heat source for small spaces, and I believe will become even more popular in the future. If simple precautions are always taken, there is no reason to fear them.
Thanks again for your comment.
Hi, where do you get your mica glass and insulating material?
you can buy mica here: http://fave.co/2l0leMG It’s very cheap if you buy it in the smaller panel sizes. It’s a naturally occurring substance but the smaller pieces are much more common, whereas the larger sections are more rare and cost a lot more…
The Rockwool or Fibreglass insulation can be purchased from any DIY store, where it is sold as loft insulation. You only need a small amount so maybe you can source some from a loft… 🙂
Im looking for one of these for my van. I have a few questions.
1. What size stove rope do you recommend?
2. What temperature does the bottom of the stove reach?
I think I’m going to create a water container around the stove to use the heat for brews and extra insulation. Ill send you some pics if it works.
thank you for your comment.
I reckon 8mm stove rope should work well to seal the lid. The insulated bottom of the stove gets up to about 150 degrees Celcius when the stove is at it’s hottest (the front face where the door is gets to about 450 degrees Celcius…).
As for the water container, that is a great idea but you have to have a very hot burn chamber to get secondary burn – if you rob heat too early in the system the burn efficiency will drop massively and you could have a lot of smoke. This is why I’m looking at using the post – secondary burn heat to heat water (wrapping a copper coil around the flue, for example).
Good luck with your build and let us know how you get on!
Love the design and I am looking to make one myself. Some of your future ideas sound great. I have one question though before I start, how well does the stove perform for cooking and boiling water? Thanks
Hi Dan, thanks for your comment. In all honesty I’ve never tried it. Life is crazy busy at the moment and I haven’t had a chance to work on the stove for a while. There is another video on YouTube where I measure the temperature with the stove running – you can see it here: https://youtu.be/LqIHgNZXo6o
The stove gets up to over 440 degrees Celcius (830 degrees Fahrenheit), so cooking and boiling water should be no problem.
joe skill says
Hi, one guy was saying to make it more like a rocket stove you should maybe have that secondary feed pipe to be more angled down. maybe it could be square metal instead of round. But the main thing would be to have it angled down so it can be self feeding. Might be a cool feature to try.
Looks like some cool stuff you do. thanks. And I would love to see your number 3 stove when its done.
Hi Joe, I have some plans in my head for a gravity feed system. I just need some time to dedicate to tinkering and time is something I am very short of at the moment. I’m looking forward to getting the Mk III out there at some point.
Jackie Hyder says
I am looking forward to seeing your MK3 design. I am setting up a camper on the back of my pick up truck. I was particularly interested in the CO2 emissions, as it will be enclosed. I am interested in using it for cooking and space heating. The man who is making my topper for the pickup works in heat and air so I know he will advise me on the CO2 stuff, but I like to inform myself as much as possible and then ask him questions. Thank for the video.
Hi Jackie. I’m working on the Mk III. It’s very exciting actually but I just have a really crazily busy life so it’s taking time… You should use a CO detector whenever you use any open flame device in an enclosed space. This includes any propane stoves, alcohol stoves, or wood burners. As long as you have a serviceable CO detector in there with you then you know you are safe. Thanks for watching / reading. Cheers, Chris
Love the stove, genius!!! Getting ready to make my own. I do a lot of tent camping while out hunting. Need a super hot and efficient stove. Before I get started I was wondering if you’ve completed the MKIII yet? Want to get your lastest design.
Again, great job.
thank you for your comment. The Mk III is coming at some point but I can’t put a date on it. We’ve just had our first baby and she is keeping us very busy!
It will be ready at some point though so stay tuned!
John Yost says
First, congratulations on becoming a father!!! 🙂
Thanks for your videos and those stoves are awesome! I’m going to use this in my Seek Outside tent for now. Then in a tiny house or wall tent when I get/build one. I’ve been thinking about a woodstove t hat burns the gas, and so glad I found your site and videos!!!
I just ordered a 50cal can and am making a list of supplies to buy.
I’m going to use copper pipe for my secondary burn.as you did in the MKI.
The only question I have as far as supplies to buy go is what size pipe you’re using for the secondary intake.
It looks like it starts out small and where you have the holes drilled, it’s bigger. It’s hard to tell though since cameras can make things closer look bigger.
Also, I lived off grid for 12 years in a log cabin I built with hand tools. Can’t wait to move out in the woods again and your stove will help. There are a few pictures of my cabin here: http://yostsurvivalskills.com/cabin-living/
Thanks again and please let me know what size pipe I should buy!
thank you very much for the congratulations! Baby Emma has stolen my heart 🙂
I’ve just had a quick look at your website and YouTube channel (I have bookmarked your them and will come back to them when I get a chance: you have a ton of things on there which are really interesting for me!) actually, it seems that we share quite a few interests…
Incredible that you lived off grid in a cabin in the woods for 12 years! Wow, what an amazing experience. I would love to share a beer with you one day and talk about that. I spent a week hiking and camping in the Canadian Rockies, solo, when I was 19 years old and it was one of the most magical experiences of my life. Going back to nature like does something to your soul… I can’t begin to imagine how those 12 years have been embedded in you. Just wow!
As for the secondary pipe for your stove I agree that copper is the way to go. I used 15 mm copper pipe on the Mk I and that worked really well. The secondary pipe was the same diameter throughout on both the Mk I & the Mk II but the water pipe on the Mk II had an adapter fitting near to the end to allow me to fit a plug, hence the apparent larger diameter. I hope this helps and I hope you will love the Mk III when that comes out. (It is coming, I just need to find the time, which is a huge challenge!)
Very best regards and I hope to talk to you again at some point.
John Yost says
Thanks much for your reply here. I especially appreciate you taking time away since I know how busy things get with a newborn! And it sounds like it’s even more difficult for you since she has stolen your heart! 🙂
I built a stove very similar to yours. Just a couple of changes to make the construction faster. I found to get the secondary burn, I had to really restrict the primary air intake. I’m surprised you got secondary burn in that one video where there was so much air coming in the rocket tube pipe covered with a pie tin.
Your solo trip in the Canadian Rockies sounds amazing. I’m jealous. I haven’t gone on an extended campout for a while. I need to get out for a few weeks this summer. And yes, there’s something about being outside like that that’s just amazing. And the solo aspect of it is probably the most important component of that magic. You learn about you out by yourself and have to face your fears- inner and outer. It’s just you and you. I loved those 12 years off-grid. I want to die living like that, but I have a few things to do in “civilization” first.
Hanging out and sharing a beer sounds great. I travel quite a bit so that’s a realistic possibility. Let me know where you are. My email is johnnieyost at yahoo. Drop me a note and let me know when is a good time to visit. And, of course, if you guys are in the States, my door is always open.
Cecilia McGowan Knoxville TN says
Chris, Your little stove has me so excited. I really, really hope, that you find the time and energy to finish development of the Mark III. I am 65 in 1.5 months and selling my house and moving into a van to travel and live. My son and I are building out the van right now. I don’t want to be restricted to warm traveling grounds.
The only major problem we haven’t made much progress on is a way to heat the van, or even partially heat it, with wood. I do not want to use liquid fuels because of condensation and the idea of gas under pressure in my living space. I am going to be cooking on an unpressurized alcohol stove. If you make your mods to your stove, with your very complete instructions, I believe I could construct and maintain it. (I don’t weld and my son will be back to his own homestead and tiny house in NC by then. They have a small woodstove that blasts them out of their 10 x 12 home, and takes cords of firewood each heating season.)
My best to Emma and your wife. Such a fantastic experience, having a young child in the house. And, it just gets better.
thank you for your comment. The Mk III will be perfect for this kind of use and I really can’t wait to get it out there. Life is so incredibly busy right now and I don’t know when I’ll have time to get the plans out to people, which is very frustrating for me too but there just aren’t enough hours in the day!…
I will find the time to do it eventually and I hope you find it useful then. In the meantime I wish you good luck with your #vanlife adventures!
Thank you for your best wishes, Emma is the biggest gift we have evr received and every day is magical thanks to her presence!
Yuji FURUHASHI says
Hi, thanks for the great video. I am Japanese and do not fully understand English, but when I saw your video, I understood it. Make an ammo can with reference to your video for this winter. Let me introduce your video on my youtube video. I look forward to the sequel. If I can make my stove, I will introduce it on my YouTube.
thank you for reaching out. I wish you the very best of luck with your stove and I’d love to see it when it’s ready.
Need some serious assistance from you. Found your video and decided to build my own stove. Not as easy for me as my tools are limited to a drill; a hacksaw with a pointed blade and needle nose pliers. Found pipe for secondary air. Having problems finishing the door and window. My problem is, overall the stove IS complete. The problem is when I start a fire, get it going well, then close the door, the fire goes out. Worse, the main air intake, which is 3 inches open puts out smoke. As much as the flue. Additionally smoke exits through the secondary. Not for long but at first, then fades, then occasionally smoke exits again.
I have reviewed your video so much I can recite it. Paid attention to as much detail as I could. Disassembled the stove making sure I didn’t miss a detail. Rebuilt, started a fire and get LOTS of smoke; close the door and the fire dies. Nothing but smoldering producing lots of smoke.
Primary air is not blocked. I believe plenty of holes on the secondary. But the fire is reduced to smoldering and smoke comes from any opening no matter how small. Open the door and the fire reignites easy and hot.
Where, how am I not getting enough air?
Also, the mica. Your link is no longer any good. I found mica for high temp that is clear but it gets all black from the smoke so I can’t see inside. I really need some guidance here please. It has taken me a month to build devoting a little time here and there as well as finding mica took time and trying to use a high temp welding paste to work hasn’t been as successful as I had hoped. Use my e-mail if necessary please.
I can see what’s happening here: the intake and flue cross sectional areas are mismatched and there is a larger volume of air coming in than smoke is going out. This will cause all of these problems. Try increasing the diameter of your flue to 3″ and add at least 1.5 metres of 4″ flue on to the top of that. Get back to me to let me know how you get on.