Making an Ammo Can Stove - jonsbushcraft.com

One way of making an
Ammo Can Stove

I made this portable stove as a source of heating for inside my canvas bell tent, it should be ideal for winter camping when temperatures drop below zero. Also, I just thought it would be a fun thing to make...

People have made such stoves in many different ways. They are mostly used in colder climates like Canada and Scandinavia. The following article shows my own design, bear in mind that this is the first stove I have ever made, I am not an expert where stove use and design is concerned so the design may not necessarily be the best. I wanted to share this project with you, but before doing any of this yourself please consider the following realistic warning:

WARNING: Fitting a wood burning stove inside a tent can potentially be very dangerous. Among many hazards, death can be caused by carbon monoxide poisoning if the stove is poorly made and designed, and/or if there is too little fresh air circulation provided by tent vent holes. Please DO YOUR OWN RESEARCH on how a stove should be used inside a tent and what types of tent are suitable etc. Do not take this article as being a fully comprehensive manual on the use of stoves in tents and the associated safety considerations. Be responsible for yourself and stay safe!

Use of the stove
Small stoves like these need to be fed fairly regularly meaning that they can't be banked up before going to sleep to keep you warm all night (which is a shame). Instead such stoves are used to keep you warm in the evening, to cook on, and importantly they provide a warm, dry climate in your tent to dry your clothes etc (which is extremely important for winter life outdoors). On extended winter trips moisture tends to build up in your clothes which will eventually make you very cold, such conditions can force you to head back indoors. So, the tent and stove provides a warm environment in which you can hang clothing up keeping it moisture free. At night you'd generally let the fire burn out, then rely on a good sleeping bag to keep you warm. Leaving a stove raging away while you are asleep could be dangerous...

My stove box will be a '50 cal' ammo box; this is a popular choice. I went for the 'Fat 50' version which is slightly wider than standard. I got this off eBay.


These pipes are intended for custom exhaust systems, but they work well for a flue pipe too. They have slotted ends meaning that I can collapse the stove down for portability. They are manufactured by Jetex, I also got these off eBay. I chose the 2 inch diameter mild steel ones.	I also purchased this 'Double end sleeve' from which to make the flange to connect the main flue pipes to the stove box. Notice how it is slightly crimped in middle, this handy feature will stop the flue sections falling down into the fire box.

	Important! This diagram shows the configuration of the flue pipes. Notice how the smaller diameter end slots down into the wider end. It is important to have the join this way around so that the creosote (a tar like substance) that condenses in the flue pipe will run down the inside of the pipes and straight back into the fire where it will be burnt. If the join was the other way around the creosote would run out between the joints creating a toxic Smokey dripping mess on the outside of the stove. (I actually had this problem and had to re-think my design; so learn from my mistake) Having the pipes slotted together as pictured will not create a smoke leakage problem as I first imagined.


Stage 1 - Making the connector/ flange to connect the flue pipes to the stove box

1. - The double end connector	2. - The connector after some metal-work modification

3. - Connector/ flange fitted through hole cut in ammo box lid	4. - Part fixed in place using pop-rivets

I made this flange from the 'Double end connector' exhaust part. I hammered the rim outwards and downwards over a hardwood form to create a 'top-hat' shaped lip which could be used to firmly attach it to the lid of the ammo box. The bottom right picture here (4) shows the home-made flange attached to the lid of the ammo box, that's what we're aiming for. The following pictures show the more detailed process of how I modified the connector component:

	Oak board with exact sized hole cut out serves as a form to bend the metal over.

	Detail showing how the connector piece is held in the form and then clamped in the vice to keep it still. The rim of the connector can then be beaten outwards into shape using a rounded head hammer.

	Beating the metal hardens it. To prevent the metal from splitting it needs to be softened again by heating it up until cherry red. Once cooled the metal can be worked again (this softening process is called annealing). I removed it from the wooden form each time I did this.

After annealing the metal several times and beating it into shape, the lip was finally flat.

To install the flange a hole needed to be cut into the ammo box lid. The ammo box handle was removed first by chiselling it off with a big screwdriver and mallet. I marked out the position of the flange, remembering to take into account the extra room needed to for riveting the flange lip to the lid... I then cut the hole out using a drill and a rounded file.

	Flange finally slotted through hole, later it will be fixed in place with pop-rivets.

Stage 2 - Making the door


	Door size is marked out. The door will overlap the opening slightly.	materials for the door: some sheet stainless steel and a section of aluminium 'piano hinge', all sourced on the internet. pieces were cut to size using a hacksaw. the strip of metal on the left will be fixed behind the left hand side of the hinge to bring the hinge level on both sides.

	The pin in the centre of the hinge is knocked through slightly, the end then crimped over very slightly using a hammer, and then knocked back into place. This will stop the pin moving or even falling out.	I cut the door opening out by firstly drilling a starter hole big enough to get a hacksaw blade in. I then gripped The loose hacksaw blade with a rag and cut along the lines, this worked surprisingly well.

		Door fixed in place with pop rivets. Bear in mind you don't want to position the rivets so that their back-sides will prevent the door from closing fully.

Stage 3 - Door Air Regulator

	After carefully marking it all out this piece was first crudely cut out with the hacksaw at some rough angles. The shape could then be refined with some files	The centre holes are cut out by firstly removing most of the unwanted metal with a drill. With hard metal like this stainless steel it's much easier to make small holes first then increase the drill bit size.


		Holes refined with a small half-round file


	Complete piece with the handle bent into shape	Now the design needed to be marked out onto the door and the appropriate parts cut out in the same way



		Finally a centre hole is drilled and the piece is secured in place with a pop-rivet. To ensure it is not too tightly secured a folded piece of paper is placed between the two pieces before riveting, it is then ripped out afterwards. This will make a snug fit but will allow the regulator to rotate.
	The finished regulator


Stage 4 - The Door Latch

	To make the door easy to open and to save burning fingers, i made the latch knob from a piece of hardwood (Holly to be exact). I'ts just fixed in place with a small screw.	These pictures should be fairly self-explanatory. I Fixed the latch in place in the same way as for the air regulator so that it could rotate...




Stage 5 - The flue damper/ baffle


	This part could be improved upon, but here's what I came up with... It's made from a food can lid and a piece of thick wire,

	Using a pin I made this series of holes	With a sharp knife I then cut from one hole to its neighbouring hole to make a series of slits.

	The metal is then forced either way to allow a metal rod to be inserted through the middle. A hammer and bit may be needed to persuade the metal into shape.	The damper before being installed with wire control handle


	The damper is located in the first piece of flue pipe. To accommodate it a hole needs to be drilled through. I then balanced the round piece of tin on top of a thick piece of dowel and passed it up the flue pipe to the exact point where I needed to pass the wire handle through the holes in the flue. The handle was then shoved all the way through both the the flue and tin disk.	Once in place I forced a small shim of metal between the wire handle and the tin disk so that they gripped each other more firmly. Look carefully at the picture on the left, you can see it at the centre.

	I bent the wire handle on the other side too to make it balance correctly. a damper is no good if it keeps falling open... Also, the tin disk inside is aligned parallel with the handles so that you can tell the position of the damper from the outside.	If a greater through-flow of air is needed the handles are simply positioned more downwards. This system is really effective.


Stage 6 Sealing the Lid


	The rubber seal from the inside of the lid needs to be levered out with a screwdriver and replaced with a length of fire rope. This will ensure no smoke escapes. Do this towards the end of the project rather than at the beginning like I did.



Stage 7 - Legs


		You could make legs in several ways. Bear in mind they will need to hold the stove high enough as to not heat the ground too much. with not having access to a welder this is what I came up with. Each leg is made from a section of metal pipe. I flattened the ends in a vice and bent them into position. I drilled a hole in one end which is used to bolt them the the base of the stove. In each corner on the underneath of the stove I drilled a hole and threaded a bolt through. Onto each bolt went a large washer and a nut to hold things permanently in place. When setting up the stove I simply slot the legs onto the bolts and tighten them down with wing-nuts. This way the legs can be removed and stored inside the stove; making it more portable. In future I'll consider changing these legs for something more robust. Currently these are a little springy...


Stage 8 Firing up, burning-in and painting

	When the stove is complete, assemble with all sections of flue pipe then light a fire inside. Get it really hot! Have both air regulators fully open. Burn for long enough that all original army green paint peels off. When cooled, use sand paper or wire wool to remove all the paint residue right back to bare metal. Now you can spray paint the whole thing with heat-proof stove paint. This will protect the metal from rusting. If you didn't remove all the original paint then your new stove paint will eventually peel off in patches.

	I also decided to add a grate inside the stove to lift the fire off the bottom somewhat. I made this simply by taking the mesh from a disposable BBQ, bending down the edges and putting it inside. It was a perfect fit without any cutting! With the fire not in direct contact with the bottom, maybe this will extend the life of the stove. NOTE: I have since learnt that many people recommend putting an inch or so of sand (or mineral soil - soil containing very little organic matter) in the bottom of the stove. With repeated use over the long term, without such protection the fire can eventually burn a hole in the bottom. this layer of sand will greatly help with extending the life of the stove. If necessary, the sand can be carried in a bag with the stove and spread out inside when the stove is assembled.


	The finished stove inside the bell tent. Get the kettle on! Notice I have put the stove on a slab of slate to prevent burning the ground sheet of my tent. Not exactly a light-weight solution but heat proof mats can be purchased which weigh very little.
	Fitting the stove in a tent
	Only fit a stove inside a tent which is compatible. Make sure there is adequate ventilation! There must be properly sized air vents in the tent at high and low levels to allow good air circulation. This is important to allow a good supply of oxygen to the fire for complete combustion. A lack of oxygen will result in incomplete combustion meaning that carbon monoxide will be generated; if this happened you'll probably fall into a deep sleep and never wake up... Use your common sense (e.g. don't position the stove too near the tent walls). Seek advice from the company who sold you the tent. Be responsible for yourself. Do some of your own research. You can buy a purpose made 'flashing kit' made for safely passing the stove pipe through the tent roof. I purchased mine from this website: http://www.belltent.co.uk/truly_portable_wood_burning_stove (see the option for buying the "flashing kit only")



	Notes on operating the stove Simply put, it's just a case of opening up the air regulators on the door and in the flue according to how hot you want the stove to burn. Generally I open and close the air regulators to a similar amount at the same time. The first couple of times you light the stove, do it outside of the tent and learn how it works. You don't want any problems on your hands inside a canvas tent! Sometimes a back-puffing problem can occur which is explained below: - Back-puffing problem I have found that operating this small stove is a lot different to a larger 'log burner' which you'd have in your house. I have sometimes experienced a problem called 'back puffing' which is where the stove starts spluttering smoke out of the door and front vent (This could be caused partly by poor design, I'm not sure). Back puffing can be caused by many things but usually I have found that it's because I got the fire burning really hot and then shut down the air regulators too quickly. The result it that the fire suddenly becomes starved of oxygen so it pulls oxygen in from wherever it can, including down the chimney! This pulls smoke with it, then when the smoke and oxygen reaches the fire it temporarily bursts into life which forces all that smoke out of any gaps in the door. This 'back puffing' can get into a continuous loop because after one 'puff' the fire immediately needs more oxygen and so pulls more oxygen down the chimney and the cycle repeats itself. Reading some info on the internet also reveals that back puffing can also be caused by a cold flue pipe which makes for a poor upward draw of smoke. If your stove back puffs, try opening up the air regulators again and then shutting them down very slowly over time. Also I have found that sometimes it's only wise to open the door when the fire has died back; like when putting more fuel on. You don't want the fire getting used to a level of oxygen that can't be maintained when the door is suddenly closed. Also It may help to keep the fire burning at a modest heat rather than banking it up and burning it like crazy! I recommend lighting your stove while it's not in the tent and practicing how best to operate it. with some practice these problems wont occur, at least not very often...

	Have fun and stay safe!


	Useful links: Recommended bell tent and stove companies: http://soulpad.co.uk/ http://www.belltent.co.uk/