Diy Jerry Can wood burning stove

[Barkclark]

Hi, new to this forum, so I don't know if this is the right forum / place for this, but I have just completed a diy wood burner from scrap metal I found around work etc. I work as a stonemason and this little project was an idea to heat up a little cutting shed in winter that I'll be building.

Question I have is that when I close the door on the stove (granted I know it's got gaps which I'll fix) it starts to smoke exponentially and the fire rapidly starts to die out! Do I need more air intakes underneath the fire? I have three holes already but I don't know if it's enough? I still have the jerry can spout in place, then the tin cans placed round it, which maybe isn't large enough to let the smoke escape? Should I cut the first tin to fit into the jerry can for the bigger diameter flue?

I was going to install a baffle to direct as much heat to the jerry can handles for cooking on, but I imagine installing this at this stage would make the smoking worse!

So far I have to keep the door open which is just as useful as an open fire and doesn't conserve the wood.

As I say I'm new to this and I basically haven't a clue haha. So any ideas / help would be much appreciated!
Many thanks,
Simon

 

[mick91]

Definitely increase the flue diameter. Probably pay you to have more holes to draw air too, I had similar problems because I used car exhaust for the flue, switched over to 4.5inch bore and that draw will suck the slippers off your feet now!

 

[S.C.M.]

Do you have a grate in your stove? or is the fire lit directly on the bottom? If you don't have a grate, try adding one, then a few more holes in the bottom for air feeding, try a larger flue... as regards to the baffle, I don't think it will really negatively affect draw except maybe when you light it. Maybe you could bodge up a removable temporary one and find out whether it's worth it.

Welcome to the forum, Simon, don't be shy, there's an introduction bit/thread/subforum good luck with your stove!
Sam

 

[Barkclark]

Double post

 

[ged]

Make sure there's plenty of ventilation in the shed when you eventually use it in there. We don't want you to be another CO statistic.

The flue needs to be bigger in diameter, clear of all obstructions and a lot taller. The way you have it now, it will tend to burn up too quickly if the flue is adequate as there will already be too much air getting in.

The way then to stop the fire overheating is to prevent air getting into the firebox, not to prevent it getting out of the flue.

 

[Barkclark]

Stainless steel grate and current size of the flue exit shown below;

 

[Barkclark]

Thanks for the replies. I have a stainless steel grate to elevate the fire above the air intakes, which I'll add more of. As for the flue, I'll remove the jerry can spout and make the exit the same diameter as the tin cans to see if that helps? Also the flue is a work in progress as I am increasing the height as I go!

As for the baffle I'll give a removable one a go to see what happens!

A CO detector will be present when it's in the shed. Also the shed will be well ventilated as there will be use of grinders etc.

Cheers Simon

 

[mrcharly]

Yeah, I think the problem is the flue outlet.

You might find the wood burns away very quickly without soem way of reducing air intake.

 

[Barkclark]

I think I'll sort out the size/restriction in the flue exit, and increase the flue length first to see how that helps things? Or do your recon tin cans are too narrow in the first place? I'll then move on to the air intakes afterwards.

 

[richardhomer]

Love it mate!

 

[ged]

I think I'll sort out the size/restriction in the flue exit, and increase the flue length first to see how that helps things? Or do your recon tin cans are too narrow in the first place? I'll then move on to the air intakes afterwards.

I think the tin cans are probably just about big enough in diameter for that size of stove - I'm thinking it's about three inches? But it needs to be clear all the way through and the neck of the jerry can is an obvious constriction.

Probably better if you can keep the flue as straight as possible too, or failing that make any bends smooth curves of large and radius rather than sharp corners.

I don't think tin cans are going to last very long, I suppose insulating the flue is out of the question?

 

[bobskie]

Looks great! I build one from an old patio heater cover a while back, starting to crack now so can't really use it anymore but it was great at the time! I have a spare jerry can laying around never thought of turning it into a stove so maybe an option for me now.

 

[Barkclark]

I think the tin cans are probably just about big enough in diameter for that size of stove - I'm thinking it's about three inches? But it needs to be clear all the way through and the neck of the jerry can is an obvious constriction.

Probably better if you can keep the flue as straight as possible too, or failing that make any bends smooth curves of large and radius rather than sharp corners.

I don't think tin cans are going to last very long, I suppose insulating the flue is out of the question?

Yeah the tin cans are about 3 inches! Once I cut into the jerry can at the spout, to widen it, I can rectify the first sharp bend with a straight flue section! As for the tin cans not lasting long, it won't really be much of a problem as they are readily to hand / easily replaced. Although saying that I have quite a few coffee cans of the same diameter, three already part of the flue which I believe are made from steel!

How do I insulate the flue? What are the benefits?

 

[Barkclark]

Looks great! I build one from an old patio heater cover a while back, starting to crack now so can't really use it anymore but it was great at the time! I have a spare jerry can laying around never thought of turning it into a stove so maybe an option for me now.

Go for it. I'm on this forum to get as much help as I can to over come several problems with the functionality of the stove. If you follow my thread, it may help you in the future to avoid the same problems if you go ahead with your build ☺.

Not found many sites through Google search about a jerry can wood burner so getting it working as efficiently as possible is trial and error so far. I originally had the idea of making a stove from a 10L mini beer keg, and there's plenty of sites where I could of copied the design knowing it would work perfectly!

The reason I started my jerry can build was that I found the jerry can in the scrap pile at work and just built it with the first bits of scrap metal that came to hand! Total cost so far has been £9 on paint!

 

[ged]

Yeah the tin cans are about 3 inches! Once I cut into the jerry can at the spout, to widen it, I can rectify the first sharp bend with a straight flue section! As for the tin cans not lasting long, it won't really be much of a problem as they are readily to hand / easily replaced. Although saying that I have quite a few coffee cans of the same diameter, three already part of the flue which I believe are made from steel!

How do I insulate the flue? What are the benefits?

I think the tin cans are really tinned steel. I just meant that they're thin steel, they're not stainless, and they will eventually rust through.
If you're going to use this as a semi-permanent fixture in your shed you probably won't want to be messing with it all the time, especially in winter when you'll want it to be working overtime!
You might be able to pick up some scrap stainless pipe from somewhere if you keep an eye out for such stuff.
It's not common like scrap mild steel but you do see the odd bit here and there. I once picked up a metre of 200mm diameter stainless flue when I was out with the dogs!

There are several ways to insulate it. You can wrap some heat-resistant insulating material (e.g. from a plumbing supplies merchant) around the flue, or encase the flue in another flue of bigger diameter and then fill the space between them with some heat-resistant insulation.
The outer doesn't get attacked by flue gases and condensates like the inner does so it can more or less be anything that won't catch fire. There are things that you can just pour into the space.
Some of the insulation materials can be a bit expensive if you get them from e.g. places that sell log burners for use in homes.
I wouldn't necessarily recommend insulating your tin cans though, the flue inner needs to be pretty well leak-proof so the insulation doesn't get soaked in combustion products, which would be bad news in lots of ways.

The main advantage of an insulated flue is that condensation (mostly tars and water) is much reduced. It's also cooler on the outside so it's safer if something touches it accidentally, and better for running through e.g. the roof.
Water rusts your flue and possibly the stove, tars can build up and cause flue fires or even blockages.
The draw is also better in an insulated flue as the flue gases keep hotter as they go up the flue - so they're less dense than they would be if they were cooler. That might be important for a short flue.
If you run an uninsulated flue through the roof you'll need something to prevent it from setting the place on fire of course.

The ready-made insulated flues that you can buy are expensive. My flues cost me as much as the wood burners they serve, or even more.
They were worth it though, I wouldn't have it any other way. If I think the flue needs cleaning I just make a big fire!

You might want to run all this past the local building inspector, if you put a heating appliance into a shed you're getting into regulated territory.
If you're in a Smoke Contol Area where wood-burning appliances are covered by air quality regulations you might also need to look into that.
One of my wood-burners had to be certified to some standard I can't remember right now.
http://smokecontrol.defra.gov.uk/appliances.php

 

[bobskie]

Here are some pictures of the stove I made, all materials were free and it lasted around 2 years of use nearly every weekend before it started to crack. It is held down by a stake in the back to keep it down and the chimney comes off for portability, of course it's still rather large but it was carried in a camper van so it was fine! I will maybe make a jerry can stove to replace it was also thinking about an empty gas bottle. Il get round to it one day!

 

[mrcharly]

Zinc fumes are not good to breath in - so having a flue made of tin cans that you are constantly renewing might be bad for your health!

 

[Barkclark]

Here are some pictures of the stove I made, all materials were free and it lasted around 2 years of use nearly every weekend before it started to crack. It is held down by a stake in the back to keep it down and the chimney comes off for portability, of course it's still rather large but it was carried in a camper van so it was fine! I will maybe make a jerry can stove to replace it was also thinking about an empty gas bottle. Il get round to it one day!

Good work! Looks cracking!

 

[Barkclark]

Wow ged cheers for all that information! It's going to help out a lot! Yeah stainless steel pipe is really the ideal solution for a flue. I suppose I'd need to weigh up the pros and cons to insulated or non isulated flue!

Mrcharly, zinc fumes didn't cross my mind. Would they burn off after the initial burn or would it be a reoccurring scenario each burn?

Does anyone know what material coffee cans are made of? The likes of nescafe / millicano? I have plenty of those, some of which already part of my flue!

 

[ged]

Wow ged cheers for all that information! It's going to help out a lot! Yeah stainless steel pipe is really the ideal solution for a flue. I suppose I'd need to weigh up the pros and cons to insulated or non isulated flue!

Mrcharly, zinc fumes didn't cross my mind. Would they burn off after the initial burn or would it be a reoccurring scenario each burn?

Does anyone know what material coffee cans are made of? The likes of nescafe / millicano? I have plenty of those, some of which already part of my flue!

Zinc burns off pretty quickly at a high enough temperature, on galvanized stuff it's only a thin layer. Once it's gone it's gone. You'll see a powdery whiteish zinc oxide coating and usually some yellowish crud looking like sulphur which will all brush off easily.

Most cans will be steel, usually plated with tin. Another common material is aluminium - many soft drinks cans for example. Some are a mixture, e.g. a steel can with aluminium lid. Use a magnet to check, if it's aluminium a magnet won't stick to it.