Wood Burner help

[k13wjd]

Right then, another wood burner topic :

Here's where i'm at. 47kg calor bottle, top cut off, 4.5 inch mild steel pipe welded directly on top.

Double A4 size door with hinges about 10 inches up, sealed with stainless plate.

Handle that was removed is inside with a grate sat on top....Whole thing is welded onto a 14 inch steel wheel, with a slot cut out. The bottom of the bottle has a 4 inch hole cut, and a slightly larger peice of steel is held in place with a peice of flat bar. Purely for easy of cleaning ashes.

Air intake to rear @ 4x2 inches

Choked intake at front from 2.5 inch exhaust pipe.

It burns well, but i think it could be better.

Should i weld in a baffle ( perhaps a brake disk covering half the flue ?

should i weld another pipe to the inside of the 2.5 inch exhaust pipe, heading half way up the primary chamber, to form a secondry heated intake ?

ANY advice very welcome !

 

[k13wjd]

the air intake is to the rear.....hence you can't see it.

 

[DrNik]

hi, a lot of your heat is going straight up the chimney you need to maximise the surface are of your fire and or flue, when i made my heater i used 6 tubes in a ring and had fresh air flowing through the tubes and the smoke/heat up the middle, that way each of the pipes sidewall makes up the centre tube

you could have a fan blowing the air from the top down the pipes and directed toward the area you want hot

if my picture is crap i'll take a picture of my flue

 

[DrNik]

you could weld bits of scrap metal on the chimney and then put an oil barrel over chimney and add a fan to blow warn air toward you,
also you'll probably find it burns it t*ts off, as it draws hard like smoking a roll up, cutting the air right back will conserve wood, but get a carbon monoxide alarm, just in case you starve it of air and your workshop fills up with fumes

 

[Shedendman]

This will give you a general idea how woodburners work or should work.
It all boils down to getting your secondly burn this is where your burner will be most efficient.
http://autonopedia.org/crafts_and_technology/Woodburners/Wood_Stoves_Part1.html

Theres no need for any fans nor grates wood burns best on a bed of ash

 

[Shedendman]

Actually,just like to correct my last statement,wood doesn't burn,its the gases that's contained in the wood burns

 

[Dev]

When it's That tall i'd have at least 2 evenly spaced plates half the size of the cross section so the hot air has to 'snake' up. The longer you can hold the heat while allowing the smoke to rise the hotter it will burn.

 

[sparkysy]

easy k13
i'm making a 47 super stove at the moment first one! the smaller ones I've made i cut the top off and welded a plate inside on an angle with about a 2.5"gap at the front and the flue out the rear with another plate welded on the top for a hotplate this works well keeps much more heat in the fire and slows the burn down! i will try and post some pics when i can work out how

 

[k13wjd]

I keep hearing this " wood burns best without a grate, and with air from above"

I tell you what, it doesn't have burn fast when the air comes from under, with a grate. Like mega fast. I'm burning 4x4 fence posts, it'll chomp through 3x1ft lengths in 15 mins.


Anyway, i'd love to know the maths behind picking a size for the intake - i'm going to weld up the 4x2 slot i cut in the rear, and cut a new one in the front.

also going to make that small pipe you see on the left into a secondry intake, by welding pipe onto the inside, and up the bottle. baffle plate will have to wait for another day.

Who knew making a stove would take so much research ! Mark 2 will have the chimney to the rear, BIG mistake in putting it directly ontop, as hotplate is now much more difficult to make !

 

[k13wjd]

http://www.autonopedia.org/renewable_energy/Woodburners/Wood_Cook_Stove_Design.html

PRINCIPLE EIGHT:

Use a grate under the fire. Do not put the sticks on the floor of the combustion chamber. Air needs to pass under the burning sticks, up through the charcoal, and into the fire. A shelf in the stove opening also lifts up sticks so air can pass underneath them. When burning sticks, it is best to have them close together and flat on the shelf, with an air space in between each stick


So by having a grate under fuel, and air entering UNDER the fuel, its effectivly pre-heated prior to being mixed with the gas for combustion. Surely thats got to work better than flooding the wood with cold air from ontop ?

 

[outofthefire]

http://www.autonopedia.org/renewable_energy/Woodburners/Wood_Cook_Stove_Design.html

PRINCIPLE EIGHT:

Use a grate under the fire. Do not put the sticks on the floor of the combustion chamber. Air needs to pass under the burning sticks, up through the charcoal, and into the fire. A shelf in the stove opening also lifts up sticks so air can pass underneath them. When burning sticks, it is best to have them close together and flat on the shelf, with an air space in between each stick


So by having a grate under fuel, and air entering UNDER the fuel, its effectivly pre-heated prior to being mixed with the gas for combustion. Surely thats got to work better than flooding the wood with cold air from ontop ?

Sorry but its not how log burners work, they are essentially just a steel box. If you have air flow from underneath, the wood burns to quickly and you stand a good chance of having a chimney fire. Ideally you need a baffle in the flue and air vents in the door, they start to work best once there is a layer of ash in the bottom, once the fire is going you close down the vents and the logs smoulder away releasing heat, there's some useful info here http://www.villager.co.uk/public/pdfs/Villager_Owners_Manual_2010.pdf

and if you need inspiration have a look at this thread http://www.britchopper.co.uk/forum/viewtopic.php?f=78&t=37483

 

[k13wjd]

Ill remove the grate as I mentioned, and Weld up my bottom vent. 3 inch primary ok? And 2.5 secondry. As I said, a pipe welded inside and traveling up to about 2/3rds the heigh of the bottle?

cheers for the advice guys. Burning pallets probably isn't gelping, it chews through the try timber like nothing ive ever seen before!

 

[outofthefire]

Burning pallets probably isn't gelping, it chews through the try timber like nothing ive ever seen before!

Thats why you need the baffle in the flue and closable vents once its lit you need to limit the oxygen, a log burner is pretty much a charcoal burner. While you've got flames roaring your wasting wood and a lot of the heat is going straight up the flue.

 

[normspanners]

From my experience I usually have the chimney travel throught the cyl 200mm ish if going in throught the top, with a plate over the end spaced off, to stop flames going straight out, so that the heat travel past it, to the roof of the cyl, the heat is then lost to the cyl, but the smoke has to pass back through the heat to get out, helping reburn any gasses that have been dragged up but not burnt. because as stated before the hot wood creates gas which then burns. You can have the air passing the wood as in rocket stove but the wood would be burnt VERY quickly. As is happening with your pallets.
The thing is, more fire= more cold air drawn in from outside and through the fire, cooling the fire and flue = you being colder.

 

[ben8vgte]

Sorry but its not how log burners work, they are essentially just a steel box. If you have air flow from underneath, the wood burns to quickly and you stand a good chance of having a chimney fire. Ideally you need a baffle in the flue and air vents in the door, they start to work best once there is a layer of ash in the bottom, once the fire is going you close down the vents and the logs smoulder away releasing heat, there's some useful info here http://www.villager.co.uk/public/pdfs/Villager_Owners_Manual_2010.pdf

and if you need inspiration have a look at this thread http://www.britchopper.co.uk/forum/viewtopic.php?f=78&t=37483

Yeah thats very true, my homemade log burner in the house was first made with a grate and air vent underneth (with door). But after a while of using it we found that if let a 2" deep bed of nails build up (from burning pallets) on the grate, it would hold the ash mostly and with the bottom door shut burn longer and much hotter. It just gets it's air now form leaks around the doors, we just open the one under the grate now to light it up. If the ash builds up a little high a quick tap with the poker allows some to fall underneth.

 

[Shedendman]

I think we could all agree to disagree with each other here.
So i think a bit of back to basics can be explained here

Also loads of usefull info on here
http://www.stovesonline.co.uk/stove_help_and_advice.html

Not that most of us really give a damn going in your freezing cold shed/garage/workshop.............1st things 1st,getting that fire on

MOD Edit - link removed at request of destination site.