probably done to death, but a few questions - Gas Bottle Burners..

[paulmitchell1984]

Ow do!

right iv been asked to do a gas bottle burner for a friend, iv done one for me which does the job but i want this to be better as its showing what i can/cant do. I will be using one of the 15kg bottles

so my questions are

1) - whats the best size chimney/flu to use, length and bore, should this go into the burner or sit on the top of the bottle?
2) - to make it multi purpose ie burn wood/coal/paper would i be better with 2 air vents, one above fire tray and one below.
3) - what would best size be for these inlets? should they go through the bottle or just be welded to the outside face
4) what would be better for sitting fire on a tray with holes in or a grill...or a removable tray ?



heres an image of the basic idea (hopefully), any suggestions/improvements ?

 

[sardine]

Wood burning doesn't need a grate, it prefers a nice deep ash bed to gasify it, and the gasses ignite above the fuel, where it draws the air in. Coal draws its air from under a grate. A 15 kg bottle would need a 100 mm flue minimum. An ash dump door in the base is a good idea, put a metal bucket under there ?

Remember to burn off all the galvanising out side before you use it, and don't breathe any of the fumes.

 

[paulmitchell1984]

im going to do the ash drop with a latch as dont want air to get in from there..

im assuming you mean the size of width for flue not the length lol.

i may just make a tray for the coal/wood then with air holes drilled in, do we think it would get hot enough to warp 3mm steel? or would a thicker base be needed.

yeah i know about the galve burning usually light a fire get it going well and walk away so not to inhale it.

thanks for reply

 

[sardine]

If you want a grate in it, you need 10 mm thick bar, sheet metal will just burn out , especially with coal.

Have a sliding plate over the ash dump ?

 

[paulmitchell1984]

10mm bar should be easy enough to sort..so if it was just a log / wood burner, what do people do just burn in bottom of the gas bottle?

not a bad idea for the plate on ash dump, hmm got another idea now

 

[slim_boy_fat]

*Cough, cough*......what about a door?

 

[pedrobedro]

*Cough, cough*......what about a door?

You drop stuff in down the chimney

 

[paulmitchell1984]

Do need a door?

Yes I know I need a door but I figured that would be fairly obvious so didn't draw one on...

 

[pedrobedro]

Do need a door?

Yes I know I need a door but I figured that would be fairly obvious so didn't draw one on...

I'd have said it's round the back

 

[fenman]

Top vent could be a door

 

[CompoSimmonite]

Have a look at outside cast iron grids for a fire heath. I found a large size (around £3) was just the right size for a gas bottle. Obviously they are square so you still need "wings" on the supports that are attached to the sides of the bottle.

 

[slim_boy_fat]

Do need a door?

Yes I know I need a door but I figured that would be fairly obvious so didn't draw one on...

It's just that some incorporate opening vents in their door design - saves more holes in the body.

 

[Wendelspanswick]

You really need a rope seal on the door to control the air supply, otherwise even if you shut the air vents it draws air from around the door.
An internal baffle below the flue helps distribute the heat to the body and stops all the heat shooting up the flue.

Mind you my 15kg burner is a bit of a disaster,
Rope seal round the door.
Nice long flue run.
Air control at base level and in the door.
Baffle plate below the flue.
Problem I have is once the fire gets going, and the air control is open it starts 'breathing', sucking in air and belching flames back out the air control like a pulse jet!
It sends foot long flames out the front.
I have increased the size of the air control and the gap between the baffle plate and the body but it hasn't improved it much.

 

[Screwdriver]

I tried a few flue sizes on mine.

Six inch draws like a doodle bug and sounds for all the world like a pulse jet engine. Whole thing gets red hot.

Four inches and it hardly goes at all, flame waft around listlessly.

Five inches happens to be the bore on an old motorcycle cylinder liner which does the job perfectly. You could always fit a damper but I never bothered.

Mine is a stove top heater so there's a baffle inside to force the flue gases to wash over the bottom of that top plate. Door overlaps and seals adequately without any other sealing required, primary air inlet is a strip with holes and I didn't get round to fitting a secondary air burner in the top.

I just burn wood on top of ashes so there's no grate and made a scoop from the scrap donor cylinder.

S.

 

[slim_boy_fat]

^^ So your kettle's always hot then?

 

[pedrobedro]

Have a look at outside cast iron grids for a fire heath. I found a large size (around £3) was just the right size for a gas bottle..

Cast iron drain grates are available for not much money in various sizes and will last longer than steel bars. Builders yards have them under £10.
If you leave the kettle on it will be like a sauna in the shed

 

[paulmitchell1984]

cheers guys, may but in a baffle to help things along then, should this be a certain percentage of the width of the bottle? ie half way accross, 3/4 away etc

 

[Screwdriver]

Aperture should be the same area as the flue.

 

[paulmitchell1984]

sorry? not following that ?

 

[Paul99]

The baffle should close off most of the top of the bottle leaving an aperture with a cross sectional area equal to that of your flue pipe above. E.g. a 5" flue pipe needs an aperture in the baffle of about 3.14 x 2.5^2 square inches etc to maintain best possible draw. In reality it doesn't need to be anywhere near that accurate unless you are deliberately targeting maximum efficiency over it being just a functional workshop heater. Personally I'd probably see what works best through a bit of trial and error.