Help needed with oven please

[takjaa]

Hi guys, I could really do with some help,
whilst out in the woods recently I thought it would be a great idea to try and build an oven out of an 55gal oil drum to cook a FULL roast for a group of around 12 friends.
in my head this seemed very simple . . dig a pit for fire - cut one end off drum (clean it out) - add a grill shelf - place drum over fire - add chimney to rear - cover most of it in mud . . tadaa!! ready for meat, goose fat spuds, honey glazed parsnips & yorkshire puds . . has anyone tried this?
as i said in my head this works perfect but after a few hours of google searching iv not found very much that resembles it but i did find someone asking about sealing the door . . uh oh didnt think about that
This is were you exceptionally smart people come in
does the oven sound like it would work?
any ideas on the door seal?
any ideas in general that would be better than mine?
Thanks guys any and all help with this would be much appreciated

[charleslockerbie]

You are essentially making a dustbin oven where an old metal dustbin is used. they do work tho ive not made one since i was in the scouts. the chimney does not go on the drum but at the end to create airflow threw the fire.

http://www.woodcraftschool.co.uk/img...ry-cooking.pdf has a description of them. But you have the idea already, enjoy the roast.

[takjaa]

thats a good link thanks v much! Im feeling a bit more confident ill pull this off now still a bit worried about the door situation tho!?
And would the oven need some sort of vent?

[charleslockerbie]

When i cant remember sealing the door, but its not to bad a seal on a dustbin. If its a neat fit im sure it would be fine and i dont think there was any vent, all i can see it doing is lowering the temp and slowing the cooking down.

[takjaa]

wicked cheers charleslockerbie, the camp roast is planned for 2 weeks time so fingers crossed! pictures will follow

[chas brookes]

Hi Takjaa
this is the oven we use made out of dustbin, fire is lit underneath with chimney to the rear. The lid is held closed by a pole held by some pegs. No vent required on oven all you are doing is drawing the heat under and around the oven.

[takjaa]

thats awsom! how long did it take to cook your meat?

[chas brookes]

Hi Takjaa
I think those two joints took about 2 hours.
The key is to have the firepit in the front deep enough to allow the heat to be drawn under the oven, they are very efficient.

[ged]

The main problem with thin steel containers is that they don't last very long when you start making fires in them. Acids and other corrosive combustion products condense on them and then they rot a lot more quickly than you'd expect. Clay ovens work just as well if not better, you don't have to lug any steel around, and they're free.

[tim_n]

Build Your Own Earth Oven: A Low-Cost, Wood-Fired Mud Oven, Simple Sourdough Bread, Perfect Loaves
Does roasts too... good book.

Got mine of fleabay for £10 inc P&P

[Matt.S]

It seems to me that most ovens are/were built so the flames and fumes were kept seperate from the food -- for obvious reasons. The main exception to this I can recall is the old style bread oven which was essentially a brick alcove -- faggots were burned inside the oven to heat the bricks, the ashes raked out and the food then baked in the radiating heat.

[brancho]

Make sure the fire hole is big enough as this took forever to warm up because ours was too small but work great when heated. I dont think the wet weather and mud covering helped.

[bilmo-p5]

It seems to me that most ovens are/were built so the flames and fumes were kept seperate from the food -- for obvious reasons.

... and what 'obvious reasons' might they be, then?

Take your average domestic gas oven for starters. Where does all the fuel burning happen?

In the bottom of the oven; so all the by-products of burning gas (primarily heat, but some lethal nasties too,) are free to waft about your grub on their way to the flue/vent.
At a more basic level; consider the portable camp oven - Coleman do a particularly good folding model which I've been using successfully for years - all the fumes heat etc. from the heat source go straight-up into the oven, past your food and vent out the top, with no apparent detriment to its contents.

With fire or stove, if the food tastes of smoke or fuel then the heat source is at fault. Simple as that! If the fuel, whatever it may be, is burning correctly it won't taint the food.
You may have seen range-type stoves with ovens to the side of the firebox, and totally sealed-off from it, This isn't because the products of fuel combustion will affect the food but because stove builders discovered that the draft induced by a chimney or flue could be utilised to drag the hot gasses under & around an oven, thus obviating the need to have the oven directly above the fire. An 'open' oven doesn't easily lend itself to this.

[Matt.S]

You make some very good points Ian, and you seem to have a more in-depth knowleddge of ovens than I do. Surely though separating the fumes from the food is a good idea since it allows more margin for error in fire construction?

[takjaa]

you guys are all legends for the help you've given me! the pictures really are awsome! & now I have that kiddy '1 week till Christmas' feeling about the camp roast

[Whittler Kev]

Please remember not to use galvanised stuff as when it heats up it gives of fumes. I think they are arsenic fumes, but I may need correcting. I know on a Youtube vid about making a gas furnace an American guy died from the fumes welding galvanised steel!

[Matt.S]

Please remember not to use galvanised stuff as when it heats up it gives of fumes. I think they are arsenic fumes, but I may need correcting. I know on a Youtube vid about making a gas furnace an American guy died from the fumes welding galvanised steel!

Zinc oxide to be precise. I don't know if it was the same chap but the blacksmith Paw Paw Wilson died from complications from breathing galvy fumes. Wasn't a short or painless death either.

[Whittler Kev]

Zinc oxide to be precise. I don't know if it was the same chap but the blacksmith Paw Paw Wilson died from complications from breathing galvy fumes. Wasn't a short or painless death either.

Thanks for the correction. Yep that's him. Paw Paw died very nasty (incurable because of the fumes) , agonising death....look him up.
http://www.anvilfire.com/iForge/tutor/safety3/index.htm

[ged]

Please remember not to use galvanised stuff as when it heats up it gives of fumes. I think they are arsenic fumes, but I may need correcting. I know on a Youtube vid about making a gas furnace an American guy died from the fumes welding galvanised steel!

Zinc oxide to be precise. I don't know if it was the same chap but the blacksmith Paw Paw Wilson died from complications from breathing galvy fumes. Wasn't a short or painless death either.

Thanks for the correction. Yep that's him. Paw Paw died very nasty (incurable because of the fumes) , agonising death....look him up.
http://www.anvilfire.com/iForge/tutor/safety3/index.htm

There's a lot of useful information here.

Especially scroll down to a question on 10 August 2008 and the reply.

I do quite a bit of welding. Sometimes I weld galvanized steel although I do try to avoid it. There's a big difference between the temperatures used in metal forming/welding and those used in cooking, even over an open fire, so the problems associated with welding galvanized steel are very different from what we're concerned with here. As far as I'm concerned when I weld galvanized steel the main problem is getting a good weld. When the zinc boils off it produces a lot of smoke but I do a lot of 'stick' welding and that produces horrendous fumes, so good ventilation is essential anyway. I usually see a yellow-coloured coating that looks like sulphur on the metal near the weld after the zinc boils off. I don't know if it is sulphur, in fact I'd have expected sulphur to have burned off, but I don't like the look of it whatever it is.

I don't think zinc oxide is very toxic but I haven't studied it. In the doses that we normally consume, zinc isn't toxic -- in fact it's necessary for life -- but when we start messing around with huge doses, who knows what's going to happen? I do know that burning wood produces very toxic fumes and I'd be a lot more worried about that than about a bit of zinc or (most of) its compounds.

The zinc that's used for galvanizing might contain other elements, including arsenic, cadmium and lead for example, all of which are known poisons which can accumulate in the body over long periods of exposure to low doses. I think that you're very unlikely to suffer in that way from cooking in a dustbin for a weekend. A few years ago I went to see my doctor as a precaution because I was melting a lot of lead (tonnes) for boat ballast. I was concerned that lead vapour might make me mad as a hatter. He told me that the major route into the body for lead is by eating it, not by breathing it, so not to worry if I take sensible precautions.

It makes a lot of sense to avoid breathing and eating combustion products. I think over-cooked (browned and burnt) food is probably at least as dangerous as anything you're likely to encounter from these ovens.

[takjaa]

...hmmm . . . anybody know if 55gal oil drums are galvanised?

[charleslockerbie]

oil drums are unlikely to be galvanised, but it is possible. Does it look galvanised?, on the bare metal does it have a patchy or a smooth experience?

[ged]

...hmmm . . . anybody know if 55gal oil drums are galvanised?

If it isn't galvanized it will probably be painted. Most unlikely to be both galvanized and painted, so if it's some colour like green or red or blue or black then it's very likely not galvanized. Zinc is a dull grey colour, a bit like dull aluminium. There will usually be runs and spots, it behaves a bit like raindrops when the steel part is lifted out of the molten zinc bath and then it freezes. Zinc is much softer than steel, you can scrape it off galvanized steel with a knife where it's thick enough. It comes off in little curls like a tiny feather stick. Don't do it if you don't want to damage the galvanizing. Some things are zinc plated, it's a much thinner layer of zinc than galvanizing and it looks even more like aluminium. It tends to be a bit shinier. It weathers/burns off much faster than proper galvanizing.

If it isn't galvanized and also isn't painted, it's probably made of polythene.