Rocket pizza oven from 55 gallon drum

[timmy]

G'day guys....

       I've been lurking around here for a while looking at ideas and thought I'd put my idea up here for comment.


Basically I want to create an outdoor pizza oven that is powered by a rocket stove but also has some thermal mass to keep temperatures more stable. I will be cooking pizza in there but I also want to use it for bread and roasts. Here's the basic design idea:

55 gallon drum (known as a 44 gallon here because we favour archaic UK measurements lying horizontally with:
A lining of 115x230x25mm firebricks + refractory mortar
2 slidable steel grate shelves that will hold some 25mm thick clay pavers to use as pizza stones
J-shaped rocket made of 150x150x3mm square steel tubing that will feed into one end of the oven (at the rear)
A chimney at the front of the oven
A hinged door at the front.

Basically I'm looking at a cross between this: www.firespeaking.com/products/barrel-oven/ and the Aprovecho oven but I want to have the smoke entering the cooking chamber. My design should also lend itself to being used as a traditional WFO.

My only concern is whether this design will capture enough of the heat and also how to make the oven heat relatively evenly.

I'd appreciate any (constructive) comments and ideas!

Cheers,

Tim

[satamax]

Hi Tim.

Check this one.

donkey32.proboards.com/thread/799/barbie-core-horiz

You will have to click on the picture links. Dunno why, they don't apear anymore.

Forget steel for the rocket part. And don't go under an 8 incher for an oven imho. On my build, i need to insulate the oven top barrel part, and may be add some mass. But that will be for next year. I need to concentrate on heating my flat and workshop for the moment. If you keep your horizontal arangement, make your oven a bell. With your chimney down low, so it traps the heat.

[timmy]

Hi,

Thanks for the input. That design looks pretty good, but I'm looking for a larger oven area if possible. I figure that the barrel-on-its-side design would trap and reflect a fair amount of heat and was thinking of putting the chimney opening lower down to prevent heat loss.

Any reason why the steel rocket is not a good idea? I figure that if it's properly insulated (e.g. surrounded in vermiculite) then it shouldn't lose too much heat and will actually conduct a fair amount of heat into the steelwork of the oven.

Cheers,

Tim

[peterberg]

Sept 21, 2013 22:06:31 GMT -8 timmy said:

Any reason why the steel rocket is not a good idea? I figure that if it's properly insulated (e.g. surrounded in vermiculite) then it shouldn't lose too much heat and will actually conduct a fair amount of heat into the steelwork of the oven.

Steel isn't a good idea, the temperatures in a good rocket combined with a low oxygen environment will result in very rapid corrosion. In fact, 3 mm of steel will be gone at some spots in about 10 hours of intensive burning. In case the steel is holding the rocket is running sub-optimal and will emit smoke. Inevitably.

[timmy]

That's a good reason!

I do have some firebricks in my garage that have been sitting there for ages.... assuming that I can just build a J-shaped rocket burn chamber from them?

How would I go about calculating the size of the rocket tube that I should use?

Cheers,

Tim

[Donkey]

What size is the chimney pipe that you will be using?
The system should maintain the same CSA (Cross Sectional Area) all the way through (not including barrel gaps, ash drops, clean-outs etc.).
Us Pi R^2 (3.14 times radius squared) to figure CSA of stovepipe, then make your brick bits (feed, burn tunnel, heat riser, etc,) the same CSA.

There's a little room for fudge factor in all this. In an 8 inch system the pipe has a CSA of 50.24 square inches (4*4*3.14). As it turns out with common firebrick, a 7" X 7" channel is a very convenient size. 7X7 is 49 square inches, which is a little bit small but works out fine anyway.
The next rule is that if you HAVE to fudge it a little bit, it is better to do it smaller and upstream. In other words, if you have to shift bricks for one reason or another, it's better to go slightly smaller over on the feed side of things, rather than the other way around.