55gal Steel Drum Build (in the thinking phase)

[doctorphreak]

Hi everyone
my name is mike and i thinking of building a oven and was lurking around the site and seen a couple of drum ovens and i have plenty of those so i would like to run a idea by you all and see if my plan is good....now please remeber no experince in this area and if there is a questionable part please let me know ....lets get started

ok i have several 55g drums here and to begin with , you need a base right well here is my idea for that....i take lets say 6 drums buried them 1/3 deep and fill them with dirt or gravel or both ( i can get all the free dirt i want ) and put all 6 together with lids on now this should provide me with a very heavy solid base right ???
then on top of these drums lay 2 layers of cement board 1/2" thick so 1" , then build a 2" concrete slab on top of these then when dried build a brick base of paver stones 2" thick then on these will go the fire brick...so i would have about a 5" thick base insulating layer under the fire bricks ....so far what do you all think......

now cut a drum 1/3 off lengthwise and that is the oven that will go on top of the fire brick and on that will go the ceramic insulation and then wire to cover then brick or concrete about 3-4" thick if i go this way stucco after....

kinda of a quick rundown im sure there will be other ideas but gives you all a look into my thought process....how does it sound.....let me know glad to be here and share my thoughts and ideas with everyone here....

[WJW]

Re: 55gal Steel Drum Build (in the thinking phase)

Welcome Mike.

I'm very new at this and just getting into my first build so take anything I say with a grain of salt. That being said, your description of a "five inch insulating layer under the firebricks" does not sound correct. You describe an inch of cement board, two inches of concrete, and two inches of pavers...none of that is insulating material. Concrete and masonry is a heat sink and will draw heat from your oven. It would take forever to get your floor saturated with heat because the heat energy would continue to migrate away from your fire toward all of that masonry until such time as the base was vey hot. That could take several hours.

You need to think of the oven as three distinct layers.
First (farthest from the fire) a structural layer. Whether its a concrete slab on blocks, or your slab on barrels, the point of that layer is just to hold everything up.

The next layer is an insulation layer. The obvious purpose of this layer is to thermally isolate your oven from everything else. Guys typically use fiberboard insulation of the type used in foundries/kilns, a cement-vermiculite mixture, or a combination of both.

Above the insulation will be the stuff that absorbs, holds, and gives up heat to the interior of your oven. This is where the whole "thermal mass" discussion comes in. The "stuff" that will hold hear will be your actual cooking surface (firebricks, soapstone, etc), and it may also be a layer of mortar or other "mass" intended to hold heat.

When it comes to mass there is no such thing as a free lunch. The more thermal mass you have, the more energy (firewood) it takes to load that mass up...it also takes more time to heat as well. The upside of lots of thermal mass however, is that all that heat energy stored in in your masonry is then slowly released back out into your oven over time. As a result, your oven stays hotter longer.

Deciding how much mass you want requires you to decide what you want to use your oven for. If it's for cooking a few pizzas you probably don't want a lot of thermal mass. If, on the other hand, you plan to bake multiple batches of bread (over a period of several hours) from a single firing...then you want a lot of thermal mass. You can tinker with the amount of thermal mass by adding masonry under the bricks and/or changing the orientation of the bricks by laying them flat or on edge.

Browse around the forum and look at the various buils to nget an idea what your options are.

As far as the integrity of your barrel stand, my only question would be the issue of frost moving the barrels if they are not buried deep enough. I live on the coast in southern california so when we get frost it's the lead story on the eleven o'clock news...but in OK you guys get some real weather at times if I recall. I have no idea if the frost under the stand is an issue, but you should at least know the answer.

Bill

[Neil2]

Re: 55gal Steel Drum Build (in the thinking phase)

I would expect that your barrels will shift and move somewhat if buried only a foot and a half or so.

Eventually they will rust out as well.