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voon 11-18-2009 11:56 PM

My portable tandoor oven build
 
I'm about to start building a portable tandoor oven inside of a 30 gallon oil drum, kind of like what Grasshopp3r described in this tandoor oven ideas? thread.

I have most of the materials already. The interior dimensions of the 30 gallon drum is 18 inches diameter by 28.5 inches height. I have a supply of regular firebrick and split firebrick, and a terracotta flower pot to serve as the tandoor pot. The flower pot is about 16 inches tall and 16.5 inches in diameter at the top. 16 inches is a bit short for the walls of a tandoor oven, particularly since there will be a wood or charcoal fire built in the very bottom. That doesn't leave much wall space above for the naan, and puts the food too close to the coals.

So my plan is to build a firebrick floor in the bottom of the barrel, then put a vertical course of firebrick on top of the oven floor, and set the flowerpot on top of the vertical course. That'll lift the pot up another 9 inches over the fire.

With the bottom of the flowerpot cut off to make the top opening of the tandoor oven, the height of the pot will be 15 inches. The bricks are 9x4.5x2.5 inches. So the floor plus the vertical course around the periphery will be 11.5 inches. Add the 15 inch height of the flower pot for a total of 26.5 inches. That gives me two inches for insulation at the bottom of the barrel underneath the firebrick floor to bring the top of the oven even with the top of the barrel. I don't mind if it ends up a little above or below the rim.

I plan to use loose vermiculite around the outside of the flowerpot above the level of the firebrick course that it sits on top of to provide insulation. But I believe I need something more substantial below the floor and between the upper vertical brick course and the walls of the barrel. I don't want too much heat to transfer to the outside of the barrel.

So here are my questions:

1) Would ceramic blanket material work between the vertical firebrick and the steel drum wall. If so, how thick should it be? Does compressing it diminish its insulating properties? Where do you buy this stuff and what names does it go by? (The brickyard where I bought the firebrick did not sell it.)

2) Would 5 to 1 vermiculite to portland cement work effectively as an insulating layer below the floor and behind the vertical course against the barrel wall? Will two inches in the bottom of the barrel be sufficient? How thick should it be between the vertical firebrick course and the wall of the barrel? Would an inch be enough? I'm thinking that anything more than an inch thick would make the usable floor of the oven too small for an adequate fire. The barrel is only 18 inches inside diameter, and the firebricks are 2.5 inches thick. I could use thinner split brick for the vertical course, if necessary.

Thanks for any help or suggestions you can offer. I hope to record my build project with stills and video cam so I can post it later. If the video works out, I'll put it on YouTube.

ThisOldGarageNJ 11-20-2009 03:25 AM

Re: My portable tandoor oven build
 
hey voon
Quote:

1) Would ceramic blanket material work between the vertical firebrick and the steel drum wall. If so, how thick should it be? Does compressing it diminish its insulating properties? Where do you buy this stuff and what names does it go by? (The brickyard where I bought the firebrick did not sell it.)
You can buy the ceramic blannket from the FB store.. you can als use the vermicrete,, portland and vermiculite.. Premixed vermicrete can be bought from a pool building supply company as thats what they use on cement pools floor and walls...
Quote:

Would 5 to 1 vermiculite to portland cement work effectively as an insulating layer below the floor and behind the vertical course against the barrel wall? Will two inches in the bottom of the barrel be sufficient? How thick should it be between the vertical firebrick course and the wall of the barrel?
4 inches is what is usually recommended,, I used a 6-1 mixture, keep in mind vermicrete has only compressive strength,, nothing structural ....

You could probably use the FB insulation on the outside of the barrel and refractory cement inside with the vermicrete to hold your bricks in place..
Im not sure how long the barrell would hold up that way but its a thought to consider...

Its an interesting project your doing,, Im curious to see it progress

Cheers and good luck
Mark

voon 11-20-2009 10:27 AM

Re: My portable tandoor oven build
 
Hey Mark,

Thank you for the information. I know that I can buy ceramic insulating blanket from the FB store, but I'm hoping to do the complete build this weekend, so I have been trying to find some place locally that sells it. No luck so far, so I'll probably go with the vermicrete mix instead.

I'll be using lump charcoal or charcoal briquettes rather than a wood fire to bring the oven up to temp, and due to the very small size of the tandoor oven, I expect it will take less time and a far less intense fire to bring it up to an even cooking temperature. The barrel is steel, surrounded by air, and it will be mounted on casters so there will be air underneath providing additional insulation. I don't have the large heat sink of a pizza oven stand to shield my oven from. I just want enough insulation to keep the outside of the barrel from overheating.

Due to the height limitations in a 30 gallon barrel, I'd prefer to use two inches of vermicrete in the bottom rather than four. But I have no experience with vermicrete, so if this sounds like a bad idea under the firing circumstances I've described, then I can go with four inches. In that case I'll just have to cut my upper vertical course of firebrick down by two inches, making them seven inches tall instead of nine. I'll be renting a table-mounted wet tile saw with a diamond blade, so that should not be a problem.

I don't need any structural strength from the vermicrete, as the barrel itself provides that. I just want to keep the outside of the barrel from getting too hot for the sake of safety and to keep from radiating my heat into the atmosphere (which is a good insulator itself). So do you think two inches of vermicrete will suffice under the circumstances I've described?

Also, will vermicrete bond the firebrick like fireplace mortar or refractory clay would?

ThisOldGarageNJ 11-20-2009 05:16 PM

Re: My portable tandoor oven build
 
VillaGok tandoor ovenhi voon... this is the link that mitchamus had posted in the other thread,,, I think it can answer your questions way better than I can.. if your worried about the outside of the barrell,, you can pour in loose perlite or vermiculite.. you can buy them at a garden supply..

will the barrel be standing straight up ??

and no, the vermicrete will not hold the firebrick in place...

I am still very curious to see your progress so please post pics as you build.. and I hope I've helped at least some

Cheers
Mark

voon 11-20-2009 09:16 PM

Re: My portable tandoor oven build
 
The VillaGok tandoor oven is lovely. I poured over that site a couple of days ago, and I picked up some very good information there. I'm already considering building one modeled after that one. He didn't use any vermicrete to isolate the firebrick floor of his oven from the structural concrete pad beneath it. I plan to do that if I build a similar one. The brick oven he built is equally stunning.

But his VillaGok tandoor is a stationary oven, whereas the barrel tandoor I'm building is intended to be portable. I want to be able to strap it into the back of my truck to take it to the park or to a campsite or to a friends house. It has to be light enough for two people to lift it, so I'm trying to keep the total weight down. That's one reason why I chose a 30 gallon barrel instead of a 55 gallon barrel.

Yes, the barrel will be upright, and I do plan to use loose vermiculite around the pot for insulation. But that won't work for the very bottom where the firebricks are, as they may shift around during transport. Besides containing the heat, that's another reason why I'm interested in bedding the brick in vermicrete. It sounds like I will need to use some fireclay mortar as well.

You have been helpful, and I appreciate it. There are a few things I haven't worked out yet, but I'm sure I will resolve them as I go. I plan to take plenty of pictures, and maybe I will make a video too. There's a chance of rain in the morning, but I'm hoping for dry weather in the afternoon. If so, then I'll be getting started tomorrow.

ThisOldGarageNJ 11-21-2009 02:56 AM

Re: My portable tandoor oven build
 
Hi Voon,

Im getting a better picture in my head now,,, I think for what your planning the 2 inches with the firebrick will be ok.. If you cut the firebrick to fit tightly in the bottom of the oven they probably wont move, though to have the fireclay mix holding them would of course be better.. Im almost willing to say you may be able to leave the outside of the barrel unwrapped, with the 2 inches of vermiculite, you might be ok.. try it and add the insulation later if you have to ..

good luck and looking forward to your results
Mark

sacwoodpusher 12-07-2010 10:33 AM

Re: My portable tandoor oven build
 
Use FB board to separate the tandoor from the base.


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