Beer Keg Tandoor

[Luke]

I thought I'd share with you my experiences in building a Tandoori Oven in a beer keg.

I have always been a fan of Indian food, even from a young age. I just love it hot and spicy. When I was a teenager I tried out for a job at the local Indian take-away making Naan bread. Needless to say, I couldn't hack the heat and resulting burnt arm! However, my interest did not dwindle in Tandoor cooking.

Why in a beer keg you ask? Because I had one sitting in the shed for about 10 years taking up space. I'm not even sure how got it in the first place (or why), but I'm guessing I had some crazy idea about making a pot belly stove, BBQ or something else like an ethanol extraction unit.

Myself and the family really enjoy Naan bread and buying it was getting expensive. I had tried making it too, and although it was OK, I couldn't get the top and bottom to cook simultaneously with the correct, crispy skin you get. I tried everything, and the best method was a red hot charcoal BBQ, cooking the bread on the grill, and flipping it over to finish the top off.

Recently I had found a few posts about home built Tandoori Ovens. Cool! Exactly what I wanted - a real Tandoor to cook the bread in. I sketched up a few ideas on a Napkin (the normal starting point for all great plans) and then translated the concept in Sketch-up.

Essentially the Tandoor is built from firebricks and a Terra Cotta pot. The keg holds everything together, and keeps the vermiculite in place providing thermal insulation for the terra cotta. The pot is actually inverted and has the base cut off. A small door was also required for ventilation at the bottom.

[Luke]

SketchUp is a great software tool for 3D images, so was really easy to visualize the finished Tandoor. Fabricating it was a whole different story...

[Luke]

Now although I am an engineer by profession, I'm not a mechanical one. Nor do I have great metal working skills or tools. But, I have a great mate who is quite talented at working with metal (well, compared to me anyway).

So a few hours at my mates place with him doing most of the work, and me doing most of the directing (my excuse was I had to take photos).

Keg lid was cut with the plasma cutter (awesome tool - I have some video of this which I will put up later). The Terra Cot pot required the top lip and the bottom to be cut off, which was done with a diamond cutter.

The cut off bottom (which I will turn into the Tandoor lid) formed a template for the hole to be cut in the lid itself! Very useful (again, a plasma cutting job)

We also cut a few fire bricks but they destroyed what was left of the diamond blade in about 4 cuts (the blade was already shagged). I did a test assembly to see how it was going to go together. See images below.

[DocDougherty]

Luke,

Cool! How many firebrick of what size support the pot?

Perhaps a few dimensions on one of the SketchUp views would help.

Any issues with beveling the firebrick so that they fit together tightly?

And what is the heat source?

Doc

[Luke]

With the diamond blade destroyed we came to a halt. I did a test fit to see how it was going to go together. You can see the vermiculite on the bottom, with a few fire bricks in for dimensioning.

The fit of the cut Terra Cotta pot is perfect.

So the next job is to cut the ventilation door (I purchased a small stainless hinge for this), mount some caster wheels on the base, and fix the lid back on. Sounds easy....wrong!

[Luke]

Hi Doc,

The keg is about 50 liters or 500mm total height. The flower pot is about 40cm OD Italian Terra.

Heat Source : Located in Australia, I have access to an interesting form of charcoal sold by Red Heads (a Swedish match company). It is wood charcoal, but unlike ordinary charcoal appears to have been ground to a fine dust, mixed with a neutral binder and then re-compressed under pressure and pushed into a hexagon shape, with a hole in the middle for better air circulation. It burns very well, quite long, is relatively clean, and generates a lot of heat.

The 40cm terra cotta pot is too big to fit inside the keg, so I cut the top lip off and bring it back to 37cm.

25mm high refractory bricks on the base, 1 layer of bricks around the edge (for the pot to sit on).

A square hole and matching gap would be provided for an air vent in the bricks. (Photos to follow).

Cheers,

Luke

[Luke]

Like all good projects, things took a bit of time to get on to the next step.

First, we needed to make a cutout for the vent at the bottom of the Tandoor. The great thing about Plasma cutters is that cut so quickly the metal never gets a chance to get hot.

The 1st photo shows the template we used for the vent. It was 5mm cardboard from a shipping box. The cardboard did not even burn (or smoke) and the entire cut was complete in 30 seconds. Keep in mind we are cutting 3mm stainless steel (well, I was impressed anyway).

We did make a little mistake with the vent. With hindsight, we should have left the door un-cut in the corners. This would have kept the door in place and made alignment of the hinge so much easier.

The hinge was clamped to the keg using a $2 G-clamp which gave us $2 G-clamp trouble (as you would expect) but it finally held. To raise the hinge above the rib, two stainless nuts were used as spacers. The nuts and hinge were then TIG welded. But as true amateurs, we forgot to turn the gas on and blew tungsten tip away on the TIG. Doh!

A quick regrind on the linisher and we tried again with the gas (Argoshield) , this time successfully as shown in the last photo. However, as I found out, there is a significant amount of difference in heat between plasma cutting (none) and TIG welding (lots). My finger can assure you of that.

[Luke]

Now it was time to re-attach the door. With a bit of mucking around we taped up the door back into place using gaffer tape as shown in the 1st image.

The hinge could then tack welded onto the door, tape removed, with additional welding for more support. It was a relief to see the ventilation door working, but there was nothing to stop the door from being pushed too far in.

This was fixed with a small tab as shown in the last image. The other tab (shelf) is to help prevent mortar falling through when we mount the pot. I will explain this bit later.

[Luke]

Now it was time to work out how to fix the lid back on! We were hoping to implement something a little more elaborate, as it would have been nice to have fixing tabs on the inside as it would be more visually pleasing...but it all got too difficult so we fixed 3 tabs on the outside.

The idea was to weld 3 x 10mm stainless nuts to the inside of the keg. The lid would then be fixed to the keg with 3 bolts through the tabs. Sounds pretty strait forward.

First task was to make the tabs using a sturdy drill press. Again, drilling stainless is not as easy as you would think.

The lid was aligned with the keg and taped up with strong gaffer tape. 3 tabs were welded into place, equally spaced around the keg. This was all fairly strait forward.

With the tabs in place, we found another excuse to use the plasma cutter. That is, to blow the hole for the bolts. It "kind of" worked as you can see from the final picture, but the holes need significant work with a step drill to finish off (complicated by a lot of flat battery drills). Still, it was probably quicker than trying to drill 3 x 12mm holes in 3mm stainless.

[Luke]

After plasma cutting the holes were a little rough. To clean these up, we used a step drill. The biggest challenge in this process was finding a battery drill with a decent battery.

With the holes cleaned up, we decided the best approach was to align the lid and tabs with bolts in the nuts, and then weld the nuts onto the keg. All seemed pretty forward. Bolts and nuts tightened but not too tight. Although tricky, the TIG hand piece could fit through the hole in the top of the keg.

The welder (Rik) did cop some arc-flash in his eyes because the welding mask LCD panel (located just above the eyes) was shielded by the keg. A small head ache was the only result, but this was an interesting safety lesson with these LCD type masks. If your LCD is obstructed from the ARC, it won't shield....

All three nuts were welded, although we had to turn up the current due to the large thermal mass of the nut and bolt.

As we tried to undo the bolts, we discovered (or should I say remembered) that Stainless Steel is notorious for galling. Well, each bolt seized up after 1/2 of a turn. We emptied a can of RP-17, various types of oils, applied heat, to no avail.

1 x 17mm spanner and a lot of torsional force and the 10mm bolts were broken off (although I thought the welds on the nut would give way, but they did not). Another wonderful lesson in mechanical engineering - torsional vs shear breaking points (and who says electronics engineers know nothing about mechanical engineering ehh???? ). Out came the Dremmel and cut off wheel to remove the nuts.

The above process was repeated, but this time with anti-seize compound on the threads. Success was the result (don't have a photo of this unfortunately).

[Luke]

With the metal work done we could pack up the welder and plasma cutter and start the brick cutting. As mentioned earlier we destroyed the 5" tile cutting wheel we used earlier, so not to be outdone this time we sourced a 9" brick cutting wheel. I'm not sure we needed the 9" wheel, but bigger is better as they say.

Those 9" grinders are one beast of a machine and seem to have a mind of their own so anyone trying this at home be extra careful.

First step was to mark up the bricks with some chalk.

Second step was to fill the bottom of the keg with some vermiculite and start laying out the bricks. The final layout was complete and although we could have left a bit more on the bricks, it turned out to be fine in the end.

The final step involved some juggling of vermiculite in the base, along with the side wall bricks and aligning the pot to sit nicely in the lid. This was not helped by things not be entirely square, but you get that with angle grinders.

[Luke]

Now, as per the plan, the next requirement was the side wall bricks. These were the 25mm fire bricks simply cut in half. A test placement around the inside perimeter of the keg showed that some smaller bricks, cut and on angle near the door, would be useful, so we cut those as well.

I was unable to find a small amount of fire rated mortar, and to be honest, the oven would actually work without any mortar, but I decided it wouldn't be an oven project with mixing mortar and getting muddy! I added a small amount of vermiculite to the mortar to assist with insulation, but with hindsight it was such a small amount the effect would be negligible. However, we are engineers and just love to overcomplicate things so we were happy.

The base bricks were set in place by packing mortar around the edges. Then the side wall bricks were placed in sequence, with the cut edge facing the brick, so as to have the terra cotta pot sit on a smooth brick edge. I probably should have partially filled the air gaps with vermiculite at this stage, but I guessed that some vermiculite would fall into those gaps anyway.

The terra cotta pot was then placed onto the wall of bricks. As mentioned earlier, it took quite a bit of effort to get the pot to square up and fit nicely into the lid cutout. This was because the terra cot pot was not cut exactly square, and it was very hard to get the base vermiculite level. After we found the magic "spot" (which required rotating the pot about 20 times) we took note of how the pot was orientated, then ensured this was put back the same way.

One concern we had was the naan slapping process. For those of you familiar with making naan bread, it takes a decent slap to get to the bread to stick to the wall of the oven. I did not want the terra cotta moving, so we cut some wedges and placed them around the pot to lock it into position. This was a very simple idea but very effective. Note that the pot is NOT mortared onto the brick wall. I still don't know if it will crack, so for future servicing I have left it without mortar.

The next tricky bit was the gap above the door (no detailed photo of this). This was packed up with small bits of broken brick (they were supported by the bracket we welded on earlier). Mortar was placed over to the top to stop any vermiculite from falling through. Mortar was also placed next to edge wedge to keep it in place. We probably went too far with the mortar, but we were in that "What else can I do with this left-over mortar" mode.....

[Luke]

With everything in place, vermiculite was carefully poured around the Terra cotta into the air gap. The lid was placed back on to the keg, and the pot nicely fitted into the lid cut-out.

Now you would have thought at this stage we would have taken 50 photos to reflect on our great job now complete...but we actually didn't take a photo of the completed unit! (Silly us).

Anyway, you can see that the lid cut-out was retained to make a lid for the Tandoori. This is only temporary was it will be too hot to handle for normal operation. I did destroy about 3 flap disks on the orbital sander in the process of de-burring the edges. That stainless steel is harder than it looks!

Last but not least, it was time to pack up and put the Tandoor aside for the mortar to set and dry, but not without first testing it with a chicken!

Test firing and manufacture of the tandoor cooking rods is next up...I'm hoping to get my hand on a thermal imaging camera for this so stay tuned for more updates....

Cheers

Luke

[Dakki]

Fantastic, Luke!

Post some action photos soon.

[Luke]

With the Tandoor ready it was time to fire it up.

First step was to light some charcoal. As mentioned earlier, the type of charcoal in use is not your normal wood charcoal, but a manufactured wood charcoal that is very dense and burns with a good even heat.

We often have a Chimenea lit when eating outdoors at night, so I used this to light the Charcoal. A few small pieces were slowly added to the bottom of the Tandoor (I took several hours to make sure everything had a chance to dry out). Temperature hovered around 150 deg cel.

[Luke]

Slowly more and more charcoal was added, and I played with the ventilation and lid positions to get an idea of how this would work. I sourced a K-type thermocouple for temperature measurement, and was quite impressed when the oven settled at 415 deg cel.

Needless to say, it was time to skewer the chicken and cook. Now I did make a few mistakes at this stage. The chicken pieces I used here had a little too much fat in them, and this subsequently melted and then caused a flare up. It wasn't too bad, but further research has revealed this can be a problem. The solution is to cook and rest, basting in your marinade between cooking times and not using too fatty cuts of meat.

The chicken turned out pretty good in the end. Shown is a photo of the chicken after 10 mins of cooking. I rested it for 10 minutes, then cooked another 10. With hind sight, this should have been 5, and the chicken was more charcoal than I would prefer, well cooked, but incredibly moist inside.

After we did the chicken, I rolled out a few naan bread for a test. Like a true amateur, the first naan just fell off my applicator into the coals. The second one was gently slapped onto the terra cotta, and promptly fell off into the coals. The third and subsequent naan were really slapped onto the terra cotta and the result was fantastic! They were light and fluffy, were crisp on top and bottom. There was some variation in cooking, but I'm sure I'll get the hang of it.

All up I was very impressed with my Tandoor oven. I'm sure going to make it a regular feature at my house. It's also been great to build this project with my mate Rik and for me this has been an excellent learning experience, particularly with some of the interesting metal work that I have not attempted before.

We are already postulating about what to do with the second keg...A charcoal spit roast bbq maybe, then again a fractional still has it's merits too.

[Joe Blowe]

Very elegant alternative to the oil drum tandoor -- well done!

[Emily_R]

Just wanted to say that this thread is a perfect example of what makes egullet so awesome! Love the project, and thanks for filling us in step-by-step!

Emily

[Nasi_Campur]

Brilliant job and step by step run down...

now, if I can just find some spare time...

[Peter the eater]

Absolutely brilliant!

...A charcoal spit roast bbq maybe

Be sure to check out this spit roaster

[Luke]

Thanks for the kind comments guys! I certainly have received a lot from egullet, so I thought it was time to put something back in!

One of the tasks that was also on the "To Do" list were are some cooking implements! Skewers (or Seekhs) are required to cook our Tandoori Chicken on, and these are not the sort of skewers you can rush out and buy.

A quick trip down to the local stainless steel merchants and I returned with two lengths of 5mm 316 stainless rod. Using a vice, some oddball scrap parts lying around the shed, we built a bending jig.

The rod was inserted into the jig, and slowly bent around the former. The rods were cut to length using a dremmel and then a point was formed using the belt sander (to assist with skewering the meat).

I found the smooth surface of the rod a bit troublesome with meat & chicken slipping down, so I did need to add some small "nicks" to make the surface a bit more grippy for the meats. I did this on a bench grinder (not shown).

[Luke]

With the meat skewers done, it was time to make some tools specifically for the naan bread. At several Indian restaurants I visit, they have a glass window for customers to observe the kitchen and in particular, the Tandoori Oven. I had watched these guys and they had two "special" implements just for making the naan. A special type of hook, to hook the Naan and stop it from falling into the coals. The second was a flat scraper, to pry the Naan off the wall of the oven.

The first tool was fairly strait forward. This was just like a Seekh buy with a bend at the end.

The Naan scraper was a little more challenging. This tool is designed to pry the naan off the oven wall. So it needs to be thin and flat, a bit like a flat blade screwdriver.

Starting with the rod again, we heated one end until cherry red using a propane burner. This was then bashed on an anvil. The process was repeated until the end was fairly flat. The end was then finished on the belt sander, with a final touch up being done with some emery cloth. The result was a professional looking instrument!

[Luke]

Here are some photos of items we have cooked since building the Tandoor.

I have also cooked Chicken and Lamb, but the fish was the real hit so we did this twice.

You may note the bottom of Naan has that authentic crisp brown finish. That is one of the keys to cooking great Naan. The Terra Cotta provides the intense heat to cook the bottom quickly, while the Charcoal radiates heat to cook the top.

The fish cooks brilliantly in the Tandoor. I guess this is because it is so hot and so quick, it has no chance to dry out. But make sure you use firm fleshed fish, and don't marinate it for more than 15 minutes.

To stop items from sliding down the skewer I place a small ball of Naan dough at the end. I need to add more notches to the Seekhs as the food items slip off too easily.

Edited May 8, 2010 by Luke (log)

[nakji]

Oh, wow. You can have your own tandoor parties! I'm so jealous. The coals you're using are the same style ones used in barbecue restaurants in Korea for meat grilling. I'm surprised that a European company makes them as well, as I'd despaired of finding them outside of Korea. They keep the heat fairly well, don't they?

Are you going to try more complex naans, like stuffed kashmiri naan or similar?

[Luke]

The Tandoori oven continues to give us great enjoyment. I have fired it up about 10 times, and each time I learn a little bit more about how to get the best from it. Being small, when cooking meats you need to be a little careful about how you skewer the meat and where you place the seekh when cooking (in relation to where the hot coals are). I'll post some pictures a great seekh kebab next time.

Here was the latest attempt of Tandoori Chicken using Vah Chefs recipe.

Cheers

Luke