Cheers from Melbourne, Au - Maybe a crazy idea Grill+Smoker+WFO

[Chicharron]

Hi All,

Been lurking around the forum for a couple of weeks (so glad I found this) but first time posting. In fact not sure if this is the right place to start with and ask questions but here we go. Let me know and I can remove this from here and place is wherever needed.

I have an idea and it's inspired by the big green egg. When I first saw it in action a few years ago I was amazed by how versatile it was. The fact that you could Grill, Smoke, and Bake/Roast with only one device caught my attention right away. Fast forward to a few weeks ago I had my very first Pizza party at home (Using my normal electric oven) and it was a huge success. I fell in love with the dynamics of it all. I invited my family over, everyone brought their toppings/sauce and we'd take turns making our own combinations.. Brilliant!

I've had the idea of having a pizza oven in my mind for some time but didn't give it much importance until we had this party. I've always been more inclined to BBQing and also due to the fact that I don't own a property.

Looking around I found the castable-type of ovens and I thought that'd be perfect for me because it'd be a lot lighter and won't cost me my an arm and a leg also. So being determined to build one of those I remembered about the BGE thus I brought back the idea of building something similar to that. Something that's "Movable" enough so that I can take it with me when I move out from one place to another.

It basically consists of a "BOX" made of refractory castable cement. It would have a firebrick floor, after that it'd have a fire deflector (maybe made out of castable as well??), and a grill over that. The idea is that if I'm looking at smoking I'd put the deflector so I cook with indirect heat but I could remove if I'm looking at grilling or maybe use the same deflector as "Pizza stone" on top of the grill to make pizzas/bread. All sitting on a Calsil Panel or Hebel blocks or something similar. Have a look at my rough sketches and you'll make more sense of it.

The basic Idea is to keep the budget low and to make it movable enough with the help of a mate or 2. Now I have lots of questions and I hope the Casting experts (I hear David S is the man) chime in and let me know if I'm insane or if this is at least remotely viable.

1. One concern I have is that in most cast builds people tend to get cracks in their domes. Most don't seem to be too concerned with it as it doesn't affect its performance all that much. However, a dome is a much stronger structure and even with cracks it stays together pretty well. Now, having flat panels like in my design I'm guessing cracks will affect it a lot more. What do you reckon? is there any way to make sure you don't get cracks (I've read about adding SS needles or something similar) or is it just the material being like that? I'm planing on building a roof or something to prevent it from getting wet.

2. Would this design with 50MM walls retain enough heat? I've read everywhere and understand that the recommendation is to make a 50MM wall then an insulation layer of ceramic blankets and then another with perlite or something similar and finally render but my concern is that it's going to get pretty bulky and heavy. I don't really mind if it doesn't retain the heat for like 48 hrs as long as it gets up to temp and maintains it fairly well and stable for a pizza night (10-15 pies or so) or so I can do long smokes. I plan on using gaskets for the lid and door as well to keep everything as controlled as possible. Would 60MM walls make any difference just so I can avoid all that?

3. Because I need to attach handles to door and lid + hinges for the lid. I'm not sure how would it structurally be affected if I drill a hole to attach those. I've never worked with these materials so I have no idea. BTW do you know what sort of Hinge I could use? I don't have access to metal work equipment or know anyone.

4. I'm trying to calculate how much it would weight but I'm not 100% sure how to calculate that from the volume of that mix.

5. I would be awesome If anyone in Melbourne could point me to suppliers for all this stuff. Why is everything so hard to find in Aussieland jeez???

6. Am I Insane to even think this was possible?

I'm sure I'll come up with a ton more questions/doubts.

I hope I don't sound too stupid :/
Cheers guys

[Chicharron]

*Edit: Not sure why my attached pictures didn't work the first time. Here they are.

[david s]

There's a reason a high thermal mass hemisphere with the flue at the front has been so popular for a couple of thousand years, it works extremely wel. A cube or rectangular box will work, but the fire will not circulate nearly as well. Likewise, having a flue at the top (updraft system) fires pretty well, but the flames dive straight for the flue and a lot of heat(fuel) is wasted. You have flames exiting out the flue with this system. A flat roof is not structurally sound like a dome and combined with a castable that does not achieve structural strength from firing (this only occurs once you take it slowly up to >1000 C). It relies on the chemical bond of the cement only and because of the continual heat cycling in the 500-600 C range expect hairline cracks. Presumably you also plan on having an outer steel skin. This needs to be made of stainless otherwise it will rust pretty fast (seen a 5 year old steel barbecue without rust recently?). Same applies for the hinges.

Regarding weight, castable refractory weighs, when set and dry just under 2 kg/litre.

Instead of trying to re-invent the wheel, without the experience of working with castable refractory, you'd be far better off building a cob oven (very low cost) and learning about controlling fire and retained heat. You can easily use a normal WFO as a smoker. Just pump a little heat into it, or wait for the temp to drop to where you want it, leave the door open a little and place some coals and smoking chips in a coffee tin, with lots of holes in it.voila.

with the set up as per your drawing, i's expect you'd have the floor way hotter than the lid and as soon as you lift the lid to place a pizza you'll lose a lot of heat from it. Once the lid is closed again you won't be able to see the pizza cooking. That also means lifting the heavy lid a min of two times per pizza. Imagine cooking 40 pizzas!

Sorry to rain on your parade, but I can see you may be heading down a path that will be expensive and likely to end in failure.I'm all for innovation, but without experience of working with the required materials it makes the task that much harder.

[Chicharron]

Don't need to be sorry david s I was actually expecting a lot of rain on my parade . I had the suspicion it wouldn't be a good idea I just thought I'd throw the idea out there to see if it was at least remotely viable.

A lot of the things you've mentioned I had already thought about (efficiency-wise) but just didn't give it too much importance as I wasn't expecting to have the perfect device, just something that was versatile and that allowed me to take with me when I moved. Looking your response and looking at the design again I actually think doing it this way would have probably been more expensive (re. stainless steel handles/hinges) and in deed less "Movable" as this would need even more casting cement to build.

I didn't mind opening the door a couple of times when making pizzas (also thought about opening a front door). I thought once you time it right you wouldn't need to open it again until you know they are done. however, 1 Really, you always need to see it cooking as temps would fluctuate a lot, and 2 it would have definitely been a pain in the ass when grilling as you tend to open it a lot more.

So I've moved on and going the small dome (24in) castable (HomeBrew) Pizza oven route. After all you're right you can still grill and smoke/grill on those. I'll post a new thread on the other section and I hope to get your input on that one as well, there's probably be a lot of slapping around on that one too I'm trying to read as much as I can to not make the least amount of stupid questions possible.

Again. Thank you very much for your feedback!! you are a great source of knowledge mate.