Mobile Pizza Oven (Pray for me)

[bearsparko]

Hi all,

First build newbe, gentle please.

OK, so I have a brief of;
1. Pompeii Type Pizza Oven
2. 100cmm -120cm max outside diameter
oh yeah,
3. I want to be able to push it around the garden.

I don't want a feature close to the house 360 days of the year and this "in principle" seems viable....

The Plan is;


And so far I have got to here;










Weight is the challenge.

The plan was for a 100mm rebar vermicrete plate directly under the firebricks. 

Last year I bought 60 bricks 230 x 114 x 76 mm, they are Morgan J23 Insulating Fire Bricks. They were cheap and I jumped at them, but I was going to use them for the dome and it appears the consensus is that it is not a good idea?

My questions are;
1. Is it really not a good idea to use this type of brick for the dome? They are lightweight, so they don't store heat, but I read somewhere that a pizza ovens made with these types of brick heat up quicker. This compromise would be OK for me, am not looking to do slow roasts etc.
2. Could I use a mix of bricks in the dome, alternate between clay fire brick and insulating fire brick (both types as half bricks) as a compromise between weight and heat storage?
3. If I don't use them for the dome, I was thinking I could use them as a layer between the vermicrete and the fire bricks on the floor of the dome? It will raise the overall height, but would be OK.
4. Or, put'em back on Ebay.....

One way or another this is happening, so any positive recommendations will be gratefully accepted.

Thanks.

[simon]

Hi bearsparko,
my concern with what you are doing is the weight of the oven. Can the casters take it, and what ground are you going to push the thing over. Uneven and or soft ground would be a worry.

If pizza/live fire cooking is your aim, then an insulated dome can work, and have a number of benefits. You will need a pizza stone or firebricks under your pizza for cooking though (I'm sure you know this already, but making sure).

If you want to take this route (and why not), there's a guy on youtube who makes small pizza ovens out of cast pumice stone. They look ideal for your needs, and would be a lot easier to make and finish.

[bearsparko]

Apr 17, 2017 13:17:32 GMT simon said:

Hi bearsparko,
my concern with what you are doing is the weight of the oven. Can the casters take it, and what ground are you going to push the thing over. Uneven and or soft ground would be a worry.

If pizza/live fire cooking is your aim, then an insulated dome can work, and have a number of benefits. You will need a pizza stone or firebricks under your pizza for cooking though (I'm sure you know this already, but making sure).

If you want to take this route (and why not), there's a guy on youtube who makes small pizza ovens out of cast pumice stone. They look ideal for your needs, and would be a lot easier to make and finish.

Hi Simon, the casters are rated to 200kg each and I expect this excludes a margin of safety, so it's there or thereabouts with regards to load capacity. The lawn is pretty flat and I am going to prepare a level area to hide it in. Not sure if I'll be able to move it on my own.......but there are no calcs to verify that. I'll just wait and see. The casters are marketed for cricket screens and grounds trailers etc.

You said that using insulating bricks for the dome is possible and there are some benefits, what do you mean by this? What about my combination idea to mix insulated and clay firebricks in the dome construction, is this daft?

I suppose my problem is that I quite fancy having a go at building the dome, but as you suggested a modular product would probably be lighter and easier....I'll take a look at the YouTube clip you mentioned.

Thanks for the tips, much appreciated.

[simon]

Apr 17, 2017 16:57:39 GMT bearsparko said:

Hi Simon, the casters are rated to 200kg each and I expect this excludes a margin of safety, so it's there or thereabouts with regards to load capacity. The lawn is pretty flat and I am going to prepare a level area to hide it in. Not sure if I'll be able to move it on my own.......but there are no calcs to verify that. I'll just wait and see. The casters are marketed for cricket screens and grounds trailers etc.

You said that using insulating bricks for the dome is possible and there are some benefits, what do you mean by this? What about my combination idea to mix insulated and clay firebricks in the dome construction, is this daft?

I suppose my problem is that I quite fancy having a go at building the dome, but as you suggested a modular product would probably be lighter and easier....I'll take a look at the YouTube clip you mentioned.

Thanks for the tips, much appreciated.

With an insulation type material oven, the benefits as I see them are...

1) You'll need much less wood. You don't have to heat up a large mass of masonry. Only the inner skin needs to be hot for the radiant heat, which will stay hot with a live fire.

2) You'll be up to cooking temps quicker, you just want the hearth or pizza stone to be up to temperature.

3) Smaller oven for any given internal dimensions. With a masonry oven, you have the thickness of the dome, then the insulation, then the outer dome/house. If the inner done is insulating, that can be it.

4) Insulating materials are usually lighter, which again will suit your needs. Those pumice ovens I mentioned, he lifts the entire dome up on his own to place on the base.

Not sure about the insulating bricks you have, but making the dome will be harder with bricks compared to a moldable/castable material, and you'll still need to make it look nice once built.

Generally you want to avoid mixing materials with masonry. I would expect you to get cracks in a dome made that way.

I understand the desire to build with bricks. However you've placed quite a limitation on yourself with the base. I should stress that I've not built or used an oven out of insulating materials, but I can't see any reason why they won't work, and the inner size on that base will be much bigger than with the normal construction design.

You could build a normal dome and not bother insulating, but it would be far from ideal! Search for temporary or portable pizza ovens on youtube. Make a hot brick space, throw pizza in, it cooks. :-)

[bearsparko]

Apr 17, 2017 17:33:40 GMT simon said:

Apr 17, 2017 16:57:39 GMT bearsparko said:

Hi Simon, the casters are rated to 200kg each and I expect this excludes a margin of safety, so it's there or thereabouts with regards to load capacity. The lawn is pretty flat and I am going to prepare a level area to hide it in. Not sure if I'll be able to move it on my own.......but there are no calcs to verify that. I'll just wait and see. The casters are marketed for cricket screens and grounds trailers etc.

You said that using insulating bricks for the dome is possible and there are some benefits, what do you mean by this? What about my combination idea to mix insulated and clay firebricks in the dome construction, is this daft?

I suppose my problem is that I quite fancy having a go at building the dome, but as you suggested a modular product would probably be lighter and easier....I'll take a look at the YouTube clip you mentioned.

Thanks for the tips, much appreciated.

With an insulation type material oven, the benefits as I see them are...

1) You'll need much less wood. You don't have to heat up a large mass of masonry. Only the inner skin needs to be hot for the radiant heat, which will stay hot with a live fire.

2) You'll be up to cooking temps quicker, you just want the hearth or pizza stone to be up to temperature.

3) Smaller oven for any given internal dimensions. With a masonry oven, you have the thickness of the dome, then the insulation, then the outer dome/house. If the inner done is insulating, that can be it.

4) Insulating materials are usually lighter, which again will suit your needs. Those pumice ovens I mentioned, he lifts the entire dome up on his own to place on the base.

Not sure about the insulating bricks you have, but making the dome will be harder with bricks compared to a moldable/castable material, and you'll still need to make it look nice once built.

Generally you want to avoid mixing materials with masonry. I would expect you to get cracks in a dome made that way.

I understand the desire to build with bricks. However you've placed quite a limitation on yourself with the base. I should stress that I've not built or used an oven out of insulating materials, but I can't see any reason why they won't work, and the inner size on that base will be much bigger than with the normal construction design.

You could build a normal dome and not bother insulating, but it would be far from ideal! Search for temporary or portable pizza ovens on youtube. Make a hot brick space, throw pizza in, it cooks. :-)

Hi Simon, I sort of discounted the Swiss Ball method a while ago, but looking at it again, it makes more sense now. I think I will investigate further. Thanks I'll post how I get on.

[oblertone]

Have a look at my build thread (below); I made a 'mobile' oven, but now it's finished it takes six blokes to move it safely, especially over rough ground. It can work, but it's not ideal.

[bearsparko]

Apr 17, 2017 22:25:28 GMT oblertone said:

Have a look at my build thread (below); I made a 'mobile' oven, but now it's finished it takes six blokes to move it safely, especially over rough ground. It can work, but it's not ideal.

LOVE IT!

But can see the issues.

Thats why I don't mind spending a bit of money on some light weight materials if it will still deliver a decent pizza.

I think its do'able I just need to decide between the methods;
1. Insulating brick dome or mix with clay fire brick
2. Gym ball pumice
3. Off the shelf light weight modular

Overtime I read something I am changing my mind......

[downunderdave]

If you plan rolling that thing over lawn then you'll need to replace the castors with larger diameter pneumatic wheels/tyres or cast a concrete path for it to roll on.

[bearsparko]

Apr 17, 2017 17:33:40 GMT simon said:

Apr 17, 2017 16:57:39 GMT bearsparko said:

Hi Simon, the casters are rated to 200kg each and I expect this excludes a margin of safety, so it's there or thereabouts with regards to load capacity. The lawn is pretty flat and I am going to prepare a level area to hide it in. Not sure if I'll be able to move it on my own.......but there are no calcs to verify that. I'll just wait and see. The casters are marketed for cricket screens and grounds trailers etc.

You said that using insulating bricks for the dome is possible and there are some benefits, what do you mean by this? What about my combination idea to mix insulated and clay firebricks in the dome construction, is this daft?

I suppose my problem is that I quite fancy having a go at building the dome, but as you suggested a modular product would probably be lighter and easier....I'll take a look at the YouTube clip you mentioned.

Thanks for the tips, much appreciated.

With an insulation type material oven, the benefits as I see them are...

1) You'll need much less wood. You don't have to heat up a large mass of masonry. Only the inner skin needs to be hot for the radiant heat, which will stay hot with a live fire.

2) You'll be up to cooking temps quicker, you just want the hearth or pizza stone to be up to temperature.

3) Smaller oven for any given internal dimensions. With a masonry oven, you have the thickness of the dome, then the insulation, then the outer dome/house. If the inner done is insulating, that can be it.

4) Insulating materials are usually lighter, which again will suit your needs. Those pumice ovens I mentioned, he lifts the entire dome up on his own to place on the base.

Not sure about the insulating bricks you have, but making the dome will be harder with bricks compared to a moldable/castable material, and you'll still need to make it look nice once built.

Generally you want to avoid mixing materials with masonry. I would expect you to get cracks in a dome made that way.

I understand the desire to build with bricks. However you've placed quite a limitation on yourself with the base. I should stress that I've not built or used an oven out of insulating materials, but I can't see any reason why they won't work, and the inner size on that base will be much bigger than with the normal construction design.

You could build a normal dome and not bother insulating, but it would be far from ideal! Search for temporary or portable pizza ovens on youtube. Make a hot brick space, throw pizza in, it cooks. :-)

Hi Simon,

I have had a look at a few options with the exercise ball construction, and I quite like this one;
www.youtube.com/watch?v=fsOBp5pDBro&feature=share

It looks much more robust than the normal type, but I think I would use vermiculite as I have a local supplier, using a 80 or 85cm exercise ball.

What do you think? Any obvious concerns?

I'm kicking off this weekend as the procrastination is getting too
Much.

Thanks.

[bearsparko]

Apr 18, 2017 21:21:49 GMT downunderdave said:

If you plan rolling that thing over lawn then you'll need to replace the castors with larger diameter pneumatic wheels/tyres or cast a concrete path for it to roll on.

Hi, yes they are 10" pneumatic casters and with just the weight of the frame it runs fine. Let's see what an additional 300kg feels like .........

[downunderdave]

If you have 3 fat friends you could try giving them a ride around the yard to test it out.

[downunderdave]

A few observations on that you tube video, firstly you'll get a better surface by coating the ball with some vegetable oil rather than the cling wrap which produces creases. Secondly you should place some wedges under the door form work so it can drop to prevent damage to the casting on removal. Thirdly the floor bricks should not extend past the dome casting. The oven should be totally encased in insulation. Lastly the stand needs diagonal bracing. A masonry stand is best, steel second best and timber the worst.
An oven made from this material is subject to abrasion damage as vermiculite or perlite concretes make the resulting casting weak. In addition Portland cement does not like temperatures exceeding 300 C and parts of the casting will definitely exceed that. Because the mix is insulative it will be difficult and take longer for heat to penetrate it and likewise for it to store heat. The upside is that it is cheap and quick to build.

[bearsparko]

Apr 20, 2017 19:57:17 GMT downunderdave said:

A few observations on that you tube video, firstly you'll get a better surface by coating the ball with some vegetable oil rather than the cling wrap which produces creases. Secondly you should place some wedges under the door form work so it can drop to prevent damage to the casting on removal. Thirdly the floor bricks should not extend past the dome casting. The oven should be totally encased in insulation. Lastly the stand needs diagonal bracing. A masonry stand is best, steel second best and timber the worst.
An oven made from this material is subject to abrasion damage as vermiculite or perlite concretes make the resulting casting weak. In addition Portland cement does not like temperatures exceeding 300 C and parts of the casting will definitely exceed that. Because the mix is insulative it will be difficult and take longer for heat to penetrate it and likewise for it to store heat. The upside is that it is cheap and quick to build.

Hi,

Couple of questions;

Why should the floor brick not extend past the dome casting?

Is there anything I can add (lime etc) to give the cement a chance?

I am abut confused about the heat issue with vermicrete. What will be the issue over time, and I have looked AFC lots of builds in this way which makes me think it must work ok.....don't really want to wast my time or money if I can help it.

Thanks for your tips.

[downunderdave]

Apr 21, 2017 6:56:38 GMT bearsparko said:

Apr 20, 2017 19:57:17 GMT downunderdave said:

A few observations on that you tube video, firstly you'll get a better surface by coating the ball with some vegetable oil rather than the cling wrap which produces creases. Secondly you should place some wedges under the door form work so it can drop to prevent damage to the casting on removal. Thirdly the floor bricks should not extend past the dome casting. The oven should be totally encased in insulation. Lastly the stand needs diagonal bracing. A masonry stand is best, steel second best and timber the worst.
An oven made from this material is subject to abrasion damage as vermiculite or perlite concretes make the resulting casting weak. In addition Portland cement does not like temperatures exceeding 300 C and parts of the casting will definitely exceed that. Because the mix is insulative it will be difficult and take longer for heat to penetrate it and likewise for it to store heat. The upside is that it is cheap and quick to build.

Hi,

Couple of questions;

Why should the floor brick not extend past the dome casting?

Is there anything I can add (lime etc) to give the cement a chance?

I am abut confused about the heat issue with vermicrete. What will be the issue over time, and I have looked AFC lots of builds in this way which makes me think it must work ok.....don't really want to wast my time or money if I can help it.

Thanks for your tips.

If the floor bricks extend past the dome base they will conduct some heat to the outside. The whole dome and floor need to be encased in insulation.

I'm sure a vermicrete dome would work, but not sure for how long. Portland cement is good for around 300 C anything north of that and it breaks down eventually turning back to powder. I'm not certain, but I'd expect in time bits would start falling off the inside of the dome starting at the apex, not what you really want on your pizza. Lime is better and good for up to 500 C, anything north of that and you need calcium aluminate cement. Clay (cob) is ok but will not truly sinter (render permanent) until it gets above 573 C and is particularly unstable from 500-650 C so it is nigh on impossible to fire the whole oven up to this range in a controlled way with wood. Vermiculite and perlite are both good for up to 1100 C. The theory of the home-brew (3:1:1:1 sand, portland cement, hydrated lime, powdered clay) is that you get decent strength from the portland and if it dies the lime will take over while the clay content will also hold it all together. In practice this brew works remarkably well for a WFO both as a mortar and as a castable. I've advised a couple of home builders who wanted to do a build on the cheap to try it as a castable and they report good results  after 5 years. Adding lime or replacing the portland with it in a vermicrete casting could work, so try it and let us know. It won't however solve the problems of the casting being weak and having insufficient thermal mass.

[simon]

Apr 20, 2017 12:21:42 GMT bearsparko said:

Hi Simon,

I have had a look at a few options with the exercise ball construction, and I quite like this one;
www.youtube.com/watch?v=fsOBp5pDBro&feature=share

It looks much more robust than the normal type, but I think I would use vermiculite as I have a local supplier, using a 80 or 85cm exercise ball.

What do you think? Any obvious concerns?

I'm kicking off this weekend as the procrastination is getting too
Much.

Thanks.

Hi, sorry for not getting back quicker, I've been offline...

That video does show a little more height than some of these exercise ball shaped ovens, which is better IMHO.

As someone else has said, it would be better (and cheaper) to just have the fire bricks for the hearth, and not extend out. Losing heat is not really an issue in your case I'd say, but you could have a very high temperature outside of the oven dome, which could burn someone/something. It would also make finishing the dome, to make it weather proof much harder.

Now what to actually cast with? Vermiculite should be fine, but Portland cement less so. As mentioned it breaks down with high heat, which is why you see various home brew mixes for mortars etc. The trouble with adding something like clay is you lose insulation, you have to source another material, and it will shrink and crack and be horrible to work with.

As already mentioned there is another type of cement that is regarded as a refractory cement, Calcium Aluminate. It will survive the heat, but it sets quickly. You will have a much shorter window of working time. It is unlikely to be stocked at a local merchants. However you will easily be able to get fast setting cements. These are a mix of Portland cement (calcium sulphates) with fast setting calcium aluminate. If you want a vermiculite dome, I'd make it with that. Make small(er) batches, mould, repeat.

Good luck.