(movable) Rocket Oven for Pizza - improvements needes!

[klenna]

Hello people.

I am going to build my first oven in the next weeks.
Very excited =)
I will build it in a squat which is under construction still, so I wanna make it somehow movable for the worst case that it still has to change position.
Also, I am in a city, which I don't know very well and neither the language, so I wanna keep it simple for the start =)
I am sympathizing most with this style from approvecho bread oven: weblife.org/capturing_heat/pdf/capturing_heat.pdf (p. 31)
(talking about the upper barrel system - the bottom part I will adjust a little bit to other models that seem lighter)

I was reading a lot through this forum, plus donkey23 plus facebook, but there was almost no thread about this type.
Is it very low profile, concerning heat efficiency? Or is it for another reason unpopular? Or is there just nobody with experience with it?

The question I came across: Do you think I can make the doors larger, circa 40cm, so that bigger pizza fit in? It would loose more heat, but as the oven might get very hot anyway, that wouldn't be such a big loss, I imagine.
Or is the extreme heat that people talk about (500°C in 30 minutes) something that you rather expect after collecting material with perfect scales or with better insulated stoves?

Thanks for your help and all the things that I could read already, internet is realy not that bad hehe
ciao!

[klenna]

Helloagain.
After I was told on permies.com, that aprovecho is not quite popular and that it's difficult to find experiences with their work, I decided to change the title of the subject.

and I also changed my plans, I found two videos, that also other people could find helpful:
www.youtube.com/watch?v=h4WDZMmkDeo

www.youtube.com/watch?v=TFjbE8coX4M

the second one is more simple and I will go for it, because I doubt I will find another barrel and also the tool-situation is not totally clear to me in the place where I live right now. but I will keep the message from the first video in mind and isolate as good as possible the combustion chamber and also try to find something for the upper part of the barrel.
as a vehicle, I would like to try a shopping cart.
unfortunately this second video exactly lacks a proper discussion under the video, which I am warned about in some of the forums.
Does anyone has an opinion about my idea?

ciao ciao, Magda

[Donkey]

Good comment on some reasons why the vertical feed is attractive.
donkey32.proboards.com/thread/865/looking-specific-input-camping-design

[klenna]

convinced.
it shouldn't be too difficult.
thanks =)

[klenna]

Hello people, who are hopefully getting their bread or back heated by a self-built rocket-to-the-moon-oven,

I built the topic's pizza-oven this summer and
YES! it makes a rocket noise and the fire is drawn up the chimney
buuut it creates quite a bit of smoke
and: it comes only up to 50°C/ 120°F
so it rather serves raw-eaters than pizzas right now...

so I will explain what I did and hope that someone has a special hint, what to change.
you will recognise, that it is in all very improvised and experimented, but still maybe someone of you can point out a major factor which is not too difficult to change and might help the whole situation for a better.



on the first sketch you can see the measurements in cm
in inch they will be:
lower pipe's diameter 11cm = 4,33''
upper pipe's diameter 13cm = 5,11''
the barrel's diamter 40 cm = 15,74''
the barrel's lenght 50cm = 19,68''

 unfortunately I forgot hte lengths of the pipes,
but I made sure that
b < a (though only slightly)
a = 1/3 of c (or even a little less)
c < d

somewhere I read that it's not a big deal that the upper pipe is slightly bigger in diameter than the lower. what do you think?
I know that the CSA should always stay the same, but the diagonal area, where a is attached to b and where b is attached to c will automatically be higher, so I assume it's only a rough number.
antoher matter with the upper and lower pipe is that they are not 100% above each other and the upper one is not so straight, it has a very small slope.




material and isolation:

the pipes and barrel are from metal, which I honestly cannot identify. As I checked, the lowest possible melting temperature would be 230°C/ 446°F and I only need up to 180°C/ 356°F and I didn't expect to high results anyhow.

apart from the loosely applied lit, which is situated where I marked the 40cm-diameter of the barrel, there should be no way for air to flew in where it's not supposed to be.

on the second sketch, you can make out the insulation I hope:
I made a mass from found clay and expanded clay and fireclay.
expanded clay is these small pearls which I think you can also put into indoor plants instead of earth - I crushed them to make the mass a smooth material. the fireclay I got from smashing ovenbricks.
this material is marked with stripes in the picture and was around 2cm/ 0,78'' or thicker.

the lower pipe is additionally surrounded by hollow bricks set around the mass, they are marked with dots in the sketch.

I didn't care too much about the isolation of the barrel and upper pipe, because I wanted it to heat up fastly instead of storing heat and when it releases heat, the cooking person will be happy during the cold times..

[klenna]

about the room:
So far, I used it only inside, with the pipe out the window, therefor I attributed a bended pipe in the end, as visible in the picture in the attachment.
the room doesn't have any heating and the whole building has almost no heating, I tried it in early november in poland, when it was around 8°C/ 46°F and moist.
and yeah, there was to much smoke coming from the end of the pipe back into the room, so that it got uncomfortable :/


concerning the insides:

I used the fin-technique in the lower pipe, the heat riser (c in the sketch), which means I attached small triangles with fireproofed glue inside to speed up the gases.

and inside the barrel I experimented with putting a fireclay brick 4cm/ 1,5'' above the lower pipe-entrance (it is lieing nect to the entrance in the picture)
and another piece hanging below the upper exit.
unfortunately I am not able to upload more attachments here, but I was inspired by this: picasaweb.google.com/Jonnygms/RocketOven#5600380213232462402
and:
picasaweb.google.com/Jonnygms/RocketOven#5600380244780230498


I add pictures in the attachment, I hope your eyes won't hurt from the bad quality.
I am not living in this city anymore and I get there only occasionally,
and I don't like to return without improvement ideas.
=)

Any comments or questions?

Best regards and thank you already with a big smile,
Magda

Attachments:

[hpmer]

First off, you're starting with only a 4" system which limits the heat output you can expect. If you can increase system size that would help A LOT.

The easiest thing to try would be the insulation around the feed tube/burn chamber/heat riser. I'd try ripping the existing stuff out and replacing it with straight insulation mixed with clay slip. Forget the fire clay. Use just enough watery clay to hold the insulating stuff together. It will be fragile so you may need to encase it in something.

To make it, crush up the stuff you have and put it in a big bucket. Add water to few inches above your material and mix it well, then let it sit for a while. The heavy stuff will settle out and the clay will stay suspended in the water.

After it settles for 30 minutes or so, you can scoop out the liquid with the suspended clay. If you have too much water you'll have to let that mix settle out which could take days. Best consistency is a thick milk shake so be careful how much water you add at the beginning.

Use this "milkshake" like mix to bind together your insulation, just enough to hold the mix together, and put in on at least 2" thick, but more is better.

By the way, I've had good success using wood ash as the insulation material, but takes a while to accumulate enough to work with.

This will maximize the heat you do get from the 4" system and likely burn more of the gases and therefore produce less smoke.

The chimney should provide some negative air pressure so I'm surprised it's smoking into the room. You might try insulating the exit pipe as well and see if that helps.

Good luck and let us know if this helps.

[klenna]

Hello hmper,

thanks a lot for your answer, it gves me some motivation powered by hope, to start crafting again when it's warmer.

wow I wouldn't have expected that the pipe needs to be that big. but now that you say it, sure, in lots of instruction papers it reads like this. there was another woman building a rocket stove but for heating and she also used a pipe sized like mine and it worked well, but yeah she had a very different design than I.

so you're saying that using fire clay in my insulation mix was a mistake and it would not be worth trying to insulate more aroud the fireclay-ceramit-clay-insulation mix that I already applied? because it sounds like this would be a very easy way to try as improvement. otherwise it could already be that much effort that I could rather start with my next oven with bigger pipes..

as I said, it will still take some time till I can try it out, but it's great that I can already collect ideas and than start immeadiately, when I'm there.
ciao
Magda

[hpmer]

You can definitely insulate around what you already have if you've got the space to do so. It's just that the heavier material around your existing pipe will absorb heat until they equalize with the burn chamber, so getting up to temperature takes longer than if it were straight insulation.

The clay (fire clay, local source, etc) and anything else that is non-insulative is denser than you want at that point of the system, but it does work well as a binder. So, what you ideally want is straight insulation materials. Perlite and vermiculite work great since they each contain a lot of air, but they don't stick together well. Coating these particles with a thin, runny clay mix helps them hold together.

Other folks have used sheets of rockwool or other types of sheet insulation, but whatever you use it should not be very heavy, but light indicating lots of entrained air which is one of the best insulators around.

Also, I'm not sure about what you mean about fins in the lower pipe. If they are too big they could be reducing the flow of gases by reducing system size at this very critical part. You want system size the same throughout.

Better to build a proven design for your first build to see how they're supposed to run. All your deviations from the basic design introduce complications that then have to be troubleshot.

Stick with the basics. They work very well. Once you get some experience you can try to improve on the original, but frankly it works pretty well as it is.

[docbb]

may I suggest that you have a look on this album