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Post by miquel on Jun 5, 2018 0:02:48 GMT -8
Hello, I want to make a BBRMH oven. Could you look at the design to see what you think?
The height of the heat riser I want to make minimum, for a BBRMH of 20 cm I think it is 115 cm, can be made shorter? Upper the heat riser I want the bricks of oven's floor, and the hot air enter to the oven's dome through sides of the floor. The separation between the heat riser and oven's floor I want it to be 5 cm, will it be enough ? The oven's exhaust I want it to be underneath oven floor in the the back part. The dome will be isolated, the BBRMH also (or just with the heat riser will be enought?) Any advice? I will be able to cook with the oven (pizzas, bread..? Thank you in advance!! |
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Post by peterberg on Jun 5, 2018 3:19:37 GMT -8
Hi Miquel,
Would you please make the file available as SketchUp version 8? Although I am using version 17, which is incidentally the last free desktop version, it would be better to choose the lowest denominator everyone could load.
And oh yes, it appears you saved it as version 18?
edit:
There happens to be a desktop version of Viewer which is able to read the latest files. I'll have a look at it tonight.
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Post by miquel on Jun 5, 2018 5:10:41 GMT -8
Hello Peter, I just modified the sketch adding more information and I saved it in 2017 and 2018 format.
sketch version 2017:
sketch version 2018:
Thanks in advance!!
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serg247
Junior Member
The mountain can not be conquered, it can allow it to ascend...
Posts: 111 
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Post by serg247 on Jun 5, 2018 6:32:11 GMT -8
Peter offered to keep the eighth version, usually in good tone, available for viewing by all. On my not old 64 bit laptop version above 16 years does not work at all. It is connected with the graphics adapter and drivers for it under Windows 8.1. Maybe it's a SketchUp policy.
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Post by miquel on Jun 7, 2018 3:47:23 GMT -8
Hello Peter,
Have you been able to watch the sketch?
Do you think I can reach temperature to make bread or pitzas?
What minimum height can I put on the heat riser?
Greetings,
Miquel
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Post by peterberg on Jun 9, 2018 8:02:13 GMT -8
The height of the heat riser I want to make minimum, for a BBRMH of 20 cm I think it is 115 cm, can be made shorter? Hi Miquel, It took some time to see what you meant but I think I have the picture now. The minimum recommended height for the riser is 115 cm, yes. You could do with a shorter one but in that case you need to do something different. Making the riser wider in steps above the port and at the end back to system size again would presumably allow the riser to be shorter, down to 75 cm. Travis did this and obtained very good results. But this construction isn't tested as yet, so you are on largely untrodden ground. See donkey32.proboards.com/thread/3330/150-batch-cookstove-short-riserUpper the heat riser I want the bricks of oven's floor, and the hot air enter to the oven's dome through sides of the floor. The separation between the heat riser and oven's floor I want it to be 5 cm, will it be enough? No, that won't be enough by far, this is a problem. Batch boxes are notoriously picky about restrictions and build like that you have a serious one. In your case I would end the riser in the dome space itself. What you've drawn is actually a bell with a sidewinder inside and an oven on top of the riser. The dome will get awfully hot, no doubt about that. The floor is another matter, it need to be heated from below. Since you want to insulate the dome lots of heat will enter the bell around the combustion core. While the oven floor is the ceiling of the bell at the same time which is normally the hottest. A 20 cm system is no small heater, when ran properly it will be hot as hell. The oven's exhaust I want it to be underneath oven floor in the back part. The exhaust is at the right place although a bit on the cramped side. Make it quite a bit larger than system size in order to avoid restriction. The dome will be isolated, the BBRMH also (or just with the heat riser will be enought?) Just the heat riser insulated would be enough. Any advice? I will be able to cook with the oven (pizzas, bread..? Yes, you will be able to cook pizzas and bread, but not at the same time. And I don't have the faintest idea what volume of fuel you need to reach that. In all probability, it would be sensible to build a bench at the side or at the back to use excess heat. The whole of the thing looks like two bells on top of each other and the top one the first bell. |
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Post by miquel on Jun 10, 2018 23:36:08 GMT -8
Hello Peter,
What distance would be the minimum between the heat riser and the roof of this (oven floor). If I finish the heat riser inside the oven's dome, I can not warm the oven floor, right?
Why are you saying you can not cook pizzas and bread at the same time (space, flavors ..?).
From what you say it looks like I'm going to need a lot of wood and time to heat the oven. If so, is not it optimal to make a rocket oven? Better a conventional oven?
I do it in 200 cm diameter because I read in a post that the 150 is too small for a oven like this, if it will enough with 150 i will go with it, because the chimney i have is this diameter. Reduce from 200 to 150 It would be a problem, right?
I put some pictures to clarify the desing i want to implement where i hide the dome.
Thank you very much!!
Miquel
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Post by peterberg on Jun 12, 2018 23:48:12 GMT -8
What distance would be the minimum between the heat riser and the roof of this (oven floor). If I finish the heat riser inside the oven's dome, I can not warm the oven floor, right? The minimum distance between heat riser and oven floor or bell ceiling (commonly called the top gap) is 1.5 times the riser diameter as recommended value. Like this it won't pose a restriction so it'll always work. Ending the riser in the oven would primarily heat the dome, that's true. But as I explained earlier, the exhaust is going down in the space under the oven which will be heated from below this way. The final exhaust from this bell structure should be close to the ground, centered at least 1 time the pipe's diameter from the ground. Why are you saying you can not cook pizzas and bread at the same time (space, flavors ..?). For cooking pizza you need quite high temps, much less for bread as I understand it. From what you say it looks like I'm going to need a lot of wood and time to heat the oven. If so, is not it optimal to make a rocket oven? Better a conventional oven? Combustion in a conventional oven isn't efficient, at all. It smokes out of the oven door and so on. A rocket burns 99% of the fuel which means there's more heat produced for the same amount of fuel. I do it in 200 cm diameter because I read in a post that the 150 is too small for a oven like this, if it will enough with 150 i will go with it, because the chimney i have is this diameter. Reduce from 200 to 150 It would be a problem, right? Yes, reducing like that would be a serious problem. What you could do is to build a 170 mm system and vent it through a 150 mm chimney provided this is straight up, round and smooth inside. Since the batch box scales up very fast, this is already a quite sizable heater. |
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Post by miquel on Jun 13, 2018 22:04:41 GMT -8
In an RMH design with bench, the recommended space is around 5 cm, right? It is not like in a bell that you want gases to be slow down. What is taken into account is that the CSA is equal to or greater than that of heat riser in order to avoid bottleneck. The idea is that the gases are relatized when entering dome oven making bell effect. I attach an image of an oven made in this way. drive.google.com/open?id=14JSWRKfVp7SAeDan0eCW9GwIW--NI0lMI do not understand what are you telling me about the chimney it has to be centered at least once a tube diameter. |
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Post by peterberg on Jun 14, 2018 6:20:08 GMT -8
In an RMH design with bench, the recommended space is around 5 cm, right? The recommended minimum space is 5 cm for the top gap in a 6" J-tube system, yes. In practise, there isn't a maximum space, that 5 cm is only there to get the very hot spot in the middle of the barrel so one would be able to cook on it. It is not like in a bell that you want gases to be slow down. What is taken into account is that the CSA is equal to or greater than that of heat riser in order to avoid bottleneck. The idea is that the gases are relatized when entering dome oven making bell effect. I attach an image of an oven made in this way. It's often misunderstood what is happening when a restriction is present and how. For example, in case the gases need to go through a 90 degrees bend at the same time, there need to be more space otherwise there would be loss of momentum. And doing 180 degrees one would need even more, I'd recommend to have at least 150% of CSA while doing a 90 degree bend and 200% CSA while doing a 180 degree bend. Those two values are in my opinion the minimum in a system where you don't want restrictions. And believe me, you want unrestricted flow in a batch box rocket. When built like the picture it could work, but almost certainly slow to start up and get smokeless if at all. I tested this in different configurations, also in a J-tube. Every time the wider option yielded better results. I do not understand what are you telling me about the chimney it has to be centered at least once a tube diameter. The chimney exit close to the floor in the side of a bell need to have some space underneath in order to ensure unrestricted flow of the gases. In short, underneath the pipe there need to be a space at least half the diameter of the pipe itself. See for clarification the red bell article, there's is a picture and some text why it is done like that. Edit: there's a big difference between slowing gases down in a bell and through a restriction. In the first case there won't be loss of momentum, in the second there is. |
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Post by miquel on Jun 19, 2018 2:11:31 GMT -8
Hello, The problem is that if the riser's output is directly in the oven, I lose a lot of space to cook, right? Is there a design that you consider optimal for this type of oven? I have searched a lot and what I have found is: - Direct exit inside oven and classic fireplace in the dome. - The design of Satamax where firewood is put directly into the dome simulating a J-Tube. - And the one I added earlier. If I add a chimney under the floor I still lose more space to cook, so I wanted to make a riser outlet under the oven so I heat the floor and the hot air comes out from the sides of the dome heating it, leaving free space for cooking.
What do you advise me? Thank you very much! |
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serg247
Junior Member
The mountain can not be conquered, it can allow it to ascend...
Posts: 111
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Post by serg247 on Jun 19, 2018 3:07:08 GMT -8
Поместите печь Помпеи над DSR. Боковая дверь DSR с входа в печь Помпеи. Его можно использовать с древесиной в DSR и в помпеевой печи.
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Post by Vortex on Jun 19, 2018 5:01:46 GMT -8
Serg, best to post in English, some people get upset about it.
Place the Pompeii oven over the DSR. Side door DSR from the entrance to the oven Pompeii. It can be used with wood in DSR and in a pomp furnace.. |
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serg247
Junior Member
The mountain can not be conquered, it can allow it to ascend...
Posts: 111
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Post by serg247 on Jun 19, 2018 8:05:19 GMT -8
A picture is worth a thousand words of Google translator.  I'll try to draw it. |
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lst
New Member
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Post by lst on Jul 18, 2018 7:32:34 GMT -8
Hello,
I'm following this thread as I want to do something similar.
Can I ask what would be the main disadvantage to have the riser directly in the oven chamber (apart from wasting cooking space)?
Also, as I understand the 'Bells sizing' article at batchrocket.eu the oven would be way too small compared to the suggested dimensions.
I am struggling with this as well. I have a pompei style oven that I want to convert to use with a rocket, but the ideal riser diameter is way too small.
A 20cm riser diameter would require 9.4m² (191 sq ft) of bell surface.
Not sure how to solve that. Or if that can be ignored.
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I'll try to draw it.