Structure questions bbr8

Hello everybody, my name is Nacho, and i am building my first bbr8.
I have learned very much here and in Pete's website.

I hope you can help me with some questions (Sorry for my english)
i attach 2 pics to understand it better.

First of all, it is a 8'' or 20cm system, with a main bell and a bench which is 20cm below.
bell and bench will have 2 layer of bricks and a ceramic blanket in between.
The passage between the bell and the bench is a step 20cm high and 45 cm wide

Second, on the top of the firebox will stand a refractory slab 50 cm wide and 50 cm depht to make an oven

My questions are:

1. As the Oven is wider than the firebox, will the smoke have free passage or it will be stopped?
2. It is necessary to have 20cm or more space surrounding the riser or it can be beside the 2 layer brick with no room for the smoke?

Thanks for reading and helping people like me, thank you very much.
Nacho

You don't need to have space on all sides between firebox core and bell walls, though if the masonry structure walls are exterior, you would increase heat loss to the outside with the core next to those walls. Just make sure you have plenty of total clearance for airflow from riser top to bell to bench, probably at least double the system cross section.  The same goes for clearance around the oven slab.

Against the existing masonry wall, you don't really need the second layer of brick in the bell/bench wall. It would largely be a matter of construction expediency whether you want to include that second layer. With the steel studs behind the bell, you don't really have room to move the bell closer to the wall, so if the extra bricks help with structural support or stability of the bell wall, you would want to keep them.

Thank you very much for your answer, i think i have no more questions. I am a bit nervous because i can start the construction now.
I'll keep posting
Seeyou!

I have another question.
As you see in the pictures, the bench is one step down, and the exhaust also is one step down.
Does It Matter if the firebox and the riser are (20cm 8' )higher than the exhaust?
Thanks!!!

What is a "bbr8."?

Batch Box Rocket 8" I figure John

Hello there, i think i can post here my improvements in the building.

I have build the floor with regular bricks, and i have tested the firebox and riser.

Testing the firebox make me feel so happy, it works!!!

Hehe is the video of the test yesterday, it works!!!

Update with the work, we have planned the exhaust pipe, it is huge
We have also make the connection between the bell and the bench with 2 holes of 200x200 mm

Thank you for watching, if you see anything incorrect please please tell me.

Lots of airflow space in that connection, looks good

I will keep updating the evolution of the rocket:

Hi Nacho;
Looking at your photos everything is looking good.
I see one spot that I have a question about.
Your secondary air tube looks to be sized for a 6" batch, not an 8".
6" uses a 2.5 x 1.5" tube and for an 8" I use a 2 x 4" Both retain the 2" riser stub
              (6.35 x 3.81 cm)                                   (5 x 10.1cm)

Yes, the secondary Air is 5cm x 3cm    2" x 1'5"  i made a mistake on that............ is It A big deal? Im afraid of destroying that part.
Thank you

Well Nacho;
It really should be larger, I suggested 5 x10 and you have 3 x 5...
I would say that is about half as large as an 8" batch should use.

However, it will work.
The performance will suffer with less oxygen.
The emissions could be much higher than Peter's design.

I would use what you have for now and work on seeking out a proper-size tube to replace it.

Nacho,

I'm looking at 6.jpg and it looks like you insulated the oven. White ovens do not work good enough even if made from steel. If yours is brick and also insulated then I doubt you can bake anything there. If this is the case, I would at least remove the insulation, so the outside would be heated by the descending exhaust.

Cristobal, that is an interesting point, I think the idea is to heat the oven from underneath using the firebox as the heat  source.  

Cristobal Cristo wrote:Nacho,

I'm looking at 6.jpg and it looks like you insulated the oven. White ovens do not work good enough even if made from steel. If yours is brick and also insulated then I doubt you can bake anything there. If this is the case, I would at least remove the insulation, so the outside would be heated by the descending exhaust.

Yes, as Fox said, the main heat for the oven will be the firebox, that is why i isolate the oven. The temperatures seems to drop a lot as the smoke goes down in the bell. i hope i can reach some good temperature in the oven. fingers crossed