CSA Question

Hi rocket scientists i am at the stage of constructing my fire box, burn tunnel etc on a 160mm rmh and struggling finding the correct CSA. In the EE Winsner book it is in inches and where MMS are given it's only for 200mm or 150mm that I can see. I'm sure for most people it's easy to work out but the maths is frying my brain at the minute! Help would be greatly appreciated!🙏

Hei, you are Building a j style or a batchbox?

Thanks for replying so quickly. It's a j tube. Batch box I feel is slightly beyond me at the minute but hopefully for my next build!
The problem is converting the CSA of the 160 circle to the square/rectangular sections.. further confusing me is the extra leeway one must allow for the rougher interior of the brick sections

I'll try to explain, the csa is nothing more than the cross section of the riser, or the area of ​​a flat figure, or in your case: a square section (16x16) or 256 cm², instead if you consider it a round section (8²x π) 201 cm²

Hi Mike;
Well, a 150mm system is 5.9" and a 160mm is 6.2"
With your mention of a burn tunnel and the Wisner's book, I suspect you are building a J-Tube RMH.

J-Tubes are forgiving on dimensions compared to a Batchbox.
The feed tube, and burn tunnel should have the same dimensions such as 160x160 mm, or 140x180mm as long as they have the same area.
Your Riser can easily be 25mm larger, but not smaller and your exit chimney can still be 160mm.
Your feed tube ideally will be apx 400mm deep
The burn tunnel roof should be 250-300mm long (4-5 Firebricks on edge)
Your riser should be around 1000mm tall

Ok so 16 or (160mm) X 16 will give me the CSA that I need? Only when I look at other equivalents, for example, the CSA of a 6" circle is 5.5 "X 5.5"...  

Thanks both for clearing that up! I think I massively over thought it. But you know when you're building a fire in your kitchen with temps that can melt the earth's crust you want to get it right eh?

If your riser is only 6" then your feed tube and burn tunnel must be that size as well, never larger.

Ah I think you may be referring to a previous post about doing a 5 min riser ? For one reason or another I sacked that idea off and decided to build theriser from split fire bricks surrounded by Morgan superwool

That works even better in this case.
Build the splits to match the feed and burn tunnel size and you are good to go.