rmh size help

I Am attempting a large heater. Using a 10x10in riser but how to Calculate all the rest. My idea is to manufacture feed box cross tube and riser out of S'S my mass will be 30ft long with 3 elbows. Please help. Thanks

If your heat riser is 10" x 10" inside dimension, your J-tube should NOT be larger, at any point, than 100 square inches.

It could be 12" x 8" = 96 sq. in...
10" x 10" = 100 sq. in...
7" x 14" = 98 sq. in...
6" x 16" = 96 sq. in...
etc.

not sure what S's material is...

Stainless steel. I have the opportunity to build out o's stainless. So should I build it all out of 10x10in square tubing

This is how I'm looking at it. What would be the correct formula to build it

I too had an unlimited supply of free stainless to build from. but after many many long hours of research i decided against it.. to go with a cast-able refractory for burn chamber and heat riser.

So my question is how to determine sizing of the j it self

I could be wrong but won't the stainless just degrade over time with the high levels of heat? Plus I thought one of the keys to the RMH was the brick's insulating properties?

Adam Bieglar : We are not a closed society, we are very much open to all, welcome to Permies.com and a Special welcome to the Rocket and Wood stove Forum Threads, with
over 20,000 fellow members around the world, you should be able to come here 24 / 7 to find someone who wants to talk about what you want to talk about ! Un-fortunately /
or fortunately, we have developed a common language and standard of measurements! The Vocabulary and the Geometry of the Original Rocket Mass Heaters RMHs, remains
unchanged, though there has been much improvement in materials used since Ianto Evans' penned "Rocket Mass Heaters'', available as a downloaded Copy $15, from
Rocketstoves,com , with over~100,000~ RMHs built world wide, most of them have been made following 'The Book', and 95% of the first time builds (that worked) were
made Following 'The Book'. There is STILL no other book in any language with more Rocket Stove family information ( and I don't make a nickel !)

Because we all need to speak a common language and measure things the same, I highly recommend this book to any one strongly considering an RMH in their future ! Read
the book and then come back here with any questions, we will then be able to walk you thru your build step by step, and improve your build along the way ! For th' Craft BIG AL !