thomas rubino

Hi Ty
Always a good idea to gather your materials ahead of time.
And buying now, rather than later, will save you some bucks for sure.

To help you with the materials, you need a definitive plan for what you will build.
A first-generation 6" Batchbox is quite different than an 8" J-Tube.
Are you thinking of a piped mass? Or perhaps a stratification bell?
What material do you want to work with?
Are you hoping to build as cheaply as possible? Or do you want a beautiful work of art?

You mentioned having a book; I assume it is the RMH builders' guide from Ernie & Erica, an excellent start to learning about RMHs, particularly J-Tubes.
You won't learn about Batchboxes or stratification chambers from it, though.
I offer a book on building the first generation Batchboxes, either as a hard copy or a PDF file
https://dragontechrmh.com/now-available-batchbox-core-construction-book/

Let us know what your plans are.

Hi Rico, perfectly acceptable to offset a barrel, leaving an inch or so to the barrel on the one side.
The other side would have 6" or more.
If you make the gap too small, you will have issues; it may stall, and smoke back, your buddy's wife might not be happy...
Perhaps 9cm ( 3.5") would work, but 6cm may not.
The CSA must remain the same in the J-Tube, and the barrel CSA should be at least 150% larger.
Page 9 in the RMH builders' guide shares that information.

What to do with the old car?
Give it to the chickens!

Mom passed in 2017, that was the last time I flew.
I have been considering a trip back east to see family, while most are still with us.
I am seriously considering driving the 2500 miles rather than dealing with air travel.

Five minutes of work with a wire feed welder will tack on a nice flat spot.

Heck yeah, I have built and used cast iron double-barrel kits several times myself and seen them in use for years.
You should not need any extra air intake; they draw in air very well.

Hi L,  yes, it can be done. I'm not sure how well floor heating will work, but in your climate, it has a chance.
Here is one https://permies.com/t/272814/RMH-heats-floor-water
Jeff lawton style https://permies.com/t/155422/Plans-water-heater
https://permies.com/t/190806/built-rocket-water-heater

Hi Cerbu;
When you follow Peter's plans to the letter, your results are virtually guaranteed!
A true master builder, we are all lucky he has chosen to freely share his designs with the world!
Thank You Peter, from the rocket mass heater community!

When I was attaching metal art to the brick bell of a mass heater, I chose to use rare-earth magnets epoxied to the bell, and my metal art attached to them.
On my double skin bell, this has worked perfectly.
I used the same method on Shorty, my single skin bell.
It seemed to work perfectly... until we had a cold morning, when I added an extra batch to Shorty.
Oh my, she really throws heat if you double up... unfortunately, standard rare-earth magnets do not hold as temperatures rise.
Permies rocket scientist Fox warned me about his attempts to use RE magnets, which failed as soon as the temperature rose.
And indeed he was spot on, as the second load in Shorty got to roaring, my metal raven art suddenly fell to the floor!
It was not damaged. But it refused to stay on the bell.
A search online and I found this https://www.kjmagnetics.com/products/high-temp-magnets?gad_campaignid=22284168230
Good to 428F or 220C. I doubt I could get the outer skin that hot on Shorty; our house is way too small.
Standard rare earth magnets are only good to 176F 80 °C

Cost is negligible, and they are holding perfectly!
If you want to add bling to your dragon, high-heat rare-earth magnets are the way to go!

Hi May
I also am not quite sure what you are describing.
If you are attaching the new room to the existing house, then the original foundation will be providing support on that side.
Your new room will be 12' deep.
If it were me, I would use soni-tube forms and pour concrete piers every eight feet 3' in the ground along the outside edge.
Set your black locust on them.
For a solid floor, depending on your floor joists, I would also add a support beam and piers at six foot.
This  beam could be supported with piers of black locust in the ground
If using concrete is not to your liking then using your black locust posts on the outside edge would work.
I have heard of B.L. posts over 100 years old still supporting buildings.