Matt Todd

Happy to see no reports of cracking with the all brick (except ceiling) bell!
Funny that you did tile on top of the fire brick roof, that's exactly what I was thinking of doing myself.
Did you use sand/clay mortar of Matt Walker fame, or a purchased refractory mortar?

L Cho wrote: Barrels can be a little hard to find here, so I was thinking about fuel oil tanks, which can be had for free. If the tank can be cleaned/purged enough to be considered safe, can I simply adjust the value of internal surface area, ISA, by raising or lowering the exhaust port?

An old fuel oil tank is exactly what I used. A 300 gallon tank has just about the perfect ISA for a 7" core. DSR2 in my case, so it could slide in.  
https://permies.com/t/151576/Sherman-Tank-DSR-Rocket-Mass

This build is really making me question the conventional wisdom that says everything above the heat riser needs to be double skinned with a refractory (usually firebrick) inner layer.

I went on a deep dive to see what temperature red clay brick is fired at and across 9 sources 800C (1472F) was the minimum and 1200C (2192F) was the maximum.

There are not many sources for temperature readings inside a brick bell, but one well documented case on the Donkey32 board measured 600C (1112F) at the bell ceiling with temps dropping quickly down the bell wall.

While I would still use firebrick in the ceiling (out of an abundance of caution) I'm really seeing no reason to continue firebrick down the inner walls. Aside from the fact that firebrick comes in splits which helps save space to make a double skin.

I see you put a thermocouple in the riser. Did you happen to put one anywhere in the bell?

Double skin serves three purposes: gas tightness, heat storage, and allowance for expansion.
It is widely accepted that you only really need the double skin above the level of the heat riser exhaust though.
So I'd skip the expensive metalwork and just do a masonry bottom and double skin top (masonry outer, refractory inner.)
That's how I'm designing my own bell. It won't hold as much heat but it will be more responsive, producing heat quicker as I want it to do.

Besides that, if you used metal it should be on the outside. It wouldn't serve much purpose inside. It's not just warping to be concerned about, it's the general expansion and contraction of metal that would be a lot different than the surround masonry making it difficult to tie it all together.

You will never (sorry) be able to fight cedar apple rust out of your local cedar trees to the point of having any positive effect on apple trees. If you want apples then they have to be varieties with rust resistance.
I say this because even if you get rid of all the cedar on your property, they're still going to be around on neighboring properties. And if yours had cedar apple rust, those likely do too.

Not sure what your overall setup is like (how the passive solar relates to the rest of the house) but I find that a 90 degree roof is ideal in my passive solar porch https://permies.com/t/173304/Solar-Porch-Passive-Solar-Retrofit
Any more admission of light would get too hot in the spring and fall. The axial tilt of the earth regulates mine simply by putting the sun higher in the sky when it's too hot out to want that direct light into the system.

David Harrold wrote:  I have never been so disappointed with a berry bush as I was with sea buckthorn.

And here I was holding off on digging them up until they produced! Doesn't sound like they'll be any better if/when they finally do give me berries. Not that I'm certain I'll even be able to dig them up with ALLLLLL the runners they've put out.   I did a post about it last summer: https://permies.com/t/224627/ready-give-Seaberry

I built a semi-finished room in my basement. The floor starts with a "air gap underlayment" that comes in rolls and looks almost like lego board. This allows you to put vinyl tile on top but keeps it slightly elevated off the floor to prevent both moisture and heat conduction. Here's an example: https://www.menards.com/main/flooring-rugs/laminate-flooring/laminate-floor-installation-tools-maintenance/dmx-air-gap-44-1-2-flooring-underlayment-kit/113-15/p-1462541330534-c-6607.htm

Chose this stuff because we do get occasional seepage after hard rains.

thomas rubino wrote:Ok, Matt;
Were you going to bolt this down or let it free-float?

Free floating, corralled by masonry so it can't shift around. Like maybe cut a notch out of a course of bricks to sit over the flange so it's held down in a way that it can still expand a bit.