- yeah, firebrick cuts pretty slick on a masonry saw, and a grinder will do it in a pinch.
I can see where you're going with the bigger fuel box idea.
I am patiently sawing 16-18" logs down to 9-12" for our little fuel feed, one by one as we bring in another load for the day. Ernie has assured me that if we ever buy another cord of firewood
, and they ask if he really wants 12" even though it will take them longer, he will say Yes. Perhaps I will get ambitious and cut down the face cord with the chainsaw. So yes, "Can I make one of your efficient mass-heaters but have a big firebox like I'm used to" is a very popular idea.
The main problem with any larger box is
- getting the fire to burn clean enough
to NEVER put creosote in the cold exchanger piping or downstream chimney,
- to make it so you can add wood
without spilling smoke into the room.
To do a true 'batch burn' where you close the door once the fire is going and don't open it again, you have to calibrate the system for your BTU needs pretty closely. These change with the seasons and weather, so you compensate for the weather by doing every day / alternate day firings. These are best done in advance of a major weather change. Even if you are a little off, the heat is still very even, compared to woodstoves or forced-air furnaces - it might be the difference of a T-shirt day or a sweater day, and you can double up and burn two fires the next day if you think
it will help. Problem is, 2 fires means 2 start-ups, the smokiest part of the burn. And smoky means creosote, in a low-temperature heat-exchanger.
To have the pleasure of using the same small heater spring, winter, and fall, and burning the amount that makes you feel cosy, without re-starting a new fire, you need to be able to feed wood while the original fire's still going. Also, sometimes you want to adjust the fire. Adjusting can be done through a relatively small hole, but adding a piece of wood needs a big-ish opening. I have never yet seen a RMH
system with a separate air feed, where you could close off the secondary air, open the fuel/air main feed, and drop in a piece of wood, without releasing some smoke. I believe this is a limitation of the human biology only having two hands, not of the stoves themselves, but we works with what we's got.
If you get it to work so you can do all these things, and it's putting out clear/white steam/fog and not a hint of blue or brown in the smoke, it will be a truly unique innovation.
Otherwise, you will just have the fanciest firebrick hearth yet seen on a rocket mass heater
Another place to look if you want some options is 'bell stoves', that's the term for a masonry heater with a mushroom-like downdraft over the initial up-riser like our RMH
's have. I don't know how much heat-exchanger they put on the bell stoves, or what kinds of feeds they use. I think they're simpler, though.
The rest of it looks good, and I do think you've innovated in a way that you can fix with minimal hassle if it doesn't work out.