Martin Polley

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since Feb 19, 2015
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Recent posts by Martin Polley

Something like this:
3 years ago
cob
Hi folks,

This is my first time working with cob (as the base for a rocket-core-powered mud oven). I have to buy sand, but I have loads of local basalt rocks (in lots of different sizes). What I'm wondering is this. Can I use some of those rocks as filler in the middle of my cob wall? This will mean less sand for me to buy, and less work because I won't need to mix as much cob.

If this is an OK approach, how much rock can I get away with before compromising the structural integrity of the cob? My gut says if I keep it less than about 50% of the thickness of the wall, and make sure that the cob on one side of the rocks has plenty of places where it connects to the cob on the other, I should be OK.

What do you guys think?
3 years ago
cob
Tried to download on my iPhone last night and it worked just fine--thanks!
Thanks Glenn. I look forward to seeing the photos
3 years ago
Hey Glenn,

Thanks for that! Actually, yours wasn't the one I saw, but it looks like they both work the same way. That's a really beautiful job you've done there with the stonework. We have lots of local basalt around here, so I'm inspired to do something similar.

Is the floor insulated? How did you incorporate insulation between and below the ducts? I'm guessing that the most effective strategy would be to insulate below the ducts (and maybe in between them too), so that you won't lose heat from the floor into the material below. But also not to insulate above the ducts to maximize the amount of heat transferred into the floor. Does this sound about right?

I'll be interested to hear how yours works when spring comes. I hope you'll post some photos here
4 years ago
Hi folks,

I'm planning on building a smallish rocket-fired oven (for pizza and bread). I've seen a fair number of posts and images on the subject, but most of them look like they'd do a good job of heating up the dome of the oven, but maybe not such a good job of heating up the hearth/floor.

There's a thread over on the donkey forums that shows an oven with channels under the floor that channel the exhaust from the heat riser into the oven (though it's not really clear where the exhaust goes after that—out the open door?). I'd guess that these channels would heat the floor up nicely.

Extending this concept a little further, I thought what would happen if the heat riser was offset relative to the oven so that these channels passed all the way across under the floor? Then the hot gases would enter the oven, flow across the inside of the dome, then exit through some sort of slot or holes at the opposite side.

Something like the attached image (which is looking from the front of the oven, with the feed tube and exhaust both at the side).

What do you think? Could this work? Or would something simpler work just as well (or better!)?

Thanks,

Martin
4 years ago