Phil Stevens

Andre Wiederkehr wrote:

How did you do that? Weld it in? How thick is the plate? I haven't built a RMH (yet!), but as I consider it I've wondered about whether the top would wear through from the intense heat, and also how to make it an effective cookstove, so this is of great interest to me.

Yes, the top will deteriorate from the heat. The middle of mine developed a few transparent spots by the time I replaced it.

I had a circular piece of 6 mm mild steel plate cut by someone with a CNC plasma rig. When I removed the remnants of the original drum top, I left about 2 cm around the outer edge and put a piece of fire rope in the indentation to seal it. The plate just sits on top and its weight seals things nicely. The photos should give you an idea how it fits together.

I've had good results just coating the exterior of a plain steel drum with linseed oil. I do it once a year on average and that keeps the rust down to a very minor feature, mostly cropping up because the RMH is in a glasshouse and sits next to a bathtub with a recirculating pump and slow sand filter, so the odd splash can happen. Nine years of service so far, and I replaced the top with a piece of heavy steel plate so I'd have a better cooking surface and because that part of the drum was spalling after a few years of use.

There are proven ways to make bad biochar, though...like using materials that have toxic gick in them, and by using methods that fail to drive off all the volatile products and leave you with charcoal that may be good for barbecues but pretty much worthless for the soil.

But as Douglas rightly points out, prior art is all around us and if we mimic natural processes we're more likely to get it right.

M Ljin wrote:Another way biochar could be incorporated into soils is worm tillage—eventually, in worm-inhabited regions, anything atop the soil surface will be incorporated by the throwing-upward of soil and disintegration of worm tunnels which happens with regularity.

Nevertheless, I am digging my biochar in this spring.

Worms will even ingest biochar if the particles are small enough. They love the stuff. I've seen photos of a kiwifruit orchard where they topdressed with biochar, then took some spade samples a year later. There were burrows lined with black extending 30 cm  down. Looking for that picture now....

I wondered because it sure looks like one. If you still have the template, you can put a nail at either end and see if a length of rope hanging from them follows that curve. It's an ideal form for arches and domes, and so easy to generate with a piece of string.

thomas rubino wrote:Hey Ben
This is how Gerry and I built the arch on Shorty.

Is that a catenary, Thomas?

If the stone is laid directly on the ground, most of the heat will go there via conduction. In a mild climate this might work, but anywhere that has cold winters will probably produce disappointing results. Getting a layer of insulation under the floor would be the way to go. I know a natural builder who has used a layer of biochar to do this, and put an earth floor on top of it. If you ran your heating tubes through the earth layer and put stone on top, you might have a solution.

tony uljee wrote:Phil is in the manuka honey producing country of the world , they might be using s/steel barrels for storing /shipping --as its required for high value medical and human consumption food products---any damaged one would be rejected for further use.

Brilliant suggestion...and the honey industry is on the skids at the moment and going through a major contraction, so there could be some excess inventory around. Most of the commodity liquids used by farmers like glycerol, molasses, and all the milking plant chemicals like teat spray and descaling acids are packaged in plastic drums. Specialty products like manuka honey would be the exception.

Those look like black soldier fly larvae to me. Do they have long, threadlike "tails" that drift behind them?

Pro tip for people with manual gearboxes: When you're coasting, it's better to put it in neutral than to ride the clutch. This saves wear and tear on the throwout bearing.