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Phil Stevens

master pollinator
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since Aug 07, 2015
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Ashhurst New Zealand
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Recent posts by Phil Stevens

You could use a pulley secured below the jug which allows the pedal to be placed out of harm's way.
4 minutes ago
Refractory grog is probably less valuable in general as thermal mass than quartz sand, but still decent. The real tradeoff would come if you were using material with lots of voids, such as pumice or perlite. Is there a separate mass for heat storage in this design which is not subject to the high temperatures of the burn chamber and riser? If so, then you don't really need refractory materials in that portion of the build.

Note that you won't be able to reconstitute and reuse fireclay pieces that have been fired as opposed to just heated and dried. It's pottery, after all. So anything in the burn tunnel or heat riser area, if you sacrifice it in a future teardown and rebuild, becomes grog.
5 hours ago
Hi Thor, and welcome to permies. You should be able to use fireclay and refractory grog to cast the firebox of this little guy. Just make sure it's fully dried out before the first firing.
They're quite happy outside of the tropics as long as it's mild. Napier, east coast NZ, about 2 hours from here at 40 degrees S:



This is one of the most common ornamental trees around NZ. You'll see them everywhere except higher elevations. Despite the popular wisdom, they're not killed by light frost. They are hardy down to minus 2 or 3 at least, and I see them planted out in the open all over this part of the island.
1 day ago
Travis, your calculations are off unless you're talking about either a really inefficient heat pump or one running at low ambient outdoor temps. A typical heat pump has a real-world COP of 3. A resistive electric heater has a COP of 1. So a bog-standard heat pump will give you three kWh (not 0.66)  of heat energy for each kWh of electrical energy that it consumes, while the glowing bar can only ever put out 1:1.

However...the COP is not linear and will be poorer if you're trying to put out really hot air or water. This can be solved by running two smaller units in series with each one only responsible for half of the heat increase. Heat pumps also can suck if the outside air temperature is really low. To get around this we can use a ground source for the evaporator side, such as a well where the groundwater temperature stays roughly constant year round.
2 days ago
Awesome! 8x8 cm is even smaller than the burn tunnel in my glasshouse RMH, so you've done well. And that is definitely an innovative use of bamboo.
3 days ago
Have a close look at the evolved and tested design of Peter van den Berg's batch box. The secondary air channel and port are critical to success in this breed of RMH. Just putting in a restriction may give you even more draft issues.
5 days ago
Aw man, that is a real blow. I'm thinking of you, Trace.
5 days ago