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Summary

A batch box style rocket mass heater, unlike a J-tube style, requires a door. But most people don't have the skills or equipment to make one. Paul and Jen discuss the experimental low-tech casserole-lid door which uses cob to make a perfect fit, and how it fared in real-world use. So far at the lab, around ten casserole-lid doors have failed, in various interesting ways. They discuss the reasons for failure, and why Paul is no longer recommending their use despite their being low-tech and cheap and easy to replace, especially if purchased from goodwill.

Paul considers that this is but one reason that batch boxes are inferior to J-tubes, and refers to the podcasts he made with Kirk “Donkey” Mobert . He also mentions that Matt Walker uses a pop-riveted metal door on his designs which more people would be able to construct. Matt also told him that all types of glass will eventually fail with that kind of use.

Jen points out that many of the failures could be down to running the rocket stove in Allerton Abbey 24/7 for around ten days, which is far longer than a RMH is usually run for, as part of the thermal inertia testing for the WOFATI design.   It may be that with more normal usage an easily replaceable, and cheap, casserole lid may still be the right solution. Currently they are testing how well a cast iron skillet functions as a door and are brainstorming further solutions.

Relevant Threads

Casserole Door - an innovative door for batch box rocket mass heaters

podcast 413 - The problem with batch box rocket mass heaters - Part 1 - relevant bit starts at 33 minutes in.
podcast 414 - The problem with batch box rocket mass heaters - Part 2

podcast 459 - annualized thermal inertia test

J tube-Batch-Box-Conversion
donkey's forum
batch box rocket mass heater plans
PEP BB rocket.sand.batch- Start and Operate Batch Box RMH
results of the 8" batch box thingy at the Innovators Gathering
rocket stove batch box info and explanation

wheaton labs official website

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This podcast was made possible thanks to:

Dr. Hugh Gill Kultur
Eivind W. Bjørkavåg
Suleiman, Karrie, and Sasquatch
Bill Crim
anonymous
Kerry JustTooLazy
Wade Luger
Jocelyn Campbell
thomas adams
Sasquatch
havokeachday
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Julia Winter, world's slowest mosaic artist
Kyle Neath
Bill Erickson
G Cooper
Lisa Goodspeed
Penny McLoughlin
Mehron Kugler
Mark
Sean Benedict
Dana Martin
Rita Bliden
Greg Martin
Candace Dahlk
Keith Kuhnsman
Eric Tolbert
Ruwan Nanayakkara
Polly Jayne Smyth
Alias
 
And tomorrow is the circus! We can go to the circus! I love the circus! We can take this tiny ad:
Rocket Mass Heater Manual - now free for a while
https://permies.com/goodies/8/rmhman
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