Win a copy of The Tourist Trail this week in the Writing forum!
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education experiences global resources the cider press projects digital market private forums all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • r ranson
  • Anne Miller
  • paul wheaton
  • Joseph Lofthouse
  • Jocelyn Campbell
  • Mike Jay
garden masters:
  • Steve Thorn
  • Dave Burton
  • Joylynn Hardesty
  • Carla Burke
  • Pearl Sutton
  • Greg Martin

Easy no-cut firebrick 4" batch box core

Posts: 2967
Location: Upstate NY, zone 5
  • Likes 2
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
A couple of years ago I built a mockup of a 4" batch box as a test, and I wanted to share the details for reference. I used ordinary hard firebricks, full size and splits (1 1/4" thick), as that was what I had on hand. A ceramic fiber board version would be more efficient for a critical installation, but this would serve for testing and occasional use, without major expense.

The pictures tell most of the story. I followed the specs at as closely as possible given the standard firebrick dimensions, 4 1/2" x 9" x 2 1/2" or 1 1/4". The port had to be a slightly different shape, but I made it the same cross sectional area, a bit shorter and a bit wider. The firebox ends up 6" wide x 9" high x 13 1/2" deep, the port is 2" wide x 4 1/2" high, sharing the firebox floor, and the riser is 3 3/4" x 4 1/2" (oriented long way in line with the firebox) x 27" high. I wired the riser bricks together for this test; you would want a more rigid and durable containment for a permanent installation. I had all new or clean firebricks, so dry fitting gave tight joints. If you have rough or chipped bricks, you would need some sealant for the joints. I used no insulation for the test, but you could easily wrap fiberglass around the core for the small heat source. Rockwool would be more durable.

It lit easily and burned fast and hot, giving pretty double rams horns from the port into the riser, and burning so clean when properly adjusted that I could stand on the ladder with my face over the riser and comfortably breathe the exhaust.
[Thumbnail for IMG_1234.JPG]
during assembly - it gets another course of firebricks on the riser
[Thumbnail for IMG_1237.JPG]
firebox and port opening
[Thumbnail for IMG_1238.JPG]
front view
[Thumbnail for IMG_1248.JPG]
[Thumbnail for IMG_1241.JPG]
burning, flames headed to port
[Thumbnail for IMG_1293.JPG]
looking down the riser - double rams horns
[Thumbnail for IMG_1296.JPG]
[Thumbnail for IMG_1301.JPG]
firebox closed for proper air supply, no primary/secondary for the test
[Thumbnail for IMG_1283.JPG]
overall view in operation
Posts: 461
Location: Wellington, New Zealand
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Anyone contemplating a batch rocket stove should start by building a 4" one like this one to just get the experience!
It will give me the powers of the gods. Not bad for a tiny ad:
Switching from electric heat to a rocket mass heater reduces your carbon footprint as much as parking 7 cars
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!