It Works and the hard part is already done for you!
Shippable Rocket Core in a Pottery Studio Cob Bench
We've used variations of this core design in dozens of Rocket installs from TinyHouse to full size house heaters, school busses to greenhouses, WOFATIs to workshops, trailer homes to treehouses, pizza ovens to water heaters. This versatile unit replaces the guesswork and learning curve with prebuilt elements that you just plug in and surround with cob or metal or masonry and your choice of radiator, thermal mass battery, stove top, oven or hot water tank.
Shippable Rocket Core (Feed not shown for clarity)
Rocket Heaters rely on a very specific internal geometry for their ability to cleanly and efficiently burn cheap (or free) scrap wood. Even experienced Rocket Heater builders can find it challenging to get the ratios just right every time. Finding the time to do a custom core design and locally sourcing the high temp materials can also be costly challenges for anyone building Rocket Heaters. Part of the reason we designed this shippable core was having to schlep materials with us to a build halfway across the country.
The Uncle Mud Shippable Rocket Heater Core: The Materials:
A durable firebrick lining handles high temperatures and hard knocks from firewood. Unlike cast refractory designs, the individual bricks in the BurnBlock and Feed are cheaply and easily replaceable.
Ceramic board insulation holds the heat in the Burn Chamber and Riser where it belongs, up to 2300 Degrees F.
A metal surround lets you easily install the core in a wide variety of mass or insulative enclosures such as cob or perlite or even sand.
The Core can also "go bare" in applications such as a Rocket water heater or oven or stove
The Design: The Burn Block:
The Burn Block Partly Wrapped in its Insulation
The Burn Block is the heart of the Shippable Core. The replaceable liner firebrick are individually notched to lock into each other and stay in place, while still being removable should they eventually crack.
Many of the early Uncle Mud Shippable Cores had the fuel feed directly into the Burn Block. The Feed allows safer more controlled burning by enclosing the firewood (up to 16" long) and providing a place to put lid bricks on top to adjust or close off airflow.
A tall, fully insulated riser creates the thrust needed to bring in combustion air and send the hot, clean, nearly completely burned exhaust gasses through up to 40 feet of heat exchanger in a cob bench or other mass storage battery.
Custom Mini Core for TinyHouse (Note: Current Feed design is wrapped in metal to match core)
Shippable Core in double-tall Workshop Radiator (mo mass storage battery, just instant heat)
Shippable Core Burn Block, uninsulated with custom 5 Minute Riser
SAFETY AND LIABILITY NOTE: Fire is both useful and dangerous. Fire is one of the primal comforts of being human. A safely contained and carefully monitored fire is a great tool, but it has been known to break containment and cause devastation, injury and death. Extracting, processing, transporting and burning fuel of any sort also tends to cause environmental degradation and pollution. Burning local biomass is a proven strategy for lowering the overall costs and consequences of the human use of fire. Where you live there will be insurance requirements, laws and building codes intended to mitigate these consequences. These regulations may not be amenable to building and using a Rocket Heater of any sort, including the Uncle Mud Shippable Rocket Heater Core.
In principle the Rocket Heater is an ideal device for lowering the financial cost and environmental impact of human existence by safely, cleanly burning local biomass, but it is by most definitions an experimental device--an "unapproved home made woodstove". The Uncle Mud Shippable Rocket Heater Core is an experimental device, a kit, a toy even. It is a useful toy that continues to provide DIY satisfaction and warmth to many, but it is not UL listed. It is not EPA approved. Your fire marshal and code officer may not approve a permit for it. Your insurance company may cancel your insurance or refuse to pay a claim if they find out you are using one. You may want to build a Rocket Heater anyway. The Uncle Mud Shippable Rocket Heater Core can help you do that.