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</gallery>
</gallery>
=== Steps of Mixing Cobb ===
=== Construction Process ===
==== The Rocket Stove====
The project started with designing, building, and prototyping the rocket stove. This consisted of first arranging the firebricks into a J-shape that makes the combustion process in rocket stoves more efficient. Once this J-shape was achieved we tested the prototype with a small fire and even with visible cracks we were able to get a steady consistent draft. Throughout combustion chamber prototypes, the overall J-shape remained, but the brick pattern and arrangement changed a few times before permanently mortaring them into place. 
 
We built this system using an 8" stove pipe heat conveyance.  The cross-sectional areas are crucial to measure and maintain throughout the RMH. The opening of the feed chamber ended up being 5" by 7".  The burn tube dimensions are 4" by 5.5".  The chimney riser dimensions are 5" by 5.5".  The space between the top of the riser chimney and the 55-gallon drum was about 1.5".  These dimensions matter greatly in terms of getting the correct draft and suction through the entire system.  A good reference we used is found in Ianto Evans Book <ref>Evans, I., and Jackson, L. (2006). Rocket Mass Heaters: Superefficient Woodstoves YOU Can Build.</ref> where he explains the correct dimensions needed for a working 55-gallon barrel project (we highly recommend to see pages ____).  The entire system measures about 42" tall and 40" from the wall behind it.
 
After solidifying the dimensions we placed the barrel and stove pipes in their determined places and temporarily closed up gaps with raw clay in order to prototype the system as a whole. We were able to get the system up to desired temperatures. We then moved on to the mortar with our final mortar recipe being ( will get them from ben). We used fire clay in the mortar mix in order to have a mortar that can withstand the expected temperatures within the burn chamber (in the barrel). On the exterior of the barrel we
 


a, b, c
a, b, c
- - - -
 


== Operation ==
== Operation ==
Line 348: Line 355:
Cobb is regarded as the first earthen material used for construction. Cob buildings from the 1400’s are still standing to this day and serve as an important reminder that cob does have longevity.<ref>Hazeltine, B., and Bull, C. (2003). Field guide to appropriate technology. Academic Press, Amsterdam.</ref> In its most popular form it is a combination of clay for strength, sand to reduce cracking by shrinkage, for strength and water to create cohesiveness. <ref>Elizabeth, L., and Adams, C. (2000). Alternative construction: contemporary natural building methods. Wiley, New York.</ref> Together these four material create a medium that is easily malleable and self-drying. It must be noted that while straw does provided other tasks such as decreasing weight of the mixture and aiding in the drying process its main purpose is to provide tensile strength. Thus many materials can be used in place of straw as long as it has tensile strength properties (i.e. herbs, pine needles, various types of grasses).
Cobb is regarded as the first earthen material used for construction. Cob buildings from the 1400’s are still standing to this day and serve as an important reminder that cob does have longevity.<ref>Hazeltine, B., and Bull, C. (2003). Field guide to appropriate technology. Academic Press, Amsterdam.</ref> In its most popular form it is a combination of clay for strength, sand to reduce cracking by shrinkage, for strength and water to create cohesiveness. <ref>Elizabeth, L., and Adams, C. (2000). Alternative construction: contemporary natural building methods. Wiley, New York.</ref> Together these four material create a medium that is easily malleable and self-drying. It must be noted that while straw does provided other tasks such as decreasing weight of the mixture and aiding in the drying process its main purpose is to provide tensile strength. Thus many materials can be used in place of straw as long as it has tensile strength properties (i.e. herbs, pine needles, various types of grasses).


==Creating and Mixing of Cobb==
===Creating and Mixing of Cobb===
The creation of cobb is specific to location, materials at hand, what makes environmental and economic sense, preferences, time allowance, and desired outcome. Due to the extreme variability of the medium there is no universal standard of cob mixture. <ref>Elizabeth, L., and Adams, C. (2000). Alternative construction: contemporary natural building methods. Wiley, New York.</ref> From review it is understood that mixtures containing more straw and water tend to see the most amount of shrinking.</ref>O. A., ., C. J., ., A. O., ., O. D.-S., and ., A. E. (2006). “Engineering Properties of Cob as a Building Material.” Journal of Applied Sciences, 6(8), 1882–1885.</ref>We will therefore be mindful of out straw and water content and create sample bricks of different mixtures to determine the best combination for our task, materials at hand, and desired outcome. The large scale mixing process will be done by foot on a tarp. I
The creation of cobb is specific to location, materials at hand, what makes environmental and economic sense, preferences, time allowance, and desired outcome. Due to the extreme variability of the medium there is no universal standard of cob mixture. <ref> Elizabeth, L., and Adams, C. (2000). Alternative construction: contemporary natural building methods. Wiley, New York.</ref>  
From review it is understood that mixtures containing more straw and water tend to see the most amount of shrinking.<ref>O. A., ., C. J., ., A. O., ., O. D.-S., and ., A. E. (2006). “Engineering Properties of Cob as a Building Material.” Journal of Applied Sciences, 6(8), 1882–1885.</ref>We will therefore be mindful of our straw and water content and create sample bricks of different mixtures to determine the best combination for our task, materials at hand, and desired outcome. However, through research and experience, large scale mixing process will be done by foot on a tarp.  


====Impacts of Moisture (concerns for maintenance)====
====Impacts of Moisture (concerns for maintenance)====

Revision as of 21:58, 9 May 2019

Template:305inprogress

Background

This will be the site of the cobb bench with the back of the bench against the face of bricks. Shown here is the full view of the existing chimney and ancient stove from before CCAT days.

In the Spring semester of 2019 our Engineering 305 Appropriate Technology course at Humboldt State University was contracted to design the following project as a living and evolving installation of AT. The project reflected integrated team work, strong communication across the institution, creative problem solving, and over 150 hours of physical labor.

Team Rocket Power was contracted the Rocket Mass Heated (RMH) cobb bench on the grounds of Humboldt State University's Campus Center for Appropriate Technology (CCAT) in front of an existing outside fireplace. CCAT is a student run instructional home that demonstrates appropriate technology to promote sustainable living and design. The cement foundation and plastered brick chimney will serve as foundation back rest for the bench where the back of the bench will be set directly against the fireplace.

Site Potential

This area is currently underutilized at CCAT as it could potentially be a communal workshop space and interactive recreation area that demonstrates appropriate technology. By interacting with a rocket mass heated bench, students and community members can learn about how appropriate technology and design stacks functionality.

Scope of Project

The Cobb Rocket Mass heated bench will provide functions of heated lounge space, cooking, and a place to bring community members together. Cobb is a building material consisted of all natural components: clay, straw, sand, and water. Thermal mass heating has been used all over the world to heat beds, floors, and earthen home structures.

Team Members

Team Rocket Power consists of Ben Nguyen, Aidan Belleau, and Michael Perez.

Team Rocket Power will design, prototype, and implement the aforementioned technology during the Spring Semester of 2019.

Problem statement

The purpose of Rocket Power is to design a locally sourced, aesthetically pleasing, and fully functioning rocket mass heated cobb bench at CCAT.

We hope this demonstration of appropriate technology will have both a utilized purpose for accessible and comfortable seating, as well as an educational tool for future generations of students.

Project Evaluation Criteria

It was important to order the priorities of the CCAT community, as well as weighing what appropriate goals are for our team. The following criteria were chosen based on initial conversations with the CCAT Co-Directors, project manager, and the project team. The scale (1-10) represents the importance level of meeting the constraint of each listed criteria (10 meaning the most crucial).

Criteria Constraints Weight
(1-10)
Function Stacking Integrate at least 4 Appropriate Tech designs
7
Safety Building method approval from risk management
10
Structure Modifications/Use of existing structure (chimney)
8
Seating Area Four or more seating spots
10
Maintenance Weather resistant
9
Cooking Capability Stove function-ability
10
Materials Logical transportation and sourced locally (on site)
10
Aesthetics Artistically inspired finished product
7
Signage Minimum of two permanent educational displays
10
Operation Clear directions and operations manual
10
Chillability Want to stay on the bench for at least an hour
5

The CCAT Co-Directors and Project Manager emphasized student and community safety, learning accessibility, and project functionality as the main priorities. This is shown in our project criteria to be the most important to achieve. Operation of the system itself is crucial to maintaining the efficiency yielded by rocket stoves, so the order of operations must be clear and concise. This will be achieved through signage and accessible resources. The current location for which the bench is central to CCAT, however the original fireplace is under utilized. This project will aim to invite more people to relax and engage with the space while learning about appropriate technology.

Proposed Timeline

Due to the fact that cobb is very time intensive process it is very important that we proactive in preparing for the building process. Our proposed timeline projects the team to test cobb mixtures as well as plaster recipes well before construction commences.

Date Action Details
2/28- 3/3 Create and secure budget Generate multiple designs of stove and bench orientation:
3/4- 3/8 Contact Risk Management. CCAT directed us to RM for project approval. Risk mitigation techniques with different alternatives concerning safety.
3/5- 3/8 Present multiple designs to client Record feedback
3/6- 3/13 Design Prototyping and Material Prototyping Create sample cobb mixtures and allow for drying
3/15- 3/22 Material Sourcing 55-Gallon drum from Scrapyard, fire brick from decommissioned Samoa Mill, stove pipe, concrete, and lime from Hensels Ace, river sand from Wes-Green Landscaping, clay sourced on-site, urbanite/filler-brick from Craigslist,
3/22- 3/29 Preparation of site Clear/clean space of debris. Place some of collected materials in their respective spaces.
4/1 - 4/7 Mitigation of Final design Addressing possible risks (exhaust, asbestos, temp and evolving structure). Usage and Maintenance manual + future cover proposal
4/8 - 4/14 PROTOTYPE Assemble test stove on site using 50 gallon schematics, test burn and observations, adjustment of airflow measurements, lastly place stove at finalized location
4/15 - 4/21 Bench Foundation and Straw Slip Mortar red bricks into framework for the outline of the bench. Apply insulating buffer layer against existing structure and ground exposure (clay-straw slip mixture).
4/21 - 5/5 Cobb Mixing and Application Shape the oven and combustion chamber covering to desired design, trimming and edging, allow a few days for cobb to dry and set between applications, most LABOR INTENSIVE section of project
5/6 - 5/13 Final Shaping and Completing Cobb Applications Artistic Design Proposals, collecting clay tiles and other aesthetic inputs, collaborations with individual designs of VF 5/10. Plaster Application Week, testing direct ratios of lime plaster wash on finished design, every other day applications of 2 coats of plaster. Exhaust chimney and securing stove pipe.
5/14 - 5/17 Clean and Organize Working Area Finishing touches on plaster. Completing Operations Manual and documentation.

Cost

The following budget breakdown has been formulated to cover all alternatives designed for the project. The tables are broken into two pieces; the first consists of the structural and natural materials needed for the rocket stove mass heated cobb bench. The second is the more expensive due to he steel stove components that will convey the heat/exhaust through the bench. Our team hopes to source donations, free, or scavenged materials to our best capabilities. While the stove piping is the most expensive aspect of the budget we have also acknowledged that used stove piping is less expensive and it's quality is questionable. Thus, we are incentivized to purchase new stove for a guaranteed quality.

Below you will find what components are necessary to build a rocket stove mass heated cobb bench and their local cost.


Bench & Plaster Materials

Material Quantity Source Cost ($) Total ($)
Local Clay 1.5 cubic yard CCAT Greenhouse Reclaim/Dug up from yard Donation 0
River Sand 1-1.5 cubic yard Wes Green Landscape Supply 40/cubic yard 60
Decomposed Granite 0.5 cubic yard Events Field Donation 0
Rice Straw 1 or 2 bales Eureka Farmstore donated after MayDay 0
Urbanite (concrete Chunks) As needed City of Arcata Donation 0
Fireclay 50lb bag Pheonix Fire Supply 10/bag 7
Quickcrete 60lb bag Hensels Ace 7/bag 7
Lime 40lb bag Hensels Ace 18 18
Tile and colored clay pieces As needed Arround CCAT, Aidan's house Donation 0
Refractory Cement 1 gallon Hensels Ace 23/gal 23
Total Cost $116

Stove & Conveyance Materials

Material Quantity Source Cost ($) Total ($)
8" Steel Stove Pipe 12 ft (5 sections of 4ft) Hensels Ace 28 per 4 ft 96
8" 90 Degree Stove Pipe Elbow 3 Hensels Ace 20 60
8" Stove Pipe Cap/Rain Guard 1 Hensels Ace 9 9
8" Stove Pipe T-fitting w/Cap 1 Hensels Ace 35 35
8 foot exhaust pipe 1 Craigslist Donation 0
Total Cost $200

Total Budget Cost: $316


Construction with Step-by-Step Photo Gallery

Construction Process

The Rocket Stove

The project started with designing, building, and prototyping the rocket stove. This consisted of first arranging the firebricks into a J-shape that makes the combustion process in rocket stoves more efficient. Once this J-shape was achieved we tested the prototype with a small fire and even with visible cracks we were able to get a steady consistent draft. Throughout combustion chamber prototypes, the overall J-shape remained, but the brick pattern and arrangement changed a few times before permanently mortaring them into place.

We built this system using an 8" stove pipe heat conveyance. The cross-sectional areas are crucial to measure and maintain throughout the RMH. The opening of the feed chamber ended up being 5" by 7". The burn tube dimensions are 4" by 5.5". The chimney riser dimensions are 5" by 5.5". The space between the top of the riser chimney and the 55-gallon drum was about 1.5". These dimensions matter greatly in terms of getting the correct draft and suction through the entire system. A good reference we used is found in Ianto Evans Book [1] where he explains the correct dimensions needed for a working 55-gallon barrel project (we highly recommend to see pages ____). The entire system measures about 42" tall and 40" from the wall behind it.

After solidifying the dimensions we placed the barrel and stove pipes in their determined places and temporarily closed up gaps with raw clay in order to prototype the system as a whole. We were able to get the system up to desired temperatures. We then moved on to the mortar with our final mortar recipe being ( will get them from ben). We used fire clay in the mortar mix in order to have a mortar that can withstand the expected temperatures within the burn chamber (in the barrel). On the exterior of the barrel we 


a, b, c


Operation

This is how to operate. It should have a brief introduction and very useful images with labels. Also it may work best for your project to use the step by step how to template {{How to}}. See #Troubleshooting for an example.

Maintenance

Introduce this maintenance section.

Schedule

This is when to maintain what.

Daily
  • A daily task
  • A daily task
Weekly
  • a weekly task
  • a weekly task
Monthly
  • a monthly task
  • a monthly task
Yearly
  • a yearly task
  • a yearly task
Every __ years
  • task
  • task

Instructions

This is how to maintain. The step by step how to template {{How to}} is most likely best for this part.

File:Bpack bike trailer - demo 1.jpg
How to Do Something

Literature Review

Rocket Mass Heater Overview

A rocket mass heater, or rocket stove, consists of a right angle ‘J’ shaped combustion chamber inside of an insulated container. This insulation container creates a draft in which the heat gasses are drafted and then pushed through piping into mass. This concept can be applied to heat earthen built furniture in homes that contain high thermal mass. [2]

Testing and Certification of RMH

Testing of rocket mass heaters for emissions efficiency is very difficult to come to conclusive data as each system will vary. Not one scenario will be exactly the same as fuel, operation, and structural design are variables. The testing would also be very expensive, ranging from $8,000 to $30,000 and would be targeted for builders who are in the business of licensing and patenting particular designs. [3]

Basics to Clean Burning

The following was adapted from the book Designing Improved Wood Burning Heating Stoves by Mark Brayden et al.[4]:


“A good combustion chamber changes wood or other biomass into heat without creating much smoke or creosote (condensed wood tars). Complete combustion of wood results in two byproducts: carbon dioxide and water vapor. In contrast, incomplete combustion creates unburned particles that cause pollution and creosote that fills chimneys and can cause chimney fires if it ignites.”

1.) Metering the fuel– Splitting wood up into small pieces (no bigger than wrist and 16 inches long) and feeding them at a consistent rate.

2.) Creating a hot fire-Managing the combustion zone where fuel, flame and air are mixed to create a fast burning and efficient coal reservoir.

3.) Insulating the combustion chamber- Crucial for mass stove heaters that store energy in materials with high insolation properties (see Understanding R-Values)

4.) Igniting escaping smoke- To ensure that the ignition chamber reaches optimal efficiency, the exiting gases from the exhaust should be just CO2 and water vapor.

5.) Providing sufficient oxygen– Starving the fire slows it, cools it down, and produces smoke.

6.) Warming and increasing velocity of cold air entering the fire– Air is warmed as it passes through a small opening (usually the same entrance where wood is fed) into the combustion chamber. For systems without a fan, make enough small holes under the door into the combustion chamber so the holes have as much cross-sectional area as the chimney exiting the stove. Position the holes so that primary air is sucked into the coals and up into the combusting wood.

7.) Creating sufficient draft– Use a tall enough chimney, double the height of the width of the internal vertical combustion chamber. An insulated chimney creates much more draft than an uninsulated chimney. High air movement entering under the fire, up though the coals, to create mixing which reduces emissions. Do not use a damper in the chimney. Design the stove to run efficiently with enough air entering and leaving the stove to burn fuel cleanly.

Do not block the air intake, reducing primary air and blocking the necessary amount of intake volume will create particulate air pollution!!

Types of Mass Heated Rocket Stoves

Different designs of the J-shaped combustion chambers have been refined by hundred of permaculturists and homesteaders worldwide. To assess the success and meet the main goal of longevity for an overall design, the below project references display ideal qualities and strategies. The examples begin with low cost and minimum design complexities and advance to high expense, technical, and professionally engineered.

J-Type Combustion Chamber and 55-Gallon Barrel

J-Combustion and 55-gal Drum.jpg

Our design was based mostly off of this layout. With an 8 inch stove pipe ducting through the bench as the exhaust. The draft in these systems allows for the most efficient and complete use of fuel energy. The J-type combustion allows for fuel to brun from the bottom-up while the horizontal flame reached high turbidity while travelling around the 90 degree riser stack.

[5]

Efficiency of Combustion, and Heat Transfer Efficiency

The Rocket Stove, created by Dr. Larry Winiarski, features an insulated fire box and short chimney (14”). Low mass insulation such as wood ash help to keep combustion temperatures high and improve burning efficiency. The high combustion temperatures also greatly reduce smoke and leads to saving of wood, making a more efficient stove. [6]

Solunit Rocket Stove

Our vision and project scope have incorporated some of the design aspects of this example into the final bench layout.

Solunit Rocket Stove (2011).jpg

Overall cost = $700

Materials:110 firebricks, 55 gallon drum, recycled water heater core, about 20 ft 8” diameter ¼” Steel Pipe, concrete, pumice, and multiple tons of cobb


[7]

Basics of Cobb

Cobb is regarded as the first earthen material used for construction. Cob buildings from the 1400’s are still standing to this day and serve as an important reminder that cob does have longevity.[8] In its most popular form it is a combination of clay for strength, sand to reduce cracking by shrinkage, for strength and water to create cohesiveness. [9] Together these four material create a medium that is easily malleable and self-drying. It must be noted that while straw does provided other tasks such as decreasing weight of the mixture and aiding in the drying process its main purpose is to provide tensile strength. Thus many materials can be used in place of straw as long as it has tensile strength properties (i.e. herbs, pine needles, various types of grasses).

Creating and Mixing of Cobb

The creation of cobb is specific to location, materials at hand, what makes environmental and economic sense, preferences, time allowance, and desired outcome. Due to the extreme variability of the medium there is no universal standard of cob mixture. [10] From review it is understood that mixtures containing more straw and water tend to see the most amount of shrinking.[11]We will therefore be mindful of our straw and water content and create sample bricks of different mixtures to determine the best combination for our task, materials at hand, and desired outcome. However, through research and experience, large scale mixing process will be done by foot on a tarp.

Impacts of Moisture (concerns for maintenance)

It is a well-known fact that Arcata, California has high humidity and precipitation for more than half of the year.[12] This is due to the fact that Arcata is located in northern California on the western coast of the United States. Moisture and humidity can affect rates of drying and can alter mixtures causing unexpected shrinking and drying outcomes mostly seen in plasters. [13] Again plaster samples of varying recipes will need to be created and subjected to tests that will be determined on a later basis. The fact of the matter is the climate of Arcata will permit a structure made out of cob to be successful in enduring heavy use for several years.[14]

Understanding R-Values

R-value measures the thermal resistance of a material. This can also be expressed as the temperature difference that will cause one unit of heat to pass through one unit of area over a period of time. Using earth to capture heat inside an RMH is essentially using different R-values to capture the thermal radiation emmitted by the combustion chamer and throughout the stove pipe to heat the seating bench.

InspectApedia provides a comprehensive R-Value table with different insulation materials and various common construction materials. [15] [16]


Thermodynamics

Heat, Temperature, and Thermal Energy Thermal Energy is an energy of the system due to the movement of its atoms and molecules as a form of energy. In this sense, a system can still sustain thermal energy even in an isolated environment. According to the first law of Thermodynamics, work or heat that changes the thermal energy also changes the pressure, volume, temperature, and other variables. This explains how high pressure inside a rocket stove chimney generates extreme heat and forces it up and out into the isolated container surrounding it. This is crucial to gaining high combustion temperatures in a small space. [17] [18]




References

Template:Reflist

  1. Evans, I., and Jackson, L. (2006). Rocket Mass Heaters: Superefficient Woodstoves YOU Can Build.
  2. Evans, I., and Jackson, L. (2006). Rocket Mass Heaters: Superefficient Woodstoves YOU Can Build.
  3. Wisner, E. (n.d.). “Rocket stove efficiency/certification .” Permies.com, <https://permies.com/t/3249/Rocket-stove-efficiency-certification> (Feb. 21, 2019).
  4. Bryden, Mark, D. Still, D. Ogle, and N. MacCarty. "Designing improved wood burning heating stoves." Aprovecho Research Center (2005).
  5. Evans, I., and Jackson, L. (2006). Rocket Mass Heaters: Superefficient Woodstoves YOU Can Build.
  6. Still, D., Kness, J., Billesten, B., Cox, G., Espenan, M., Nael, J. B., Nicholas, D., Subramanian, M., and Zettler, D. F. (1996). “Efficiency of combustion, Operator Expertise, and Heat Transfer Efficiency.” Fuel Efficient Wood Stoves and Hayboxes.
  7. Solunit Rocket Stove (2008) I love cob!, Green Web Hosting [online]. http://ilovecob.com/archive/solunit-rocket
  8. Hazeltine, B., and Bull, C. (2003). Field guide to appropriate technology. Academic Press, Amsterdam.
  9. Elizabeth, L., and Adams, C. (2000). Alternative construction: contemporary natural building methods. Wiley, New York.
  10. Elizabeth, L., and Adams, C. (2000). Alternative construction: contemporary natural building methods. Wiley, New York.
  11. O. A., ., C. J., ., A. O., ., O. D.-S., and ., A. E. (2006). “Engineering Properties of Cob as a Building Material.” Journal of Applied Sciences, 6(8), 1882–1885.
  12. “Climate-Data.org.” (2015). Climate Sahara: Temperature, Climograph, Climate table for Sahara - Climate-Data.org, Climate-Data.org, <https://en.climate-data.org/north-america/united-states-of-america/california/arcata-15733/> (Feb. 20, 2019).
  13. O. A., ., C. J., ., A. O., ., O. D.-S., and ., A. E. (2006). “Engineering Properties of Cob as a Building Material.” Journal of Applied Sciences, 6(8), 1882–1885.
  14. “Where Does Cob Work?” (n.d.). Green Home Building: Earthships, <http://www.greenhomebuilding.com/QandA/cob/where.htm>(Feb. 19, 2019).
  15. "R-values of Insulation and Other Building Materials." Archtoolbox.com. Accessed February 21, 2019. https://www.archtoolbox.com/materials-systems/thermal-moisture-protection/rvalues.html.
  16. Inspectapedia.com. (2018). R-Values of Materials: Table of Insulation R-Values and Properties for Various Insulation Materials & Building Materials (brick, block, wood, soil, air gaps, etc). https://inspectapedia.com/insulation/Insulation-Values-Table.php [Accessed 21 Feb. 2019].
  17. Knight, R. d. (n.d.). Physics for scientists and engineers: a strategic approach.
  18. Still, D., Kness, J., Billesten, B., Cox, G., Espenan, M., Nael, J. B., Nicholas, D., Subramanian, M., and Zettler, D. F. (1996). “Efficiency of combustion, Operator Expertise, and Heat Transfer Efficiency.” Fuel Efficient Wood Stoves and Hayboxes. .
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