Multidisciplinary Senior Design ConferenceKate Gleason College of Engineering

Rochester Institute of TechnologyRochester, New York 14623

Project Number: P18416

TEAM S.E.A.T

Cody ArmesIndustrial and Systems Engineering

Sam DickensonMechanical Engineering

Matt LoReIndustrial Design

Ryan WatersMechanical Engineering

Tim WilliamsIndustrial and Systems

Engineering

ABSTRACT

The purpose of this project was to design and develop a manufacturing system for a concrete Arborloo (toilet) to be implemented in Haiti. Given a design for the Arborloo from the previous team, a manufacturing system needed to be designed that incorporated materials that are found, bought, or easily shipped to Haiti. With set requirements given by the customer, the system must fully manufacture an Arborloo, from gathering and sorting materials, to mixing and pouring the concrete, and finally molding and curing each of the components. Along with the manufacturing system, a mix needed to be designed so that each part of the Arborloo was as strong and light as possible.

INTRODUCTION

In rural areas of developing countries, adequate sanitation and sewage facilities are rare. The hygiene practices of more developed nations are an unknown standard in countries such as Haiti. Because of this, open defecation is rather common due to the lack of standards and facilities. This situation leads to poor health, disease outbreaks, and unnecessary deaths from E. Coli, Cholera, and other bacterial infections.

Arborloos provide a simple and inexpensive solution to this sanitation problem. The concept and design are simple; moveable concrete bases placed over pits to act as a simplistic toilet to collect feces. Once the pit is filled, it can be covered with dirt and can be used as a fertilization region to plant things such as trees. The ring base can be moved to a new pit, thus greatly reducing the contamination from bacteria. However, their bases are relatively difficult to manufacture, being heavy and needing to be constructed in place with advanced skills and tools.

A lighter-weight, portable prototype has been developed by former teams to combat the issue of transportation to these remote regions. The prototype utilizes a three ring design, allowing for lighter parts to allow for ease of moving. However, a concrete mix needed to be developed to ensure each ring is light and strong, but also utilizes materials that are easily available in Haiti. The manufacturing process also needs to utilize materials and labor found in Haiti as a way to set up a business that can be maintained to help boost the local economy. The biggest constraints of this system are cost, available resources, and use of time in order to constantly produce Arborloos.

Copyright © 2018 Rochester Institute of Technology

PROJECT REQUIREMENTS

Table 1: Mapping of Customer Requirements to Requisite Engineering Requirements

SYSTEM DESIGN

The scope of the project is to design a manufacturing system so there are several subsystems that were designed and incorporated into the final process. These subsystems include biochar manufacturing, aggregate sizing/sorting, bottle stringing, mixture of concrete, and part molds. Each of these systems was designed for minimal cost, ease of use, and quality of components.

BIOCHAR PRODUCTION

The process of producing the required biochar for the Arborloo is fairly simple to complete, although it requires constant user attention. Using a simple conical pit, that material to be charred is stacked into the pit and set ablaze, as can be seen in Fig. 1. While the fire is still going, more fuel is continuously added to the pit, to keep feeding the fire and prevent the original fuel from becoming too hot and over-charring. This process is continued until a bed of charcoal has formed, which is the desired byproduct of the pyritization process. When the charcoal bed reaches the desired size, the pit is quenched with water to extinguish the fire. Any fuel that was not completely pyrolyzed can now be removed from the pit, leaving behind only the desired charcoal. At this point, an initial breakup process is performed while the charcoal is still in the pit, to create a mass of smaller pieces that easier to work with further. At this stage, the biochar production is complete, and the produced biochar moves to the aggregate sizing and sorting area.

One advantage of the biochar production method used is its versatility of possible fuel types. While charcoal is typically thought of as a byproduct of burning wood, it can also be generated from a variety of different fuel sources, such as agricultural waste products, a fuel source explicitly explored by this project. It was found that when using agricultural waste as the fuel source, the produced biochar ranged from approximately 20-30% of the original volume used as fuel. This volume reduction compares with that experienced when producing charcoal from wood, as such it was established that biochar production could be performed using almost exclusively agricultural waste as the fuel source, to improve overall sustainability of the project.

Proceedings of the Multi-Disciplinary Senior Design Conference Page 3

Figure 1: Representative Picture of Biochar Pit Kiln

AGGREGATE SIZING / SORTING

This subsystem utilizes several sized screens that allow specific sized particles to fall through.  The screens are attached to square wooden frames and stacked on top of each other. The frames are positioned at an angle to allow the sized particles to fall through the larger screens but slide down the smaller screens into a feed ramp that deposits each specific size of particles in different buckets, as shown in Fig. 2.  This design allows for the user to dump large amounts of both biochar and gravel onto the screens, then quickly size and sort it for use with minimal effort.

Figure 2: CAD Model of Sifter Table

BOTTLE STRINGING

The bottle stringing system is the most complex of all the systems. A representative model is shown below in Fig. 3.  A bearing bottle stringer is mounted to a bracket that is attached to the outside of a 5-gallon bucket.  A hole is drilled through the outside of the bucket in line with the bearings of the stringer to allow for the bottle sting to be threaded into. Two holes are drilled on either side of the bucket, perpendicular to the stringer hole, which fits a piece of ½” PVC tube through it.  The PVC tube has a narrow slot cut lengthwise down the shaft of it, and has a handle attached on the outside. The bottle is started on the stringer, fed through the hole, and then attached to the PVC tube, which is rotated to wind the string around.  Once the bottle is strung, shears are placed in the slot of the PVC which allows the string to be cut. The diameter of the PVC tube allows for the pieces to be between 2 and 3 inches, which is caught by the bucket, as the string is springy and can go flying.

Copyright © 2018 Rochester Institute of Technology

Figure 3: CAD Model of Bottle Stringing Assembly

CONCRETE MIXTURE

The concrete mixture is comprised of 6 ingredients; cement, sand, gravel, biochar, bottle string, and water. The mix used is designed from previous teams, who already designed a lightweight mix, but has been tweaked to add strength, as our mix is load-bearing.  The mix is as follows:

1. 35% Cement2. 25% Sand3. 20% Biochar Particles4. 15% Gravel5. 5% Biochar Dust6. 0.423 lbs. per cubic foot Bottle String

(% by volume)

PART MOLDS

The parts of the Arborloo were designed by a previous team but were never actually made.  Keeping this design, mold negatives were initially designed. Due to cost of material, the negatives were CNC machined out of high-density foam that was easily available.  The actual molds are vacuum formed, however the foam deforms from the heat, so concrete was poured into the negatives to make positives that are then formed over with plastic.  This was a rather redundant process, however, other options were either too expensive or did not yield a quality part. Also, the foam, concrete mix, and forming material were all free or donated so the molds were virtually costless to make this way. Figure 4 below shows a representation of one of the molds designed, and how it would be used during manufacturing. Refer to the projects design package for the rest of the mold drawings.

Figure 4: CAD Drawing of Middle Ring Two Part Mold

Proceedings of the Multi-Disciplinary Senior Design Conference Page 5

FEASABILITY

The entire design utilizes human power, allowing the need and cost of electricity to be mitigated to practically zero. This is ideal for the location the manufacturing process is to take place in, as electricity is not as readily available in Haiti as it is in the US. Additionally, this aids in keeping the production cost down, as it is one les recurring cost to worry about.  Each subsystem is light enough to be carried by a single person, and small enough to easily fit in the bed of a pick-up truck.

One of the major concerns of the design was how the ABS thermoformed molds would hold up under the weight of the concrete as it was poured and set. Initial simulations of the material in an unsupported configuration showed excessive material displacements (~0.25”) of the mold material when the concrete was in its liquid state. It was then decided that the molds could be buried in sand when being poured to provide extra support to the material and maintain the proper shape. Simulations were run of the heaviest ring poured into the mold, half buried in a sand-like material. The results are shown below in Fig. 5.

Figure 5: Simulation of Base Ring in Sand (Displacement on Left, von Mises Stress on Right)

In this configuration, the maximum displacement was reduced to <0.0003”, with a maximum von Mises stress of ~7.5 psi, well below the ~4300 psi limit of the ABS material. These simulations proved the viability of the mold material and allowed the team to be comfortable to move forward with the mold material selection. When the actual material was purchased and formed, it was performed much better than expected, not requiring the supporting sand when the molds were poured.

One remaining question of the mold material feasibility is how the ABS material will hold up in the long term. Unfortunately, due to the polymeric nature of the ABS, life cycle analysis was extremely difficult to perform, as the parameters required to perform the analysis were difficult to obtain, as well as being specific to material configurations. This is not yet a major concern, but something that must be considered going forward.

RESULTS AND DISCUSSION

This section should describe your final prototype (product or process), whether it met specs (results of testing), and how you evaluated its success. Most conference papers include enough information for your work to be reproducible.

After determining the desired mixture, completing the design of our subsystems, and finalizing the production of the vacuum formed molds, the final prototype was produced, and is shown below in Figure 6. The finished Arborloo prototype shown here proves our theory that forming vacuum formed molds and pouring into those will produce quality results. When pouring our concrete mix into the molds, the group had a difficult time using the two part molds the way we designed them to be used. When the molds were bolted together, there wasn’t much room for the high slump mix to be poured into the molds. The team ended up carefully filling the molds from one corner and allowing the mix to travel through the rest of the mold with the help of gravity. The surface finish on the Arborloo is extremely smooth, and the rings are light. The edges of each ring will need to be cleaned up with some sort of concrete sander, since there was a little concrete that leaked out from the seams of the two part molds.

Copyright © 2018 Rochester Institute of Technology

Figure 6: Complete Arborloo Prototype

The final prototype Arborloo meets the majority of the specifications created by the customer and the group itself. In Table 1, the “Actual Values” listed in the final column of the chart indicate the values that the group found after production of the prototype was complete. As for the formal test plans that were created to help evaluate the performance of the Arborloo, we have not yet completed those but we believe the prototype will succeed.

CONCLUSIONS AND RECOMMENDATIONS

This section should include a critical evaluation of project successes and failures, and what you would do differently if you could repeat the project. It’s also important to provide recommendations for future work.

Overall, the process of designing a process and manufacturing an Arborloo was considered to be a success.

REFERENCES

1. ASTM C39/C39M-17 Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, ASTM International, West Conshohocken, PA, 2017, https://doi.org/10.1520/C0039_C0039M-17

2. ASTM C293/C293M-16 Standard Test Method for Flexural Strength of Center Point Loading Concrete Specimens, ASTM International, West Conshohocken, PA, 2017, https://doi.org/10.1520/C0293_C0293M-16

3. Multidisciplinary Senior Design Project P17485, BIOCHAR CONCRETE ROOFING SHEETS FOR NICARAGUA 2.0, Rochester Institute of Technology, NY, 2017, https://edge.rit.edu/edge/P17485

ACKNOWLEDGMENTSKathleen Draper from the Ithaka InstituteAl from Faro IndustriesJohn from Manitou ConcreteSarah BrownellSamantha Huselstein

Be sure to acknowledge your sponsor and customer as well as other individuals who have significantly helped your team throughout the project. Acknowledgments may be made to individuals or institutions.