P18414: SOIL Composting Toilet and Urine Management
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

Summarize:

Critical Project Updates

As a team, we were faced with several options on how to proceed with our designs and scope. We struggled with deciding how to best focus our efforts moving forward: whether it was to develop two different diverter designs, focus all our efforts on perfecting a single design, or to meet the needs of our customer and try to implement a complex system not in our current scope. To make this decision, a PUGH analysis was completed to decide the best use of our efforts. The table can be found below with our team approved standings.

After deciding to focus our time and resources on perfecting a single diverter design, our engineering metrics needed to be refined to accommodate our focused design project. These PUGH updates can be found below.

Critical Project Updates PUGH

Critical Project Updates PUGH

Critical Project Updates PUGH

These newly familiarized engineering metrics could then be used to determine appropriate testing measures for each metric at hand. The customer requirements originally formulated were also modified to meet the need of our client now that the project has been updated. The updated engineering metrics and customer requirements can be seen below and can also be downloaded using the provided link.

Removed ER

Removed ER

Removed CR

Removed CR

Updated ER and CR with revised test plans

High Level Overview of Design Development

Much of the work completed during this phase has been a continuation of work started during the Preliminary Detailed Design phase. The work has consisted of finalizing our design concepts and feasibility analysis so that during MSD II next semester we are able to begin prototyping our design immediately.

Our plans for this phase can be found below.

Detailed Design Review Mapping

As always, we have made the effort to include our client at every possible opportunity in this process. It was important that we sought insight from our clients in all the decisions made to ensure the overall satisfaction of our customer.

Notes from our weekly meetings with our SOIL clients can be found below.

Soil Weekly Call Notes

Diverter Feasibility - Completed

The U-shaped diverter design was chosen over the slotted slope design. A CAD model was developed for the diverter. The dimensions used in the model were designed to fit with the existing toilet frame and urine collection jug.

Multiple views of the CAD modeled U-shaped diverter can be seen below.

U-Shaped Diverter CAD

U-Shaped Diverter CAD

Urine Diverter Von Mises Stress Analysis

Urine Diverter Von Mises Stress Analysis

U-Shaped Diverter Multiple Views

Urine Diverter FEA

Diverter Toilet Assembly

Ergonomic feasibility analysis was also completed to account for the user experience with the diverter. A 'nut ridge' analysis was completed, specifically analyzing the dimension of testicular hanging length. This analysis was necessary to optimize the dimensions of the diverter to prevent any unwanted touching between the user and the diverter.

Corresponding images can be seen below.

Buttock-Popiteal

Buttock-Popiteal

Hip Breadth

Hip Breadth

Male Hang

Male Hang

Male Hang v2.

Male Hang v2.

Popliteal

Popliteal

All Ergo Stuff

Male Anatomy Research

Ergo Cls

A test to determine the force the diverter can withstand was also completed. While it was assumed that no one stream of urine would be forceful enough to cause the diverter to yield, this metric more pertains to circumstances where the diverter is removed from the toilet system and forcefully scrubbed during cleaning. We wanted to ensure that our design was sturdy enough to withstand typical cleaning measures.

The results for this test can be found below.

A material compatibility test was also completed to justify that the types of plastic we are considering for the design would not have any adverse reactions to common chemicals the diverter might come in contact with, such as bleach during cleaning. Only two types of plastics have been tested at this point, ABS and polypropylene. Acrylic has been ordered and is currently being shipped to the MSD office. More types of plastic would ideally be testing. Unfortunately, a limiting factor in this design process is the materials available to our customers in Haiti. The only plastic supplier in Haiti, Haiti Plastics, has been reached out to numerous times at this point in the process, but no reply has been received.

Results of the corrosion due to cleaning materials test can be found here.

Base Feasibility - Completed

The CAD drawing of the base completed in the prior phase were necessary for continuing the feasibility analysis.

Visuals of the multiple views of the toilet base can be seen below.

Base Toilet Assembly

Although the test for force the toilet base can withstand was completed in the prior phase, updated program techniques as well as contact with subject matter experts helped to better represent the true force the base can withstand and provide us with accurate values to base our engineering calculations on.

An updated analysis with appropriate visuals of the force the toilet base can withstand can be found below.

1st Principal Stress

1st Principal Stress

3rd Principal Stress

3rd Principal Stress

FEA Report

Toilet Feasibility - Completed

The complete toilet CAD model can be seen below.

Complete Toilet Assembly

In addition to performing analysis on the individual subsystems of the toilet, it was important to look at the toilet as a whole.

The systems architecture completed prior to this phase helped to identify where most of our efforts should be put.

The systems architecture can be seen below for reference.

Systems Architecture

Systems Architecture

The weight of the toilet was also considered during the design. It was necessary to keep the toilet under 200 Newtons. This was decided as a target based on a reasonable weight the typical user could lift for situations of cleaning and moving the toilet. While we did not yet have a complete toilet prototype to test, preliminary testing could be completed through the above CAD models by inputting the material properties.

Results from this preliminary analysis can be found below in our Bill of Material document.

Bill of Materials with Weight

Bill of Materials with Weight

Additional feasibility analysis was also done for the cost of the toilet as a whole. The cost was determined through summing the individual components of the toilet to obtain an overall total cost.

The results from this study can be found below.

Estimated Cost

Estimated Cost

Cost Analysis

Bill of Material (BOM)

The Bill of Materials (BOM) was developed through various resources to best approximate the true design of the current Ekolakay toilet model. Through collaboration with the clients at SOIL, we were able to accurately represent the list of materials needed to construct a dry toilet.

An image of the BOM can be seen below. A link to the full document can also be found beneath the image.

Bill of Materials

Bill of Materials

Bill of Materials

Test Plans

Initial test plans were written during the preliminary detailed design phase. However, after receiving feedback from the preliminary detailed design review, as a team, we went back and refined our engineering metrics and customer requirements from the initial stages of this process to better represent the current scope of our project. The test protocols below are the revised versions to fit our scope.

A directory of protocols can be seen below along with their current status.

Test Plan Plan

Test Plan Plan

Percent of Diverted Urine

Seat Surface Height From Ground

Range of Motion of Seat When in Use

Force Toilet Can Withstand

Weight of Toilet

Cost of Toilet

Number of Components

Collection Container Accessibility

Corrosion due to Cleaning Materials

In addition to these protocols dealing solely with factors which can be controlled, a proposal for human subjects testing was also submitted for approval. Using human subjects would allow for the collection of data for percent of urine diverted, as well as numerous other human factors, such as comfort level, aesthetic appeal, general sanitation, are also planned to be collected from this testing.

A copy of the intended test protocol, abstract, informed consent form, and post-testing survey can be found below.

Human Subjects Testing Protocol

Testing Abstract

Informed Consent Form

Toilet User Survey

Design and Flowcharts

While the different CAD drawings can be found throughout the previous headings of this page, they have also been compiled here as a directory.

Diverter Toilet Assembly

Base Toilet Assembly

Complete Toilet Assembly

Our team has also been working closely with an industrial design student to help create professional images of proposed designs.

This work can be found below.

SOIL Logo

SOIL Logo

Diverter Render

Diverter Render

Diverter Render

Diverter Render

Risk Assessment

The risks have been updated for this portion of the design process.

An image highlighting the main risks associated with this phase can be found below, as well as the running master list of risks.

DDR Risks

DDR Risks

Risk Table

Design Review Materials

This section will be updated accordingly with the feedback received from the review.

Plans for next phase

Our team vision for MSD II can be found in the attachment below.

Team Vision for MSD II

Our Gantt chart for our planned process throughout the rest of the academic year can be seen below.

Project Plan for MSD II

Project Plan for MSD II

And each of our individual visions can be found in the attachments below.

Rozie

Tessa

Nicole

Chris

Jeff


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