P19011: Wheelchair Accessible Restroom
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Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

The team's goal for this phase was to test and tear down the previous team's prototype to analyze the performance of the device and determine if any parts could be re-purposed for our device. The team would determine a Bill of Materials and create a budget outline for our device.

The team accomplished:

Engineering Analysis of Previous Prototype

The team analyzed the existing prototype to see how it functioned, and determine if there were any components or materials from the prototype that could be reused to save money on supplies.

The team found that the device had trouble raising for the first time, and rose haltingly. Once the device was raised, the team could not get the device to lower, even with an applied weight of roughly 200 pounds, which exceeds the previous team's threshold requirement of 155 pounds to lower the seat. The team took a hammer to the device and eventually after applying large amounts of force were able to forceabley lower the seat back to its original height. The device would not raise again, and the cylinders were then stuck in the lower position. The team noticed that the water being expelled from the hydraulic cylinders was dirty and had small particles in it, leading the team to suspect that the insides of the cylinders had rusted.

Links to video testing of the previous prototype can be found here, here, and here.

public/Photo Gallery/Teardown/20181029_142732.jpg The device would not lower with team member Nate sitting on it.

The device would not lower with one of the team members sitting on the seat. The exhaust liquid also had particles in it and was a muddy brown color when it exited from the hydraulic cylinders. The team ended up having to force the device to return to its lower position.

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The team decided to deconstruct the hydraulic cylinders to see if they could be modified to meet the needs of the new device. Large amounts of rust were found on the inside of the cylinders, explaining why the device had gotten stuck in use due to the increased friction from the rust.

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Design Developments

Initial Feedback Survey

The team also worked with a contact to send out a survey to get initial opinions from the target population. The team received 6 responses. The questions and response data is shown below.

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Fluids Analysis

Projections of minimum operating pressure and user weight were developed to determine what size cylinders would be best to use in our designs. 2.5" cylinders were determined to be the initial size to test.

Fluids Analysis

Fluids Analysis

Link to live document here

Drawings, Schematics, Flow Charts, Simulations

Paper models were constructed to look at various ways the lifting mechanism could be set up and be aesthetically pleasing.

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Fusion 360 models of the handle design were developed to look at feasible layouts that would help with both functionality and support.

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Fusion 360 models of potential cylinder covers for the frame and base of the device was designed to look at how the device could be made to be both supportive, aesthetically pleasing, and a smaller footprint as to not interfere with the movement of a wheelchair.

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3D designs of the cylinder assembly were created to determine all parts and sizes of materials needed, and to provide schematics for assembly and test in the next phase.

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Bill of Material (BOM)

The following is a preliminary Bill of Materials developed by the team and is subject to minor changes as the team progresses in the development of the design.

Preliminary Bill of Materials

Preliminary Bill of Materials

Link to the live document here

Test Plans

Testing Requirements

Testing Requirements

Testing Requirements

Link to live document here

Human Subjects Research

In order to complete human testing of the device in the future, the team organized a proposal to the IRB and is pending approval.

Link to the Human Testing Procedure document here

Link to the Human Testing Survey Questions document here

Technical Test Plans

Testing plans outline

Testing plans outline

An outline to the tests the team plans to conduct can be found here

The team will test the functionality of the hydraulic cylinder system. Link to the test plan document here

Hydraulic System Test Design

The team developed designs of how to set up a hydraulic system to create the lifting mechanism in the device. Below are two iterations of the design process.

Preliminary Set-up Design 1.

Preliminary Set-up Design 1.

This design uses PVC pipes to reduce cost and prevent the formation of rust on the inner portion of the cylinders that would hinder proper functionality of the device. This is the design that the team will move forward in creating a prototype of and use in the testing phase.

Preliminary Set-up Design 2.

Preliminary Set-up Design 2.

Risk Assessment

Risk Assessment

Risk Assessment

Link to live document here

Design Review Materials

Notes from the Preliminary Design Review can be found here

Plans for next phase

During the next phase the team plans to hold refine the designs and drawings of the device, finalize the bill of materials for our plans, and further develop the details of the device. Any orders for material will be placed so assembly and testing can begin as soon as the team returns from winter break.

Links to each team members' Three Week Plan:

Rachel Ackles

Rachel Berry

Nate Bracalente

Don Phan

Daniel Vetere


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