Approach Page for Individual Wiki Report
| Date: 29 November 2006 |
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Table of Contents |
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| Author: James Watson | Team: Solar Car |
Requirements
There were several requirements to consider for an optimal windshield wiper that would work with the solar car, including:
- Avioding the unnecessary use of electrical power
- Ensuring that the wiper blade maintains contact with the canopy
- Meeting the race requirement that the blade be able to wipe 0.1 square meters of windshield area
- Making the wiper assembly easy for the driver to use so as not to distract him/her from driving
- Making the wiper assembly easy to manufacture and assemble
- Minimizing the wiper’s size and weight so as not to add to an already heavy car
- Minimizing cost
Specifications
These non-quantifiable requirements were then converted to more specific metrics from which the specifications could be determined. The metrics could either be defined with a yes or no answer or be quantified with a specific value. Although there were many metrics to be considered, the six most important metrics were determined to be:
- Electrical power consumption [Watts]
- Cost of parts and manufacture [$]
- Force required from user for operation [Newtons]
- Area cleared by wiper blade [Square Meters]
- Operable without altering driver posture [Yes/No]
- Wiper leaves no water after swipe [Yes/No]
Concept Generation and Sketches
After researching how traditional wipers work on howstuffworks.com and other sources, I performed the original concept generation for this design problem using a mindmap technique. For a description of what a mindmap entails, please see the Lab 1 Assignment and Supporting Materials for the Fall 2006 ME 4000 class. An image of my mindmap can be seen and dowloaded below.
Figure 1: Watson’s Mindmap
Since avioding the unnecessary use of electrical power seemed to be crucial to the development of the solar car as a whole, most of the designs that I brainstormed were powered by the driver alone. I tried to make the operation of the various asseblies as obvious as possible in my sketches. As a part of Lab 3 I further explored some of the designs I felt were most viable. More detailed sketches of those designs can be seen below.
Figure 2: Watson’s First and Second Design Sketches
Initial Downselect and Design Refinement
As a part of Lab 6 I was asked to choose two designs to further develop. I used a ranking system based on the engineering metrics mentioned in the specifications section of this page. The most important metrics were weighted most heavily, while those that were less crucial received a lower weight. Then each potential design was rated for how well it would perform in each metric. A composite score was assigned to each design and they were ranked accordingly. I chose to refine the two designs that were ranked as the best. My design selection matrix, which is a spreadsheet showing the values and rankings each design received, can be downloaded here. The two best designs involved the traditional worm gear driven assembly commonly used in most cars, and a long lever arm which would be swiveled back and forth by the driver. The worm gear assembly scored exceptionally well in the ease of use category, whereas the long lever arm assembly scored well in the aviodance of electrical power use, low cost, and ease of implementation categories. In order to further develop the concepts involved with these two designs, solid models and assemblies were created in Pro E, a 3D modeling sofware package. The models I made were intended to use as many commercial off the shelf parts as possible, while keeping the design specific to my solar car application. Images of the assemblies of the designs I further developed can be seen below.
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| Figure 3: Watson’s First Design Refinement | Figure 4: Watson’s Second Design Refinement |
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