Windshield Wiper Assembly Re-design

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Contents

Executive Summary

Updates since Report 1

Please provide any updates to the wiki report on the analysis of our current product (see report 1 revision assignment)

Research and Observations

After interviewing several people and conducting online research (the interviews and key points from the research can be seen in http://ddl.me.cmu.edu/ddwiki/index.php/Windshield_wiper_ideas page ), there were several key problems that came up. From the interviews, the problems we wanted to address were poor winter performance, difficulty in changing the wiper blade, and the desire for a more environmental solution. From research we saw that lack of proper maintenance was an extremely common problem. So we focused on ways to improve the user’s experience in the winter, and on ways to encourage the user to change their blades more often by making the process easier and/or more environmentally sound.


The problem of lack of proper maintenance is twofold: One, people simply don’t remember to change their wipers or are not aware that the wipers need to be changed; two, the difficulty of changing them makes users avoid this task till they can have someone else perform the task. To combat these issues, we have come up with several ideas. Some examples are: to make the rubber of the blades change color like toothbrushes to indicate the need to replace the wiper; to change the latching mechanisms to make it more user friendly; and/or to make wipers where only the rubber need be replaced, and make the rubber attachment point easier to change. The latter option would be more environmentally friendly and would also allow users to buy several rubber pieces at once, making it very easy to change out the rubber piece when ever their visibility is not optimal. Simply changing the latching mechanism on the wiper blades seems promising, but there are simpler latching designs for blades and this would not address the environmental angle. Making the wipers change color seems like a very good idea but would be out of the realm of interest for this project.


To deal with the poor winter performance, we looked at heating the blades and/or adding an extra blade to the assembly. The extra blade would be of a harder material and would scrape the windshield for the user. Adding a heated blade could make this task easier for the wipers to perform.


On top of the interviews, we tested different conditions on a 2003 Toyota Corolla and documented some of the process. First we tested out the wiper fluid:
Image:ww-clean.JPG
This particular car performed well in cleaning the windshield. The fluid shot out under a good amount of pressure and covered key parts of the windshield.
However, looking at the next picture we can see a negative part of the cleaning process.
Image:ww-dirty.JPG
Notice that belowed the wiper (which we have raised) is a spattering of dirty that has accumulated. This tells up that the blade sits in dirt while it is not in use and thus is not perectly clean.
Then we dumped some leaves on the car and tested how the wipers performed:
Image:ww-leaves.JPG
In this first image the leaves are stuck underneath the blades and when we tried to wipe the windshield the leaves were dragged across, greatly diminishing the effectiveness of the wipers.
Image:ww-singlestuck.JPG
In this second image there is a leaf shown that got stuck in the frame of the wipers. This did not effect the performance of the wipers, however it distracted the driver of the vehicle creating a great safety risk.
After this we took a hose and sprayed the car at various pressure levels to simulate different rain conditions.
Image:ww-rain.JPG
We observed the wipers working and noted a few things.

  • The water from the second wiper was being pushed to the drivers side then back within a cycle
  • When the water pressure got to a certain point it was simply not safe to drive the car, no matter what wiper setting you are at
  • Under a normal rain condition it is better to run your wipers at the slower constant speed, that at the highest speed setting

Top Design Concepts

We performed a detailed analysis of our top four design concepts to help decide which is the best idea.

Compressed Air System

The compressed air system is our most revolutionary idea. This system would get rid of the wipers all together. The basic idea of this design is that we would used compressed air to blow the rain off of the windshield. As shown in the figure on the right, several hoses would run of the main air line to nozzles along the bottom of the windshield. When it is raining you would simply turn on the compressed air system and the water would be blown off the windshield. The placement of the nozzles at the bottom of the windshield is effective because it works with the direction of air flow due to the cars movement. A compressor would be stored in the trunk of the car. It would have to be about a 25 gallon compressor, to allow for times of heavy use. Also, in conjunction with the compression system a wax coating, such as Rain-X would be used. This coating causes water to bead and be more easily removed from the windshield.

Durability

The compressed air system has no moving parts, so it's durability is quite high. The nozzles would be firmly fixed in the hood and thus, would not be suspect to much damage. The compressor itself would be stored in the back of the car, most likely in a boxed out space in the trunk. Within a confined space, the compressor would not be damaged by any goods stored in the trunk. On it's own, a compressor is made to be durable as they are often used in shops.

Ease of Maintenance

The immobility of the system does not make it easy to maintain. This set-up would be significantly more difficult to maintain than the current wiper system. The compressor itself would be replaceable, but costly to replace and heavy to move. The nozzle and hose components are mostly internal and would thus require getting inside the body of the car and would probably require specialized maintenance, another costly requirement.

Affordability

Overall, this system is more expensive than the current set-up. While the required maintenance of the compressed air system would be less frequent than the current windshield wiper system, the costs of repairs would be much greater overall. Another thing to consider in terms of cost is the power required by the compressor. Running a compressor while driving would eat up a significantly larger amount of gas if the compressor used was gas powered. If the compressor was battery powered again, the batteries would cost a lot of money and would require more gas if they were recharged while driving.

Effectiveness in All Weather Types

The compressed air system would work better in certain weather situations than in others. The current leaf problem would be eliminated because there could be a short burst of compressed air to shoot the leaves off the windshield. In the winter the compressed air system would actually perform worse than the current wiper system. More power would be required to move snow off the windshield and it may cause ice to freeze to the windshield more quickly.

Percentage of windshield covered

One of the greatest advantages to the compressed air system is the percentage of the windshield covered. Since the nozzles are at the bottom of the windshield and spread out pointing up, the entire windshield is covered by the air.

Visibility

Without testing it is not very clear how the compressed air would affect visibility. The air blowing the droplets would probably cause them to streak and depending on the amount of rain this streaking could actually reduce visibility. However, we feel that it would only reduce visibility in very heavy rain conditions, which are unsafe to drive in with normal wipers. In light rain conditions this system would actually be better. It would be easy to see through the thin layer of water and there would be no wipers to get in the way of visibility.

Heated Blades

Image:HeatedWipers.JPG

Adding a heating element to the blades is an effective way to prevent icicles from forming on the windshield wipers and hindering their ability to clear the windshield in the winter. Heating the blades is a decided improvement over non-heated blades, although the group has ultimately rejected this as a project idea for two reasons:

1) This significantly adds to the cost of the blades. Unless this feature was combined with others to create a "luxury blade", as we may in fact do, most car consumers are not going to want to spend twice the money on blades with a seldom-useful feature.

2) This product already exists. After brainstorming and deciding that heating the blades is an improvement, we became aware of companies already making and selling this type of blade.

   http://www.blizzardblade.com/Place%20Order.htm
   http://www.everblades.com/HEATFLEXX.htm


The pros and cons of the heated blades are discussed below, but in conclusion, we will not simply add a heating element to wiper blades. We are still considering the possibility of adding a heating element to a different project idea, as an added feature to our "luxury blades".


Durability

Adding a heating element to the blades should not adversely affect durability. The rubber part that contacts the windshield might now need to be made of silicon, similar to existing heated blades. We have no reason to believe that these silicon blades should wear out faster than traditional blades, although laboratory tests to confirm this fact should be done if the group decides to heat the blades.

Ease of Maintenance

Heated blades will only be slightly more difficult to maintain, although there will be more parts that could possibly break. The heated blades will be more difficult to install since the heating wire must somehow be connected to the car battery. Each time the car owner puts on a new pair of heated blades, he or she will have to reconnect this wire to the blade heater.

Affordability

Heated blades will likely double the expense of the windshield wiper replacement blades.

Effectiveness in All Weather Types

This will improve the effectiveness of the blades in the winter. In wet and cold weather, sometimes icicles will form on the wiper blades. The icicles prevent the rubber portion of the blade from effectively clearing the windshield. Heat will melt these icicles and improve the performance of the wipers.

Heating the blades will, however, NOT have a significant effect in either a) melting all of the snow/ice on a windshield, or b) freeing the blades if they are frozen closed. These two problems will remain a significant source of difficulty in maintaining visibility in the winter. Back of the envelope calculations indicate that heat from the blades would take 300 minutes to melt the ice on a frozen windshield (see below). The heating elements are unlikely to free the blades if they are frozen to the car/windshield, since everywhere from the motor, up the arm of the wiper, and the blade is typically frozen, and the heating element will only melt the ice around the blade itself.

Back of the Envelope Calculations: assume ice (32 degrees F) is covering a 6 square foot windshield, 1/4" thick. Blades output 30 Watts of heat, each.

12 V * 2.5 Amps = 30 Watts. 2 blades = 60 Watts. Latent Energy of Fusion = energy to melt ice = 80 calories per gram = 334720 joules per kilogram. An icy windshield is roughly 6 sqr. feet = .56 Meters Square. 1/4 inch thick = 0.003556 M^3 of ice. Density of ice = .931 gram/cm^3. Icy windshield = 3560 cm^3. Mass of ice = 3.3 KG of ice on windshield. Need 3.3 * 334720 = 1,104,576 Joules to melt the windshield. 60 joules/second. = 306 minutes to melt the ice.


Percentage of windshield covered

Heating the blades will not affect the area covered by the windshield wipers.

Visibility

This feature will improve visibility during the winter, when icicles would otherwise form on the blades.

Exchangeable Blades/Rubber

Common Problems affecting wiper blades:
Image:wiperblade_problems.gif Image:exchangeblade.gif
How to change Wiper Blades Just the Rubber part:
Taking them out:
http://www.expertvillage.com/evplayer.aspx?flv=wiper-blade-disassemble
Putting them in:
http://www.expertvillage.com/evplayer.aspx?flv=wiper-blade-assemble

The idea here is to have the rubber part of the blade be easily removed and put back in. As they are now one has to line up three pieces, two metal and one rubber, then slid them through each holding bracket on the windshield wiper blade. Please see the videos below to get a better idea of the current configuration and how they are taken off and put back on. The redesign would have one rubber piece that would have a some what stiffer back with mushroom shaped knobs that could be snapped in to a hole where the holder for the current design is. That way a user could bye a starter back that would have the redesigned blade and several rubber pieces. This product could be marketed to people too two groups of customers: One the environmentally conscious and two the higher end market as a more efficient alternative. The picture above is to demonstrate that most problems with wiper blades come from the rubber piece. The drawing is a demonstration of the new model.

Durability

The durability would be the same as the current model but it would be less important because of the easy of replacement.

Ease of Maintenance

This would make maintenance of wiper blades much simpler and better for the environment by cutting down on wasted material.

Affordability

The rubber pieces are very cheap if you try and buy them now and the changes suggested should not raise the price that much. Furthermore it would be much cheaper then replacing the whole blade, on the order of 0.30 to $30, which is what most people do now.

Effectiveness in All Weather Types

This would stay the same.

Percentage of windshield covered

This would stay the same.

Visibility

This would stay the same.

Multiple Blades (flap or rotating)

  • top design at this time
  • keep current rubber blade for rain
  • add blade made out of hard plastic for ice/snow/leaves
  • wiper blade subassembly will rotate to change to this setting
  • Variation: position hard blade so it can flab down into place
    • the wiper blade subassembly will not need to rotate
  • future decisions: angle of hard blade, how to implement rotation

Durability

Ease of Maintenance

Affordability

Effectiveness in All Weather Types

Percentage of windshield covered

Visibility

Design Comparisons

Pugh Chart

Criteria Weight Standard Windshield Wiper Compressed Air System Heated Blades Exchangeable Blades Multiple Blades
Durable 1 0 + - 0 -
Easy to change 2 0 - 0 ++ -
Affordable 2 0 -- - ++ -
Effective for all weather 3 0 -- + 0 ++
Percentage of windshield covered 1 0 ++ 0 0 0
Visibility 3 0 + + 0 +
+ 0 6 6 8 9
0 12 0 3 8 1
- 0 12 3 0 5
Net Score 0 -6 3 8 4

VOA

also, although the client didn't specifically ask for a VOA, I have asked you to provide one as part of your way of communicating the opportunity.

Gandt Chart

In addition, each report should include a Gantt chart or alternative method to map out the team plan for design and prototyping through the remainder of the semester. Be as detailed and specific to your particular project as you can, and assign roles for team members as appropriate.

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