Windshield Wiper Assembly Re-design

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Contents

Executive Summary

Since our previous report we have been working on identifying problems with the current windshield wiper system and identifying design solutions that address these problems. We came up with four top design ideas including heated blades, easily removable blades, compressed air system, and a multiple blade system. After analysis of each idea we came out with a multiple blade system as our top idea that we will pursue. As evidenced by our pugh chart, we will also consider incorporating the easily removable blade and heated blade ideas into our final design.

Our decision began with simultaneous brainstorming and market research. We conducted several interviews and based on those and our own experiences we created a list of problems people have with the current system. We then had a few brainstorming sessions, ending up with a list of 97 ideas for design changes and improvements. The raw market research and list of ideas can be found here: http://ddl.me.cmu.edu/ddwiki/index.php/Windshield_wiper_ideas . The most common problems we found were that leaves were getting stuck under or in the blades, the blades were ineffective in the winter at cleaning ice off the windshield, people wanted a more environmentally friendly disposal solution, and that the blades should be longer lasting.

To address these concerns we came up with many ideas and narrowed them down to the top four. The first is heated blades, in which the blades of the wipers would be heated for easier snow and ice removal. The second is easily removable blades, in which the rubber part of the blade is made to snap into the wiper so that exchanging them is easier and more environmentally friendly. The third is a compressed air system that would eliminate blades all together and would be very good at removing leaves and other loose debris from the windshield. The final is a multiple-blade system that would incorporate both a rubber wiper for rain and a hard plastic scraper for removing snow and ice.

We used a Pugh chart to analyse each idea and found that we could easily remove the compressed air system as a possible solution because it ended up with a net score of -4. The top scorer was the easily removable blades, which ended up with a net score of 8. We decided however, to go with a multiple blade system as our final product because it was a more interesting and innovative solution and it still netted a score of 4. Since heated blades, with a score of 3, and easily removable blades both scored positively and are more minor design problems we will be looking into incorporating one or both with the multiple blade idea.

Updates since Report 1

Please refer to the Discussion tab ( http://ddl.me.cmu.edu/ddwiki/index.php/Talk:Windshield_wiper_assembly ) to see modifications made to Report 1.

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


VOA

The VOA chart is used as a tool to identify areas with problems in our product. It provides a simple graph portraying the user's experience with the product. Areas that are low scoring in the VOA may either be areas for improvement or areas that the customer is not very concerned with. Design modifications that we make could increase the user's feeling of adventure and identity, as well as benefit environmental, enabling, craftsmanship and durability ratings.

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)

To address the ineffectiveness of current wipers in snow and ice, we thought of a multiple blade solution. In this design the current rubber blade will not be altered, but a second blade made out of hard plastic would be added. To best implement this design we thought of three variations: a 180 degree rotation, a tilt design, and a flap design. These are described in detail below. For all of these designs, the second blade is electronically activated from an extra setting on the wiper settings controls. Once in this mode, the user will be able to choose a speed for the second blade similar to the rubber blade.

For any multiple blade design an important concern is providing enough torque to effectively scrape ice or snow off the windshield. If the motor needs to supply more torque, more fuel will be burned and more emissions will be released. Another important concern is the optimal angle of the second blade on the windshield. As we pursue this design in greater detail we will need to do research and calculations to find the optimal angle for scraping.

Image:180rotation.jpg

The sketch above shows the 180 degree rotation design. To switch blades, the entire wiper arm subassembly will rotate. This design requires extra wiring and extra joints which will be used to lift the blade off of the windshield in order to switch to the other blade. A concern with this design is that the two blades could obstruct the view for the driver while in motion.

Image:tilt.jpg

A tilt design will still require the wiper arm subassembly to rotate, but is simpler in that the arm will not need to completely lift off of the windshield in order to turn. Also, the necessary rotation is significantly less than the 180 degree design. This will cause less wear and tear on the joints and materials as well as a faster and more efficient change of blades.

Image:flap.jpg

The last variation is a flap design. The second blade will be mounted on the wiper arm assembly, hinged on one end and pivot down into place when the user chooses this setting. While extra wiring will still be needed, the wiper arm assembly will not need to rotate so this is an advantage.


Durability

The Multiple Blade design is less durable than the original wiper design since more components are added. The wiper blade subassembly will either have to rotate or the second blade will have to move into contact with the windshield. Either way, this design is significantly more complex than the current one because more degrees of freedom are added. Additional wiring in the wiper assembly could potentially cause more problems. The durability of the wiper assembly is decreased with the multiple blade solution.

Ease of Maintenance

Since an additional wiring component is added with this design, the wiper blade subassembly will be slightly more difficult to change. To address this, we could combine the exchangeable blade design so that the user only has to change the rubber blade. We expect the second blade to be more durable than the rubber one because it is made out of a hard plastic material, so this blade will rarely, if ever, need to be changed. Therefore, the ease of maintenance on this design is better than the original if exchangeable blades are used, but worse than the original if the entire wiper blade subassembly need to be changed.

Affordability

A multiple blade windshield wiper will cost the consumer more money due to the added parts and electrical components.

Effectiveness in All Weather Types

The main benefit of multiple blades is that the windshield wiper assembly works well in all types of weather. The second blade is used for scraping off large pieces of snow and can be used to break up ice on the windshield and scrape this away. It is also more effective for getting leaves and other debris off the windshield because there is less chance leaves will stick under the plastic blade.

Percentage of windshield covered

This will remain the same as the original windshield wiper assembly.

Visibility

The visibility is increased in the multiple blade design since the windshield will stay clear in all types of weather. However, it is important that the second blade does not obstruct the view of the driver or this will decrease visibility. We assume that we can achieve an increase in visibility as we continue in further design of this concept.

Design Comparisons

Pugh Chart

We constructed a pugh chart in order to compare our four design concepts. The categories on the left of the chart are the most important issues for our product. We assume that all the wiper designs have the same level of safety because they have no direct interaction with people while in use. The standard windshield wiper design is used as a control and all values are set to zero. Every other design receives a + or - accordingly. Our results indicate that the compressed air system is the worst idea mainly due to increased cost and effectiveness for al weather. Heated blades are second to worse due to their durability and affordability, and multiple blades are only a little better since they are more effective in different types of weather. Exchangeable blades received the highest net score because they have no apparent disadvantages compared with the standard design, and are more easy to change and affordable.

Even though multiple blade design did not score the highest, we feel that it would be an interesting project because it is an innovative solution for all types of weather conditions. With these results from the pugh chart in mind, we would like to combine other high scoring ideas into our final design, incorporating one or both of the heated and exchangeable blades designs. This will provide a windshield wiper that is both effective for all types of weather and environmentally friendly.

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

Gantt Chart

To plan the completion of our project, we have included a Gantt Chart. Detailed descriptions of the tasks can be found below.

Image:WiperGantt.JPG

* Ice Scraper Research: Analyze what type of motion is most effective for removing ice.  Perform a torque analysis to determine if the existing linkage mechanism is sufficiently strong for chipping away ice.  Additionally, research the material needed to create an ice scraper.
* Sketch Design Alternatives: Figure out ways to mount/activate the scraper blade.  Rough design sketches.
* Begin making design decisions, with the end result of a prototype design.
* Construct the first prototype.  Includes obtaining materials.
* Prototype Evaluation: critically evaluate our first prototype's performance, what needs to be improved, what worked well.
* Mechanism Brainstorming: Decide on the group's "final design" using experience from first prototype.  All features and major design components should be "tentatively finalized".
* Prototype Redesign: Translate design ideas into parts to be made for the 2nd prototype.  Fully define all dimensions, prepare for manufacturing, etc.
* 2nd Prototype Construction: Build the 2nd prototype.
* Finalize Design: Make minor changes to parts based on results of 2nd prototype.  These part and assembly designs will be made into our final product.
* Construct final prototype: Build the 3rd and final prototype/product.
* Prepare Final Report: Report on our design and the key analyses we used to reach the design.
* Prepare Poster/Demo: Obtain a mock "windshield" and setup our final product to demonstrate it's effective cleaning capabilities.
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