RAIN SENSING WIPERS
INTRODUCTION
Background
Windshield wipers are used to clean the windshield of a car so that the driver has an unobstructed view of the road. A typical wipe angle for a passenger car is about 67 degrees. The blades are 12-30 in (30-76 cm) long with lengths increasing in 2-in (5-cm) increments.
History
The history of the windshield wiper began with the invention of the automobile. Most transportation vehicles did not have wipers. Horse-drawn carriages and trucks moved at slow speeds, and glass was not needed to protect the driver or passengers or to act as a windbreak.
The first windshield wipers were brushes. Inventor J. H. Apjohn came up with a method of moving two brushes up and down on a vertical plate glass windshield in 1903. In the same year, Mary Anderson devised a swinging arm that swept rain off the windshield when the driver moved a lever located inside the car. Anderson patented her invention of the mechanical windshield wiper in 1905, and it became standard equipment by 1913. Electric motors were not used yet to power automobile essentials or accessories, and Anderson's device had a drawback. Without another power source, a driver had to use one hand to move the lever. The driver's other hand steered the car (with either a wheel or steering tiller) and worked the stick-mounted gear shift and brake grips standing on the floor of the car or outside the driver's side on the running board.
Rubber strips replaced brushes as the cleaning tools on wipers in 1905. Unfortunately, the hazardous need for drivers to wipe windshields while driving was not eliminated until 1917. The solution was to use an electric motor to move a single wiper with a long rubber blade back and forth. Hawaiian dentist Dr. Ormand Wall invented the automatic wiper by placing an electric motor in the top center of the windshield so the wiper arced down over the hood of the car in a semi-circular or rainbow shape. Wipers were one of the first electrical devices in automobiles after the electric starter was developed in 1912. Most wipers on cars before 1930 were paired and hung down from the top of the windshield. They were moved to the base of the windshield as electrical systems became more complicated.
Windshield washers were added to the wiper on/off levers, and these required spray nozzles in front of the windshield, a tank for washer fluid in the engine compartment, and electrical connections to coordinate these operations. In 1962, Bob Kearns invented the intermittent wiper with intervals and speeds that the driver could change. The advent of electronic systems with fuses and circuit breakers to operate, regulate, and coordinate electrical components expanded the possibilities for more diverse wipers. Wipers were added to headlights in the 1980s, requiring connections between the lighting and wiper systems. In the 1990s, microsensors were built into windshields to detect rain on the windshield, activate the wipers, and adjust speed and intermittent use for the amount of rain.

Raw Materials
The manufacturer purchases all of the parts from companies that specialize in fabricating parts from aluminum and steel, rubber blades, plastic bushings for the linkages, and the motors. Windshield wipers and windshield wiper systems (with motors) are different assemblies; some manufacturers make both, and others produce wipers only.
The connecting and drive links and the pivots that move the wipers are made of galvanized steel. Galvanization is the process of applying zinc coating to steel to protect it from corrosion. Drive arms for boats and vehicles used in the marine industry are made of stainless steel that resists damage from salt water. The wiper suspension and claws are also galvanized steel. The galvanizing zinc coating is easier to paint than uncoated steel. Steel is also the material in the small parts of wipers, such as washers, screws, nuts, springs, and brackets.
The blade frame is made from aluminum. The blades are made of natural rubber or synthetic compounds. Some rubber blades are composites of soft rubber on the wiping edge (the squeegee surface) and firm rubber that supports the wiping edge in the rest of the blade.
Other materials that comprise parts of windshield wipers are rubber for washers in the pivots and plastic bushings that line holes for connecting parts of the linkage. The wiper suspension is typically painted black. If the wiper manufacturer also builds wiper systems, motors are purchased from subcontractors. The motors are contained in steel housings and include permanent magnet motors wound with copper wire. Each housing has connections for the electrical wires that are part of the vehicle and wiring harnesses are furnished specific to operating the wipers. Each motor also contains one or more electronic circuits depending on the sophistication of the system that the motor controls.
Design
Windshield wipers are designed and made to clear water from a windshield. Most cars have two wipers on the windshield, and they may have one on the rear window and one on each headlight. The wiper parts visible from outside the car are the rubber blade, the wiper arm holding the blade, a spring linkage, and parts of the wiper pivots. The wiper itself has up to six parts called pressure points or claws that are small arms under the wiper. The claws distribute pressure from the wiper along the back of the blade. This is described as a balance beam with a suspension system, where the wiper is the beam and the claws are the suspension components. The claws keep the blade flexed against the windshield to distribute even pressure to clean the glass all along the blade. More claws usually distribute the pressure better and are suited to large or highly curved windshields.
Although the rubber is the familiar part of the blade, the blade actually includes a metal strip called a blade frame with a slot along the length of the frame and replacement holes in the frame. The replacement holes provide access for replacing the rubber blade with a refill. The blade on its aluminum frame can also be changed as a unit.
The standard two windshield wipers are usually operated as a single-motor, tandem scheme with one wiper on the driver's side and one positioned near the middle of the windshield that moves across the passenger's view. The wipers are secured to pivots. A wiper and pivot are mounted on brackets at both ends of a long rod called the connecting link, and, as the force from the motor pushes on the driver's end of the connecting link, it in turn moves the other wiper. The connecting link is attached to another long rod called the drive link near the wiper motor. A slender spring linkage ties the pivot to the drive link to return the wiper to its resting or park position, hug the wiper close to the windshield, and keep it attached to the car if the links are damaged.
Between the motor and the drive link, a linkage system consisting of a cam (another short rod) and pivot, a gear output shaft, and a worm gear controls the force of the motor delivered to the drive arm. The worm gear slows the speed of the motor while multiplying its torque (force). The gear allows a small motor to produce enough force to move the blades across the glass. This description is based on using a single motor to drive both wipers. If one motor powers each wiper, more links are needed to move the two wipers together in a so-called unitized motor system.
This multiplied force is required to accelerate the blades from being stopped at both

Windshield wiper systems. ends of their movement, to resist the friction of the rubber against the glass, to resist the friction of the rubber on dirt on the glass, and to oppose wind pressure on the windshield.
The tandem scheme is the most common because the blades produce overlapping cleared areas on the windshield with the greatest overlap in front of the driver. An opposed scheme with two blades begins with both blades on the windshield toward the sides of the car, and the blades overlap as they both pivot toward the center of the windshield. A single wiper that swings in an arc from the center of the windshield is also used. The single-arm controlled wiper is the most complex; as it sweeps over the glass, the wiper arm lengthens toward the car sides and retracts again as it points straight up at the middle of the windshield. Each of the two wipers in the tandem and opposed operating schemes and the one wiper in the single-wiper scheme make an arc with a single radius and so are called radial arm wipers. The single-arm-controlled wiper produces a multiple-radius arc.
The electric motor, worm gear, gear shaft, cam, drive link, and pivots are built into the underside of the dash. The connecting link and wiper pivots are located below the windshield and behind the trim molding. Wipers called depressed wipers also rest behind the molding when they are not being used. Non-depressed wipers are above the windshield trim molding even at rest and are visible from outside the car and from the passenger compartment. In the passenger compartment, the wiper's on/off lever is usually attached to the steering column. When the wipers are turned on, an electronic circuit inside the wiper motor starts it. When the wipers are turned off the circuit stops the power to the wiper motor. Intermittent operation of the wipers is basically short on-and-off periods for the wiper motor that the circuit also regulates.
The Manufacturing Process 1. Wiper manufacturers carry large stocks of materials provided by subcontractors. As the materials are received, the receiving inspectors confirm that the types and quantities of parts are correct, compile an inventory, and store the parts. 2. The worker begins by putting together the pivot shaft for each wiper. The pivot shaft is made of a set of fasteners and spacers that hold the wiper arm securely while allowing it to pivot and sweep the design wipe angle. The shaft assembly includes the pivot shaft itself and (from the end near the small connecting link to the tip of the shaft) a rubber washer, metal washer, nut, nut cap, knurled driver, washer, and acorn nut. The knurled driver is a type of nut with ridges on the sides that grip any attachment. The wiper arm will sit on the knurled driver, which keeps it from shifting out of position on the shaft, and the washer and acorn nut hold the arm on the shaft. The pivot shaft is then attached to the small connecting link with a washer and spring clip. A pin on the pivot shaft can be inserted in any one of three pin positions when the shaft is attached to the link, depending on the design for the pivot and link. 3. For a single-arm wiper scheme, a U-shaped, galvanized steel bracket is fixed to the small connecting link on the only pivot shaft with two shaft screws. The other end of the bracket will be attached to the drive link later. For a scheme with two wipers, the small connecting link for the wiper on the passenger's side is joined with a bracket to the end of the longer connecting link with shaft screws. Similarly, a bracket is put on the small connecting link for the driver's side wiper, and it is attached to the opposite end of the longer connecting link. Later, this end will also be attached to the drive link. 4. The drive link will be attached to the motor in the next step. The motor with the worm gear reduction and other linkage is a stock item provided by a vendor, and the wiper system manufacturer does not make any changes to it. The drive link must be secured precisely on the cam (drive arm) on the end of the gear shaft so the wiper will sweep correctly but also so it can be parked in the right position under the car molding. The connection between the cam and the drive link will be fixed by using another bracket called the mirror bracket. 5. To set the angle between the drive link and the cam and motor, the motor, cam, mirror bracket, and drive link are put inside a die set. The die set is an outline-like pattern made of steel with areas fitted for the four parts. Wiper system makers have a collection of die sets with various angles for mounting

A tandem system motor. the drive link to the motor. The bracket is put on the drive link with a set of screws. The bracket is then attached to the cam. 6. With the angle established, the cam is checked for fit with the drive shaft. Spacer washers are added (if needed) between the cam and drive shaft, and the two are connected with a set of motor nuts and screws. For a single-wiper scheme, the bracket with the single small link and pivot is screwed on the drive link. For a scheme with two wipers, the bracket on the end of the long connecting link that also supports the driver's side pivot and small connecting link is fastened to the drive link. 7. In the final steps in assembling the windshield wiper system, linkages made of springs are added to connect each pivot shaft to the drive link. The wiper arms and blades are connected to the pivots. The starter on the motor is also moved into the park position, and the wipers are placed in their park positions. 8. If the customer is purchasing windshield wiper systems, accessories may be included. A system of washers with water bottles, tubing, and controls for the dash is the most common accessory set. A wiring harness with the washer controls and the other electrical connections for the wipers is provided with the motor. 9. The completed windshield wipers are given a final quality control inspection as described below and transferred to the packing area. Depending on the items ordered, each set consisting of wipers, a motor system, and accessories is boxed with operating, maintenance, and return information.
The separate boxes are bundled together and packed in shipping cartons if the customer ordered several items.
Quality Control
During assembly, the workers observe the conditions of the parts during their work, but their only specific quality control activity is to check the operation of the motors by turning them on to make sure they start and by listening to the sounds they make as indications of performance.
The last inspection is performed when the assemblies are complete and before the wipers and systems are packed. The manufacturing director or final quality control inspectors look at the general appearance of the assemblies, confirm that the wipers have been sized and angled correctly for their sweep, and check that the assemblies are in the park position. The director or inspectors also check to see that the correct accessories are ready to be packed with the assemblies.
Byproducts/Waste
Small quantities of steel and aluminum scraps from trimmings or rejected or damaged parts are collected in bins and sold to salvage dealers who, in turn, sell them to metal manufacturers who melt the scrap down for recycling. Packaging from received parts is also collected and recycled.
The Future
As of 2002, windshield wipers and wiper systems are evolving because of changes in automobiles and other vehicles, technical improvements, and consumer demand. Wiper blades are as much as 30 in (76 cm) long, creating more resistance as they clean the windshield. Night-vision screens for windshields are in development, and these also increase resistance and change the dimensions needed for wipers. Blades are being improved with increasingly flexible rubber, so-called "boots" that fit around the blades to keep out ice and snow, and nonstick coatings on the squeegee edges of the blades to keep oil and wax from adhering and aging them.
Motor systems are also being increased in voltage to power longer wipers and more accessories. Engineers are investigating fully automated systems that do not require any actions by drivers to start and stop wiper systems. Inventors expect the capabilities of the rain-detecting sensors available in the late 1990s to widen to prompt the wipers to clean dirty windshields with no rain, for example. Windshield wipers are among most reliable automotive deviceshe design life of a wiper system is 1.5 million wipes.
Executive Summary
This proposal examines the windshield wiper system in a '96 Corsica, in hopes of either improving the design or manufacturing process. For the time being we have focused on product dissection and analysis. Our product, windshield wipers, are mainly used by customers for removing precipitation from the windshield so as to increase driving visibility and safety. Every automobile on the road has a windshield wiper system to be used for this purpose. Due to the fact that the main purpose of this product is safety, it is highly important for the product to be reliable and functional. Ease of use is also a high priority because of fast-acting scenarios that customers may find themselves in. Lower in importance are maintainability and cost, so that people are encouraged and can maintain their systems to a usable level. The design for assembly and for manufacturing seems to be well thought out. There is a relatively low part count and very few fasteners. None of the parts are that intricate and all are big enough clamped down and easily manipulated while being small enough that they are not heavy or unwieldy.
Based on traditional FMEA the greatest risk of failure is in the hose, followed by the thermal mount. A scenario-based FMEA was done on the hose and thermal mount and the expected cost of the thermal mount greatly exceeded the cost of a failure in the hose. Thus, it is actually more important that the thermal mount be well designed than the hose, even though the hose has a higher expected failure. The recommended action for the hose would be to increase the wall thickness. The recommended action for the thermal mount is the safe-guard the rubber against corrosion.
For an environmental standpoint, the production of the windshield wiper assembly is most harmful in the production of power for manufacture of steel parts. This is evidenced by our analysis using EIO-LCA software that claims that most toxic waste is emitted during “motor vehicle parts manufacture.” In our analysis we also take End of Life into account and choose how each part will be reused, recycled, or disposed of in a landfill. From this analysis, most of the parts on the current assembly will not be reused thereby harming the environment.
This product seems to have already gone through DFMA considerations, based on analysis during the dissection of it. Most parts are either cast or injection molded, which is a good process for high-volume parts. It may be better if the parts could be more standardized. There are very few parts with the same exact shape, though it seems like it is possible to accomplish that. Assembly of the system is time consuming because of all the press fit parts. Also, if there is error in press-fitting those parts are essentially rendered useless. However, for durability purposes this is a good method of keeping components together.
Customer Needs
Standard usage of windshield wipers is on automobiles. Whether they be in material transportation vehicles (semi-truck), public transportation vehicles(buses), or personal use vehicles (family sedan), their use is the same. They function primarily to remove precipitation from the front windshield so that the driver of the vehicle can safely see where they are going. If the windshield wipers are not functioning properly then it creates a dangerous driving condition. Thus, the most important need for the customer is reliability. Ease of use is also very important for the customer. For example, if someone is driving and it starts to pour, they need to be able to trigger the windshield wipers immediately, so that their field of view is not disturbed. A low cost and easily maintainable system are grouped together in importance for this product. Windshield wipers have a definitive life cycle and when that is up, they must be replaced. Depending on frequency of use, this can be as much as an annual need for change. Therefore, it is necessary to have a system that vehicle users can maintain themselves. Windshield wipers are readily available in most stores and have a few common locking mechanisms that are robust and easy to use. The need to change windshield wipers also results in a need to keep costs down. Since this is mainly a safety product it is important to encourage customers to maintain their wipers at a usable level. By making new wipers cheap and easy to switch manufacturers ensure that their customers are continuing to safely maintain their systems. The design for assembly and for manufacturing seems to be well thought out. There is a relatively low part count and very few fasteners. None of the parts are that intricate and all are big enough clamped down and easily manipulated while being small enough that they are not heavy or unwieldy.
Stakeholders
Persons who are effected by the product in use, design, manufacturing, and sales: * Motor Vehicle Users (cars, busses, trucks) * Car Dealers * Design Engineers, Material Engineers, Manufacturing Engineers (system designers) * Automotive Retail Stores (parts seller) * Material Suppliers (raw materials used in manufacturing) * Manufacturing Plant (where parts are made)
Product Usage

Fully assembled view of the windshield wiper system.
This product comes standard with motorized vehicles. The purpose of the product is to keep the windshield clean and free from water or debris, with the ultimate goal of improved driver visibility.
At least in most cars, including the '96 Corsica from which our dissected wipers were taken, the windshield wipers must be manually activated. Thus, the first step in the wiper usage process is that the user must decide that he or she wants to activate the wipers.
This decision is typically made for one of two reasons: * The driver decides that the windshield is dirty and wants to wash/clean the windshield. * The driver's visibility is blocked and wants to remove material from on top of the windshield. Situations such as these typically include: * Raining * Snowing * Hailing * Excessive leaves/flowers on windshield
Once the vehicle driver decides that they would like the windshield wipers to clean the windshield, he or she must shift a lever, typically behind the steering wheel and to the right. The controls are designed so that the driver can feel for the control stick and shift the wipers on without needing to take their eyes off of the road.
Windshield wipers typically have multiple modes. The cleaning mode of the wipers typically involves spraying wiper fluid onto the windshield, and then using the wipers to spread the fluid around and remove the dirty wiper fluid from the center of the windshield. After the squirt, the wipers will perform 2 or 3 passes of the windshield, and then automatically stop. From the controls perspective, the control stick will usually need to be "nudged" to activate the cleaning function, but then will snap back to it's original position.
The remaining modes of operation are all continuous. The control stick will snap to a new position and will continue to operate the wipers until the driver intentionally returns the stick to it's original position or disconnects power to the wipers by shutting the car off. The wipers will continually sweep back and forth over the windshield, clearing it of water, snow, or most anything else. This mode includes different speeds of wiping. An intermittent mode causes the wipers to pause between each wipe. This setting is best for minor drizzles of rain because the user requires much less windshield wiping than full on downpours. Most cars require the driver to manually select a wiper speed to optimize visibility, however some newer cars automatically adjust the wiper speed by measuring water flow or adjusting to the vehicle's speed (the faster a car is going, the more water will hit the windshield during rain) [1].
What do the wiper's do? There are multiple styles of windshield wipers, but most cars utilize a system of 2 wiper arms working in tandem to cover the entire windshield. The 2 wiper arms are typically linked such that they are always parallel. This was the case with the '96 Corsica wipers. Both wipers typically rotate about a fixed point at the end of the wiper arm, and rotate from their resting horizontal positions (out of view of the driver). Most wipers typically rotate to slightly above vertical. The two wipers combined cover a majority, but not 100% of the windshield.
The mechanical analysis section of this report covers the specific kinematic characteristics of the '96 Corsica wipers. This animation shows the wiper mechanism in action, with the orange links representing the wiper arms, covering the windshield.

To better understand the animation, we have included a list of the parts that we converted to "2d links" in ADAMS. * Link 1 in the drawing (pink) connects to the motor, and is part #2 in our parts list. * Link 2 in the drawing (green) is attached to Link 1 at a pin joint. #3 in our parts list. * Link 3 connects and synchronizes the 2 windshield wipers. #15 in parts list. * Link 2 and 3 connect to joint 1. This is "Wiper Connection Subassembly 2". Displaced from the connection between links 2 and 3, this joint is pin jointed to a location on the vehicle. Link #2's motion relative to this pivot point causes link 2 and the wiper itself to rotate. * Joint 2 is "Wiper Connection Subassembly 2". Only Link 2 and the right wiper connect here, but this entire subassembly rotates about the point where this subassembly is fixed to the car.

See the image below for a visual reference of how the wiper's work together to cover the majority of the windshield:

Parts List Part # | Part Name | Quantity | Weight (grams) | Function | Material | Manufacturing Process | Picture | 1 | Motor Connection Nut | 1 | 6 | Holds the entire wiper assembly to the motor | Steel | Cast | | 2 | Motor Connection Link (1L) | 1 | 62 | Link connecting the spinning motor to Link 1 | Steel | Stamped and bent, with the knob pressed into it | | 3 | Link 1 (LN3) | 1 | 158 | Link that drives the motion of the windshield wipers | Steel | Stamped and bent, with the knobs pressed into it | | 4 | Rubber Connections | 2 | Unable to detach | Caps on Link 1 that are used to attach to the metal knobs in the connection links | Rubber | Injection molded and pressed onto the link | | | WIPER CONNECTION SUBASSEMBLY 1 | | | | | | | 5 | | Rubber cap | 1 | 0 | Rubber cap that goes over the wiper connection point in the subassembly | Rubber | Injection molded, loose fit | | 6 | | Hex Screws | 3 | 7 | Screw to bolt wiper connection subassembly into car | Steel | Cast | | 7 | | Washers | 3 | | Washers to go with hex screws | Steel | Cast | | 8 | | Rubber thermal mount | 1 | 31 | Rubber around subassembly to allow for mounting | Rubber | Injection Molded | | | | RIGID SUBASSEMBLY | | | All pieces in this subassembly are still attached together and therefore do not have individual pictures. We determined the components by observations | | | | 9 | | | 7L Link | 1 | | Connection to N2 Link 2, which causes the wipers to move | Steel | Stamped and bent, with the metal pin pressed in | | 10 | | | Pin | 2 | | Pin that acts as the connection point to N2 Link 2 and Link 1 | Steel | Cast, pressed into 7L Link | | 11 | | | Press Fit Ring | 1 | | Ring around the cylindrical shaft | Steel | Molded, press fit onto shaft | | 12 | | | Washer | 1 | | Washer around shaft | Steel | Cast | | 13 | | | Cylindrical Rings | 2 | | Two metal rings around the shaft of the assembly that allows for rotations, act like bearings | Steel | Cast, loose fit atop grease to allow for rotation | | 14 | | | Cap | 1 | | Cap on top of shaft that holds the shaft pieces together | Steel | Cast, press fit together with shaft | | 15 | N2 Link 2 | 1 | 255 | Link which rotates both wipers with rubber connectors at each end | Steel | Cast with pressed on injection molded rubber connectors | | | WIPER CONNECTION SUBASSEMBLY 2 | | | | | | | 16 | | Rubber cap | 1 | 0 | Rubber cap that goes over the wiper connection point in the subassembly | Rubber | Injection molded, loose fit | | 17 | | Hex Screws | 3 | 7 | Screw to bolt wiper connection subassembly into car | Steel | Cast | | 18 | | Washers | 3 | | Washers to go with hex screws | Steel | Cast | | 19 | | Rubber thermal mount | 1 | 31 | Rubber around subassembly to allow for mounting | Rubber | Injection Molded | | | | RIGID SUBASSEMBLY | | | All pieces in this subassembly are still attached together and therefore do not have individual pictures. We determined the components by observations | | | | 20 | | | Straight Bar Link | 1 | | Connection to N2 Link 2, which causes the wipers to move | Steel | Cast, with the metal pin pressed in | | 21 | | | Pin | 1 | | Pin that acts as the connection point to N2 Link 2 | Steel | Cast, pressed into 7L Link | | 22 | | | Press Fit Ring | 1 | | The cap is pressed into this to keep the assembly together | Steel | Molded, press fit onto shaft | | 23 | | | Washer | 1 | | Washer around shaft | Steel | Cast | | 24 | | | Cylindrical Rings | 2 | | Two metal rings around the shaft of the assembly that allows for rotations, act like bearings | Steel | Cast, loose fit atop grease to allow for rotation | | 25 | | | Cap | 1 | | Cap on top of shaft that holds the shaft pieces together | Steel | Cast, press fit together with shaft | | 26 | Wiper Nut | 1 | 5 | Holds the windshield wipers to the rigid subassemblies | Steel | Cast | | | WIPER ARM SUBASSEMBLY | 2 | | | | | | 27 | | Hose | 1 | 5 | Rubber hose that transfers wiper fluid to the sprayer | Rubber | Injection molded | | 28 | | Nozzle | 1 | 2 | Nozzle that sprays wiper fluid on windshield | Plastic | Injection Molded | | 30 | | Spring | 1 | 24 | Spring that keeps wipers pressed against windshield | Steel | Cast steel wound into spring shape | | 31 | | Spring Connector | 1 | 0 | Connector between the spring and the wiper arm | Plastic | Cast | | | | WIPER ARM SKELETON SUBASSEMBLY | | 255 | | | | | 32 | | | Link | 1 | | Main link that extension arm and base arm are attached to | Steel | Cast | | 33 | | | Base Arm | 1 | | Arm attached to the link that connects the wipers to the wiper connection subassembly | Steel | Cast | | 34 | | | Extension Arm | 1 | | Arm extending out of base arm, attaches to wiper blade | Steel | Molded, pressed into base arm with tabs | | 35 | | | Tip | 1 | | Extra metal thickness around the top of the extension arm | Steel | Cast | | 36 | | | Conection metal Pin | 2 | | Piece that connects into wiper blade | Steel | Cast | | | WIPER BLADE SUBASSEMBLY | 2 | | | | | | 37 | | Metal Blade | 2 | 10 | Metal links that keep the rubber blade in its holder | Steel | Stamped | | 38 | | Rubber Wiper | 1 | 21 | Rubber piece that wipes the windshield | Rubber | Injection Molded | | | | BLADE SUBASSEMBLY | | 255 | | | | | 39 | | | Metal Base | 1 | | Base that all parts are connected to | Steel | Cast | | 40 | | | Plastic Parts | 4 | | Moveable plastic links that connect to the base and allow the blade to be slightly flexible | Plastic | Injection Molded | | 41 | | | Plastic Locking Mechanism | 1 | | Mechanism that locks the Wiper into the wiper arm | Plastic | Injection Molded | |
Failure Modes and Effects Analysis

FMEA is a technique used by engineers to identify and correct potential failures in design and manufacture before the parts reach the customer.Traditional FMEA ranks each failure mode according to a Risk Priority Number (RPN) which is defined as Severity x Occurence x Detection. The chart below shows an analysis of the most important failure modes in the windshield wiper assembly. According to the values for RPN, a failure occuring in the hose has the highest risk followed by the thermal mount.

Traditional FMEA Item and Function | Failure Mode | Effects of Failure | S | Causes of Failure | O | Design Controls | D | RPN | Recommended Actions | Responsibility | Motor connection link * Rigid bar that transmits rotational power from the motor to Link LN3 | Loose connection | Little or no mechanical power transmitted to Link LN3 | 9 | Loosening of the motor connection nut due to vibrations in the motor | 3 | Test running at a high voltage | 4 | 108 | Ensure connection nut is well torqued; Dampen vibrations from motor | Design Engineering and Manufacturer | Rubber Connections * Attaches to connection links | Corrosion | Doesn't connect other links and fails to transmit power to links | 6 | Tensile stress and chemical corrosion weakens the rubber with time | 3 | Test strength and elasticity | 8 | 144 | Strengthen rubber against corrosion | Materials Engineer | Rubber Thermal Mount * Protects "Rigid Subassembly" and allows for mounting | Corrosion | Does not mount properly in car; Fails to rotate the wiper arm | 7 | Overheating and use over time causes corrosion | 4 | Run under extreme temperature conditions | 7 | 196 | Strengthen rubber against corrosion | Materials Engineer | Cylindrical Rings * Within "Rigid Subassembly" these act like bearings and allow for wiper arm rotation | Loss of grease | Causes grinding; Fails to rotate the wiper arm | 5 | Excessive use | 5 | Test wear and tear on part | 4 | 100 | Increase lubrication during assembly | Design Engineering and Manufacturer | Hose * Transmits wiper fluid | Holes | Cause wiper fluid to leak and not reach the nozzle | 6 | Extreme temperature conditions can cause cracking; Foreign objects on windshield can puncture the hose | 9 | Run under extreme temperature conditions | 4 | 216 | Increase thickness of rubber or strengthen for extreme temperatures | Design and Materials Engineer | Nozzle * Sprays wiper fluid | Chipping or breaking | Will not spray the wiper fluid onto the window | 6 | Foreign objects on windshield can break plastic; Over-stressing easily causes cracking | 9 | Test strength of part when dropped, etc | 3 | 162 | Use more durable plastic | Materials Engineer | Spring Connector * Ensures that spring stays in place | Chipping or breaking | Does not secure spring thereby letting the wiper arms move away from the windshield | 7 | Foreign objects on windshield can break plastic; Over-stressing with taught spring causes cracking | 7 | Test strength of part when pulled tight by spring, dropped | 3 | 147 | Use more durable plastic | Materials Engineer |

Scenario-Based FMEA is a slightly different approach that includes the cost of correcting a potential failure. A sample of this is shown in a chart below, in which the hose failure is compared against a failure in the thermal mount. Risk is calculated as the expected cost, which is the probability of the scenario multiplied by its failure cost. Scenario-Based FMEA is defined as follows:

ExpectedCost = p1x[1 − p2]xp3xc where p1 is the probability of the inital cause, 1-p2 is the probability not to detect the intermediate effect, p3 is the probability of the end effect, and c is the cost of the effect.

Note that in this example, the cost of replacing the hose is estimated at $0.30 and the cost of replacing the thermal mount includes a labor cost of checking and positioning the parts within the subassembly, estimated at $30. Clearly, the expected cost of replacing the hose is much less than checking and repairing the rubber thermal mount. For this reason, it is important for engineers to perform both a Tradition and Scenario-Based approach to FMEA.

Scenario-Based FMEA Cause | Probability of Cause | Intermediate effect | Probatility of intermediate effect | End Effect | Probability of end effect given the cause | Cost of the Effect | Expected Cost | Hole in hose | .90 | Fluid doesn't reach nozzle | .80 | No fluid reaches windshield | .70 | $0.30 | 0.0378 | Rubber corrodes on Thermal Mount | .40 | Parts fall out of place | .30 | Wiper arms stationary | .25 | $30 | 2.1 |
Design For Manufacturing and Assembly (DFMA)
Design For Assembly (DFA)
All and all this assembly seemed well designed for assembly. One aspect to the windshield wiper assembly that seemed well thought out was that ball joints were used for all bends in the assembly. These are reasonably easy to pop on. The easy of connection increases the speed that the operators can assemble the components together and also creates a more ergonomically friendly work environment for them.
This assembly is relatively light, which makes it easy to transport around. If the product has to travel between multiple operators, there is no special machinery necessary, a simple cart would suffice.
The way the parts are oriented is such that there is no need to flip the assembly being that all points of attachment can be accessed from the top. Also the same size wrench could be used on all nuts lowing the amount of tolling though there are different kinds of nuts. So, the operators can lay out the assembly in a single orientation and attach all the nuts.
There is some room for optimization for assembly though it might hurt other aspects of the windshield wiper, such as: The rods used to transfer the motion of the motor to the wipers are all different. If there was a way to make these the same it could help the assembly process as well as the manufacturing process.
The actual windshield wiper blades seem to use a rivet gun to attach the several arced pieces. The arced pieces are ascending in size and are symmetric making it pretty clear what order they go on.
An advantage to the way the wiper was engineered is that besides at the base, where a nut is used to hold the wiper on, there are no extra parts used for connection. As in, things are either riveted on or held in place by hooking on to the base. This not only helps in the assembly process but also helps insure that a driver would not have to deal with small parts flying off there wipers.
Design For Manufacture (DFM)
After reviewing each component of the windshield wiper assembly we have determined that the part was well designed for manufacture. They use simple processes such as casting or injection molding for most parts. These manufacturing processes are designed for efficient high volume part flow.
Since our product is used on all motor vehicles it is important that the manufacturing process be able to support high volumes. The post ball joints are pressed into the links. The tolerances concerning the ball joints do not have to be very tight, they could be off by a good deal and still not hurt the assembly. This means that less components will have to be thrown away due to slight manufacturing faults, saving on cost and waste.
All parts are rectangular, don’t taper, and are variations on each other. This makes the dies required for casting very simple. The use of similar parts also decreases the chance manufacturing errors especially at the beginning of the design period. Injection modeling was also used around the wiper connection point, where the rubber mount is molded around the rigid subassembly. This may not be optimal as it would add an extra step to manufacturing that might be dealt with more efficiently in the assembly process.
Most of the connections between two parts done in manufacturing was press fitting, which is efficient, as a machine can do the work more quickly and more safely. The size of the parts themselves as well as the shapes are simple and reasonably big which makes it easy to clamp the pieces down for press fitting.
The windshield wiper pieces were cast or injection molded--most are a hard plastic; the middle piece is metal. While these parts have many features to them, casting and injection molding are made for exactly that purpose. Perhaps the complication level of these parts could be decreased to try to eliminate random machine tolerance error. However, overall the windshield wiper assembly must have gone through design for manufacture considerations.
Design For Environment (DFE)
End of Life Analysis
It is always better to reuse when possible rather than recycle because recycling requires energy and resources to disassemble the materials. Thus, during disassembly of the windshield wipers the metal links will be checked for damage and sorted. The parts still in good quality will be reused and the damaged parts will be recycled through melting and reshaping. Sorting the metal links adds an additional labor time, but some of this will be balanced out by saving costs in buying brand new parts.
Ideally, all of the other metal parts: washers, nuts, screws, springs, and pins would be recycled. With time threading wears down, washers become bent, and springs loose their elasticity making it impossible for them to be reused in a new wiper assembly. However, the two Rigid Subassemblies in the Wiper Subassemblies have a special case. They are too hard to decompose (they cannot be taken apart by hand) so they will be put in a landfill. This will affect the pin, press fit ring, washer, cap, and cylindrical rings that would otherwise be recycled.
The rubber connections and plastic parts of the assembly will be thrown away in a landfill because it is not cost effective to recycle or reuse them. Plastic parts are easily broken during use or decomposition and it is very cheap to use the same molds to make new parts. Rubber connections become corroded with use therefore eliminating them as a candidate for reuse. Also, recycled rubber cannot be used as a replacement for new or synthetic rubber due to the current devulcanization process.
To summarize, the end of life evaluation of the current model of the windshield wiper assembly requires that 25 parts will be placed in a landfill, 12 parts will be recycled, and 4 parts will be sorted and either recycled or reused.
EIO-LCA Analysis
Within the "Vehicles and other Transportation Equipment" industry group, the windshield wiper assembly falls into the "Motor vehicle parts manufacturing" industry sector. For our analysis we used an economic activity of $1 million to ensure that preliminary manufacturing costs do not affect the analysis results.
Using data from the EIOLCA tutorial, the following table displays the top contributors of greenhouse gas emissions. Sector | GWP MTCO2E | CO2 MTCO2E | CH4 MTCO2E | N2O MTCO2E | CFCs MTCO2E | Total for all Sector | 793 | 663 | 73.3 | 15.7 | 41 | Power generation and supply | 237 | 234 | 0 | 0 | 2.85 | Iron and steel mills | 124 | 124 | 0 | 0 | 0 | Truck transportation | 51.8 | 51 | 0.079 | 0.712 | 0 | Motor vehicle parts manufacturing | 47 | 47 | 0 | 0 | 0 | Waste management and remediation services | 32.3 | 5.11 | 27.2 | 0.039 | 0 |

The economic activity associated with the "Motor Vehicle Parts Manufacturing" industry sector is based on 1997 data, so an inflation in USD must be taken into account. Sector | Total Economic $mill | Value Added $mill | Direct Economic % | Total for all Sectors | 2.47 | 0.964 | 69.2 | Motor vehicle parts manufacturing | 1.11 | 0.313 | 98.7 | Wholesale trade | 0.118 | 0.079 | 52.3 | Iron and steel mills | 0.098 | 0.023 | 64.4 | Management of companies and enterprises | 0.070 | 0.049 | 47.9 | Semiconductors and related device manufacturing | 0.045 | 0.028 | 69.8 |
Toxic releases are mostly associated with "Copper, nickel, lead, and zinc mining" and "Gold, silver, and other metal ore mining". This indicates that the most harmful step of the life cycle is the first - mining the metals that are used to make the windshield assembly.

Our product is made mostly of steel components. The production and manufacturing of these components is most responsible for greenhouse gas emissions. Transportation of our product is the second most, but due to it's small size, large quantities of our product can be transported at the same time. This requires less transportation overall and decreases the greenhouse gases due to transportation. Use of the windshield wipers requires additional fuel to be burned to provide electricity and support the extra weight of the wiper motor. It is difficult to calculate exactly how much additional fuel the windshield wiper assembly requires, but we assume that the negative effects of this is less than during the manufacturing process.
Mechanical Analysis
To understand the kinematics of the windshield wiper mechanism, we (1) measured the wiper assembly peices and created a 2D ADAMS representation of the linkage, and (2) completed an angular velocity calculation to relate the velocity of the windshield wiper to the velocity of the motor.
Our ADAMS model of the wiper assembly is not entirely accurate because the true wiper assembly is not a 2D system. The linkage bars have bends in different axes, so modeling the system in a plane will introduce error. Secondly, measurements could not be 100% accurate since we were trying to estimate the "2D distance" of the linkage bars. Finally, the group had to make an assumption as to how the mechanism was mounted into a car. The windshield wipers both are mounted at a hinge point, and the motor is also fixed. The relative distance between these fixed points is essential to analyze the linkage. To keep things simple, we decided that in our planar model we would assume that the left wiper hinge and the motor joint would be vertically aligned. We did not get a chance to confirm how close this assumption is to true since we could not examine the wiper specimen whilst still attached to a working car.
Nonetheless, the ADAMS model proves to be useful. If anything, it gives insight into how the linkage is able to convert continuous constant speed motor rotation into the wiper motion. Below is an animation of the ADAMS model, and a link to the full sized animation.

* http://andrew.cmu.edu/klipkin/wiperanimation.gif

We also wished to analyze the relative velocities present in the wiper system. The motor is able to turn at different speeds based on whether the driver wants the wipers to move quickly or slowly, so there was no single speed we could input as the motor speed. As such, we decided to see how the wiper moved relative to the motor speed.
In terms of cycles, it is clear that the wipers make one full "wipe" for every full rotation of the motor output shaft. A full "wipe" includes the trip from the starting position, across the windshield to the extreme position, and fully back. This is a 1:1 ratio.
However, at specific moments, the angular velocities of the wipers and motor do not match. While the motor ideally outputs a constant angular velocity, the wipers have variable angular velocities, including two points in the trajectory where they are instantaneously stationary (the starting position and extreme position, where the wiper is changing direction).
To understand these relative velocities, we calculated the angular velocity of the wiper relative to the angular velocity of the motor at the point when the wipers are at 45 degrees. It is important to understand that the wiper angular velocity is changing and that these calculations are only valid for this particular instant in the wiper cycle.

1) Calculating all bar locations and orientations. The lengths of all of the bars are known and the orientation of the wiper blades is known (45 degrees). The below picture illustrates the 2d schematic.

Since the orientation and length of CD is known, and the location of D is known, the location of C at this point in time is known. This can be used to create triangle abc, which will be used for the law of cosines and the calculation of all bar orientations.

2) Create kinematic relationships and understand the relative velocities of each member. * V(b) = V(a) + V(b|a). V(a) = 0, so V(b) = V(b|a). The magnitude of V(b|a) = 3 * w (ab). The direction of V(b) is perpendicular to AB. * V(c) = V(b) + V(c|b). The magnitude of V(c|b) = 15 * w(bc). The direction of V(c|b) is perpendicular to BC. * V(c) also = V(d) + V(c|d). V(d) = 0, so V(c) = V(c|d). The magnitude of V(c|d) = 5*w(cd), and the direction is perpendicular to DC.

The directions of V(c), V(c|b), and V(b) are known. Their velocities are known in terms of w(ab), w(bc), and w(cd). Since V(c) = V(b) + V(c|b), a triangle can be created.

The law of sines can be used. sin Y / 15 W(cd) = sin X / W(ab).
Solving this provides that W(cd), the angular velocity of the wiper, is .6333 * W(ab), the angular velocity of the motor.
Again, this calculation is only good for this point in time, but the same process could be repeated to relate the angular motor velocity to the angular wiper velocity at any point.
From this analysis, it is clear that increasing the motor velocity will increase the wiper velocity and decrease the time it takes for the wiper to cover the windshield. At each point there exists a linear coefficient relating motor angular velocity to wiper angular velocity. Doubling the speed of the motor will exactly double the "normal" angular velocity of the wipers at all points in it's trajectory. This insight is useful for programming in the different "modes" of the wipers, since doubling the speed of the motor exactly halves the time for the wiper to complete 1 "wipe cycle".
This ratio of wiper-to-motor speed could be changed. By slightly modifying the lengths of the links, the trajectory of the wipers could be changed. A tradeoff exists between the torque exerted from the motor and the torque available to drive the wipers if it were to encounter resistance. However, in most wiper applications, intense torque is not requ

The first windshield wipers were operated manually by moving a lever inside the car back and forth. Today, most of us take our electric windshield wipers for granted. The wipers faithfully keep the windowclear, moving back and forth across the windshield countless times as they sweep the water away. On their highest speed, they move impressively fast, sometimes shaking the car from side to side. What kind of a mechanism can move the wiper arms so effectively and so reliably?
Windshield wipers are found on car windshields, some car headlights,airplanes and even on the space shuttle. In this article, we'll take a look inside windshield wipers, learn about the blades and the controls and then explore a new rain-sensing wiper control system!
DID YOU KNOW?
Windshield wiper systems are designed to wipe 1.5 million times in their lifetime!
Inside the Wipers
The wipers combine two mechanical technologies to perform their task: * A combination electric motor and worm gearreduction provides power to the wipers. * A neat linkage converts the rotational output of the motor into the back-and-forth motion of the wipers.
Motor and Gear Reduction
It takes a lot of force to accelerate the wiper blades back and forth across the windshield so quickly. In order to generate this type of force, a worm gear is used on the output of a small electric motor.
The worm gear reduction can multiply the torque of the motor by about 50 times, while slowing the output speed of the electric motor by 50 times as well. The output of the gear reduction operates a linkage that moves the wipers back and forth.
Inside the motor/gear assembly is an electronic circuit that senses when the wipers are in their down position. The circuit maintains power to the wipers until they are parked at the bottom of the windshield, then cuts the power to the motor. This circuit also parks the wipers between wipes when they are on their intermittent setting.
Linkage
A short cam is attached to the output shaft of the gear reduction. This cam spins around as the wiper motor turns. The cam is connected to a long rod; as the cam spins, it moves the rod back and forth. The long rod is connected to a short rod that actuates the wiper blade on the driver's side. Another long rod transmits the force from the driver-side to the passenger-side wiper blade.
Now let's talk about some details of the wiper blades.

This wiper blade is supported in six places for an even pressure distribution against the windshield.
Wiper Blades
Wiper blades are like squeegees. The arms of the wiper drag a thinrubber strip across the windshield to clear away the water.
When the blade is new, the rubber is clean and has no nicks or cracks. It wipes the water away without leaving streaks. When the wiper blades age, nicks or cracks form, road grime builds up on the edge and it doesn't make as tight a seal against the window, so it leaves streaks. Sometimes you can get a little extra life out of your wiper blade by wiping the edge with a cloth soaked in window cleaner until no more dirt comes off the blade.
Another key to streak-free operation is even pressure over the length of the rubber blades. Wiper blades are designed to attach in a single point in the middle, but a series of arms branch out from the middle like a tree, so the blade is actually connected in six to eight places. If ice or snow forms on these arms, it can make the distribution of pressure uneven, causing streaks under part of the blade. Some wiper manufacturers make a special winter blade with a rubber boot covering the arm assembly to keep snow and ice out.

Some of the different wiper blade schemes used by various cars
Pivot Points
Most cars have pretty much the same wiper design: Two blades move together to clean the windshield. One of the blades pivots from a point close to the driver's side of the car, and the other blade pivots from near the middle of the windshield. This is the Tandem Systemin the figure below. This design clears most of the windshield that is in the driver's field of view.
There are a couple of other designs on some cars. Mercedes uses a single wiper arm that extends and retracts as it sweeps across the window -- Single Arm (Controlled) in the figure above. This design also provides good coverage, but is more complicated than the standard dual-wiper systems. Some cars use wiper blades that are mounted on opposite sides of the windshield and move in the opposite direction, and some vehicles have a single wiper mounted in the middle. These systems don't provide as much coverage for the driver as the standard two-blade system.

A typical wiper control stalk
Wiper Controls
Most wipers have a low and a high speed, as well as an intermittent setting. When the wipers are on low and high speed, the motor runs continuously. But in the intermittent setting, the wipers stop momentarily between each wipe. There are many different kinds of switches for wipers. Some cars have just one intermittent speed, others have 10 discrete settings and still others have a sliding scale that can be set for almost any time interval.
Whichever kind of controls your car has, setting them just right can be tricky -- too fast and the windshield gets dry and the wipers squeak; too slow and your visibility is blocked by raindrops. Compounding this is the fact that the amount of water hitting the windshield changes as your car speeds up and slows down. It can require almost constant attention to keep the wipers operating properly. Carmakers may finally have conquered this problem with the holy grail of wiper technology -- the rain-sensing wiper

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Windscreen wiper on a parked car. In this common design, the force from the arm is distributed evenly with a series of linkages known as a whippletree.

A common windscreen wiper arm and blade
A windscreen wiper or windshield wiper is a device used to remove rain and debris from a windscreen or windshield. Almost all motor vehicles, including trains, aircraft andwatercraft, are equipped with such wipers, which are usually a legal requirement.
A wiper generally consists of an arm, pivoting at one end and with a long rubber blade attached to the other. The blade is swung back and forth over the glass, pushing water from its surface. The speed is normally adjustable, with several continuous speeds and often one or more "intermittent" settings. Most automobiles use two synchronized radial type arms, while many commercial vehicles use one or more pantograph arms. Geometry

A common alternative design for a "wiper" (also called a clear view screen) on a ship. A round portion of the windscreen has two layers, the outer one of which is spun at high speed to shed water.

Simple parallelogram linkages on a boat windscreen.
Most wipers are of the pivot (or radial) type: they are attached to a single arm, which in turn is attached to the motor. These are commonly found on many cars, trucks, trains, boats, airplanes, etc.
Another type of wiper design is pantograph-based (see Fig. 6, below), which are used on many commercial vehicles, especially buses with large windscreens. Pantograph wipers feature two arms for each blade, with the blade assembly itself supported on a horizontal bar connecting the two arms. One of the arms is attached to the motor, while the other is on an idle pivot.[citation needed] The pantograph mechanism, while being more complex, allows the blade to cover more of the windscreen on each wipe. However, it also usually requires the wiper to be "parked" in the middle of the windscreen, where it may partially obstruct the driver's view when not in use. Some larger cars in the late '70s and early '80s, especially LH driver American cars[citation needed], had a pantograph wiper on the driver's side, with a conventional pivot on the passenger side.
Mercedes-Benz pioneered a system called the Monoblade, based on cantilevers (see Fig. 5, below), in which a single arm extends outward to reach the top corners of the windscreen, and pulls in at the ends and middle of the stroke, sweeping out a somewhat 'M'-shaped path. This way, a single blade is able to cover more of the windscreen, and displace the residual streaks away from the center of the windscreen.
Assymetric wiper arrangements are usually configured to clear more windscreen area on the driver's side, and so are mostly mirrored for left and right-hand-drive vehicles. One exception is found on Renault Clios, where the wipers always sweep towards the left. On right-hand-drive models, a linkage allows the right-hand wiper to move outwards towards the corner of the windscreen and clear more area. *
Fig. 1: most common geometry, found on vast majority of vehicles *
Fig. 2: Mercedes-Benz W114, W168, W169; VW Sharan, Mitsubishi Delica,Honda Civic, Oldsmobile Cutlass Supreme (Fifth Generation), someminivans, some school buses, Peugeot 307,Peugeot 308, Citroën C4,Citroën Xsara Picasso,Mitsubishi Grandis, Opel Zafira *
Fig. 3: SEAT Altea, SEAT León Mk2, SEAT ToledoMk3 *
Fig. 4: VAZ-1111 Oka, Fiat Panda Mk1/SEAT Marbella,Fiat Uno (1983–1995),Citroën AX, Citroën BX,Citroën ZX, SEAT Ibiza Mk1 *
Fig. 5: Subaru XT,Mercedes-Benz W124,W201, W202, W210 *
Fig. 6: Buses, someschool buses, Mercedes-Benz O305 *
Fig. 7: MAN, Toyota FJ Cruiser, Jaguar E-type,MGB, MG Midget, Austin Healey Sprite (a 1968 US-only ruling required a certain percentage of the windscreen to be wiped). *
Fig. 8: obsolete, found on some older firetrucks *
Fig. 9: U.S. militarywheeled vehicles,jeepneys, some school buses *
Fig. 10: Like Fig. 1 but mirrored, Mercedes-Benz W140
]Unusual wiper geometries * Renault Twingo Mk1 * Citroen C1/Peugeot 107/Toyota Aygo

Windscreen washer in operation
Windscreen washer
Most windscreen wipers operate together with a windscreen (or windshield) washer; apump that supplies a mixture of water, alcohol, and detergent (a blend called windshield washer fluid) from a tank to the windscreen. The fluid is dispensed through smallnozzles mounted on the hood. Conventional nozzles are usually used, but some designs use a fluidic oscillator to disperse the fluid more effectively.
In warmer climates, water may also work, but it can freeze in colder climates, damaging the pump. Although automobile antifreeze is chemically similar to windscreen wiper fluid, it should not be used because it can damage paint. The earliest documented idea for having a windshield wiper unit hooked up to a windshield washer fluid reservoir was in 1931, Richland Auto Parts Co, Mansfield, Ohio [9]
Hidden wipers
Some larger cars are equipped with hidden wipers (or depressed-park wipers). When wipers are switched off in standard non-hidden designs, a "parking" mechanism or circuit moves the wipers to the lower extreme of the wiped area near the bottom of the windscreen, but still in sight. For designs that hide the wipers, the windscreen extends below the rear edge of the hood, and the wipers park themselves below the wiping range at the bottom of the windscreen, but out of sight.