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Sunday, July 26, 2009
Friday, July 24, 2009
Amazing suspension system !!!! ( Bose Active Suspension)
The challenge
Every automotive suspension has two goals: passenger comfort and vehicle control. Comfort is provided by isolating the vehicle's passengers from road disturbances like bumps or potholes.
Control is achieved by keeping the car body from rolling and pitching excessively, and maintaining good contact between the tire and the road.
Unfortunately, these goals are in conflict. In a luxury sedan the suspension is usually designed with an emphasis on comfort, but the result is a vehicle that rolls and pitches while driving and during turning and braking.
In sports cars, where the emphasis is on control, the suspension is designed to reduce roll and pitch, but comfort is sacrificed.
Bose engineers took a unique approach to solving this problem, and the result is an entirely new approach to suspension design
The Bose suspension required significant advancements in four key disciplines: linear electromagnetic motors, power amplifiers, control algorithms, and computation speed. Bose took on the challenge of the first three disciplines and bet on developments that industry would make on the fourth item.
Prototypes of the Bose suspension have been installed in standard production vehicles. These research vehicles have been tested on a wide variety of roads, on tracks, and on durability courses.
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Compnents
The Bose® suspension system includes a linear electromagnetic motor and power amplifier at each wheel, and a set of control algorithms. This proprietary combination of suspension hardware and control software makes it possible, for the first time, to combine superior comfort and superior control in the same vehicle.
Linear electromagnetic motor
A linear electromagnetic motor is installed at each wheel of a Bose equipped vehicle. Inside the linear electromagnetic motor are magnets and coils of wire. When electrical power is applied to the coils, the motor retracts and extends, creating motion between the wheel and car body.
One of the key advantages of an electromagnetic approach is speed. The linear electromagnetic motor responds quickly enough to counter the effects of bumps and potholes, maintaining a comfortable ride. Additionally, the motor has been designed for maximum strength in a small package, allowing it to put out enough force to prevent the car from rolling and pitching during aggressive driving maneuvers
Power amplifier
The power amplifier delivers electrical power to the motor in response to signals from the control algorithms. The amplifiers are based on switching amplification technologies pioneered by Dr. Bose at MIT in the early 1960s — technologies that led to the founding of Bose Corporation in 1964.
The regenerative power amplifiers allow power to flow into the linear electromagnetic motor and also allow power to be returned from the motor. For example, when the Bose suspension encounters a pothole, power is used to extend the motor and isolate the vehicle's occupants from the disturbance. On the far side of the pothole, the motor operates as a generator and returns power back through the amplifier. In so doing, the Bose suspension requires less than a third of the power of a typical vehicle's air conditioner system.
Control algorithms
The Bose suspension system is controlled by a set of mathematical algorithms developed over the 24 years of research. These control algorithms operate by observing sensor measurements taken from around the car and sending commands to the power amplifiers installed in each corner of the vehicle. The goal of the control algorithms is to allow the car to glide smoothly over roads and to eliminate roll and pitch during driving
watch this video it's for real
Saturday, June 20, 2009
Clutches
Clutches are useful in devices that have two rotating shafts. In these devices, one of the shafts is typically driven by a motor or pulley, and the other shaft drives another device. In a drill, for instance, one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so that they can either be locked together and spin at the same speed, or be decoupled and spin at different speeds.
To understand how a clutch works, it helps to know a little bit about friction, which is a measure of how hard it is to slide one object over another.
In a car's clutch, a flywheel connects to the engine, and a clutch plate connects to the transmission. You can see what this looks like in the figure below.
When your foot is off the pedal, the springs push the pressure plate against the clutch disc, which in turn presses against the flywheel. This locks the engine to the transmission input shaft, causing them to spin at the same speed.
From the 1950s to the 1970s, you could count on getting between 50,000 and 70,000 miles from your car's clutch. Clutches can now last for more than 80,000 miles if you use them gently and maintain them well. If not cared for, clutches can start to break down at 35,000 miles. Trucks that are consistently overloaded or that frequently tow heavy loads can also have problems with relatively new clutches.
The most common problem with clutches is that the friction material on the disc wears out. The friction material on a clutch disc is very similar to the friction material on the pads of a disc brake or the shoes of a drum brake -- after a while, it wears away. When most or all of the friction material is gone, the clutch will start to slip, and eventually it won't transmit any power from the engine to the wheels.
-Leaky or defective slave and/or master clutch cylinders - Leaks keep the cylinders from building the necessary amount of pressure.
-Air in the hydraulic line - Air affects the hydraulics by taking up space the fluid needs to build pressure.
-Misadjusted linkage - When your foot hits the pedal, the linkage transmits the wrong amount of force.
-Mismatched clutch components - Not all aftermarket parts work with your clutch.
Another problem associated with clutches is a worn throw-out bearing, sometimes called a clutch release bearing. This bearing applies force to the fingers of the spinning pressure plate to release the clutch. If you hear a rumbling sound when the clutch engages, you might have a problem with the throw-out.
Clutch Diagnostic Test
If you find that your clutch has failed, here is an at-home diagnostic test that anyone can perform:
1-Start your car, set the parking break, and put the car in neutral.
2-With your car idling, listen for a growling noise without pushing the clutch in. If you hear something, it's most likely a problem with the transmission. If you don't hear a noise, proceed to step three.
3-With the car still in neutral, begin to push the clutch and listen for noise. If you hear a chirping noise as you press, it's most likely the clutch release, or throw-out bearing. If you don't hear a noise, proceed to step four.
4-Push the clutch all the way to the floor. If you hear a squealing noise, it's probably the pilot bearing or bushing.
If you don't hear any noise during these four steps, then your problem is probably not the clutch. If you hear the noise at idle and it goes away when the clutch is pressed, it may be an issue in the contact point between the fork and pivot ball.
Friday, June 12, 2009
Great video (motion of engine)
learn how engine works from inside
Note : it will be useful if you read the (engine post ) befor you watch this video
Thursday, June 11, 2009
Differential Unit
-To aim the engine power at the wheels
For the non-driven wheels on your car -- the front wheels on a rear-wheel drive car, the back wheels on a front-wheel drive car -- this is not an issue. There is no connection between them, so they spin independently. But the driven wheels are linked together so that a single engine and transmission can turn both wheels. If your car did not have a differential, the wheels would have to be locked together, forced to spin at the same speed. This would make turning difficult and hard on your car: For the car to be able to turn, one tire would have to slip. With modern tires and concrete roads, a great deal of force is required to make a tire slip. That force would have to be transmitted through the axle from one wheel to another, putting a heavy strain on the axle components.
The differential is a device that splits the engine torque two ways, allowing each output to spin at a different speed.
We will start with the simplest type of differential, called an open differential. First we'll need to explore some terminology: The image below labels the components of an open differential
When a car is driving straight down the road, both drive wheels are spinning at the same speed. The input pinion is turning the ring gear and cage, and none of the pinions within the cage are rotating -- both side gears are effectively locked to the cage.
Note that the input pinion is a smaller gear than the ring gear; this is the last gear reduction in the car. You may have heard terms like rear axle ratio or final drive ratio. These refer to the gear ratio in the differential. If the final drive ratio is 4.10, then the ring gear has 4.10 times as many teeth as the input pinion gear. When a car makes a turn, the wheels must spin at different speeds.
The most powerful car in the world !!!!!!VERON
-The car with the most horsepower?
-The car with the fastest top speed and acceleration?
-The most expensive car?
-A W-16 engine that can produce 1,001 horsepower
-A top speed of 250+ mph (400+ kph)
-A zero-to-60 time of three seconds
-A zero-to-180 time of 14 seconds
-A price tag somewhere in the $1.2 million range.
Bugatti did two things to create a compact engine capable of producing 1,000 hp.
If you stuff twice as much air in each cylinder, you can burn twice as much gasoline. In reality, it's not quite a perfect ratio like that, but you get the idea. The Bugatti uses a maximum turbo boost of 18 PSI to double the output power of its engine.
Therefore, turbocharging allows Bugatti to cut the size of the engine from 16 liters back down to a more manageable 8 liters.
To generate that much air pressure, the Bugatti requires four separate turbochargers arranged around the engine.
The second thing Bugatti engineers did, both to keep the RPM redline high and to lower lag time when you press the accelerator, was to double the number of cylinders. The Bugatti has a very rare 16-cylinder engine.
There are two easy ways to create a 16-cylinder engine.
One way would be to put two V-8 engines in-line with each other. You connect the output shaft of the two V-8s together.
Another would be to put two in-line 8-cylinder engines beside one another. The latter technique is, in fact, the way Bugatti created its first 16-cylinder cars in the early 20th century.
For the Veyron, Bugatti chose a much more challenging path. Essentially, Bugatti merged two V-8 engines onto one another, and then let both of them share the same crankshaft. This configuration creates the W-16 engine found in the Veyron. The two V's create a W!!!!!!!!!!!!
Special Features
The special features of the Bugatti W-16 engine are amazing. For example:
-The engine has four valves per cylinder, for a total of 64 valves.
-It has electronically controlled, continuously variable cam timing to create optimal performance at different engine rpm settings.
-Seven gears
-A dual clutch system
-Sequential shifting
-A paddle-driven, computer-controlled shifting system
This computer-controlled system is identical to the sort of system found in a Formula 1 car or a Champ car. There is no clutch pedal or shift lever for the driver to operate -- the computer controls the clutch disks as well as the actual shifting. The computer is able to shift gears in 0.2 seconds.
The Body
According to one of the Veyron's designers, the biggest challenge in creating the Veyron was the aerodynamics. How do you keep a 250-mph passenger car on the road?
The Veyron's dimensions help to some extent. The car is 79 inches (200 cm) wide, 176 inches (447 cm) long and only 48 inches (122 cm) high. Keep in mind that a Hummer 2 is 81.2 inches wide. The Bugatti is extremely wide for its height.
The underside of the Veyron, like an F-1 car, is streamlined and venturi-shaped to increase downforce. There is also a wing in the back of the Veyron (see below) that extends automatically at high speed to increase downforce and keep the car glued to the road. According to Popular Science: Hypercar, "With the moving tail spoiler we've got enough downforce now, about 100 kg (221 pounds) at the rear and 80 kg (177 pounds) at the front at top speed."
If you look at the above photo, you'll notice two snorkel-like devices, one on either side of the engine, on the roof of the car. The Veyron uses these to manage airflow. The Veyron has three reasons for managing airflow:
At maximum power, the engine is consuming 45,000 liters of air per minute.
At maximum power, the engine is burning 1.33 gallons of gasoline per minute and needs to dissipate all of that heat through its radiators.
When stopping, the brakes need to dissipate heat ?- especially important when rapidly accelerating and braking on twisty road courses.
You can see how the Veyron handles these requirements in the photo below.
The engine of the Veryon sits behind the driver, so roof-mounted snorkels, the rear-deck vents and side-mounted scoops bring air to the engine and rear brakes.
The size of the engine and transmission, along with the four-wheel-drive system and the four drive shafts, along with the opulence of the passenger compartment and the car's oversized dimensions, all add weight. Even though the body is sculpted in carbon fiber to minimize its mass, the car weighs in at about 4,300 pounds (1,950 kg). For comparison, a Dodge Viper weighs about 1,000 pounds (454 kg) less.
The Tires and Interior
Even the tires for the Veyron are unique. They're specially designed by Michelin to handle the stress of driving at 250 mph. The tires need to be sticky like a race car's and able to handle 1.3 G's on the skidpad. However, they also need to last longer than the 70 or so miles of a typical race tire.
Michelin therefore created completely new tires to handle the Veyron's unique requirements. In the rear, the tires are 14.4 inches (36.6 cm) wide. Specifically, the tires measure 245/690 R 520 A front and 365/710 R 540 A rear, where 245 and 365 are the width in millimeters (9.5 and 14.4 inches respectively). The rims are 520 mm and 540 mm in diameter (approximately 20 inches). These tires, in other words, are massive -- the rears are the widest ever produced for a passenger car.
The tires use the Michelin PAX system. Their pressure is monitored automatically, and they can run flat for approximately 125 miles (201 km) at 50 mph (80 kph). According to Michelin, the run-flat detection system "plays an integral role in active safety in PAX System. Its role is to inform you of a loss of pressure, either gradual or sudden." Once warned of an air leak by the PAX system, you can reduce your speed and head toward a tire repair center.
One advantage of the PAX system and its run-flat ability is that it eliminates the need for a spare tire
The Interior
The Veyron seats two in lavish style. The interior is swathed almost completely in leather -- the dash, seats, floor and sides are all leather. Only the instruments and a few metal trim pieces interrupt the leather experience.
The car also surrounds its occupants with every sort of electronic nicety, including a remarkable stereo system, navigation system, etc.
Is all of this worth a million bucks? Who knows. But regardless, the Veyron represents a remarkable technological achievement.
The Veyron is also likely to represent the far end of the automotive performance spectrum for some time to come. To create a car much faster will require adding even more weight, and delivering even more power to the wheels. The added weight means diminishing returns in the power-to-weight domain. Additional power means more wheelspin.
Look at a Champ car and consider how radical its appearance is compared to a passenger car. Consider also that a Champ car does not go much faster than the Veyron. The Veyron probably approaches the outer limits of the passenger car envelope, and we are unlikely to see much beyond the Veyron in terms of performance.
This is, in other words, as good as it gets.
Anti-lock brake system
-Speed sensors
-Pump
-Valves
-Controller
Speed Sensors
The anti-lock braking system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel, or in some cases in the differential, provide this information.
Valves
There is a valve in the brake line of each brake controlled by the ABS. On some systems, the valve has three positions:
-In position one, the valve is open; pressure from the master cylinder is passed right through to the brake.
-In position two, the valve blocks the line, isolating that brake from the master cylinder. This prevents the pressure from rising further should the driver push the brake pedal harder.
-In position three, the valve releases some of the pressure from the brake.
Pump
Since the valve is able to release pressure from the brakes, there has to be some way to put that pressure back. That is what the pump does; when a valve reduces the pressure in a line, the pump is there to get the pressure back up.
ControllerThe controller is a computer in the car. It watches the speed sensors and controls the valves.
ABS at Work
There are many different variations and control algorithms for ABS systems. We will discuss how one of the simpler systems works.
The controller monitors the speed sensors at all times. It is looking for decelerations in the wheel that are out of the ordinary. Right before a wheel locks up, it will experience a rapid deceleration.
If left unchecked, the wheel would stop much more quickly than any car could. It might take a car five seconds to stop from 60 mph (96.6 kph) under ideal conditions, but a wheel that locks up could stop spinning in less than a second.
The ABS controller knows that such a rapid deceleration is impossible, so it reduces the pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the deceleration again. It can do this very quickly, before the tire can actually significantly change speed. The result is that the tire slows down at the same rate as the car, with the brakes keeping the tires very near the point at which they will start to lock up. This gives the system maximum braking power.
When the ABS system is in operation you will feel a pulsing in the brake pedal; this comes from the rapid opening and closing of the valves. Some ABS systems can cycle up to 15 times per second.
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Anti-Lock Brake Types
Anti-lock braking systems use different schemes depending on the type of brakes in use. We will refer to them by the number of channels -- that is, how many valves that are individually controlled -- and the number of speed sensors.
Four-channel,
four-sensor ABSThis is the best scheme. There is a speed sensor on all four wheels and a separate valve for all four wheels. With this setup, the controller monitors each wheel individually to make sure it is achieving maximum braking force.
Three-channel,
three-sensor ABSThis scheme, commonly found on pickup trucks with four-wheel ABS, has a speed sensor and a valve for each of the front wheels, with one valve and one sensor for both rear wheels. The speed sensor for the rear wheels is located in the rear axle.
This system provides individual control of the front wheels, so they can both achieve maximum braking force. The rear wheels, however, are monitored together; they both have to start to lock up before the ABS will activate on the rear. With this system, it is possible that one of the rear wheels will lock during a stop, reducing brake effectiveness.
One-channel,
one-sensor ABSThis system is commonly found on pickup trucks with rear-wheel ABS. It has one valve, which controls both rear wheels, and one speed sensor, located in the rear axle.
This system operates the same as the rear end of a three-channel system. The rear wheels are monitored together and they both have to start to lock up before the ABS kicks in. In this system it is also possible that one of the rear wheels will lock, reducing brake effectiveness.
This system is easy to identify. Usually there will be one brake line going through a T-fitting to both rear wheels. You can locate the speed sensor by looking for an electrical connection near the differential on the rear-axle housing.
ETS (Electronic Traction System)
Traction control helps limit tire slip in acceleration on slippery surfaces. In the past, drivers had to feather the gas pedal to prevent the drive wheels from spinning wildly on slippery pavement. Many of today's vehicles employ electronic controls to limit power delivery for the driver, eliminating wheel slip and helping the driver accelerate under control.
Powerful rear-drive cars from the sixties often had a primitive form of traction control called a limited slip rear differential. Sometimes referred to as Positraction, a limited-slip rear axle will mechanically transfer power to the rear wheel with the most traction, helping to reduce, but not eliminate wheel spin. While limited-slip rear axles are still in use in many front- and rear-drive vehicles today, the device can't completely eliminate wheel slip. Hence, a more sophisticated system was needed.
Enter electronic traction control. In modern vehicles, traction-control systems utilize the same wheel-speed sensors employed by the antilock braking system. These sensors measure differences in rotational speed to determine if the wheels that are receiving power have lost traction. When the traction-control system determines that one wheel is spinning more quickly than the others, it automatically "pumps" the brake to that wheel to reduce its speed and lessen wheel slip. In most cases, individual wheel braking is enough to control wheel slip. However, some traction-control systems also reduce engine power to the slipping wheels. On a few of these vehicles, drivers may sense pulsations of the gas pedal when the system is reducing engine power much like a brake pedal pulsates when the antilock braking system is working.
Many people mistakenly believe that traction control will prevent their vehicle from getting stuck in the snow. This couldn't be further from the truth.
In my point of view this is not an exraordenary system because traction control does not have the ability to increase traction; it just attempts to prevent a vehicle's wheels from spinning.
and ander some conditions accelerating more , may cause your car loses traction
Monday, June 8, 2009
Amazing stability system(ESC)
ESC
During normal driving, ESC works in the background, continuously monitoring steering and vehicle direction. ESC compares the driver's intended direction (by measuring steering angle) to the vehicle's actual direction (by measuring lateral acceleration, vehicle rotation (yaw), and individual road wheel speeds).
ESC only intervenes when it detects loss of steering control, i.e. when the vehicle is not going where the driver is steering.
This may happen, for example, when skidding during emergency evasive swerves, understeer or oversteer during poorly judged turns on slippery roads, or hydroplaning. ESC measures the direction of the skid, and then applies the brakes to individual wheels asymmetrically in order to create torque about the vehicle's vertical axis, opposing the skid and bringing the vehicle back in line with the driver's commanded direction. Additionally, the system may reduce engine power or operate the transmission to slow the vehicle down.
Oversteering
Understeering
ESC can work on any surface, from dry pavement to frozen lakes. It reacte to and corrects skidding much faster and more effectively than the typical human driver, often before the driver is even aware of any imminent loss of control. In fact, this led to some concern that ESC could allow drivers to become overconfident in their vehicle's handling and/or their own driving skills. For this reason, ESC systems typically inform the driver when they intervene, so that the driver knows that the vehicle's handling limits have been approached. Most activate a dashboard indicator light and/or alert tone; some intentionally allow the vehicle's corrected course to deviate very slightly from the driver-commanded direction, even if it is possible to more precisely match it.
Indeed, all ESC manufacturers emphasize that the system is not a performance enhancement nor a replacement for safe driving practices, but rather a safety technology to assist the driver in recovering from dangerous situations. ESC does not increase traction, so it does not enable faster cornering (although it can facilitate better-controlled cornering). More generally, ESC works within inherent limits of the vehicle's handling and available traction between the tires and road. A reckless maneuver can still exceed these limits, resulting in loss of control. For example, in a severe hydroplaning scenario, the wheel(s) that ESC would use to correct a skid may not even initially be in contact with the road, reducing its effectiveness.
In July 2004, on the Crown Majesta, Toyota offered a Vehicle Dynamics Integrated Management (VDIM) system that incorporated formerly independent systems including ESC and worked not only after the skid was detected but also worked to prevent the skid from occurring in the first place. Using electric variable gear ratio steering power steering this more advanced systems could also alter steering gear ratios and steering torque levels to assist the driver in evasive maneuvers.
Sunday, June 7, 2009
More you need to know about power and torque
One engine is a turbocharged Caterpillar C-12 diesel truck engine. This engine weighs about 2,000 pounds, and has a displacement of 732 cubic inches (12 liters).
The other engine is a highly modified Ford Mustang Cobra engine, with a displacement of 280 cubic inches (4.6 liters); it has an added supercharger and weighs about 400 pounds. They both produce a maximum of about 430 horsepower (hp), but only one of these engines is suitable for pulling a heavy truck. The reason lies partly in the power/torque curve shown above.
When the animation pauses, you can see that the Caterpillar engine produces 1,650 lb-ft of torque at 1200 rpm, which is 377 hp. At 5,600 rpm, the Mustang engine also makes 377 hp, but it only makes 354 lb-ft of torque. If you have read the article on gear ratios, you might be thinking of a way to help the Mustang engine produce the same 1,650 lb-ft of torque. If you put a gear reduction of 4.66:1 on the Mustang engine, the output speed would be (5,600/4.66 rpm) 1,200 rpm, and the torque would be (4.66 * 354 lb-ft) 1,650 lb-ft -- exactly the same as the big Caterpillar engine.
Now you might be wondering, why don't big trucks use small gas engines instead of big diesel engines? In the scenario above, the big Caterpillar engine is loafing along at 1,200 rpm, nice and slow, producing 377 horsepower. Meanwhile, the small gas engine is screaming along at 5,600 rpm. The small gas engine is not going to last very long at that speed and power output. The big truck engine is designed to last years, and to drive hundreds of thousands of miles each year it lasts.
The Honda
The last was no surprise, given Honda's origins as a motorcycle maker, its long-time emphasis on engineering -- and its occasional involvement in auto racing. Accord became still sportier for 1989, when notchback coupe models were added and top-line LXi versions gained a firmer suspension and steering. Even so, the Honda Accord remained firmly focused on family-friendly transportation. Underlining that point was the new fourth-generation design for 1990, which grew to nearly midsize-car dimensions and offered station wagon models instead of hatchbacks.
Since then, the Honda Accord has been redesigned three more times, each generation adding size, power, refinement and new features to the successful formula. That frequent updating helps explain Accord's continued strong appeal. So does a consistent high level of customer satisfaction, not to mention the consistently strong resale values that have come to be associated with the Honda brand.
This article traces the evolution of the Honda Accord from the original 1977 models to the latest 2007 versions. It's divided by the seven design generations that span these model years.
Each section begins with a description of the major design and engineering features for that generation. It then discusses the significant changes to Accord for each model year within the generation.
©2007 Honda via WieckAs evidenced by the 1990 Honda Accord, the model has constantly evolved.
Beginning with the 1990-1993 generation, each section also includes a segment entitled "Honda Accord Reliability." This lists the car's notable trouble spots as reported by owners and mechanics, and includes problems covered in company-issued service bulletins.
In addition, each section starting with the 1990-1993 generation concludes with "Honda Accord Safety Recalls. These are recalls issued by the U.S. government's National Highway Traffic Safety Administration.
The Accord is to Honda what the Camry is Toyota: a popular mainstream car that makes a major contribution to its maker's bottom line -- and public image. Each model has its pluses and minuses, yet are closely matched in design concept, price, market position, and other respects. No wonder they've competed so long to top each year's new-car sales chart. Accord has its faults, of course, as does Camry.
A new generation of tires
Michelin first announced the Tweel in 2005. The name is a combination of the words tire and wheel because the Tweel doesn’t use a traditional wheel hub assembly.
A solid inner hub mounts to the axle. That’s surrounded by polyurethane spokes arrayed in a pattern of wedges. A shear band is stretched across the spokes, forming the outer edge of the tire (the part that comes in contact with the road). The tension of the shear band on the spokes and the strength of the spokes themselves replace the air pressure of a traditional tire. The tread is then attached to the shear band. The Tweel looks sort of like a very large, futuristic bicycle wheel.
When the Tweel is put to the road, the spokes absorb road impacts the same way air pressure does in pneumatic tires. The tread and shear bands deform temporarily as the spokes bend, then quickly spring back into shape. Tweels can be made with different spoke tensions, allowing for different handling characteristics.
More pliant spokes result in a more comfortable ride with improved handling. The lateral stiffness of the Tweel is also adjustable. However, you can’t adjust a Tweel once it has been manufactured. You’ll have to select a different Tweel. For testing, Michelin equipped an Audi A4 with Tweels made with five times as much lateral stiffness as a pneumatic tire, resulting in “very responsive handling” [Source: Michelin].
Michelin reports that “the Tweel prototype… is within five percent of the rolling resistance and mass levels of current pneumatic tires. That translates to mean within one percent of the fue economy” of the tires on your own car. Since the Tweel is very early in its development, Michelin could be expected to improve those numbers.
The Future of Airless Tires
The Tweel does have several flaws (aside from the name). The worst is vibration. Above 50 mph, the Tweel vibrates considerably. That in itself might not be a problem, but it causes two other things: noise and heat. A fast moving Tweel is unpleasantly loud [Source: CBS News]. Long-distance driving at high speeds generates more heat than Michelin engineers would like.
Another problem involves the tire industry. Making Tweels is quite a different process than making a pneumatic tire. The sheer scale of the changes that would need to be made to numerous factories, not to mention tire balancing and mounting equipment in thousands of auto repair shops, presents a significant (though not insurmountable) obstacle to the broad adoption of airless tires.
Because of these flaws, Michelin is not planning to roll out the Tweel to consumers any time soon. “Radial tire technology will continue as the standard for a long time to come,” said Michelin’s press release touting Tweel development. They are initially working on Tweel use in low-speed applications, such as on construction vehicles. The Tweel is perfect for such use because the high-speed vibration problems won’t come into play, and the ruggedness of the airless design will be a major advantage on a construction site. Michelin is also exploring military use of the Tweel.
At a public demonstration of the Tweel, Michelin placed prototypes on the iBOT, a personal mobility device for physically impaired people, and the Segway Centaur, a four-wheeled ATV-type vehicle that uses Segway’s self-balancing technology.
Thursday, June 4, 2009
Car Stability
Measure of how difficult it is to move an object from a position of balance or equilibrium with respect to gravity.
An object displaced from equilibrium does not remain in its new position if its weight, acting vertically downwards through its centre of mass, no longer passes through the line of action of the contact force (the force exerted by the surface on which the object is resting), acting vertically upwards through the object's new base. If the lines of action of these two opposite but equal forces do not coincide they will form a couple and create a moment (see moment of a force) that will cause the object either to return to its original rest position or to topple over into another position.
An object in stable equilibrium returns to its rest position after being displaced slightly. This form of equilibrium is found in objects that are difficult to topple over; these usually possess a relatively wide base and a low centre of mass – for example, a cone resting on its flat base on a horizontal surface. When such an object is tilted slightly its centre of mass is raised and the line of action of its weight no longer coincides with that of the contact force exerted by its new, smaller base area. The moment created will tend to lower the centre of mass and so the cone will fall back to its original position.
An object in unstable equilibrium does not remain at rest if displaced, but falls into a new position; it does not return to its original rest position. Objects possessing this form of equilibrium are easily toppled and usually have a relatively small base and a high centre of mass – for example, a cone balancing on its point, or apex, on a horizontal surface.
An object in neutral equilibrium stays at rest if it is moved into a new position – neither moving back to its original position nor on any further. This form of equilibrium is found in objects that are able to roll, such as a cone resting on its curved side placed on a horizontal surface. When such an object is rolled its centre of mass remains in the same position, neither rising nor falling, and the line of action of its weight continues to coincide with the contact force; no moment is created and so its equilibrium is maintained
- the hight of the car( the more the hight the less the stability)
- size of the wheels ( the wider the tires the more stability)
- width of the car (the more the width the more stability)
- aerodynamics (the smoother the side profile the more stability)
- suspension ( the tougher the suspension is the more the stability in curves)
( effect of tough suspension on the stability)
But the problem is the the tougher the suspension the less comfort
Don't worry there is a system combined between stability and comfort
is called (bose active suspension)
Wednesday, June 3, 2009
Power & torque
Max torque : 150 Ipft @ 3500 rpm
What's that ?
, what does it describe?
and how important is it?
first you to know the meaning of them actully!!!!!!!!!!!!!!!!!
wheels to get the motion this is called (torque)Car Engines
If you put a tiny amount of high-energy fuel (like gasoline) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. You can use that energy to propel a potato 500 feet. In this case, the energy is translated into potato motion. You can also use it for more interesting purposes. For example, if you can create a cycle that allows you to set off explosions like this hundreds of times per minute, and if you can harness that energy in a useful way, what you have is the core of a car engine!
Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. They are:
-Intake stroke
-Compression stroke
-Combustion stroke
-Exhaust stroke
The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work.
Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful.
When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down.
Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe.
Now the engine is ready for the next cycle, so it intakes another charge of air and gas.
Notice that the motion that comes out of an internal combustion engine is rotational, while the motion produced by a potato cannon is linear (straight line). In an engine the linear motion of the pistons is converted into rotational motion by the crankshaft. The rotational motion is nice because we plan to turn (rotate) the car's wheels with it anyway.
Source : http://www.howstuffworks.com/
