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Oversteer
Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of the vehicle to changes in steering angle associated with changes in lateral acceleration. This sensitivity is defined for a level road for a given steady state operating condition by the Society of Automotive Engineers (SAE) in document J670SAE International Surface Vehicle Recommended Practice, "Vehicle Dynamics Terminology", SAE Standard J670, Rev. 2008-01-24 and by the International Organization for Standardization (ISO) in document 8855.International Organization for Standardization, "Road vehicles – Vehicle dynamics and road-holding ability – Vocabulary", ISO Standard 8855, Rev. 2010 Whether the vehicle is understeer or oversteer depends on the rate of change of the understeer angle. The Understeer Angle is the amount of additional steering (at the road wheels, not the hand wheel) that must be added in any given steady-state maneuver beyond the Ackermann steer angle. The Ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinout (driving)
An automobile skid is an automobile handling condition where one or more tires are Slip (vehicle dynamics), slipping relative to the road, and the overall handling of the vehicle has been affected. Subtypes of skid include: * fishtailing, where the vehicle yaws back and forth across the direction of motion. * ''spin'' or ''spinout'' where a vehicle rotates in one direction during the skid. * understeer and oversteer where front or rear wheels lose traction during cornering, causing a vehicle to follow a larger or smaller turning radius. * ''burnout'' where a vehicle slips or spins its tires during acceleration. * ''lockup'' where a vehicle skids during braking (with or without directional or yaw changes). __TOC__ Slip and skid Tire slip, and related slip angle (angle of motion relative to tire), describe the performance of an individual tire. Important concepts about slip and skid include circle of forces or circle of traction, and cornering force. To a first approximation, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drifting (motorsport)
Drifting is a driving technique where the driver purposely Understeer and oversteer, oversteers, with loss of traction, while maintaining control and driving the car through the entirety of a corner or a turn. The technique causes the rear slip angle to exceed the front slip angle to such an extent that often the front wheels are pointing in the opposite direction to the turn (e.g. car is turning left, wheels are pointed right or vice versa, also known as opposite lock or Countersteering#Other uses, counter-steering). Drifting is traditionally performed using three methods: clutch kicking (where the clutch is rapidly disengaged and re-engaged with the intention of upsetting the grip of the rear wheels), weight transfer (using techniques such as the Scandinavian flick), and employing a handbrake turn. This sense of ''drift'' is not to be confused with the ''four wheel drift'', a classic cornering technique established in Grand Prix motor racing, Grand Prix and sports car racing. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fishtailing
Fishtailing is a vehicle handling problem which occurs when the rear wheels lose traction, resulting in oversteer. This can be caused by low-friction surfaces (sand, gravel, rain, snow, ice, etc.). Rear-wheel drive, Rear-drive vehicles with sufficient power can induce this loss of traction on any surface, which is called Understeer and oversteer, power-oversteer. Mechanics and causes Accidental fishtailing During fishtailing, the rear end of the car skids to one side, which must be offset by the driver counter-steering, which is turning the front wheels in the same direction as the skid, (e.g. left if the rear swings left) and reducing engine power. Over-correction will result in a skid in the opposite direction; hence the name. Without a proper driver's reaction, the fishtailing vehicle will spin completely. Friction is the main reason this action is effective. If a car is moving across a surface in any direction other than the direction it is pointed, it is Skid (automobi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vehicle Dynamics
Vehicle dynamics is the study of vehicle motion, e.g., how a vehicle's forward movement changes in response to driver inputs, propulsion system outputs, ambient conditions, air/surface/water conditions, etc. Vehicle dynamics is a part of engineering primarily based on classical mechanics. It may be applied for motorized vehicles (such as automobiles), bicycles and motorcycles, aircraft, and watercraft. Factors affecting vehicle dynamics The aspects of a vehicle's design which affect the dynamics can be grouped into drivetrain and braking, suspension and steering, distribution of mass, aerodynamics and tires. Drivetrain and braking * Automobile layout (i.e. location of engine and driven wheels) * Powertrain * Braking system Suspension and steering Some attributes relate to the geometry of the suspension, steering and chassis. These include: * Ackermann steering geometry * Axle track * Camber angle * Caster angle * Ride height * Roll center * Scrub radius * Stee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opposite Lock
Opposite lock, also commonly known as countersteer, is a colloquial term used to mean the steering associated with the deliberate use of oversteer to turn a vehicle rapidly without losing momentum. It is typified by the classic rallying style of rear-wheel drive cars, where a car travels around a bend with a large drift angle. The terms "opposite lock" and "counter-steering" refer to the position of the steering wheel during the maneuver, which is turned in the opposite direction to that of the bend. The technique works best on loose or wet surfaces where the friction between the tires and the road is not too high, but can also be used on asphalt or other surfaces with high friction if the vehicle has enough power to maintain speed. Before entry to the bend, the car is turned towards the bend slightly, but quickly, so as to cause a rotating motion that induces the rear of the car to slide outwards. Power is applied which applies further sideways movement. At the same time, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bundorf Analysis
A Bundorf analysis is a measure of the characteristics of a vehicle that govern its understeer balance. The understeer is measured in units of degrees of additional yaw per g of lateral acceleration. An imaginary example Hence the total under-steer is 11.0 deg/g minus 6.9 deg/g, or 4.1 deg/g. Negative values are over-steering, positive values are under-steering, for that axle. If the under-steer contribution of the rear axle is greater than that of the front axle you get negative under-steer, which is known as oversteer. The analysis is only applicable while the parameters remain constant, and thus only up to about 0.4 g. Explanation of terms Load transfer effect and cornering stiffness of tire. As load transfers across the vehicle the tire's ability to provide cornering force for a given slip angle changes. The latter is known as the cornering stiffness of the tire. See also Tire load sensitivity Aligning torque. The tire does not just generate a lateral force, it gene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornering Force
Cornering force or side force is the lateral (i.e., parallel to wheel axis) force produced by a vehicle tire during cornering. Cornering force is generated by tire slip and is proportional to slip angle at low slip angles. The rate at which cornering force builds up is described by relaxation length. Slip angle describes the deformation of the tire contact patch, and this deflection of the contact patch deforms the tire in a fashion akin to a spring. As with deformation of a spring, deformation of the tire contact patch generates a reaction force in the tire; the cornering force. Integrating the force generated by every tread element along the contact patch length gives the total cornering force. Although the term, "tread element" is used, the compliance in the tire that leads to this effect is actually a combination of sidewall deflection and deflection of the rubber within the contact patch. The exact ratio of sidewall compliance to tread compliance is a factor in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self Aligning Torque
Self aligning torque (SAT), also known as aligning torque or aligning moment (Mz, moment about the z direction), is the torque that a tire creates as it rolls along, which tends to steer it, i.e. rotate it around its vertical axis. In the presence of a non-zero slip angle, this torque tends to steer the tire toward the direction in which it is traveling, hence its name. The magnitude of this torque can be calculated as the product of the lateral force generated at the contact patch and the distance behind the wheel centre at which that force acts. This distance is known as the pneumatic trail. The steering torque around a non-vertical steer axis with non-zero mechanical trail is given by: : Even if the slip angle and camber angle are zero, and the road is flat, this torque will still be generated due to asymmetries in the tire's construction and the asymmetrical shape and pressure distribution of the contact patch. Typically for a production tire this torque reaches a maxi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weight Transfer
Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects: *the change in load borne by different wheels of even perfectly rigid vehicles during acceleration *the change in center of mass (CoM) location relative to the wheels because of suspension compliance or cargo shifting or sloshing In the automobile industry, weight transfer customarily refers to the change in load borne by different wheels during acceleration. This would be more properly referred to as load transfer, and that is the expression used in the motorcycle industry, while weight transfer on motorcycles, to a lesser extent on automobiles, and cargo movement on either is due to a change in the CoM location relative to the wheels. This article uses this latter pair of definitions. Load transfer In wheeled vehicles, load transfer is the measurable change of load borne by different wheels during acceleration (both longitudinal and lateral). This includes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SAE International
SAE International is a global professional association and standards organization based in Warrendale, Pennsylvania, United States. Formerly the Society of Automotive Engineers, the organization adopted its current name in 2006 to reflect both its international membership and the increased scope of its activities beyond automotive engineering and the automotive industry to include aerospace and other transport industries, as well as commercial vehicles including autonomous vehicles such as self-driving cars, trucks, surface vessels, drones, and related technologies. SAE International has over 138,000 global members. Membership is granted to individuals, rather than companies. Aside from its standardization efforts, SAE International also devotes resources to projects and programs in STEM education, professional certification, and collegiate design competitions. History In the early 1900s there were dozens of automobile manufacturers in the United States, and many more w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camber Thrust
Camber thrust and camber force are terms used to describe the force generated perpendicular to the direction of travel of a rolling tire due to its camber angle and finite contact patch. Camber thrust is generated when a point on the outer surface of a leaned and rotating tire, that would normally follow a path that is elliptical when projected onto the ground, is forced to follow a straight path while coming in contact with the ground, due to friction. This deviation towards the direction of the lean causes a deformation in the tire tread and carcass that is transmitted to the vehicle as a force in the direction of the lean. Camber thrust is approximately linearly proportional to camber angle for small angles, reaches its steady-state value nearly instantaneously after a change in camber angle, and so does not have an associated relaxation length. Bias-ply tires have been found to generate more camber thrust than radial tires. Camber stiffness is a parameter used to describe the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tyre Load Sensitivity
Tire load sensitivity describes the behaviour of tires under load. Conventional pneumatic tires do not behave as classical friction theory would suggest. The load sensitivity of most real tires in their typical operating range is such that the coefficient of friction decreases as the vertical load, Fz, increases. The maximum lateral force that can be developed does increase as the vertical load increases, but at a diminishing rate. Behaviour Coulomb friction theory says that the maximum horizontal force developed should be proportional to the vertical load on the tire. In practice, the maximum horizontal force Fy that can be generated is proportional, roughly, to the vertical load Fz raised to the power of somewhere between 0.7 and 0.9, typically. Production car tires typically develop this maximum lateral force, or cornering force, at a slip angle of 6-10 degrees, although this angle increases as the vertical load on the tire increases. Formula 1 car tires may reach a peak si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
