Citizendia
Your Ad Here

The front suspension components of a Ford Model T.
The front suspension components of a Ford Model T. The Ford Model T (colloquially known as the Tin Lizzie and also the Flivver) was an Automobile produced by Henry Ford 's Ford

Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. A spring is a flexible elastic object used to store mechanical Energy. A shock absorber in common parlance (or damper in technical use is a mechanical device designed to smooth out or dampen shock impulse and dissipate A mechanical linkage is a series of rigid links connected with joints to form a closed chain or a series of closed chains Vehicles, derived from the Latin word vehiculum, are non-living Means of transport. A wheel is a circular device that is capable of rotating on its axis facilitating movement or transportation whilst supporting a load ( Mass) or performing labour in machines Suspension systems serve a dual purpose – contributing to the car's handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations. Car handling and vehicle handling is a description of the way wheeled vehicles perform transverse to their direction of motion particularly during cornering and swerving A brake is a device for slowing or stopping the motion of a Machine or Vehicle, or alternatively a device to restrain it from starting to move again These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension of a car may be different. For Front-wheel drive cars, rear suspension has few constraints and a variety of Beam axles and Independent suspensions are used

This article is primarily about four-wheeled (or more) vehicle suspension. For information on two-wheeled vehicles' suspensions see the suspension (motorcycle), motorcycle fork, bicycle suspension, and bicycle fork articles. A motorcycle's suspension is similar to the suspension in an automobile in its purpose Suspension systems serve a dual purpose - contributing to the vehicle's handling and braking for good active A motorcycle fork is the portion of a Motorcycle to which the front wheel and the Handlebars are connected usually incorporates the front suspension Bicycle suspension refers to the system or systems used to suspend the rider and all or part of the bicycle in order to protect them from the roughness of the terrain over A bicycle fork is the portion of a Bicycle that holds the front wheel and allows the rider to steer and balance the bicycle

Contents

History

Leaf springs have been around since the early Egyptians. Originally called laminated or carriage spring, a leaf spring is a simple form of spring, commonly used for the suspension in

Ancient military engineers used leaf springs in the form of bows to power their siege engines, with little success at first. The use of leaf springs in catapults was later refined and made to work years later. Springs were not only made of metal, a sturdy tree branch could be used as a spring, such as with a bow.

Early suspension devices were developed for stagecoaches in early modern Britain. For other meanings see Stagecoach (disambiguation. A stagecoach (also called diligence) is a type of four-wheeled enclosed Early Modern Britain is the History of the island of Great Britain roughly corresponding to the 16th 17th and 18th centuries The physical laws of damping were not discovered until the 19th century. Damping is any effect either deliberately engendered or inherent to a system that tends to reduce the amplitude of Oscillations of an oscillatory system

Important properties

Spring rate

Further information: Spring rate

The Spring rate (or suspension rate) is a component in setting the vehicle's ride height or its location in the suspension stroke. A spring is a flexible elastic object used to store mechanical Energy. Vehicles which carry heavy loads will often have heavier springs to compensate for the additional weight that would otherwise collapse a vehicle to the bottom of its travel (stroke). Heavier springs are also used in performance applications when the suspension is constantly forced to the bottom of its stroke causing a reduction in the useful amount of suspension travel which may also lead to harsh bottoming.

Springs that are too hard or too soft will both effectively cause the vehicle to have no suspension at all. Vehicles that commonly experience suspension loads heavier than normal have heavy or hard springs with a spring rate close to the upper limit for that vehicle's weight. This allows the vehicle to perform properly under a heavy load when control is limited by the inertia of the load. The vis insita or innate force of matter is a power of resisting by which every body as much as in it lies endeavors to preserve in its present state whether it be of rest or of moving Riding in an empty truck used for carrying loads can be uncomfortable for passengers because of its high spring rate relative to the weight of the vehicle. A race car would also be described as having heavy springs and would also be uncomfortably bumpy. However, even though we say they both have heavy springs, the actual spring rates for a 2000 lb race car and a 10,000 lb truck are very different. A luxury car, taxi, or passenger bus would be described as having soft springs. Vehicles with worn out or damaged springs ride lower to the ground which reduces the overall amount of compression available to the suspension and increases the amount of body lean. Performance vehicles can sometimes have spring rate requirements other than vehicle weight and load.

Mathematics of the spring rate

Spring rate is a ratio used to measure how resistant a spring is to being compressed or expanded during the spring's deflection. A ratio is an expression which compares quantities relative to each other The magnitude of the spring force increases as deflection increases according to Hooke's Law. In Mechanics, and Physics, Hooke's law of elasticity is an approximation that states that the amount by which a material body is deformed (the Briefly, this can be stated as

F = -kx \,

where

F is the force the spring exerts
k is the spring rate of the spring.
x is the displacement from equilibrium length i. e. the length at which the spring is neither compressed or stretched.

Spring rate is confined to a narrow interval by the weight of the vehicle, the load the vehicle will carry, and to a lesser extent by suspension geometry and performance desires.

Spring rates typically have units of N/mm (or lbf/in). The newton (symbol N) is the SI derived unit of Force, named after Isaac Newton in recognition of his work on Classical The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to This article deals with the unit of force For the unit of mass see Pound (mass. Inches redirects here To see the Les Savy Fav album see Inches. An example of a linear spring rate is 500 lbf/in. For every inch the spring is compressed, it exerts 500 lbf. A non-linear spring rate is one for which the relation between the spring's compression and the force exerted cannot be fitted adequately to a linear model. For example, the first inch exerts 500 lbf force, the second inch exerts an additional 550 lbf (for a total of 1050 lbf), the third inch exerts another 600 lbf (for a total of 1650 lbf). In contrast a 500 lbf/in linear spring compressed to 3 inches will only exert 1500 lbf.

The spring rate of a coil spring may be calculated by a simple algebraic equation or it may be measured in a spring testing machine. The spring constant k can be calculated as follows:

k = \frac{d^4E}{8ND^3} \,

where d is the wire diameter, E is the spring's elastic modulus (e. An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substance's tendency to be deformed elastically (i g. , about 30,000,000 lbf/in² or 207 GPa for steel), and N is the number of wraps and D is the diameter of the coil. The pound per square inch or more accurately pound-force per square inch (symbol psi or lbf/in² or lbf/in²) is a unit of

Wheel rate

Wheel rate is the effective spring rate when measured at the wheel. This is as opposed to simply measuring the spring rate alone.

Wheel rate is usually equal to or considerably less than the spring rate. Commonly, springs are mounted on control arms, swing arms or some other pivoting suspension member. Consider the example above where the spring rate was calculated to be 500lbs/inch, if you were to move the wheel 1 inch (without moving the car), the spring more than likely compresses a smaller amount. Lets assume the spring moved 0. 75 inches, the lever arm ratio would be 0. 75 to 1. The wheel rate is calculated by taking the square of the ratio (0. 5625) times the spring rate. Squaring the ratio is because the ratio has two effects on the wheel rate. The ratio applies to both the force and distance traveled.

Wheel rate on independent suspension is fairly straight-forward. However, special consideration must be taken with some non-independent suspension designs. Take the case of the straight axle. When viewed from the front or rear, the wheel rate can be measured by the means above. Yet because the wheels are not independent, when viewed from the side under acceleration or braking the pivot point is at infinity (because both wheels have moved) and the spring is directly inline with the wheel contact patch. The result is often that the effective wheel rate under cornering is different than it is under acceleration and braking. This variation in wheel rate may be minimized by locating the spring as close to the wheel as possible.

Roll couple percentage

Roll couple percentage is the effective wheel rates, in roll, of each axle of the vehicle as a ratio of the vehicle's total roll rate. Roll Couple Percentage is critical in accurately balancing the handling of a vehicle.

A vehicle with a roll couple percentage of 70% will transfer 70% of its sprung weight transfer at the front of the vehicle during cornering.

Weight transfer

Weight transfer during cornering, acceleration or braking is usually calculated per individual wheel and compared with the static weights for the same wheels. Cornering wheel weights requires knowing the static wheel weights and adding or subtracting the unsprung, sprung and jacking forces at each wheel. Some auto racing circles use false terms, or combine things like jacking forces and sprung weight transfer and call it by terms like "side bite". They are either unknowing by ignorance or intentionally confusing competitors by not dealing with vehicle fundamentals and using commonly accepted anthropomorphic terms. Anthropomorphism is the attribution of uniquely Human characteristics to non-human creatures and beings natural and supernatural phenomena material states and objects

Unsprung weight transfer

Unsprung Weight Transfer is calculated based on the weight of the vehicles components that are not supported by the springs. This includes tires, wheels, brakes, spindles, half the control arm's weight and other components. These components are then (for calculation purposes) assumed to be connected to a vehicle with zero sprung weight. They are then put through the same dynamic loads. The weight transfer for cornering in the front would be equal to the total unsprung front weight times the G-Force times the front unsprung center of gravity height divided by the front track width. Likewise for the rear.

Sprung weight transfer

Sprung Weight Transfer is the weight transferred by only the weight of the vehicle resting on the springs not the total vehicle weight. Calculating this requires knowing the vehicles sprung weight (total weight less the unsprung weight), the front and rear roll center heights and the sprung center of gravity height (used to calculate the roll moment arm length). In a vehicle with a suspension, such as an Automobile, Motorcycle or a Tank, sprung mass (or sprung weight) is the portion of the Calculating the front and rear sprung weight transfer will also require knowing the roll couple percentage.

The roll axis is the line through the front and rear roll centers that the vehicle rolls around during cornering. The distance from this axis to the sprung center of gravity height is the roll moment arm length. The total sprung weight transfer is equal to the G-force times the sprung weight times the roll moment arm length divided by the effective track width. g-force (also G-force, g-load) is a measurement of an object's Acceleration expressed in g s The front sprung weight transfer is calculated by multiplying the roll couple percentage times the total sprung weight transfer. The rear is just the total minus the front transfer.

Jacking forces

Jacking forces can be thought of as the centripetal force pushing diagonally upward from the tire contact patch into the suspension roll center. The front jacking force is calculated by taking the front sprung weight times the G-force times the front roll center height divided by the front track width. The rear is calculated the same way except at the rear.

Travel

Travel is the measure of distance from the bottom of the suspension stroke (such as when the vehicle is on a jack and the wheel hangs freely), to the top of the suspension stroke (such as when the vehicles wheel can no longer travel in an upward direction toward the vehicle). Bottoming or lifting a wheel can cause serious control problems or directly cause damage. "Bottoming" can be either the suspension, tires, fenders, etc. running out of space to move or the body or other components of the car hitting the road. The control problems caused by lifting a wheel are less severe if the wheel lifts when the spring reaches its unloaded shape than they are if travel is limited by contact of suspension members. (See Triumph TR3B. The Triumph TR3"B" is a sports car and was produced by the Triumph Motor Company (Standard Motor Company in 1962 )

Damping

Damping (not to be confused with dampening) is the control of motion or oscillation, as seen with the use of hydraulic gates and valves in a vehicles shock absorber. Damping is any effect either deliberately engendered or inherent to a system that tends to reduce the amplitude of Oscillations of an oscillatory system This may also vary, intentionally or unintentionally. Like spring rate, the optimal damping for comfort may be less than for control.

Damping controls the travel speed and resistance of the vehicles suspension. An undamped car will oscillate up and down. With proper damping levels, the car will settle back to a normal state in a minimal amount of time. Most damping in modern vehicles can be controlled by increasing or decreasing the resistance to fluid flow in the shock absorber.

Camber control

See dependent and independent below.

Camber changes with wheel travel and with body roll. Camber angle is the angle made by the Wheel of an automobile specifically it is the angle between the vertical axis of the wheel and the vertical axis of the vehicle when A tire wears and brakes best at -1 to -2 degrees of camber from vertical. A brake is a device for slowing or stopping the motion of a Machine or Vehicle, or alternatively a device to restrain it from starting to move again Depending on the tire, it may hold the road best at a slightly different angle. Small changes in camber, front and rear, are used to tune handling.

Roll center height

This is important to body roll and to front to rear roll moment distribution. However, the roll moment distribution in most cars is set more by the antiroll bars than the RCH. A sway bar (also stabilizer bar anti-sway bar roll bar or anti-roll bar ARB) is an Automobile suspension It may affect the tendency to roll over.

Instant center

A tire's force vector points from the contact patch of the tire through a point referred to as the "instant center". This imaginary point is the effective geometric point at which the suspension force vectors are transmitted to the chassis. Another way of looking at this is to imagine each suspension control arm mounted only at the frame. The axis that the arm rotates around creates an imaginary line running through the vehicle. Forces, as far as suspension geomentry are concerned, are transmitted either along this axis (usually front to rear) or through this axis at a right angle (usually right to left and intersects the ball joint). When you intersect the force lines of the upper and lower control arms, where they cross is the Instant Center. The Instant Centers when viewed from the front or side may not seem to have much of a relation to each other until you imagine the points in three dimensions. Sometimes the Instant Center is at ground level or at a distant point due to parallel control arms.

The instant center can also be thought of as having the effect of converting multilink suspension into a single control arm which pivots at the Instant Center. This is only true at a given suspension deflection, because an unequal length, multi-link system has an instant center that moves as the suspension is deflected.

Anti-dive and anti-squat

Anti-dive and anti-squat are expressed in terms of percentage and refer to the front diving under braking and the rear squating under acceleration. They can be thought of as the counterparts for braking and acceleration as roll center height is to cornering. The main reason for the difference is due to the different design goals between front and rear suspension, whereas suspension is usually symmetrical between the left and right of the vehicle.

Anti-dive and anti-squat percentage are always calculated with respect to a vertical plane that intersects the vehicle's Center of Gravity. Consider Anti-dive first. Locate the front Instant Centers of the suspension from the vehicle's side view. Draw a line fron the tire contact patch through the Instant Center, this is the tire force vector. Now draw a line straight down from the vehicle's center of gravity. The Anti-dive is the ratio between the height of where the tire force vector crosses the center of gravity plane expressed as a percentage. An Anti-dive ratio of 50% would mean the force vector under braking crosses half way between the ground and the center of gravity.

Anti-squat is the counterpart to Anti-dive and is for the rear suspension under acceleration.

Anti-dive and anti-squat may or may not be desirable depending on the suspension design. Independent suspension using multiple control arms can be an issue if the percentage is too high (say over 30%). A percentage of 100% in this case would indicate the suspension is taking 100% of the weight transfer under braking instead of the springs. This effectively binds the suspension and turns the independent suspension into no suspension like a go-cart. However, in the case of leaf spring rear suspension the Anti-squat can often exceed 100% (meaning the rear may actually raise under acceleration) yet because there isn't a second arm to bind against and the suspension can freely move. Traction bars are often added to drag racing cars with leaf spring rear to increase the Anti-squat to its maximum. This has the effect of forcing the rear of the car in the air and the tires onto the ground for better traction.

Flexibility and vibration modes of the suspension elements

In modern cars, the flexibility is mainly in the rubber bushings.

Isolation from high frequency shock

For most purposes, the weight of the suspension components is unimportant, but at high frequencies, caused by road surface roughness, the parts isolated by rubber bushings act as a multistage filter to suppress noise and vibration better than can be done with only the tires and springs. (The springs work mainly in the vertical direction. )

Contribution to unsprung weight and total weight

These are usually small, except that the suspension is related to whether the brakes and differential(s) are sprung.

Space occupied

Designs differ as to how much space they take up and where it is located. It is generally accepted that MacPherson struts are the most compact arrangement for front-engined vehicles, where space between the wheels is required to place the engine. The MacPherson strut is a type of car suspension system widely used in modern vehicles named after Earl S

Force distribution

The suspension attachment must match the frame design in geometry, strength and rigidity.

Air resistance (drag)

Certain modern vehicles have height adjustable suspension in order to improve aerodynamics and fuel efficiency. Height adjustable suspension is a feature of certain Automobile Suspension (vehicle systems that allow the motorist to vary the Ride height or ground And modern formula cars, that have exposed wheels and suspension, typically use streamlined tubing rather than simple round tubing for their suspension arms to reduce drag. Also typical is the use of rocker arm, push rod, or pull rod type suspensions, that among other things, places the spring/damper unit inboard and out of the air stream to further reduce air resistance.

Cost

Production methods improve, but cost is always a factor. The continued use of the solid rear axle, with unsprung differential, especially on heavy vehicles, seems to be the most obvious example.

Springs and dampers

Most suspensions use springs to absorb impacts and dampers (or shock absorbers) to control spring motions. A spring is a flexible elastic object used to store mechanical Energy. A shock absorber in common parlance (or damper in technical use is a mechanical device designed to smooth out or dampen shock impulse and dissipate Some notable exceptions are the hydropneumatic systems, which can be treated as an integrated unit of gas spring and damping components, used by the French manufacturer Citroën and the hydrolastic, hydragas and rubber cone systems used by the British Motor Corporation, most notably on the Mini. Hydropneumatic is a type of Automotive suspension system, invented by Citroën, and fitted to Citroën cars as well as being adapted by other car manufacturers Citroën (pronounced See-Troh-Enn is a French Automobile manufacturer, founded in 1919 by André Citroën. Hydrolastic is a type of space-efficient automotive suspension system used in many cars produced by British Motor Corporation (BMC and its successor companies Hydrolastic is a type of space-efficient automotive suspension system used in many cars produced by British Motor Corporation (BMC and its successor companies The British Motor Corporation (BMC was a UK vehicle company formed by the merger of the Austin Motor Company and the Nuffield Organisation (parent The Mini is a small car that was produced by the British Motor Corporation (BMC and its successors from 1959 until 2000 A number of different types of each have been used:

Conventional passive, semi-active/active, and interconnected suspensions

Traditional springs and dampers are referred to as passive suspensions. If the suspension is externally controlled then it is a semi-active or active suspension.

Semi-active suspensions include devices such as air springs and switchable shock absorbers, various self-levelling solutions, as well as systems like Hydropneumatic, Hydrolastic, and Hydragas suspensions. Self-levelling refers to an Automobile suspension system that maintains a constant Ride height of the vehicle above the road regardless of load Hydropneumatic is a type of Automotive suspension system, invented by Citroën, and fitted to Citroën cars as well as being adapted by other car manufacturers Hydrolastic is a type of space-efficient automotive suspension system used in many cars produced by British Motor Corporation (BMC and its successor companies Hydrolastic is a type of space-efficient automotive suspension system used in many cars produced by British Motor Corporation (BMC and its successor companies Delphi currently sells shock absorbers filled with a magneto-rheological fluid, whose viscosity can be changed electromagnetically, thereby giving variable control without switching valves, which is faster and thus more effective. A magnetorheological fluid (MR fluid is a type of Smart fluid.

For example, a hydropneumatic Citroën will "know" how far off the ground the car is supposed to be and constantly reset to achieve that level, regardless of load. It will not instantly compensate for body roll due to cornering however. Citroën's system adds about 1% to the cost of the car versus passive steel springs.

Fully active suspensions use electronic monitoring of vehicle conditions, coupled with the means to impact vehicle suspension and behavior in real time to directly control the motion of the car. Lotus Cars developed several prototypes, and introduced them to F1, where they have been fairly effective, but have now been banned. Lotus Cars is a British manufacturer of sports and racing cars based at Hethel, Norfolk, England. Nissan introduced a low bandwidth active suspension in circa 1990 as an option that added an extra 20% to the price of luxury models. Citroën has also developed several active suspension models (see hydractive). Hydropneumatic is a type of Automotive suspension system, invented by Citroën, and fitted to Citroën cars as well as being adapted by other car manufacturers A recently publicised fully active system from Bose Corporation uses linear electric motors, ie solenoids, in place of hydraulic or pneumatic actuators that have generally been used up until recently. The most advanced suspension system is Active Body Control, introduced in 1999 on the top-of-the-line Mercedes-Benz CL-Class. Active Body Control, or ABC is the Mercedes-Benz Brand name used to describe fully- Active suspension, that allows control of the vehicle body motions and The Mercedes-Benz CL-Class is a full-sized Grand tourer produced by the German Automaker Mercedes-Benz, which stands for Comfort

With the help of control system, various semi-active/active suspensions could realize an improved design compromise among different vibrations modes of the vehicle, namely bounce, roll, pitch and warp modes. However, the applications of these advanced suspensions are constrained by the cost, packaging, weight, reliability, and/or the other challenges.

Interconnected suspension, unlike semi-active/active suspensions, could easily decouple different vehicle vibration modes in a passive manner. The interconnections can be realized by various means, such as mechanical, hydraulic and pneumatic. Anti-roll bars are one of the typical examples of mechanical interconnections, while it has been stated that fluidic interconnections offer greater potential and flexibility in improving both the stiffness and damping properties. Considering the considerable commercial potentials of hydro-pneumatic technology (Corolla, 1996), interconnected hydropneumatic suspenisons have also been explored in some recent studies, and their potnetial benefits in enhancing vehicle ride and handling have been demonstrated. The control system can also be used for further improving performance of interconnected suspensions. Apart from academic research, an Australian company, Kinetic, is having some success (WRC: 3 Championships, Dakar Rally: 2 Championships, Lexus GX470 2004 4x4 of the year with KDSS, 2005 PACE award) with various passive or semi-active systems, which generally decouple at least two vehicle modes (roll, warp (articulation), pitch and/or heave (bounce)) to simultaneous control each mode’s stiffness and damping, by using interconnected shock absorbers, and other methods. The WRc Group is a privately-owned group of companies providing research and consultancy on water supply waste treatment and the public The Dakar Rally (or simply " The Dakar " formerly known as "The Paris Dakar" or "Paris to Dakar Rally" and now as "The Lisboa Dakar" is In 1999 Kinetic was bought out by Tenneco.

Historically, the first mass production car with front to rear mechanical interconnected suspension was the 1948 Citroën 2CV. The Citroën 2CV ( French: deux chevaux vapeur, literally "two steam Horses quot from the Tax horsepower rating was an Economy car The suspension of the 2CV was extremely soft — it had low roll stiffness, but its pitch stiffness was increased by using an interconnected suspension. The leading arm / trailing arm swinging arm, fore-aft linked suspension system together with inboard front brakes had a much smaller unsprung weight than existing coil spring or leaf designs. A trailing-arm suspension is an Automobile suspension design in which one or more arms (or "links" are connected between (and perpendicular to and forward In a ground Vehicle with a suspension, the unsprung weight (or more properly the unsprung mass) is the mass of the suspension Wheels The interconnection transmitted some of the force deflecting a front wheel up over a bump, to push the rear wheel down on the same side. When the rear wheel met that bump a moment later, it did the same in reverse, keeping the car level front to rear. The 2CV had a design brief to be able to be driven at speed over a ploughed field. It originally featured friction dampers and tuned mass dampers. A tuned mass damper, also known as an active mass damper ( AMD) or harmonic absorber, is a device mounted in structures to prevent discomfort damage or Later models had tuned mass dampers at the front with telescopic dampers / shock absorbers front and rear. A tuned mass damper, also known as an active mass damper ( AMD) or harmonic absorber, is a device mounted in structures to prevent discomfort damage or A shock absorber in common parlance (or damper in technical use is a mechanical device designed to smooth out or dampen shock impulse and dissipate

Some of the last post war Packard models also featured interconnected suspension. Packard was an American luxury Automobile marque built by the Packard Motor Car Company of Detroit Michigan, and later by the Studebaker-Packard Corporation The original Mini and some more recent British Leyland models also featured interlinking, when fitted with Moulton's Hydrolastic or Hydragas suspensions[1].

Springs

Pneumatic spring on a semitrailer
Pneumatic spring on a semitrailer

Dampers or shock absorbers

The shock absorbers damp out the (otherwise resonant) motions of a vehicle up and down on its springs. Originally called laminated or carriage spring, a leaf spring is a simple form of spring, commonly used for the suspension in A torsion bar suspension, also known as a Torsion spring suspension or incorrectly torsion beam, is a general term for any Vehicle suspension A Coil spring, also known as a helical spring, is a mechanical device which is typically used to store energy and subsequently release it to absorb shock or to maintain A mechanical bushing is a cylindrical lining designed to reduce friction and wear inside a hole or constrict and restrain motion of mechanical parts Air suspension is a type of vehicle suspension powered by an engine driven or electric air pump or Compressor. They also must damp out much of the wheel bounce when the unsprung weight of a wheel, hub, axle and sometimes brakes and differential bounces up and down on the springiness of a tire. In a ground Vehicle with a suspension, the unsprung weight (or more properly the unsprung mass) is the mass of the suspension Wheels This article deals with the concept of a differential in mechanical engineering. The regular bumps found on dirt roads (nicknamed "corduroy", but properly washboarding) are caused by this wheel bounce. A Corduroy road or log road is a type of Road made by placing Sand -covered Logs Perpendicular to the direction of the road over a low Washboarding is the name in North America of the process which results in roads (particularly Gravel roads or Dirt roads developing a series of regular bumps

Suspension types

Suspension systems can be broadly classified into two subgroups - dependent and independent. These terms refer to the ability of opposite wheels to move independently of each other.

A dependent suspension normally has a beam (a simple 'cart' axle) or (driven) live axle that holds wheels parallel to each other and perpendicular to the axle. A live axle is a type of Beam axle suspension system that uses the Driveshafts that transmit power to the wheels to connect the wheels laterally so that When the camber of one wheel changes, the camber of the opposite wheel changes in the same way (by convention on one side this is a positive change in camber and on the other side this a negative change). Camber angle is the angle made by the Wheel of an automobile specifically it is the angle between the vertical axis of the wheel and the vertical axis of the vehicle when Di-Dion suspensions would also be in this category as they rigidly connect the wheels together.

An independent suspension allows wheels to rise and fall on their own without affecting the opposite wheel. Independent suspension is a broad term for any Automobile suspension system that allows each wheel on the same Axle to move vertically (i Suspensions with other devices, such as anti-roll bars that link the wheels in some way are still classed as independent. A sway bar (also stabilizer bar anti-sway bar roll bar or anti-roll bar ARB) is an Automobile suspension

A third type is a semi-dependent suspension. In this case, the motion of one wheel does affect the position of the other but they are not rigidly attached to each other. A Twist-beam rear suspension is such a system. The Twist-beam rear suspension is a type of automobile suspension based on a large H shaped member

Dependent suspensions

Dependent systems may be differentiated by the system of linkages used to locate them, both longitudinally and transversely. Often both functions are combined in a set of linkages.

Examples of location linkages include:

In a front engine, rear-drive vehicle, dependent rear suspension is either "live axle" or deDion axle, depending on whether or not the differential is carried on the axle. A de Dion tube is an Automobile suspension technology It is a sophisticated form of non- Independent suspension and is a considerable improvement over Live axle is simpler but the unsprung weight contributes to wheel bounce.

Because it assures constant camber, dependent (and semi-independent) suspension is most common on vehicles that need to carry large loads as a proportion of the vehicle weight, that have relatively soft springs and that do not (for cost and simplicity reasons) use active suspensions. The use of dependent front suspension has become limited to heavier commercial vehicles.

Independent suspensions

Main article: Independent suspension

The variety of independent systems is greater and includes:

Because the wheels are not constrained to remain perpendicular to a flat road surface in turning, braking and varying load conditions, control of the wheel camber is an important issue. Swinging arm was common in small cars that were sprung softly and could carry large loads, because the camber is independent of load. Some active and semi-active suspensions maintain the ride height, and therefore the camber, independent of load. In sports cars, optimal camber change when turning is more important. A sports car is a term used to describe a class of Automobile.

Wishbone and multi-link allow the engineer more control over the geometry, to arrive at the best compromise, than swing axle, MacPherson strut or swinging arm do; however the cost and space requirements may be greater. Semi-trailing arm is in between, being a variable compromise between the geometries of swinging arm and swing axle.

Armoured fighting vehicle suspension

This Grant I tank's suspension has road wheels mounted on wheel trucks, or bogies.
This Grant I tank's suspension has road wheels mounted on wheel trucks, or bogies. The Medium Tank M3 was an American Tank used during World War II. A bogie (ˈboʊgi (BŌ-gē is a Wheeled wagon or trolley In mechanics terms a bogie is a Chassis or framework carrying wheels attached to a vehicle

Military AFVs, including tanks, have specialized suspension requirements. An armoured fighting vehicle ( AFV) is a military Vehicle, protected by armour and armed with Weapons Most AFVs are equipped for driving in rugged A tank is a tracked, Armoured fighting vehicle designed for Front-line combat which combines Operational mobility and tactical They can weigh more than seventy tons and are required to move at high speed over very rough ground. Their suspension components must be protected from land mines and antitank weapons. A land mine is an Explosive device designed to be placed on or in the ground to explode when triggered by an operator or the Proximity of a vehicle person Anti-tank refers to any method of combating military Armored fighting vehicles notably Tanks The most common anti-tank systems Tracked AFVs can have as many as nine road wheels on each side. Continuous tracks are large (modular tracks used on the so-called caterpillar Tanks construction equipment and certain other off-road vehicles Many wheeled AFVs have six or eight wheels, to help them ride over rough and soft ground. A wheel is a circular device that is capable of rotating on its axis facilitating movement or transportation whilst supporting a load ( Mass) or performing labour in machines

The earliest tanks of the Great War had fixed suspensions—with no movement whatsoever. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All This unsatisfactory situation was improved with leaf spring suspensions adopted from agricultural machinery, but even these had very limited travel. Originally called laminated or carriage spring, a leaf spring is a simple form of spring, commonly used for the suspension in

Speeds increased due to more powerful engines, and the quality of ride had to be improved. In the 1930s, the Christie suspension was developed, which allowed the use of coil springs inside a vehicle's armoured hull, by redirecting the direction of travel using a bell crank. The Christie suspension is a suspension system developed by Walter Christie for his Tank designs A Coil spring, also known as a helical spring, is a mechanical device which is typically used to store energy and subsequently release it to absorb shock or to maintain A bell crank is a type of crank that changes motion around a 90 degree angle Horstmann suspension was a variation which used a combination of bell crank and exterior coil springs, in use from the 1930s to the 1990s. Horstmann suspension is a type of Tank and other tracked Armoured fighting vehicle suspension devised by the British Engineer

By the Second World War the other common type was torsion-bar suspension, getting spring force from twisting bars inside the hull—this had less travel than the Christie type, but was significantly more compact, allowing the installation of larger turret rings and heavier main armament. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including A torsion bar suspension, also known as a Torsion spring suspension or incorrectly torsion beam, is a general term for any Vehicle suspension The torsion-bar suspension, sometimes including shock absorbers, has been the dominant heavy armored vehicle suspension since the Second World War. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including

See also


References

  1. ^ Alex Moulton Mgf Hydragas

External links

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
 Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic