Suspension is the term given to the system of springs A spring is an elastic object used to store mechanical energy. Springs are usually made out of hardened steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication. Some non-ferrous metals are also used including phosphor bronze and titanium for parts requiring corrosion, shock absorbers A shock absorber is a mechanical device (one kind of dashpot) designed to smooth out or damp shock impulse, and dissipate kinetic energy and linkages A mechanical linkage is a series of rigid links connected with joints to form a closed chain, or a series of closed chains. Each link has two or more joints, and the joints have various degrees of freedom to allow motion between the links. A linkage is called a mechanism if two or more links are movable with respect to a fixed link. Mechanical that connects a vehicle A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured (e.g. bicycles, cars, motorcycles, trains, ships, boats, and aircraft) to its wheels A wheel is a circular device that is capable of rotating on an axle through its centre, facilitating movement or transportation while supporting a load , or performing labour in machines. Common examples are found in transport applications. A wheel, together with an axle overcomes friction by facilitating motion by rolling. In order for wheels to. Suspension systems serve a dual purpose – contributing to the car's roadholding/handling 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. It also includes their stability when moving in a straight line. Handling and braking are the major components of a vehicle's "active" safety. The maximum lateral and braking Most commonly brakes use friction to convert kinetic energy into heat, though other methods of energy conversion may be employed. For example regenerative braking converts much of the energy to electrical energy, which may be stored for later use. Other methods convert kinetic energy into potential energy in such stored forms as pressurized air or for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations,etc. These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension For front-wheel drive cars, rear suspension has few constraints and a variety of beam axles and independent suspensions are used of a car may be different.
This article is primarily about four-wheeled (or more) vehicle suspension. For information on two-wheeled vehicles' suspensions see the suspension (motorcycle) The typical motorcycle has a pair of fork tubes for the front suspension, and a swingarm with one or two shock absorbers for the rear suspension, motorcycle fork A motorcycle fork connects a motorcycle's front wheel and axle to its frame, typically via a pair of triple clamps. It typically incorporates the front suspension and front brake, and allows the bike to be steered via handlebars attached to the upper triple tree, bicycle suspension A bicycle suspension is 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 which they travel. Bicycle suspensions are used primarily on mountain bikes, but are also common on hybrid bicycles, and can even be found on some road bicycles, and bicycle fork A bicycle fork is the portion of a bicycle that holds the front wheel and allows the rider to steer and balance the bicycle. A fork consists of two dropouts which hold the front wheel axle, two blades which join at a fork crown, and a steerer or steering tube to which the handlebars attach allowing the user to steer the bicycle. The steerer of the articles.
History
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Leaf springs Originally called laminated or carriage spring, a leaf spring is a simple form of spring, commonly used for the suspension in wheeled vehicles. It is also one of the oldest forms of springing, dating back to medieval times have been around since the early Egyptians.
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.
Horse drawn vehicles
By the early 19th century most British horse carriages were equipped with springs; wooden springs in the case of light one-horse vehicles to avoid taxation, and steel springs in larger vehicles. These were made of low-carbon steel and usually took the form of multiple layer leaf springs Originally called laminated or carriage spring, a leaf spring is a simple form of spring, commonly used for the suspension in wheeled vehicles. It is also one of the oldest forms of springing, dating back to medieval times.[1]
The British steel springs were not well suited for use on America's rough roads of the time, and could even cause coaches to collapse if cornered too fast. In the 1820s, the Abbot Downing Company of Concord, New Hampshire The city of Concord is the capital of the state of New Hampshire in the United States. It is also the county seat of Merrimack County. As of the 2000 census, its population was 40,765, with an estimated 2008 population of 42,255 developed a system whereby the bodies of stagecoaches A stagecoach is a type of four-wheeled closed coach for passengers and goods, strongly sprung and drawn by four horses, usually four-in-hand. Widely used before the introduction of railway transport, it made regular trips between stages or stations, which were places of rest provided for stagecoach travelers. The business of running stagecoaches were supported on leather straps called "thoroughbraces", which gave a swinging motion instead of the jolting up and down of a spring suspension (the stagecoach itself was sometimes called a "thoroughbrace")
Automobiles
Henri Fournier on his uniquely dampened and racewinning 'Mors Machine', photo taken 1902Automobiles were initially developed as self-propelled versions of horse drawn vehicles. However, horse drawn vehicles had been designed for relatively slow speeds and their suspension was not well suited to the higher speeds permitted by the internal combustion engine.
In 1901 Mors The Mors automobile factory was an early French car manufacturer. It was one of the first to take part in automobile racing, beginning in 1897, due to the belief of the company founder, Émile Mors, in racing's technical and promotional benefits. By the turn of the century, automobile racing had become largely a contest between Mors and Panhard of Germany first fitted an automobile with shock absorbers A shock absorber is a mechanical device (one kind of dashpot) designed to smooth out or damp shock impulse, and dissipate kinetic energy. With the advantage of having a dampened suspension system in his 'Mors Machine', Henri Fournier was able to win the prestigegous Paris - Berlin race on June 20th 1901. Fourniers superior time was 11 hrs 46 min 10 sec, while the best competitor was Léonce Girardot in a Panhard at the time 12 hrs 15 min 40 sec[2].
In 1920 Leyland used torsion bars A torsion bar suspension, also known as a torsion spring suspension or incorrectly torsion beam, is a general term for any vehicle suspension that uses a torsion bar as its main weight bearing spring. One end of a long metal bar is attached firmly to the vehicle chassis; the opposite end terminates in a lever, mounted perpendicular to the bar, in a suspension system. In 1922 independent front suspension was pioneered on the Lancia Lambda The Lancia Lambda was an innovative automobile produced from 1922 through 1931. It was the first car to feature a load-bearing monocoque-type body, and it also pioneered the use of an independent suspension . Lancia even invented a shock absorber for the car. Approximately 11,200 Lambdas were produced and became more common in mass market cars from 1932.[3]
Important properties
Citroën BX The Citroën BX is a family car that was produced by the French manufacturer Citroën between 1982 and 1994. In total, 2,315,739 BXs were built during its 12-year history.[citation needed] The hatchback was discontinued in 1993 with the arrival of the Xantia, but the estate continued for another year Hydropneumatic suspension 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, notably Rolls-Royce, Mercedes-Benz and Peugeot. It was also used on Berliet trucks. Similar systems are also used on some military vehicles - maximum to minimum demonstrationSpring rate
Further information: Spring rate A spring is an elastic object used to store mechanical energy. Springs are usually made out of hardened steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication. Some non-ferrous metals are also used including phosphor bronze and titanium for parts requiring corrosionThe spring rate (or suspension rate) is a component in setting the vehicle's ride height or its location in the suspension stroke. 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 where the loading conditions experienced are more extreme.
Springs that are too hard or too soft cause the suspension to become ineffective because they fail to properly isolate the vehicle from the road. 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 Inertia is the resistance of any physical object to a change in its state of motion. It is represented numerically by an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by applied forces. Inertia comes from the Latin word, " of the load. 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 In mathematics, a ratio is a relationship between two numbers of the same kind , usually expressed as "a to b" or a:b, sometimes expressed arithmetically as a dimensionless quotient of the two, which explicitly indicates how many times the first number contains the second used to measure how resistant a spring is to being compressed or expanded during the spring's deflection. 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 extension of a spring is in direct proportion with the load added to it as long as this load does not exceed the elastic limit. Materials for which Hooke's law is a useful approximation are known as linear-elastic or "Hookean" materials. Hooke's. Briefly, this can be stated as
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,load the vehicle will carry, and to a lesser extent by suspension geometry and performance desires.
Spring rates typically have units of N The newton is the SI derived unit of force, named after Isaac Newton in recognition of his work on classical mechanics/mm The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length (or lbf The pound-force is a unit of force in systems of measurement including English Engineering units and British Gravitational units. It is equivalent to 4.44822162 newtons. In most contexts, the shorter name "pound" is used, but this can introduce confusion with the mass unit of the same name/in An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot. A corresponding unit of area is the square inch and a corresponding unit of volume is the cubic inch. The inch is usually the universal unit of measurement in). 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:
where d is the wire diameter, G is the spring's shear modulus The shear modulus is concerned with the deformation of a solid when it experiences a force parallel to one of its surfaces while its opposite face experiences an opposing force . In the case of an object that's shaped like a rectangular prism, it will deform into a parallelepiped. Anisotropic materials such as wood and paper exhibit differing (e.g., about 12,000,000 lbf/in² or 80 GPa Grades are standardized measurements of varying levels of comprehension within a subject area. Grades can be assigned in letters , as a range (for example 1.0 - 4.0), as descriptors (excellent, great, satisfactory, needs improvement), in percentages, or, as is common in some post-secondary institutions in some countries, as a Grade Point Average ( for steel), and N is the number of wraps and D is the diameter of the coil.
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 500 lbs/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 from what 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 just as a ratio of the vehicle's total roll rate. Roll Couple Percentage is critical in accurately balancing the handling of a vehicle. It is commonly adjusted through the use of anti-roll bars, but can also be changed through the use of different springs.
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. This is also commonly known as "Total Lateral Load Transfer Distribution" or "TLLTD".
Sat, 31 Jul 2010 14:39:27 GMT+00:00
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Q. In vehicle suspension design is it desirable to minimize the mass of all components. You have been asked to select a material and dimensions for a light-weight spring to replace the steel leaf-spring of an existing truck suspension. The existing leaf-spring is a beam, shown schematically in the Figure below. The new spring must have the same length L and stiffness S as the existing one, and must deflect through a maximum safe displacement max without failure. The width b and thickness t are not constrained. Derive a material index for the selection of a material for this application. Note that this is a problem with two free variables: b and t; and there are two constraints, one on safe deflection max and the other on stiffness S. Use… [cont.]
Asked by cap03h - Sat Oct 21 12:30:19 2006 - - 1 Answers - 0 Comments
A. chrome cobalt steel
Answered by imphilthe - Sat Oct 21 12:36:52 2006
