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suspensionsystem-hcghfgh170916121455 (1).ppt
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- 2. Suspension Introduction • Suspensionis the term given to the system of springs, dampers (shock absorbers) and linkages that connects a vehicle to its wheels. • Suspension systems serve a dual purpose – contributing to the car's handling and braking for good active safety and keeping vehicle occupants ‘comfortable’ and reasonably well isolated from road noise, bumps, and vibrations . • These goals are generally at odds, so the tuning of the suspension involves finding the right compromise. The suspension also protects the vehicle itself from damage and wear. • The design of front and rear suspension of a car may be different from one another.
- 3. Suspension System • Soa suspension linkage system of some sort is needed to enable the wheel to move up & down vertically.
- 4. Two Perspectives • RIDE– Also known as Isolation • Ability to smooth out a bumpy road • HANDLING – Also know as control • Ability to safely accelerate, corner & brake
- 5. The purpose ofthe suspension is to provide the vehicle with the following: 1. A smooth ride 2. Accurate steering 3. Responsive handling 4. Support the weight of a vehicle 5. Maintain acceptable tire wear Purpose
- 6. Desirable Characteristics • Minimizeresponse to external disturbances. • Ensure satisfactory control response characteristics. • Ensure no major or uncontrollable instabilities. • Provide satisfactory information flow to the driver. • Remain consistent in behaviour with changing environmental factors such as rough surface, change in surface coefficient etc.
- 7. Main Types Dependent –when a solid axel is used - movement at one wheel will in some way affect the opposite wheel – older cars and commercial vehicles. Advantages - simple construction and almost eliminates camber change reducing tyre wear Independent – Each wheel is free to react to whatever change in surface without directly affecting the others – most modern cars. Advantages - Better ride & handling
- 8. Suspension Change Effects Suspensiontravel results in changes in wheel orientation which can cause steer effects, other than those input by the driver. • Scrub • Camber • Castor • Aligning torque • (anti-dive geometry can promote castor change) • Vertical travel of the unsprung mass - bump steer • Roll of the sprung mass - roll steer • Drive torque • Flexibility of the suspension mechanism can cause compliance steer
- 9. Sprung and UnsprungMasses • Sprung Mass – All that part of the vehicle which is carried by the components of the suspension. • Unsprung Mass - The parts of the vehicle that move directly according to the contours of the road.
- 10. Unsprung Weight • Asuspension system has to be designed to allow the wheels to move up and down quickly over bumps and dips without affecting the entire weight of the car or truck. • This weight is called unsprung weight. • For best handling and ride, the unsprung weight should be kept as low as possible. • Sprung weight is the term used to identify the weight of the car or truck, which does not move up and down and is supported or sprung by the suspension.
- 11. Overall Function • Unevennature of road surface causes vertical acceleration of unsprung mass. • Suspension allows the sprung mass to ride relatively undisturbed while the unsprung mass follows the contours of the road. • I.E. Suspension system separates the energy of the vertical acceleration of the wheels from the body
- 12. Suspension Terms Heave –normally when both wheels are moving up in relation to the chassis Bump – one or more wheels moving upwards in relation to the chassis Rebound – when the wheel is moving down in relation to the chassis Roll – The movement of the chassis in relation to the wheels
- 13. • Early suspensionsystems on old horse wagons, buggies, and older vehicles used a solid axle for front and rear wheels. Types of Suspensions
- 15. Independent Suspension • Mostvehicles today use a separate control arm-type of suspension for each front wheel which allows for movement of one front wheel without affecting the other front wheel. • This type of suspension is called independent front suspension.
- 16. Springs • A suspensionspring serves two purposes. • First, it acts as a buffer between the suspension and frame to absorb vertical wheel and suspension movement without passing it on to the frame. • Second, each spring transfers part of the vehicle weight to the suspension component it rests on, which transfers it to the wheels.
- 17. Spring Materials Most springsare made of a tempered steel alloy known as spring steel, usually chrome silicon or chrome-vanadium alloy.
- 18. COIL SPRINGS Coil springsare made of special round spring steel wrapped in a helix shape. The strength and handling characteristics of a coil spring depend on the following. 1. Coil diameter 2. Number of coils 3. Height of spring 4. Diameter of the steel coil that forms the spring
- 20. • The largerthe diameter of the steel, the “stiffer” the spring. • The shorter the height of the spring, the stiffer the spring. • The fewer the coils, the stiffer the spring. Continued…
- 21. • Springs aredesigned to provide desired ride and handling and come in a variety of spring ends.
- 22. Spring Rate • Springrate, also called deflection rate, is a value that reflects how much weight it takes to compress a spring a certain amount. • A constant-rate spring continues to compress at the same rate throughout its complete range of deflection.
- 24. • A variable-ratespring may compress one inch under a 100- pound load, but only compress an additional half an inch under a 200-pound load.
- 25. • Before aspring is installed on a vehicle or any load is placed on it, it is at its uncompressed length, or free length. • Once installed, the weight of the corner of the vehicle resting on the spring is called its static load.
- 26. Coil Spring Mounting •Coil springs are usually installed in a spring pocket or spring seat. • Hard rubber or plastic cushions or insulators are usually mounted between the coil spring and the spring seat.
- 27. Spring Coatings • Allsprings are painted or coated with epoxy to help prevent breakage. • A scratch, nick or pit caused by corrosion can cause a stress riser that can lead to spring failure.
- 28. Instead of cuttingsprings to lower a vehicle, there are several methods available that are preferred if the vehicle must be lowered: 1. replacement springs 2. replacement spindles
- 29. Leaf Springs • Leafsprings are constructed of one or more strips of long, narrow spring steel. • These metal strips, called leaves, are assembled with plastic or synthetic rubber insulators between the leaves, allowing freedom of movement during spring operation.
- 30. • The endsof the spring are rolled or looped to form eyes. Rubber bushings are installed in the eyes of the spring and act as noise and vibration insulators.
- 31. The leaves areheld together by a center bolt, also called a centering pin.
- 32. • One endof a leaf spring is mounted to a hanger with a bolt and rubber bushings directly attached to the frame. • The other end of the leaf spring is attached to the frame with movable mounting hangers called shackles.
- 33. Rebound or springalignment clips help prevent the leaves from separating whenever the leaf spring is rebounding from hitting a bump or rise in the roadway.
- 34. • Single leafsteel springs, called mono leaf, are used on some vehicles. • A single or mono leaf spring is usually tapered to produce a variable spring rate.
- 35. To provide additionalload-carrying capacity, especially on trucks and vans, auxiliary or helper leaves are commonly used.
- 36. Composite Leaf Springs •Fiberglass-reinforced epoxy plastic leaf springs have been used on production vehicles. • Using 70% fiberglass with 30% epoxy composite. • Leaf spring rate increases when the thickness increases, and decreases as the length increases.
- 38. A torsion baris a spring which is a long, round, hardened steel bar similar to a coil spring except for a straight bar. Torsion Bars
- 39. • One endis attached to the lower control arm of a front suspension and the other end to the frame. • When the wheels hit a bump, the bar twists and then untwists.
- 41. Suspension Principles 1. Transverse(or side-to-side) wheel support. Transverse links are also called lateral links.
- 42. 2. Longitudinal (front-to-back)wheel support. Some suspension designs use an additional member to control forward-back movement
- 43. Steering Knuckles A steeringknuckle is hard to classify either as part of the suspension or as part of the wheel. A knuckle serves two purposes: To join the suspension to the wheel To provide pivot points between the suspension and wheel
- 44. The only knucklethat uses a kingpin is a steering knuckle on an I-beam or twin I-beam front suspension. The steering axis is the vertical center of the kingpin.
- 45. A control armis a suspension link that connects a knuckle or wheel flange to the frame. Control Arms
- 46. Ball joints areactually ball-and-socket joints, similar to the joints in a person's shoulder. Ball joints allow the front wheels to move up and down, as well as side to side (for steering). Ball Joints
- 47. • If thecoil spring is attached to the top of the upper control arm, then the upper ball joint is carrying the weight of the vehicle and is called the load-carrying ball joint. • The lower ball joint is called the non load carrying or follower ball joint.
- 48. If the coilspring is attached to the lower control arm, then the lower ball joint is the load-carrying ball joint and the upper joint is the follower ball joint.
- 49. Ball Joint Design Thereare two basic designs of ball joints: 1. Compression Loaded 2. Tension Loaded. A ball joint that does not support the weight of the vehicle and acts as a suspension pivot is often called a follower ball joint or a friction ball joint.
- 51. Some vehicles areequipped with round steel rods which are attached between the lower control arm at one end and the frame of the vehicle with rubber bushings, called strut rod bushings, at the other end. Strut Rods
- 52. Continued… • Strut rodsare also called tension or compression rods or simply TC rods. • Some vehicle manufacturers call the strut rod a drag rod because it was attached in front of the wheels, and therefore acted on the lower control arm as if to drag the wheels behind their attachment points.
- 53. • If astrut rod has a nut on both sides of the bushings, then the strut rod is used to adjust caster.
- 54. Stabilizer Bars • Mostcars and trucks are equipped with a stabilizer bar on the front suspension, which is a round, hardened steel bar (usually SAE 4560 or 4340 steel) attached to both lower control arms with bolts and rubber bushing washers called stabilizer bar bushings.
- 55. • A stabilizerbar is also called an anti-sway bar (sway bar) or anti-roll bar (roll bar). • A stabilizer bar operates by twisting the bar if one side of the vehicle moves up or down in relation to the other side, such as during cornering, hitting bumps, or driving over uneven road surfaces.
- 56. Stabilizer links connectthe ends of the stabilizer bar to the lower control arm.
- 57. • The Stablizerbar pulls down on the mounting bushing when the vehicle is hoisted off the ground, allowing the front suspension to drop down. • These bushings are a common source of noise, especially when cold. • Lubricating the bushings with paste silicone grease often cures the noise
- 58. Shock Absorbers • Shockabsorbers are used on all conventional suspension systems to dampen and control the motion of the vehicle's springs. • Without shock absorbers (dampers), the vehicle would continue to bounce after hitting bumps. • The major purpose of any shock or strut is to control ride and handling. • Standard shock absorbers do not support the weight of a vehicle. • The springs support the weight of the vehicle; the shock absorbers control the actions and reactions of the springs. • Shock absorbers are also called dampers.
- 61. • Some vehiclessuch as Ford Mustang use four shock absorbers on the rear suspension. The vertical shock absorbers control vertical body movement with the rear coil springs. • The longitudinal shocks help control rear axle during acceleration and deceleration.
- 62. • As awheel rolls over a bump, the wheel moves toward the body and compresses the spring(s) of the vehicle. • As the spring compresses, it stores energy. • The spring then releases this stored energy, causing the body of the vehicle to rise (rebound).
- 63. The hydraulic shockabsorber operates on the principle of fluid being forced through a small opening (orifice). Shock Absorber Operation
- 65. Gas-Charged Shocks • Mostshock absorbers on new vehicles are gas charged. • Pressurizing the oil inside the shock absorber helps smooth the ride over rough roads. • This pressure helps prevent air pockets from forming in the shock absorber oil as it passes through the small passages in the shock.
- 66. • Some gas-chargedshock absorbers use a single tube that contains two pistons that separate the high- pressure gas from the working fluid. • Single tube shocks are also called monotube or DeCarbon after the French inventor of the principle and manufacturer of suspension components.
- 67. Remote reservoir shockabsorbers are units designed for heavy-duty use that use a separate container for the working fluid. Remote Reservoir Shocks
- 68. Air Shocks/Struts • Air-inflatableshocks are standard shock absorbers with an air chamber with a rubber bag built into the dust cover (top) of the shock. • Air-inflatable shock absorbers or struts are used in the rear of vehicles to provide proper vehicle ride height while carrying heavy loads. • A rubber tube forms an inflatable air chamber at the top of an air shock • The higher the air pressure in the chamber, the stiffer the shock
- 70. Air Springs • Someelectronically controlled suspension systems use air springs. • A basic air spring consists of a rubber air chamber, generally closed at the bottom by a piston fitted into a control arm, or by a strut shock absorber.
- 71. Continued… • Some airsprings are in effect auxiliary springs inside a coil- spring strut. • In these designs, the coil spring supports the weight of the vehicle, while the air spring raises or lowers the body to adjust ride height according to load.
- 72. A coil-over shockabsorber uses the force of an external coil spring to boost the performance of the basic shock absorber.
- 73. Hydraulic Shock Absrober •A coil-over shock absorber uses the force of an external coil spring to boost the performance of the basic shock absorber. • A coil-cover shock is a standard hydraulic shock absorber with a coil wrapped around it to increase stiffness and to take some of the carrying weight off the spring.
- 74. Struts • A strutis a sturdy shock absorber that is also a structural component of the suspension. • A strut is a suspension link as well as a shock absorber.
- 75. MacPherson Struts • TheMacPherson strut, which is named after Earle S. MacPherson, who developed the suspension design in the late 1940s and patented it in 1953, is the most commonly used type.
- 76. Modified Struts • Unlikea MacPherson unit, a modified strut does not include a spring as part of the assembly and is used in the front on some vehicles and on the rear of others.
- 77. Bump Stops • Allsuspension systems have a limit of travel. • If the vehicle hits a large bump in the road, the wheels are forced upward toward the vehicle with tremendous force. • Instead of allowing the metal components of the suspension to hit the frame or body of the vehicle, a rubber or foam bumper is used to absorb and isolate the suspension from the frame or body. • These bumpers are called bump stops, suspension bumpers, strike-out bumpers, or jounce bumpers. Jounce means jolt.
- 78. • Suspension bumpersare used on all suspension systems to prevent metal-to-metal contact between the suspension and the frame or body of the vehicle when the suspension “bottoms out” over large bumps or dips in the road.