Automobile Engineering

Automobile EngineeringMac Pherson StrutWheelsTyresPrepared by,Nirmal Gowtham RJ (111111058)Nitesh Kumar (111111059)Nitin Varman (111111060)P.Arun Pandian (111111061)P.Kiran Prasad (111111063)P.Praveen (111111064)Mac Pherson StrutIndependent type of car Suspension system commonly used in many modern motor vehicles. This includes both front and rear suspensions, but usually located at the front of the car. It provides a steering pivot (known as a kingpin) as well as a suspension mountings for the wheel.

Kinematic ModelThe steering gear is either connected directly to the lower shock absorber housing, or to an arm from the front or back of the spindle. It physically twists the strut and shock absorber housing to turn the wheel. The spring is seated in a special plate at the top of the assembly which allows this twisting to take place. If the spring or this plate are worn, you'll get a loud 'clonk' on full lock as the spring frees up and jumps into place.

Monocoque with MacphersonIn 1957 Colin Chapman of Lotus applied the design to the rear suspension of the Lotus Elite. MacPherson strut suspension at the rear of an automobile are now commonly called Chapman struts.To be really successful, the MacPherson strut required the introduction of monocoque construction. This is because it needs a substantial vertical space and a strong top mount, which monocoque can provide and also by distributing stresses greatly increases the set up's results in the handling stakes.

Maintenance of MacPhersonThe McPherson strut also has a steering arm built into the lower inner portion. This assembly is simple and can be pre manufactured into a unit at the assembly line. By removing the upper control arm, it allows for more width in the engine bay, aiding in any maintenance work or engine design requirements.

Cost effectiveness with anti roll bars

This is useful for smaller cars, particularly with transverse-mounted engines such as FF drive designed vehicles. Further simplification is possible by substituting an anti-roll bar (torsion bar) for the radius arm.It offers an easy method to set suspension geometry. Ultimately making the production overheads more cost effective and making this a very common design set up in today's marketplace.

Disadvantages comparing to double wishboneThe quality of ride it produces and the handling of the car may suffer or be less effective then other set ups with more Suspension geometry adjustmentsGeometric analysis has shown that MacPherson Strut design can not allow vertical movement of the wheel without some degree of either camber angle change, sideways movement (or both). Double wishbone suspension is favoured for Motorsport applications, due to the above fact.

DisadvantagesWith the MacPherson Strut set up, the wheel tends to lean with the body, leading to understeer under extreme cornering. In a FF designed car, adding to the already natural tendency for understeer is far from ideal. The ideal situation would be neutral handling, so this might benefit other drive-chain set ups.Another disadvantage of the design is that it tends to transmit noise and vibration from the road directly into the body shell of the car. This results in higher road noise levels and sometimes a harsh feeling to the handling compared to a double wishbones set up. This results in manufacturer's adding extra noise insulation in a bid to reduce the negative effects, which can lead to some weight gains as expected.

Conclusion-MacPherson StrutThus depending on the application MacPherson type of suspension is used. Wherever more space is required for service and maintenance mac pherson shall be used.

Wheels and Tyres

TerminologySteel Wheels A very popular design of wheel. Very strong and cheap to produce.Alloy Wheels Attractive and light weight, but can be difficult to clean.Spooked Wheels Used on older sports vehicles, but cannot be fitted with tubeless tyres.Divided rims the rims are made in two halves which are bolted together, the rims must never be separated while the tyre is inflated.Split rims the tyre is held in place by a large circlip, do not remove the tyre unless you have been properly trained

TerminologyRadial Ply Tyre The main plies of the tyre run at 90 degrees from one bead to the other.Cross Ply Tyre The main plies of the tyre run at 45 degrees from one bead to the other.Plies Layers of strong fabric which are built up to give the tyre its strength and shapeBead Loops of steel which are the anchorage point for the plies.Tread This provides the grip with the road surface, the pattern assists in clearing any water away Side Wall This connects the beads to the tread of the tyreWheelsWheels have two partsCenter (i.e., flange) and rimDrop center (i.e., rim well) Facilitates removal and installation of tireSafety beads Keep the tire bead on bead seatMethods to center wheels on hubHub-centric: center of wheel has machined counterbore that pilots on machined area of hubStud-centric: wheels locate on wheel studs

Custom WheelsSeveral typesAluminum wheels: cast, forged, or rolledRace cars: use alloy wheelsCustom wheels for street use: single piece castings of light alloy aluminumWheel offsetDifference between rim centerline and mounting surface of the wheelNegative offset: increases track width of tiresPositive offset: found on front-wheel-drive cars

Wheel - Basics

Centre mounting sectionRimMost standard wheels are made of steel.Some vehicles are fitted with alloy wheels that are made of magnesium or aluminium.The rim holds the tyre.The well of the wheel allows thetyre to be removed and refitted The centre section is welded to the rim.The pilot bore fits to the hub.Wheel FixingWheel studs and nuts attach the wheel to the hubThe wheel studs press through the hub or axle flange.The taper on the wheel nuts secures and centres the wheel.Wheel studs usually have a right-hand thread.If it is a left-hand thread, it can be marked with L.Metric threads can be marked with M or METRIC

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Wheel SizesTyresBasic FunctionsThe tyre acts as the primary suspension, cushioning the vehicle from the effects of a rough surface.It also provides frictional contact with the road surface. This allows the driving wheels to move the vehicle.The front tyres allows the wheels to steer .The tyres allow the brakes to slow or stop the vehicle

Pneumatic TyresThe tyre is a flexible casing, which contains air.Tyres are manufactured from reinforced synthetic rubber.The tyre is made from an inner layer of fabric plies, which are wrapped around bead wires at the inner edges.The bead wires hold the tyre in position on the wheel rim.The fabric plies are coated with rubber, which is moulded to form the side walls and tread of the tyre. Behind the tread is a reinforcing band, usually made of steel,rayon,or glass fibre. Modern tyres are mostly tubeless, so they have a thin layer of rubber coating inside to act as a seal.

Tyre ConstructionCross ply tyres are not used on any mass produced modern cars. However, the construction details are useful to show how tyre technology has developed.Several textile plies are laid across each other, running from bead to bead in alternate directions.The number of plies depends on the size of the tyre and the load it has to carry.The same number of plies is used on the crown and the sidewalls.

Tyre ConstructionRadial Ply tyres consist of a carcass ply formed by textile arcs running from one bead to the other.Each ply which is laid in an arc at an angle of 90 degrees to the direction the tyre rolls.At the top of the tyre crown (under the tread), there is a belt made up of several plies reinforced with metal wire, laid on top of the carcass ply.These crown plies, laid one on top of the other, overlap at an angle determined by the type of the tyre.

Tubeless TiresInner liner bonded to tireSeals air into tireThicker than liner on tube-type tireSafer than tube-typeDoes not go flat immediately when punctured

Load RatingHow much weight a tire can safely support at a specified air pressureAmount of load: determined by area of tire and air pressure Gross weight rating (GVW or GVWR) includes weight of vehicle, passengers, and luggageCurb weight: weight of vehicle without passengers or luggageDOT symbol signifies the tire meets DOT safety standards

Tyre Specifications P 205/55 V R 16TYPEP - PASSENGERT - TEMPORARYLT - LIGHT TRUCKC - COMMERCIALWIDTH(MILLIMETERS)145-315ASPECT RATIO(HEIGHT/WIDTH %)55, 60, 65 70 ETCTYPEB - BIAS-BELTEDD - DIAGONAL BIAS R - RADIALRIM DIAMETER(INCHES) 13, 14 ETCP 205/55 V R 16P 205/55 V R 16P 205/55 V R 16P 205/55 V R 16P 205/55 V R 16P 205/55 V R 16P 205/55 V R 16SPEED RATINGB (31 MPH) - V (150 MPH) -Z (OVER 150 MPH)

Special Service TyreThis is a space-saver spare tyre.Used to replace flat tyre.It is not used for rotation (swapping).It uses a special wheel.Speed and pressure restrictions apply.It has no hub caps or wheel covers.

Bibliographywww.carbible.comwww.wikipedia.comwww.autoworks.com