wheel & battery

8/2/2019 Wheel & Battery

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ME 423T AUTOMOBILE ENGINEERING


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Regular tyre maintenance and wheel alignment reduces fuel consumption andprevents undue tyre wear.

Worn shock absorbers and weak springs can also contribute to the waste of fuel.

Correctly aligned wheels extend tyre life and improve fuel efficiency They also help safe steering of the vehicle and comfortable ride

Wheel out of balance leads to hard steering, rough riding and rapid tire wear Static balance & Dynamic balance

WHEEL BALANCING


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STATIC BALANCE

A wheel that is statically out of balance is heavier in one section thanin another.

A statically balanced wheel may notbe dynamically balanced


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DYNAMIC BALANCE To check dynamic balance ,the wheel is spun and indicating device

in the wheel balancer indicates the place and appx. amount thedynamically out of balance.

Dynamic unbalance causes the wheels to wobble at or above aparticular speed.

No more than 8 ounces should be added to a rim


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WHEELS


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TYRES Function Interpose a cushion between the road and car wheels - shocks To carry load of the vehicle Provide frictional contact between wheels and road, so that good

traction is secured

Desirable tire properties Load carrying capacity

Must be of max. strength to take weight ,road shocks etc. Must be strong enough to resist local deformation

Cushioning Should be able to absorb high frequency vibration set up by the road surface

Wheel balance Must be properly balanced

Non skidding

Good thread pattern giving nice gripping Must be easily detachable with minimum effort Power consumption

Synthetic tyre consume more power than natural Should be easy to clean and of good external appearance


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TYPES OF TYRES Solid

Pneumatic

With inner tube

Tubeless


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CONVENTIONAL TYRE WITH TUBE

Consists of two main parts Carcass Basic structure taking mainly the various loads

Consists of number of plies wound in a particular fashionfrom the cords of rayon or any other materials

Vulcanizing Process of heating the rubber under pressure Number of layers of cord varies Passenger car 4, Truck -14

Tread - Part of the tyre which contacts the road surface Ribs provide traction edges required for gripping Grooves provide passage for the quick escape of any

foreign matters

A valve stem For inflating or deflating the tube


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TUBE Tube flexible

Amount of air pressure depends on the type of tire and operation Passenger cars : 22 30 psi Trucks & buses : 100 psi

Importance of maintaining tyre pressure Under inflation severe flexing of tire plies, side walls, excessive heat,

premature failure Over inflation overloads the components of the tyre, causes excessive

tread wear and hard riding


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TUBELESS TYRE No separate tube Advantages

Lesser unsprung weight Better cooling Slower leakage of air Simpler assembly Improved safety


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Puncture sealing tire/tubes - Coating of plastic material,hardens to seal

the hole,Tube : Material : butyl


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CARCASS TYPE

Cross ply or bias ply Ply cords are woven at an angle (30 40) to the tyre axis Two layers run in opposite direction

Radial ply Ply cords run in radial direction Number of break strips in circumferential direction to provide lateral

stability

Belted bias ply Combination of above two types


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COMPARISON OF RADIAL AND BIAS PLY TIRES

The side walls of radial ply tyres can bend readily. Shock absorbing deflection is about 25 % more than the cross ply tyres

Lower rolling resistance lower sidewall rigidity- lower fuel consm.

Longer tread life

While taking turns, a radial tyre has less tendency to lift off from theroad


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More road contact for radial tyres Breaker strips

Heavier steering at low speeds Due to the highly flexible sidewalls ,their bulge appears due to which

tyre seems to be under inflated


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TYRE SECTION

Aspect ratio = Tyre section height/ Tyre section width

Lower aspect ratio

Advantages better load carrying capacity Less wear better performance at high speed


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TYRE DESIGNATIONS

Tire Size : 8 x 15 (m xn)n : Diameter of the rim, m : m inches larger in radius than rim

Width, speed rating,diameter (SR upto 170kmph, HR upto 210 kmph, VR above 210 kmph), 145 SR -13

Width, rim diameter, ply rating 9.00 20 -12

Load/size relationship, tyre construction, aspect ratio, Rim size ininches FR 78 -15


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AUTOMOBILE ELECTRICAL SYSTEM

Lighting system Ignition system Starting system Generator


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BATTERY Heart of the electrical system Lead acid type , consisting of 3 or 6 cells, 12V

Positives plates consists of grid filled with paste of lead peroxide

Negative plates consists of grid filled with paste of lead

Grid made of an allot of lead and antimony

Post strap to hold plates

Plates are separated by separators

Porous rubber, perforated cellulose

Electrolyte

Sulfuric acid

Battery case Moulded from ebonite

Or bituminous


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CHEMICAL REACTIONS

H2SO 4 = H 2 (pos) + SO 4 (neg.)H2 +PbO 2 = H2O +PbO (Pos)PbO +SO4 + PbSO4 (Pos)

Pb +SO4 + PbSO4 (Neg.)

Charged DischargedLead Sulfuric Spongy Lead Water Lead EnergyPeroxide acid lead Sulfate SulfatePbO2 + 2H2SO4 + Pb = PbSO4 + 2H2O + PbSO4 + QPos Electrolyte Neg. Pos. Water Neg .


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BATTERY CAPACITY Maximum current that a cell can furnish is dependent on the area of plate

surface in contact Standard Capacity rating

20 hour rating in ampere hours (quantity of energy furnished by acurrent of 1 amp for 1 hour)

Indicates the lighting ability of the battery Discharging the battery at a current rate equal to 1/20 of the

manufacturer's ampere hour rating 6 V, 120 amp hour 6 amp for 20 hrs before its terminal voltage

drops to 5.25 V 12 amp 10hrs 3 amp 40hrs


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Measure of ability of the battery to furnish electrical energy to thestarting motor at low temperatures (Cold rating at F) Indication of the cold weather starting ability of the battery By the number of minutes required for a battery to drop to a

terminal voltage of 1 V per cell when continuously discharged ata rate of 150 amp(12 V)

The terminal voltage 5 seconds after the beginning of such a thedischarge


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Hydrometer To measure the sp.gravity of the electrolyte

Reading Condition1.260 1.280 Full charge1.230 1.250 charge1.20 1.220 charge

1.170- 1.190 Very little life1.110 1.130 Completely discharged


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BATTERY LIFE

Depends on the material Way of use

Overcharging Faulty regulator/generator dry water Under charging Sulfated Sulfate crystals causes plates to

buckle and break Mechanical breakage Excessive loads Starting motor Addition of distilled water


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BATTERY CHARGING

Charging methods Slow charge method Small current for long time Quick charge method Large current for short time

Rate of current varies with the time of charging

Dynamo speed also varies Dynamo out put must be regulated by automatic means, so that

voltage is maintained at the value required by the battery condition Voltage regulator

Connection of dynamo with battery (during starting) Cut out or Reverse- current relay

Automatic control in charging system is essential


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CHARGING CIRCUIT

Responsible to keep the battery charged for regular supply ofelectric current to various electrical systems. DC Generator

Battery Ampere-meter Cut out/Voltage/Current Regulator

Necessity of regulators


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DC GENERATORS


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REGULATORS


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CUT OUT (REVERSE CURRENT DELAY)

Cut out unit consists two coils Fine wire voltage or shunt coil Thick wire current or series coil

The value of the dynamo voltage at which the cut out contact closeis usually between 12.7 to 13.3 V


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VOLTAGE REGULATOR

Causes generator to provide a charging rate in reverse ratio to the state of charge ofbattery

Variable resistance increases or decreases the effective resistance in generator field Battery (full charge) & No electrical load resistance remains in the generator field Battery (Partial charge) & with load resistance is kept only for a small portion of time


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CURRENT/VOLTAGE REGULATOR


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When the load requirement is high and the battery is low, the currentregulator operates to prevent the generator output from exceedingthe safe maximum

When load requirement is reduced and the battery come up tocharge, Voltage regulator operates

Current and voltage regulator will not operates simultaneously.


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