Introduction:Introduction:

NAME : SANDEEP BRANCH : M.E. ROLL NO. : 12321

TRAINING INFO:

TRAINEE AT: CHEVROLET BRANCH: HISAR DEPARTMENT: DENTING,

ASSEMBELING PAINTING WHEEL ALIGNMENT

The beginning of a journey called life!

M.D. –

Abhishek Gupta

Superviser:

Samunder Singh

Body Shop Manager:

Bhoop Singh

Foreman:

Sunil

Of Vibhushan Chevrolet Hisar

CHEVROLETCHEVROLET

CHEVROLET is a leading Automobile Industry in India.

It is the branch of GENERAL MOTORS, no. 1 international automobile company.

Chevrolet was racing car industry initialy established by a racer William Durant, a successful buggy manufacturer from Flint, Michigan, and Louis Chevrolet, a well known car racer.

CHEVROLETCHEVROLET

Its products are:-BEAT

-SPARK -CAPTIVA -CRUIZE -TAVERA

-AVEO

BRIEF OF MY TRAINING:

From 16th June, 2011 to 28th July

16th June to 25th June: - Denting 26th June to 13th July: - Assembling 14th July to 18th July: - Painting 19th July to 24th July: - Wheel alignment 24th July to 28th July: - Under Superviser

STUDY OF WHEEL BALANCING

Tire balance, also referred to as tire unbalance or imbalance, describes the distribution of mass within an automobile tire or the wheel to which it is attached. When the tire rotates, asymmetries of mass cause the wheel to wobble, which can cause ride disturbances, usually vertical and lateral vibrations. It can also result in a wobbling of the steering wheel. The ride disturbance, due to unbalance, usually increases with speed. Vehicle suspensions can become excited by tire unbalance forces when the speed of the wheel reaches a point that its rotating frequency equals the suspension’s resonant frequency.

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Tires are inspected in factories and repair shops by two methods: static balancers and dynamic balancers. Tires with high unbalance forces are downgraded or rejected. When tires are fitted to wheels at the point of sale, they are measured again, and correction weights are applied to counteract the combined effect of the tire and wheel unbalance. After sale, tires may be rebalanced if driver perceives excessive vibration

Static balance

Static balance can be measured by a static balancing machine where the tire is placed in its vertical axis on a non-rotating spindle tool. The spot on the tire with the greatest mass is acted upon by gravity to deflect the tooling downward. The amount of deflection indicates the magnitude of the unbalance. The angle of the deflection indicates the angular location of the unbalance. In tire manufacturing factories static balancers operate by use of sensors mounted to the spindle assembly.

. In tire retail shops static balancers are most usually non-rotating bubble balancers, where the magnitude and angle of the unbalance is observed by looking at the center bubble in an oil-filled glass sighting gauge. While some very small shops which lack specialized machines still do this process, they have been largely replaced in larger shops with machines.

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Dynamic balance describes the forces generated by asymmetric mass distribution when the tire is rotated, usually at a high speed. In the tire factory the tire is mounted on a balancing machine test wheel, the assembly is accelerated up to a speed of 300 RPM or higher, and sensors measure the forces of unbalance as the tire rotates. These forces are resolved into static and couple values for the inner and outer planes of the wheel, and compared to the unbalance tolerance (the maximum allowable manufacturing limits)

Dynamic balance:

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If the tire is not checked, it has the potential to wobble and perform poorly. In tire retail shops tire/wheel assemblies are checked on a spin-balancer, which determines the amount and angle of unbalance. Balance weights are then fitted to the outer and inner flanges of the wheel. Dynamic balance is better (it is more comprehensive) than static balance alone, because both couple and static forces are measured and corrected.

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The dynamic balance can only be conducted if the driver comes to garage and has the garage check for imbalances. With the increased use of electronics, the unbalance or imbalance condition might be estimated by electronics in real-time and independent of the driver's detection capability. Recently, a SAE paper did the exactly same: using sensors such as the ABS wheel speed sensors for a brake control module to detect an imbalanced tire or tires in real-time.

The physics of dynamic balance

Physics of tire imbalance

Mathematically, the moment of inertia of the wheel is a tensor. That is, to a first approximation (neglecting deformations due to its elasticity) the wheel and axle assembly are a rigid rotor to which the engine and brakes apply a torque vector aligned with the axle. If that torque vector is not aligned with the principal axis of the moment of inertia, the resultant angular acceleration will be in a different direction from the applied torque. Whenever a rotor is forced to rotate about an axis that is not a principal axis, an external torque is needed.

This is not a torque about the rotation axis (as in a driving or braking torque), but is a torque perpendicular to that direction. If the rotor is suspended by bearings, this torque is created by reaction forces in the bearings (acting perpendicular to the shaft). These reaction forces turn with the shaft as the rotor turns, at every point producing exactly the torque needed to keep the wheel rotating about the non-principal axis. These reaction forces can excite the structure to which they are attached. In the case of a car, the suspension elements can vibrate giving an uncomfortable feel to the car occupants.

In practical terms, the wheel will wobble. Automotive technicians reduce the wobble to an acceptable level when balancing the wheel by adding small weights to the inner and outer wheel rims. Balancing is not to be confused with wheel alignment.

Balancing machine

A balancing machine is a measuring tool used for balancing rotating machine parts such as rotors for electric motors, fans, turbines, disc brakes, disc drives, propellers and pumps. The machine usually consists of two rigid pedestals, with suspension and bearings on top supporting a mounting platform. The unit under test is bolted to the platform and is rotated either with a belt-, air-, or end-drive. As the part is rotated, the vibration in the suspension is detected with sensors and that information is used to determine the amount of unbalance in the part. Along with phase information, the machine can determine how much and where to add weights to balance the part.

 

Photo of wheel balancing machine

Result of wheel unbalancing

Specifications….

Rim Width 1.5 – 20 Inch Rim Diameter 10 – 30 Inch Max. Wheel Diameter 1067 mm Max. Wheel Width 530 mm Max. Wheel Weight 75 kg Power Supply 240 Volt Gross Weight 133 kg

Machine Features: 

• Easy Auto Select 2 function • Bright & Easy to read digital display • Auto sense sonar device for automatic detection of rim

data • Automatic Megastick for unlimited weight positions • Automatic start of the machine by closing the wheel

guard • Automatic stop into the right-hand correction position • Optimisation program to compensate the unbalance of

tyre and rim • Durable weight tray with ample storage for wheel

weights

PROCESS OF WHEEL BALANCING:-  Remove the wheel from the vehicle. Fix wheel on the wheel balancing machine with the help of

zinc cones, as shown in above figure. Switch on power supply, UPS and the wheel balancing

machine. Press start button and give little support initial rotation to

the wheel by hand. Now wheel will start rotating with a speed of 300 rpm

aprrox. Now press the brake pad of machine which near the base

of the machine.

Monitor will show the result of the unbalance weight and will show the required weight of either sides, as shown in figure above:

Now rotate the tire manually for adjusting the weight requiring positioning.

Now fix the required weights on inner and outer flanges. Wheel is balanced now.

Some pics of other jobs….

Thanks…..

for your attention