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TYPES OF CHASSIS FRAMES: There are three types of frames

1. Conventional frame

2. Integral frame

3. Semi-integral frame

1. Conventional frame:

It has two long side members and 5 to 6 cross members joined together with the help

of rivets and bolts. The frame sections are used generally.

a. Channel Section – Good resistance to bending

b. Tabular Section – Good resistance to Torsion

c. Box Section – Good resistance to both bending and Torsion

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2. Integral Frame:

This frame is used now a day in most of the cars. There is no frame and all the assembly

units are attached to the body. All the functions of the frame carried out by the body

itself. Due to elimination of long frame it is cheaper and due to less weight most

economical also. Only disadvantage is repairing is difficult.

3. Semi – Integral Frame:

In some vehicles half frame is fixed in the front end on which engine gear box and front

suspension is mounted. It has the advantage when the vehicle is met with accident the

front frame can be taken easily to replace the damaged chassis frame. This type of frame

is used in some of the European and American cars.

Three types of steel sections are most commonly used for making frames:

(a) Channel section,

(b) Tubular section, and

(c) Box section

VARIOUS TYPES OF FRAME

Ladder Frame

So named for its resemblance to a ladder, the ladder frame is the simplest and oldest of

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all designs. It consists merely of two symmetrical rails, or beams, and cross member

connecting them. Originally seen on almost all vehicles, the ladder frame was gradually

phased out on cars around the 1940s in favor of perimeter frames and is now seen

mainly on trucks.

This design offers good beam resistance because of its continuous rails from front to

rear, but poor resistance to torsion or warping if simple, perpendicular cross members

are used. Also, the vehicle's overall height will be higher due to the floor pan sitting

above the frame instead of inside it.

Backbone tube

Backbone chassis is a type of an automobile construction chassis that is similar to the

body-on-frame design. Instead of a two-dimensional ladder type structure, it consists of

a strong tubular backbone (usually rectangular in cross section) that connects the front

and rear suspension attachment areas. A body is then placed on this structure.

Perimeter Frame

Similar to a ladder frame, but the middle sections of the frame rails sit outboard of the

front and rear rails just behind the rocker panels/sill panels. This was done to allow for a

lower floor pan, and therefore lower overall vehicle in passenger cars. This was the

prevalent design for cars in the United States, but not in the rest of the world, until the

uni-body gained popularity and is still used on US full frame cars. It allowed for annual

model changes introduced in the 1950s to increase sales, but without costly structural

changes.

In addition to a lowered roof, the perimeter frame allows for more comfortable lower

seating positions and offers better safety in the event of a side impact. However, the

reason this design isn't used on all vehicles is that it lacks stiffness, because the

transition areas from front to center and center to rear reduce beam and torsional

resistance, hence the use of torque boxes, and soft suspension settings.

Superleggera

An Italian term (meaning "super-light") for sports-car construction using a

threedimensional frame that consists of a cage of narrow tubes that, besides being

under the body, run up the fenders and over the radiator, cowl, and roof, and under the

rear window; it resembles a geodesic structure. The body, which is not stress-bearing, is

attached to the outside of the frame and is often made of aluminum.

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Unibody

By far the most common design in use today sometimes referred to as a sort of frame.

But the distinction still serves a purpose: if a unibody is damaged in an accident, getting

bent or warped, in effect its frame is too, and the vehicle undrivable. If the body of a

body-on-frame vehicle is similarly damaged, it might be torn in places from the frame,

which may still be straight, in which case the vehicle is simpler and cheaper to repair.

Sub frame

The sub frame, or stub frame, is a boxed frame section that attaches to a unibody. Seen

primarily on the front end of cars, it's also sometimes used in the rear. Both the front

and rear are used to attach the suspension to the vehicle and either may contain the

engine and transmission.

The most prolific example is the 1967-1981 Chevrolet Camaro.

Calculation of stresses on section

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BENDING MOMENT

Frame Material A car’s frame is the strong skeleton upon which the car is constructed. The frame should

be constructed out of material that is sturdy and dependable. The automobile frame is

the base of the car. It must be strong and stable. There are a few such materials that a

car’s frame can be constructed of. An automobile can be made out of more than one

material. Most vehicles currently use steel. Some vehicles may use aluminum,

magnesium, or a combination of materials. The main composites utilized in the

construction of vehicle chassis are titanium alloys,

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aluminum alloys and steel alloys. Each metal has diverse properties and multiple

applications. The cost of each composite greatly varies.

The vehicle’s chassis has to be rigid so that it can stand up to any force that is affects it.

This is important for the suspension. On the chance that the chassis bends a little, the

vehicle is not going to act as it would have. The suspension will be modified. The chassis

cannot be totally rigid as it will become easily broken and thus become unusable. It

must be neither too rigid nor too flexible.

Types of Frames

This chassis can be one of several different models of chassis. The first model that was

designed is the ladder frame. This particular frame is one that is usually made from

metal and is similar to the form of a ladder. It is inexpensive to build and can handle

heavy loads. It was utilized in older model cars, sport utility vehicles, trucks and buses.

The chassis can also take the shape of a space frame. This model is designed utilizing a

number of small tubes to make a chassis that is three-dimensional. The tubes are placed

to manage the stress that is put on the frame. These models are extremely precise and

rigid. They are designed from different materials and usually exceptionally expensive.

These types of frames are used for competition vehicles and sporty road vehicles.

The frame can be designed as a one-piece structure. This is called monocoque. Large

metal sheets are stamped with a large stamping device. The parts are fused together to

form the chassis of the vehicle. The fusing method is automated. This makes this

particular frame quick to create. It has a low tolerance. This design accounts for most of

the vehicles currently made. It is made usually made of steel. The chassis is made to

withstand almost any impact. Aluminum is sometimes used in the body of this type of

chassis to reduce the weight. It is inexpensive and offers collision protection. It is also

not as rigid as some other frames because it does not use tubes in the construction of

the frame.

The last type of frame can be called a mixture of the space frame and monocoque. The

construction begins as a monocoque chassis and is completed with a space frame build.

It is easy and inexpensive to make. It has the best of both frames.

TESTING OF FRAMES The frame as core component of a commercial vehicle has to withstand without any

serious damage the load and stress of a complete vehicle lifetime and needs therefore

thoroughly testing with representative load data, derived of real case use. Also other

chassis parts like axles, suspension, steering or add on parts have to be validated with

dynamic loads and proof their durability prior to vehicle testing and final release. Engine

and drivetrain components are additionally tested on our drivetrain test benches.

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Most fatigue tests are performed as realistic multi-channel tests under consideration of

all acting torques and forces with up to 22 actuators. Finally we have in addition our

own proving ground, where we perform functional and durability tests with the

complete vehicle.

With our expertise to measure and establish load data, we are able to establish

representative test procedures, which reflect a vehicle lifetime of 1 million km in 150 to

500h test duration.

Wheels and tyres

Vehicle wheels have developed from wooden spoked wheels via cast wheels to the

sheet metal disc wheel of today. This is the most commonly used wheel in motor vehicle

engineering at the present time. The wheel must be able to resist and transmit all forces

which act between the road and the vehicle.

The following essential demands are made on the vehicle:

− Adequate rim stability

− Firm fit of the tyre on the rim

− Firm and secure connection with the wheel hub

− Good dissipation of frictional heat

− Adequate space for accommodating the brake system

The following travelling comfort is demanded:

− Vertical and lateral impact must be as small as possible

− Unbalance at circumference must be kept low

− Attractive design

− Simple fitting of tyres to the rim and of wheel to the hub

Production should be based on the following:

− Low production price

− Long service life

− Low weight of the rim and small mass moment of inertia

Types of wheel

Wheels can be distinguished by the materials used for production and the design. Five

of the most common types are listed below:

− Wire−spoked wheels

− Sheet metal wheels, double wall welded

− Disc wheels

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− cast light metal wheels

− cast steel wheels

With regard to the rim base two types are distinguished:

− Wide base rim

− Well−base rim

The wide base rim is in sections to allow easy fitting and removal of the tyre. It can

either be halved along its circumference, or divided by a detachable wheel ring with

locking spring. If it is to be divided along the circumference the two rim halves are

connected and held together by bolts. Tapered bead seat rims are similar to wide base

rims. They are used for heavy Lorries. Pitting the larger and stiffer tyres used for these

vehicles makes the devision of the rim necessary, and so the rims are divided into two or

three sections.

There are different ways of dividing them. The centrally divided simples wheel and the

triplex wheel are used. This triplex wheel is divided three times along its circumference,

but each ring is a closed section.

The tapered bead seat rim has virtually replaced the wide base rim in motor vehicle

engineering. Its advantage in comparison to the wide base is that the bead seat inclines

5° to the rim flange. The bead of the tyre is pressed onto the tapered bead seat rim by

the tyre pressure. In this way the tapered bead seat rim and the flange prevent the bead

from tipping. Fig shows a tyre fitted to a tapered bead seat rim.

For vehicles up to about 5 tonnes pay weight disc wheels are mainly used.

Steel wires, known as bead cores, run around the circumference of tyres. These steel

wires are closed and not ductile. In the well−base rim this recess helps in fitting the tyre.

The tyre and bead are pressed into the well−base at one side, and then pressed inwards

or outwards across the rim flange on the opposite side.

The tyre is always pressed into the well−base at the opposite side to the valve.

Asymmetric rims are used in agricultural machines and construction machinery. These

vehicles manly have rims with a broadened well−base. They are also called wide−base

rims. In order to gain more space for the brakes the well−base is shifted asymmetrically

to the outer rim flange. The 15 tapered rim is undivided, but has a particularly strongly

inclined bead. The inclination is 15°. This type of rim is used in lorries. The rim is linked

to the wheel hub by the wheel disc, but it is disconnectable. The rim diameter must

always be larger than the wheel hub diameter. In the wheel disc there are clearance

holes which are standardised. In Fig. 5 these clearance holes are shown.

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When mounting the wheel at the wheel hub you must ensure that the wheel nuts

correspond to the clearance holes so that the wheel fits firmly and safely.

Then wheel nuts can loosen when stressed and loaded. Centring of the wheel on the

wheel hub can be done either by means of the wheel nuts or centring pins. Another

method of centring is the use of a centre hole in the wheel disc. Holes and slots are

made in the wheel disc to cool the brakes. The wheel nuts and the axle nuts can be

covered by a hub cap.

Tyres

The tyres of the vehicle are intended to moderate the effects of uneven road surfaces, to

improve the driving qualities and to make high speeds possible by low ground friction.

Today pneumatic types are used exclusively.

The rubber tyre tread is to guarantee that the tyres have a good road grip and protect

the vehicle against skidding and side−slipping. To obtain a good road grip various tread

patterns are available. The term 'tyre' includes the rim band, the tube and the tyre. The

rim band is put between the rim and the tube to prevent friction between them. Such

friction would lead to the premature destruction of the tube. The tyres used in modern

vehicles are mostly low−pressure tyres. They are elastic and tend not to sink into the

ground. The tread pattern should guarantee a good grip on the road. The lateral

grooves on the tread help to prevent skidding, and the transversal grooves improve

motion. Grip can be improved by narrow lateral and transversal grooves. Pneumatic

tyres consist of several rubberised cord plies and the rubberised tread. These two

sections are connected by vulcanisation, i.e. heat treatment under pressure.

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Tires basically fall into two categories of construction: (1) bias, and (2) radial

The cords of the plies in a bias-ply tire run diagonally from bead to bead. This results in

a tire with good sidewall strength, a smooth ride, and adequate handling.

Bias-ply tires also are cheaper to manufacture. However, bias-ply tires suffer from tread

squirm, and they run hotter than other types of tire. This results in increased wear and a

higher potential for failure.

Initially, the cord materials were natural materials, such as cotton or linen. The first

manmade material to be used was rayon, and this was super ceded by nylon (Woehrle,

1995a). Nylon eventually died out due to its tendency for "flat spotting" (Woehrle,

1995a). When a car with nylon-reinforced tires remained stationary for even a brief time,

the tire would deform. The deformity would remain for only a short distance when the

car was driven, but until the tire regained its round shape, it produced an annoying

thump. In a competitive market, this resulted in a poor first impression and hurt the

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sales of cars so equipped.

A Follow-on to the bias-ply tire was the belted bias tire. This tire contained the usual

bias plies, but they were reinforced with circumferential belts, initially made of Fiberglass

(Woehrle, 1995a). These tires ran cooler than regular bias-ply tires and provided better

tread life and stopping power. However, they also produced a stiffer ride and were more

expensive than bias-ply tires.

The other category of tire construction is the radial tire. The plies in this tire ran directly

across the tire from bead to bead. Radial tires provide the longest tread life because

they run cooler, and they also provide excellent grip. They are more expensive than

bias-ply tires, and the softer sidewall is more susceptible to punctures. Furthermore,

radial tires exhibit lower rolling resistance, which translates into increased fuel economy

for the vehicle. Radial tires require some type of circumferential belt for reinforcement.

Fiberglass has been used, but the most popular choice has been steel belts.

Functions of tyres Tires play an important role as an automobile component. Many parts may make up a

car but usually one part is limited to one function. Despite its simple appearance, a tire

differs from other parts in that it has numerous functions.

Thus, a tire supports the weight of the car, reduces the impact from the road and at the

same time, transmits the power to propel, brake and steer on the road. It also functions

to maintain a car’s movement. In order to complete such tasks, a tire must be structured

to be a resilient vessel of air.

A tube is used to maintain its major function of maintaining air pressure but a tube

alone cannot maintain the high pressure needed to withstand the great weight. In

addition, the tube lacks the strength to withstand all of the exterior damage and impact

from driving on the road. The carcass is entrusted with this function.

The carcass is an inner layer that protects the tube that contains the high-pressure air

and supports vertical load. A thick rubber is attached to the parts that meet the road to

withstand exterior damage and wear. Tread patterns are chosen according to car

movement and safety demands. A solid structure is necessary to make sure the tires are

securely assembled onto rims.

According to improvements in automobile quality and capability as well as the

diversification of usage, the capabilities and performance of tires are becoming more

complex and diversified.