2.
Classification of vehicle, layout with reference to
power plant, steering location and drive, chassis,
construction and details (frames, sub-frames,
defects in frame, frameless vehicles, vehicle
dimensions), details of chassis & body materials,
Integrated body construction, BIW type and
corresponding design parameters, Vehicle interior
system (dash board & seating system), Console
design, Pillar trims (Type A, B, C), head roofs.
UNIT 1-TOPICS
3.
There are three main general classifications of the various types of vehicles.
They are:
Single unit vehicles or load carriers.
Articulated vehicles
Heavy tractor vehicles.
CLASSIFICATION OF VEHICLES
AUTOMOBILES
PASSENGER
VEHICLES
LIGHT
VEHICLES
HEAVY
VEHICLES
GOODS
VEHICLES
LIGHT
VEHICLES
HEAVY
VEHICLES
8.
Single unit vehicles or load carriers:
Vehicles are conventional 4 wheel type with two axle design in which
the front axle is a steering non – driving axle and rear axle is the
driving axle.
Articulated Vehicles:
3 wheeler vehicle with single steering wheel in front and a conventional
rear – driving axle.
It can turned about its own tail due to the three wheel construction and
has a greater handling ability in unusual places.
The coupling mechanism between semi – trailer and tractor in most of
these vehicles is designed for automatic connection and coupling up.
A lever is provided within the drivers approach for coupling operation.
A pair of retractable wheels in front can be raised or lowered
automatically along with the coupling and uncoupling operation.
Heavy tractor vehicles:
To move heavy loads tractor or independent tractor vehicles are used.
They commonly operate in pair either in tendon or as puller or pusher.
Figures like 4x2, 4x4, 6x4 etc are commonly used in the classification of
vehicles, where the first figure represents the total number of wheels
and the second figure the number of driving wheels.
9.
Broad classification of cars present in the Indian market:
ESTATE/STATION
WAGON
SPORTS UTILITY VEHICLE
MULTI-PURPOSE VEHICLE
MULTI-UTILITY VEHICLE
SEDAN/NOTCHBACK
HATCHBACK
PICK-UP TRUCK
VAN
10.
Carries passengers in the sitting position and also accommodates their
luggage.
Light motor vehicles designed to carry passengers and sometimes goods,
are broadly classified as follows:
Saloon/Sedan car . E.g:Indigo Manza, Swift Dzire, Logan
Saloon cars have an enclosed compartment to accommodate a row
of front and row of rear seats without any partition between the
driver and rear passenger seats.
A separate luggage space is made either at the front or the rear
based on the location of the engine.
One or two doors are provided on each side of the car but if the car
is a hatchback a door replaces the luggage space. E.g. Nano, Indica,
Jazz, Punto
MOTOR CAR
11.
Coupe
The coupe is the outcome of changes in
saloon car design and has two doors, two
front seats and a hard roof.
When two additional small seats are
provided at the rear, the layout is known as
2+2.
Convertible
Normally cars of this type have two doors
and two seats but sometimes two extra seats
are also provided.
Generally these have a soft folding roof and
wind-up windows to make the compartment
either open or closed.
Estate car/station wagon
In this type the passenger roof of saloon is
completely extended to the back end so that
rear space is increased.
For access a rear door is provided and
sometimes the rear seats are designed to
collapse to provide additional space for
carrying goods.
E.g. Indigo Marina, Octavia.
12.
Pick – up
This type of vehicle is generally classified as
a two – door front – seating van with an
open back to carry mixed collection of
goods. E.g. Xenon, Scorpio Getaway
VANS
These are light goods vehicles used for long
distances or door – door delivery.
They have seats in the front for the driver and
for only one or two passengers.
The engine is usually located over or just in
front of the front axle. E.g. Winger, Ace Magic,
Omni.
13.
COACHES
Coaches carry passengers travelling on long distance and hence the
interior is designed to provide the best possible comfort and to
minimize fatigue.
For better visibility for passengers large panelled windows are
provided on either side extending the full length of the vehicle and
across the back seats.
Most coaches have two axle arrangement but sometimes an extra axle is
used at the rear for more comfort.
Engines may be mounted longitudinally in the front (position 1) or in
the mid – position horizontally (position 2) or at the rear transversely
(position 3).
The location of the engine and transmission depends much on the
length of the coach, the number of passenger seats, the luggage space
and high or low floorboard and seat mounting requirements.
14.
Commercial vehicles used for the
transportation of heavy goods are generally
referred to as lorries.
Vehicles are grouped into two categories
Rigid truck
Articulated vehicles
Rigid trucks are further classified based on the
number of wheel hubs and the number of drive
axle hubs
A four wheeler (4 x 2) truck with two
driving wheels
A six wheeler (6 x 2) truck with two driving
wheels
A six wheeler (6 x 4) truck with four
driving wheels
An eight wheeler (8 x 4) truck with four
driving wheels.
LORRIES/TRUCKS
15.
Articulated vehicles use a tractor unit for providing the propulsive power
and a semi-trailer for carrying the payload.
The tractor uses a short rigid chassis and two or three axles.
The front axle carries the steered road wheels and the rear axle is the
driving (live) one.
The middle axle may either function as an additional drive axle or for dual
steering.
Fifth wheel coupling : Fifth wheel coupling is the swivel mechanism used to
attach the trailer to the tractor unit
Articulated vehicle further classified as:
4 wheeler and 2 wheel trailer (rigid 4 x 2 tractor and single axle 2
articulated trailer)
6 wheeler tandem drive axle tractor and 4 wheel trailer ( rigid 6 x 4
tractor and tandem axle 4 articulated trailer)
6 wheeler dual steer axle tractor and six wheel trailer ( rigid 6 x 2 tractor
and tri – axle 6 articulated trailer)
ARTICULATED TRACTOR & SEMI TRAILER
16.
Side view and underside view of
a conventional 18-wheeler semi-
trailer truck with an enclosed
cargo space. The underside view
shows the arrangement of the
18 tires (wheels).
Shown in blue in the underside
view are the axles, drive shaft,
and differentials.
The legend for labelled parts of
the truck is as follows:
1. tractor unit
2. semi-trailer (detachable)
3. engine compartment
4. cabin
5. sleeper (not present in all
trucks)
6. air dam
7. fuel tanks
8. fifth wheel coupling
9. enclosed cargo space
10. landing gear - legs for when
semi-trailer is detached
11. tandem axles
17.
Typical Engine Configurations – 4 types
Front engine, front wheel drive
Front engine, rear wheel drive
Front engine, front wheel drive
can help with the drive-ability of
the vehicle. The engine weight
over the driven wheels gives
greater traction. This can be
particularly useful in adverse
weather conditions.
Front engine, rear wheel drive
configuration has the advantage
of better weight distribution.
However, some traction can be
lost because the bulk of the
weight is not over the driving
wheels.
18.
Typical Engine Configurations….
Rear engine, rear wheel drive
Rear engine, rear wheel drive
provides a larger load to the rear
driving wheels. However, it can
become ‘tail heavy’ which affects
handling of the vehicle. It also reduces
luggage space (which is now in the
front), as the passenger seats need to
be moved forward in order to
accommodate the engine.
Mid-engine, rear wheel drive
Mid-engine, rear wheel drive
engines provide good vehicle
handling and good traction at the
rear wheels. They are normally
found on two-seat sports cars where
these factors are important.
19.
FOUR WHEEL DRIVE
This arrangement is safer because of distribution of the drive
to all four wheels.
The sharing of the load between the four wheels during acceleration
reduces the risks of wheel spin specifically on slippery surfaces like
snow and mud.
In addition the positive drive to each wheel during braking minimizes
the possibility of wheel lock- up.
On an icy road or across off-highway a two-wheel-drive vehicle soon
becomes non-drivable due to the loss of grip of one of the driving
wheels which causes the wheel to spin.
20.
Vehicle System Location -
Fuel Systems
Fuel tank
Fuel filler cap
and neck
Fuel filter
Fuel
injectors
Fuel pump
21.
Vehicle System Location -
Suspension System
Rear shock
absorbers
Rear hub
Lower arms
Front strut
assembly
Front
hubs
Rear coil
springs
The front strut assemblies
typically comprise a spring
and a shock absorber. These
devices control the
suspension stiffness.
The lower arms allow lateral
movement of the suspension
system and connect the front
hub to the vehicle body.
.
The rear suspension
assemblies also contain
springs and shock absorbers.
The system shown has a solid
rear axle and is known as
‘non-independent rear
suspension’. Independent rear
suspension systems are
available that do not use a
solid rear axle
22.
Vehicle System Location - Steering
System
Steering
wheel
Track
rod end
Steering column
Front
hub
Steering
rack
The steering wheel allows the
driver to control the direction
of the vehicle
The steering column transmits
the action of the steering
wheel to the steering rack
The steering rack changes a
turning movement into the
side-to-side movement
required to turn the wheels
The track rod (ball joint)
allows vertical and horizontal
movement of the steering
system
The front hub
connects the steering
rack to the wheel
23.
Vehicle System Location -
Braking System
Drum brake
assembly
Handbrake
Disc
brake
assembly
The disc and drum brake
assemblies help to bring the
vehicle to a stop. Disc brakes
can be found on either the
front or rear of a vehicle, and
drum brakes are normally
found on the rear of a vehicle
Disc brakes typically
comprise:
a disc, calliper, and brake
pads
Drum brakes typically
comprise: a brake drum, wheel
cylinder and brake shoes
The handbrake provides a mechanical linkage to
the brakes and can be used to stop the vehicle if
the hydraulic system fails. It can also be used to
hold the vehicle stationary when it is parked
24.
Vehicle System Location - Braking
System
Master cylinder and reservoir
ABS modulator
The master cylinder has a
hydraulic piston that provides
power to the
brakes by pressurizing the brake
fluid when the brake pedal is
depressed by the driver
The brake servo provides an
increase in power exerted to the
master cylinder, so helping to
reduce effort given by the driver
at the brake pedal
The ABS modulator consists of a
pump and a number of solenoid
valves that control brake
pressure to each wheel when the
ABS is activated
25.
Vehicle System Location – Single
Exhaust System
Catalytic
converter
Exhaust manifold
Silencers
Tailpipe
The exhaust manifold
connects the exhaust ports
of the engine to the exhaust
pipe
The catalytic converter
removes harmful gases
from the exhaust fumes, so
they are not released into
the atmosphere
The silencer reduces the
noise from the exhaust by
dampening pressure
pulsations
The tailpipe is where the
remaining exhaust gas is
released outside the
vehicle body from the
silencer
26.
Main parts of the Automobile
The body
The main function of the body is to provide comfort and
protection t the passengers besides giving a good look.
The body includes the passenger compartment, the truck,
the bumpers, the fenders, the radiator grill, the hood,
interior trim, glass and paint.
27.
Vehicle Body
Components
Roof
Front wing
Front
bumper
Rear quarter
Rear
bumper
The roof, front wings
and rear quarters
can be used to help
strengthen the
vehicle body. Other
parts can also help to
strengthen the
vehicle body e.g.
glass, doors, sub-
frames, chassis and
floor-pan
28.
Parts of the Vehicle Body
Bonnet
Boot lid/ Tailgate
Doors
30.
The chassis
The chassis forms the
complete operating unit
and is capable of running
with its own power.
It is an assembly of
vehicle without body.
The chassis includes the
frame, wheels, axles,
springs, shock absorbers,
engine, clutch, gearbox,
propeller shaft and
universal joints,
differential and half
shafts, steering, brakes
and accelerator, fuel tank,
storage battery, radiator
and silencer.
32.
Two methods of body and chassis construction, the separate body and
chassis construction and the integral construction.
In separate body and chassis construction, the body is fixed to chassis
frame by means of a number of body bolts, passing through the base of the
body and the frame.
In the integral construction, the body and the chassis frame are combined
as one eliminating the mountings.
The integral construction is also called as chassis – less or unibody
construction.
Unlike commercial vehicles, which have a separate cab attached to a
chassis, car bodies are now mostly integral construction which is frameless
mono box construction.
CHASSIS & BODY CONSTRUCTION
33.
• The Body is made as a separate unit and then
joined with ladder frame.
What it is?
• It supports all the systems in a car such as the
Engine, Transmission system, Steering system,
Suspension system, etc. E.g. Tata Safari, Sumo
Grande
What it does?
34.
• The ladder frame is absent, the body itself is the
frame
What it is?
• It supports all the systems in a car such as the
Engine, Transmission system, Steering system,
Suspension system, etc. e.g. Indica Vista, Indigo
Manza
What it does?
35.
• The benefit is higher load
capacity and strength
• Disadvantage is the body tends
to vibrate easily and the overall
vehicle handling and
refinement is lower
• Used mostly for SUV’s and
bigger vehicles
• Advantage is less rattles and
squeaks are developed.
Handling is also better due to
the higher body rigidity
• Only major drawback is the
load carrying capacity is lower
• Used mostly in cars
36.
FRAME
There are two distinct forms of construction in common use:
The conventional pressed steel frame to which all the mechanical units
are attached and on which the body is superimposed.
The integral or frameless construction, in which the body structure is so
designed as to combine the functions of body and frame, the units
normally attached to the frame then being attached directly to the
body.
The frameless construction is however possible only in the case of a
closed car, since the roof, screen pillars, door pillars and rear panel are
essential load – taking parts of the structure.
The frameless construction has the following advantages over the
conventional framed construction:
i. Reduced weight and consequent saving in fuel consumption.
ii. During collision the body crumbles, thereby absorbing the shock due
to impact and thus providing safety to the passengers.
iii. Lower manufacturing cost.
iv. Compared to framed construction lower body position may be
obtained, thus resulting in increased stability of the automobile.
37.
Disadvantage of frameless construction
i. Reduction of strength and durability.
ii. Economical only if frameless construction is adopted in mass
production.
iii. Increased cost of repairs in case of damage to body during accidents.
iv. Topless cars are difficult to design with the frameless construction.
Frame construction
A simplified diagram representing the frame shows the longitudinal
members A and the members B.
The frame is upswept at the rear and front to accommodate the
movement of axles due to springing. It also keeps the chassis height
low.
The frame is narrowed down at the front to have a better steering lock,
which gives a smaller turning circle.
The extension of the chassis frame ahead of the front axle is called
front overhang whereas its extension beyond the rear axle is called
rear overhang.
38.
SUB FRAMES
Components are mounted on a separate frame
called sub-frame.
The sub-frame is further supported by the
main frame at three points.
In this way the components are isolated from
the effects of twisting and flexing of the main
frame.
Advantages of sub-frames are:
The mass of the sub-frame alone helps to damp
vibrations.
The provisions of sub-frame simplifies
production on the assembly line and facilitates
subsequent overhaul or repair.
39.
DEFECTS IN FRAMES
The only prominent defect that usually occurs in the frames due to
accidents is the alignment fault.
This may be checked by means of plumb line.
The vehicle is placed on a level surface and by suspending plumb
line from different points on each side of the frame, their position
on the ground is marked
The vehicle is taken away and the diagonals are measured
between corresponding points.
These should not differ by more than 7 or 8 mm.
If any of the corresponding diagonals do differ by more than this
amount, the frame is out of alignment.
The possible cause then may be one of the following:
The dumb irons or side members may be bent.
Cross members may be buckled.
Some rivets may be loose or broken.
If the damage to the frame members is small, they can be repaired
by means of a hydraulic jack and wringing irons.
If the damage is more, the bent frame member may be heated to
straighten it.
Alternative may be to cut the damaged part and weld a new one
instead.
40.
FRAMELESS CONSTRUCTION
In this type of construction heavy side members used in conventional
construction are eliminated and the floor is strengthened by cross –
members and the body, all welded together.
41.
VEHICLE DIMENSIONS
Wheel track – This is transverse distance between the tyre to ground
centers on the near – side an the off – side.
Wheel base – This is the longitudinal distance between the centre lines of
the front and the rear axles.
Chassis-member cross sections.
A. Square solid bar.
B. Round solid bar.
C. Circular tube with longitudinal slit.
D. Circular closed tube.
E. C-section.
F. Rectangular box section.
G. Top-hat-section.
H. I-section.
I. Channel flitch plate.
42.
Around 1934, the all-steel body construction was introduced so that a
separate frame could be eliminated.
This frameless or integral construction provides a stiff, light construction,
which is specifically suitable for mass-produced vehicles.
Since 1945 light cars have used integral construction. When suitably
designed the body shell is capable of withstanding the various frame
stresses.
The floor and roof panels resist the sagging effect caused by the weight of
the occupants.
Since these two members are widely spaced, thin sheet metal is used to
form a strong and lightweight box like structure.
To increase torsional stiffness of the body the scuttle at the front is
strengthened and behind the rear seat squab cross ties are used or a ribbed
metal panel is fitted.
The thickness of the sheet metal depends on the stress to be taken by the
panel. Structural members such as sills, rails and pillars are often about 1.1
mm thick, whereas panels such as the roof are 0.9 mm thick.
Component attachment points are reinforced with thicker section. Some
cases use a separate sub-frame to mount engine and other members.
Sometimes this sub-frame is connected to the body by rubber insulation
mountings.
INTEGRAL CONSTRUCTION
43.
A very low (0.1 percent) carbon steel is used to provide extremely good
ductility required for the pressing of the panels.
The low strength, 278 MN/m2, of this steel requires stiffening of the
structural members, which is achieved by spot welding into position of
intricate sections, formed out of thin steel sheet.
INTEGRAL CONSTRUCTION
44.
A modified construction is necessary in case the roof cannot be fully
utilized as a compression member.
This situation occurs on drop-head coupe models and where a sunshine
roof, or very thin door pillars are used.
To achieve the required strength in these cases a strong under-body frame
is used. In addition, the body-shell parts, which are subjected to torsion, are
provided with extra stiffness.
A body-shell is normally fabricated either by spot-welding the panels,
pillars and pressings together to form a strong box, or by buildings a
skeleton or space frame which provides a high structural strength.
To this frame is attached the shell, aluminium or glass-reinforced plastic
(GRP) body panels, doors, roof, etc.
Steel is the most common material used for manufacturing of vehicle in
high volume, because production costs become lower once the initial
investment on body jigs and other facilities has been recovered.
The vibration of the panels, which produces an unwanted noise called
drumming, is avoided by fixing a sound-damping material on the inside of
the panels.
The driver and passengers are enclosed in a rigid cell for their safety.
45.
The front and rear of this rigid compartment are fixed with sub-frames,
which are designed to concertina on impact .
The crumple zones of the body absorb the shock of a collision so that the
rate of deceleration experienced by the occupants is reduced.
46.
Body in white or BIW refers to the stage in automotive design
or automobile manufacturing in which a car body's sheet metal
components have been welded together — but before moving parts (doors,
hoods, and deck lids as well as fenders) the motor, chassis sub-assemblies,
or trim (glass, seats, upholstery, electronics, etc.) have been added and
before painting.
BODY IN WHITE
48.
Body components
Windows and door pillars (3,5,6 and 8).
Windscreen and rear window rails(2).
Cantrails(4).
Roof structure.
49.
Window and door pillars (Fig.(3, 5, 6, and 8))
Window screen and door pillars are identified by a
letter coding; the front windscreen to door pillars
are referred to as A post, the centre side door pillars
as BC post and the rear door to quarter panel as D
post. These are illustrated in Fig
50.
These pillars form the part of the body structure which
supports the roof.
The short form A pillar and rear D pillar enclose the
windscreen and quarter windows and provide the glazing
side channels, whilst the centre BC pillar extends the full
height of the passenger compartment from roof to floor and
supports the rear side door hinges.
The front and rear pillars act as struts (compressive
members) which transfer a proportion of the bending effect,
due to underbody sag of the wheelbase, to each end of the
cantrails which thereby become reactive struts, opposing
horizontal bending of the passenger compartment at floor
level.
The central BC pillar however acts as ties (tensile members),
transferring some degree of support from the mid-span of the
cantrails to the floor structure.
52.
The main requirements of the steel sheet used for
making car bodies are as follows:
Low tensile strength and high ductility for ease of
forming.
Easily assembled to form a body unit.
Light in weight.
Cheap as possible.
Materials required to make body
parts
53.
Low-carbon steel has these properties and is
produced in the large quantities for this purpose.
A typical composition is:
Carbon 0.080%
Silicon 0.002%
Sulphur 0.020%
Phosphorous 0.020%
Manganese 0.350%
Materials required to make body
parts
54.
The liquid steel is cast into large ingots for sub-
sequent hot-rolling to sheet.
Typical sheet thick-nesses in general use are:
10g 3.25mm and 12 g 2.65mm - used for brackets
and supports and heavy internal construction.
14g 2.03mm, 16g 1.63mm and 18g 1.22mm - used in
the panel assemblies which take the stress and
load,(floor, bulkhead, sills, sub-frames, cross-
member and inner stress panels).
20g 0.95mm and 22g 0.711mm - used for the outer
panel construction(skin panels, doors , bonnet , boot
lid , roof , wing panels).
Materials required to make body
parts
55.
Console design-dashboard pod
The dashboard pod is a binnacle
that sits on top of the dashboard
and is ideal for mounting a radio,
extension speaker etc. It is a small
version of the instrument pod that
houses the speedometer which
comes standard in all vehicles. Our
dash pods are finished in a vinyl
that matches the dashboard crash
pad. Most crash pads have a
vacuum formed finish. Many of our
dash pods are vacuum formed and
are an exact colour and grain
match.
56.
Console design-half length Centre floor
console
Available for all
transmission types,
column shift, manual
floor shift, and
automatic floor shift.
Suitable for bucket
seats. This design sits
neatly under the
dashboard and supplies
as much flat facia as
possible.
57.
Console design- full length Centre
floor console
Available for all transmission types,
column shift, manual floor shift, and
automatic floor shift. Suitable for
bucket seats only. This design supplies
as much flat facia as possible. It comes
complete with a storage bin and a
hinged lid that forms a padded
armrest. The storage bin is upholstered
on the inside and includes a removable
lining that is held in place by Velcro
tape. This console is also available for
vehicles with a handbrake between the
bucket seats. The T-bar auto consoles
are designed to house the genuine
selector cover plate. The selector cover
plate is not supplied with the console.
58.
The inside of the
storage bin is fully
lined and comes
complete with a
removable velcro
mounted vinyl bag. The
lid/armrest is attached
to a heavy duty steel
hinge and is held in the
open position by a
black webbing
retaining strap.
59.
This console is the same as the back section of the full length
centre floor console. Suitable for bucket seats only.
It comes complete with a storage bin and a hinged lid that
forms a padded armrest.
The storage bin is upholstered on the inside and includes a
removable lining that is held in place by Velcro tape.
Centre compartments are also available for vehicles with a
handbrake between the bucket seats. The photos show the most
common designs of centre floor compartment (i.e. plain or with
tray.)
However, there are a large variety of individual designs for
particular models. A radio can be mounted into most centre
compartments inside the storage bin or in a separate facia
panel. If we don't have a pattern for a centre compartment for
your vehicle we can make one with a flat base by using your
measurements. This only applies to vehicles without a
handbrake between the seats.
Console design- Centre floor
compartment
60.
Console design-"L" Shaped Floor Tray
and "U" Shaped Floor Tray
This console mounts on
the transmission
tunnel, fitting around
the gear lever and
transfer lever. It
consists of two or three
open storage trays.
61.
VEHICLE INTERIOR SYSTEMS
VEHICLE DASHBOARD
A dashboard (also called dash, instrument panel, or fascia) is a control
panel placed in front of the driver of an automobile, housing
instrumentation and controls for operation of the vehicle.
Editor's Notes
A line from which a weight is suspended to determine verticality or depth- plumbline.
Sagging – under weight or pressure
Stiffness is the rigidity of an object — the extent to which it resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is
The stiffness, k, of a body is a measure of the resistance offered by an elastic body to deformation. For an elastic body with a single degree of freedom (for example, stretching or compression of a rod), the stiffness is defined as
where, k=f/δ
F is the force applied on the body δ is the displacement produced by the force along the same degree of freedom (for instance, the change in length of a stretched spring) In the International System of Units, stiffness is typically measured in newtons per metre. In English Units, stiffness is typically measured in pounds(lbs) per inch.
re·in·force:To give more force or effectiveness to; strengthen: The news reinforced her hopes.
2. To strengthen (a military force) with additional personnel or equipment.
3. To strengthen by adding extra support or material.
4. To increase the number or amount of; augment.
MN/m^2 - meganewton/metre ^2
Spot welding (RSW)[1] is a process in which contacting metal surfaces are joined by the heat obtained from resistance to electric current. Work-pieces are held together under pressure exerted by electrodes. Typically the sheets are in the 0.5 to 3 mm (0.020 to 0.12 in) thickness range. The process uses two shaped copper alloy electrodes to concentrate welding current into a small "spot" and to simultaneously clamp the sheets together. Forcing a large current through the spot will melt the metal and form the weld. The attractive feature of spot welding is that a lot of energy can be delivered to the spot in a very short time (approximately ten milliseconds).[2] That permits the welding to occur without excessive heating of the remainder of the sheet.