The Body (Overview)
The Body
The body shell is a fairly complex assortment of large steel sections. These
sections have been stamped into specific shapes which make up the body of your car. These parts
are designed to do many jobs at once; protect the occupants from the elements and in collisions,
provide solid mounts for all other systems, and to slice through the air with minimal resistance.
The body also has one other job which is usually important to the owner... it has to look good!
Although the zillions of parts that make up a car are all very important, it is also important
that the car's body be able to make riding in a car bearable for you. Early cars were so uncomfortable
to ride in, that the human body could stand it only for short periods of time. Auto bodies
have come a long way since then. The body and the suspension system now give us a smooth ride,
and cushion us from the jarring of the road. The idea is that the body of the car should go
forward with as little up-and-down, and side-to-side movement as possible.
Frame (Chassis)
The frame provides a firm structure for the body, as well a good anchor point for the suspension
system. There are two types of frames; integral frames (you've probably heard of them as "unibody")
and conventional frames.
A conventional frame is basically a "one-piece" frame, or two "one-piece"
frames fastened together. The frame is extremely rigid in order to keep all the other parts
of the car in perfect alignment. The manufacturer takes this type of frame and attaches all
the other parts of the car to it, like the way a sculptor starts with a wire frame to build
his sculpture on and give it shape. To keep things smooth, rubber insulator blocks, or "pads"
are placed between the frame and the other car parts. Because the conventional frame is so
important to the structure of your car, (without it, your car would be a pile of doors, hoses,
seats, wires and metal) it is usually constructed of heavy steel and welded or cold riveted
together. Cold riveting keeps the rivets from shrinking after they cool off.
The integral, or unibody, frame is just the opposite. With this type of frame, the body parts
are used to structurally strengthen the entire car, and all of the sections are welded into
one piece. Sometimes the parts of the body and the suspension system are attached and reinforced.
Also, some unibody frames have partial front and rear frames for attaching the engine and suspension
members.
Crash/Safety Features
What actually happens in a collision? The first part of that answer is that there are two
collisions. The first collision occurs when the vehicle runs into another object. The second
collision is when the occupant(s) hit the inside of the car. Neither a seat belt nor an air
bag can do anything about the first collision, but they can be a great help to you in the second
collision. They can minimize the impact between you and the interior of the car.
Safety belt use is more than a personal right. Injuries and fatalities resulting from motor
vehicle accidents are reflected in the rising costs of auto and health insurance, and costs
to employers in the form of lost days at work. The taxpayer also loses by having to support
emergency medical response teams and social programs for the disabled.
Excuses, excuses!
- "Seat belts are too uncomfortable."
Of course, in a car accident -- without your seat belt -- you would smash into the steering
column, slam into the dashboard, or crash through the windshield. This too, can be very uncomfortable.
- "Seat belts wrinkle my clothes."
Sometimes. Sitting also wrinkles clothes. Wearing clothes wrinkles clothes. Flying through
a windshield REALLY wrinkles clothes.
- "Only nerds wear seat belts."
Really? It turns out that -- without seat belts -- nerds, jocks, cheerleaders, "A"
students and average students would all fly through the windshield at the same rate.
- "I'm a good driver."
Nice as that is, good drivers can get hit by bad drivers, drunk drivers, or other good drivers
with mechanical failures. Very few people intend to have accidents.
- "Seat belts restrict my freedom of movement."
This is true. Without your seat belt, you have all the freedom in the world--to crash into
your windshield, to slam into your car's interior, or to be thrown from your car and slide
along the pavement. Freedom is great.
- "It's too embarrassing to ask friends to use their seat belts."
In 1984, 46,000 people died in car accidents. That same year, not one person died of embarrassment.
Safety in car design was recognized as being important even in the earliest cars. In recent
years, however, it has become a fundamental subject in its own right. Active safety measures
have been designed to reduce the likelihood of a car being involved in an accident in the first
place, while passive safety measures assume that a collision is inevitable and then aim to
reduce the severity of the injuries to the road users involved.
Until the late 1800's the British had a 2 mph speed limit for cars. There was an excellent
reason for this. It was also required, for safety's sake, that each car carry two passengers
with a third person walking in front. The job of the third person was to walk in front of the
car to warn everyone that it was coming!
Seat Belts and Air Bags
The first federal study of automobile air bags in actual traffic accidents has found that
air bags used in conjunction with seat belts are far more effective than seat belts alone.
Air bags reduce the risk of death in head-on collisions by 26% and in all serious accidents
by 13%.
Contrasting earlier findings that did not involve actual road conditions, the study showed
that air bags protected occupants in ways that seat belts alone, did not. The air bag spread
out the violent impact of a crash and kept occupants from smashing against the steering wheel,
dashboard or windshield.
Having an air bag and wearing an effective seat belt offers the best protection of all. Not
only are you protected from frontal crashes by the air bag -- you are also protected by the
seat belt in all other types of crashes.
Studies show that 60% of the people killed or injured in automobile accidents would have
been saved from serious injury by safety belts. Unfortunately, many people choose not to wear
them.
With an "effective" safety belt (one that is worn and operating correctly), your
body will stop, in a crash, before you have a chance to hit or go through the windshield and
parts of your car.
Seat belts are especially important in small cars, because your chances of being killed or
badly hurt in a collision with a big car is eight times greater. Wearing your belt will greatly
improve your chances of survival.
In a Department of Transportation study made public on June 26, 1992, it was announced that
air bags are far more effective than seat belts alone. Air bags can reduce the risk of death
in a head-on collision by 26% and in all serious accidents by 13%. However, the DOT cautioned
that air bags work this well ONLY when occupants were wearing a properly buckled seat belt
over lap and shoulder. Other studies have shown that WITHOUT A BELT, AIR BAGS ARE OF SLIGHT
BENEFIT.
Air bags are only useful in frontal crashes, so it is not a good idea to skip your seat belt
because you have an air bag. Air bags provide very effective protection in frontal crashes,
inflating instantly to protect the driver or passenger that has a air bag. They spread the
impact of the crash over the individual's head and chest and protect fragile body parts from
the car's hard surfaces.
More than 6 million cars (about 4% of cars on the road today) have air bags, but the majority
of them have air bags on the driver's side only. Federal officials estimate that air bags have
inflated in more than 57,000 accidents since they were introduced, six years prior to 1992,
and saved about 300 lives.
This report came out in the middle of the most sweeping safety overhaul since the introduction
of the seat belt almost 30 years ago. For the first time, most new cars sold in the US in 1992
have driver's side airbags. Within 6 years, federal law will require that every new car, light
truck and van have air bags on both sides.
The main concern of car safety research in the last few years has been the development of
passive safety design features, where the aim is to improve the "crash-worthiness"
of vehicles. The fundamental aim of good passive safety design is to ensure that only tolerable
loads are applied to a car occupant's body during a crash. This is done first by restraining
the occupant within the passenger compartment by means of a seat belt or other device, so that
chances of making contact with the interior parts of the car are reduced. Secondly, when contacts
cannot be avoided, the structures which are likely to be hit by the occupants must be designed
to collapse and cushion them.
It is important for the designers to have some knowledge of the forces that the human body
can withstand, but as yet this branch of biomechanics has not been fully researched. Work is
done at low impact energy levels using volunteers, but for high speed crashes it is necessary
to use dummies.
The relationship between dummy performance and that of a real person in a crash is complex,
and it may be that these differences are very considerable. To reduce this problem, some work
is currently being done using human cadavers.
In spite of the difficulties in this area, many basic improvements have been introduced into
cars in recent years. These include anti-burst door latches, safety glass, energy-absorbing
steering wheels and columns, head restraints and various seat belt systems.
The benefits of the three-point seat belts have been firmly established: over 50% of fatal
and serious injuries to car occupants would be avoided if all occupants wore their seat belts.
Most states now have a law that both passengers and driver must have seat belts buckled while
in motion. Those states which do not enforce a seat belt law for all passengers have an effective
law for children under five years of age to be strapped in.
Rust Prevention
Rust is very bad for your car. It will also depreciate the value of your car more than any
other problem. It is the most difficult and expensive problem to fix.
The best way to protect your car against rust is to keep the body clean and check it regularly.
If you see a light brown stain, don't ignore it, have it fixed before it gets worse. Although
most rust problems can be repaired, if it involves chrome parts, you will need to replace them.
The major cause of rust is salt on the roads. The salt carries moisture into every nook and
cranny of your car. Rising temperatures bring on salt-caused oxidation. This makes the salt
already in your car worse in the spring. Heat in your garage will also bring out the worst
in the salt. Acid rain is also bad for your car's body; it ruins the paint that protects the
metal of the body.
Undercoating is not rustproofing. Its job is to deaden sound. If any salt or moisture gets
into the undercoating, it aids in the rusting process.
To prevent rust:
- Keep your car clean and well waxed.
- Rinse the underside with water when salt is in use or if you live in a salty area.
- Keep your wheel wells clean and free from material that holds moisture, such as dirt or
leaves.
- Make sure that all drain holes in the frame, floor and bottoms of doors are clear.
- After you wash your car, open the doors to let the water drain out.
Rust proofing is a treatment of waxy paste sprayed inside the body panels by an "after
market" specialist. The specialist drills holes in hidden areas, sprays in the paste,
and plugs the holes. Another type of rustproofing is a clear silicon-based spray that is applied
to your paint to protect it from chemicals and pollution. Modern cars come with good built-in
corrosion protection and warranties against corrosion. You might wind up sealing in the corrosives
you are trying to protect against. Also, many car manufacturers void your corrosion warranty
if you have your car rustproofed. The best course is to take the rust preventative measures
listed above.
Door Locks
Door locks must keep the door from opening in a crash situation and resist break-ins, but
it should also be possible to open them if you lose the key. The door handle acts as a lever
that pulls on a rod. The rod rotates the door latch. The various types of lock mechanisms interrupt
the action of the door latch. The "striker" is a mechanism attached to the door post,
or part of the car body. It holds the door shut or allows it to be opened when the door handle
rotates the latch. The striker's job is to keep the door closed under normal conditions, or
to hold the door closed if the door post starts to bend away from the door in a crash.
Power door lock mechanisms are operated by electric solenoids. Anti-burst door locks are
a relatively cheap development, that have proven to be one of the most successful but unrecognized
benefits of crash protective design.
Studies have shown that it is much better to remain in a car than to be thrown out, because
if a person is thrown out, serious injury may result from contact with the road surface, and
there is a great risk of being run over by one's own or another vehicle. It is, therefore,
important that the doors should stay shut during a collision, and the design of a latch to
do this has been perfected and introduced into almost all cars in the world.
An anti-burst latch provides resistance to tension forces of up to 3000 lb. (1360 kg) in
all directions, by having a lock striker on the door which completely encircles a ring or plate
mounted on the door frame. The system is designed so that it resists the forces generated in
a collision both by the occupant striking the door on the inside and by the force of the impact
on the outside. The result is that ejection, which was established as a leading cause of death
to car occupants in 1956, has now been reduced until it has relatively little importance.
Window Winding Mechanisms
There are two types of window winding mechanisms; hand cranked and power.
Hand cranks work two ways. With "window winders," the crank turns a "sector
gear" that pivots a pair of arms. The arms raise the "window carrier" and the
glass. Some cars have fixed glazing in the rear doors so that the window cannot go up or down.
The other type of window crank is a tape mechanism. It winds up a ladder-like tape made of
plastic links. The plastic links are wound on to or off a spool to raise or lower the glass.
The tape mechanism was introduced in 1980 GM cars. It saves weight and space. Its parts will
not corrode when rainwater gets into the door, and it needs no lubrication.
First introduced in 1946, power windows use a small electric motor inside the door. The motor
turns the crank that raises the window.
Door and vent windows are made of laminated "safety" plate glass, which is a sandwich
of glass and clear plastic. The plastic acts as a soft, protective barrier, keeping the glass
in place, if it is struck during a collision. The glass sticks to the plastic even when shattered.
Side Beam
The door's inner panel has crossbars, or heavy metal beams to provide strength to the door,
and to protect the passenger from injury in the event of a collision.
Door
A door consists of an inner and an outer panel. The inner panel provides strength. The outer
panel is just a metal cover, or "skin." The inner panel has a variety of holes and
stems for the attachment to the window mechanisms and locks. The upper part of the door is
the window glass that rides in grooves on two sides of the door frame.
Door Hinges
The door hinge is a jointed, flexible device on which the door opens and closes. Its foundation
is the center body pillar. The door is attached to the center body pillar by the hinge.
Seats
There are basically two types of seats; bench seats or bucket seats.
A bucket seat is a low, separate seat for one person. Although we think of them as relatively
new, it is interesting to note that in 1905 Henry Ford's first model A had bucket seats.
Bench seats are a continuous cushion and backrest across the width of the car (although some
vans might have them running along the length of the van). Bucket seats are single units with
a separation between the left and right seats.
Usually vinyl leather and fabric are used for upholstery. "Flatsprings" are used
for comfort. A flatspring is a piece of wire that is bent into a zigzag pattern. Both ends
of the wire are attached to the seat frame, with additional lengths added every six inches.
Foam padding is used to cover the flatsprings.
The front seats ride on rails that are bolted to the floor. This arrangement allows the seats
to move backwards and forwards to suit the driver or passenger. The seat adjustment lever is
attached to a latch that fits into teeth along the rail. Moving the lever releases the seat,
and allows the seat to move. At any point of the seat's movement, releasing the lever engages
the latch with one of the teeth. Usually there is also a pull-spring; this draws the seat forward
when the latch is released.
The rear seat usually doesn't move, because it is secured to the floor of the car. It's backrest
is attached to the partition between the passenger compartment and trunk.
Door Handle
The door handle is used to open the door, and as a way to release the door latch. It mates
with a toothed wheel at the side panel of the door, called a rotor. When the door is closed,
one of the teeth contacts the striker and causes the rotor to turn one tooth. If the door is
completely closed, the rotor engages with the striker. The door can't open because the rotor
is locked. When you unlock the door, the rotor can rotate and the door opens.
Windshield
Up until 1935 many cars had hinged windshields that could be folded on the hood of the car
or opened up. Today, most windshields are stationary. They are fixed in place with a weather-strip
made of rubber. The strip has a groove on the inside and a groove on the outside. The inside
groove holds the glass; the outside groove holds the metal rim of the windshield opening in
place. The glass "floats" in a plastic sealant that is spread out between the edge
of the glass and the frame of the windshield.
Windshields are made of laminated safety plate glass, which is a sandwich of glass and clear
plastic. The plastic acts as a soft, protective barrier, keeping the glass in place, if it
is struck during a collision. The glass sticks to the plastic to eliminate glass from flying
around the interior and injuring someone.
Safety glass for windscreens was one of the first passive safety devices introduced into
cars in the 1930s, but its use remains a controversial question. North America and Scandinavia
favor a laminated glass, which consists of two sheets of annealed glass, separated by a layer
of transparent plastic. The rest of Europe and Japan favor toughened glass because it is cheaper.
This type is a single sheet of glass which is heat strengthened, and which on impact fractures
into small cubic fragments without very sharp edges. In recent years, laminated glass has been
improved by changes in the properties of the plastic interlayer. Research has demonstrated
that this new laminated glass is about 4 times safer than toughened glass, but because it is
more expensive, controversy continues as to whether or not toughened glass windscreens should
be banned by legislative action and replaced by laminated glass.
Recent developments have combined the benefits of both laminated and toughened material in
that a laminated construction is used, but the sheet next to the inside of the car is made
of toughened glass.
Spoiler
A spoiler is a kind of wing that is mounted on the rear of the car in a horizontal position.
Its function is to provide high speed stability. For most cars, the spoiler is purely cosmetic;
a car has to be going over 100 mph to take advantage of the aerodynamics of the spoiler.
Some mini-vans also make use of a spoiler, but it's upside down, and angled. The purpose
of this type of spoiler is simply to keep the rain off the rear window.
Air Dam
An air dam is a projection of the body shell underneath the front of the chassis. Its function
is to reduce the amount of air turbulence and drag underneath the car, and to channel air to
the radiator.
Floor Pan
The floor pan is at the bottom of the car assembly. This is the foundation of the body shell.
The floor pan is stamped with bulges and curves to accommodate the spatial requirements of
the engine, transmission and rear axle, as well as the passenger compartment. A second floor
pan is often used for the trunk of the car. If the car has a separate frame, the floor pan
is bolted to the side rails buffered by large rubber cushions. With unibody construction, the
floor pan is attached to the several metal pieces that make up the chassis center section.
Firewall and "A" Pillars
The firewall separates the passenger and engine sections of the car. It's a flat piece of
steel stamped with curves and punched with holes and openings for wires, tubes, and levers
that extend into the passenger compartment. It goes up both sides of the dashboard and stops
where it meets the roof panel. These pillars formed by the firewall provide the frame for the
windshield and are called "A" pillars.
Rear Quarter Panel
The rear quarter panel is the body skin, or sheet metal, that runs from the rearmost part
of the rear door edge, around the back and to the rear door on the other side of the car. On
many cars, the rear quarter panels are integral with the roof.
The rear quarter panel is composed of an outer skin and inner panels. The inner panels are
reinforcements for the rear of the passenger compartment, the trunk, and the wheel housings.
Without the inner panels, there would be severe vibration and weak construction in the back
of the car.
Bumpers
Bumpers are made of heavy sheet metal and are mounted on the front and rear of the car. Bumpers
are bent and formed into specific shapes in order to absorb and deliver momentum during a collision.
In the event of a collision, the bumper absorbs some of the impact, which decreases damage
to the car and its occupants. It also protects the front of the car by diverting all of the
car's momentum to the object with which it has collided.
The bumper is mounted to the car's chassis with special impact absorbers. These shock absorbers
are often spring loaded. In slow speed collisions, this allows the bumper to compress, and
then extend back to its original position.
All bumpers are designed to absorb the energy of the impact. They do this through a series
of valves and air chambers. Some car bumpers have hydraulic chambers. In the event of a collision,
the absorption unit allows air and/or hydraulic fluid to pass through small openings. Forcing
the air/fluid through the valve openings absorbs the energy from the collision.
The bumper's job is to minimize damage, primarily to the occupants of the vehicle and to
the vehicle itself. US law requires cars to pass special crash tests at various speeds. In
order to pass, the car's damage level during the crash must be below a specific dollar level.
This protects the consumer and is also very important for keeping the cost of automobile insurance
to a minimum.
Sometimes bumpers are constructed with built-in "crumple zones." Crumple zones
are designed to absorb impact; they will flex on impact. As the metal flexes, the action of
the bending metal converts the kinetic energy of the car into heat. Kinetic energy is the energy
an object possesses while it is in motion.
Hood
The car's hood is another type of door. It also consists of an inner and an outer panel.
The inner panel provides strength. The outer panel is just a metal cover, or "skin".
The underside of the hood is often covered with a sound-absorbing material. Some high performance
cars have openings in the hood to allow the engine to "breathe" easier. "Hood
scoops" are used to channel outside air directly to the air filter, which gives improved
performance and efficiency.
Trunk Lid
The trunk lid is another type of door. It consists of an inner and an outer panel. The inner
panel provides strength. The outer panel is just a metal cover, or "skin".
Radiator Grille
The radiator grille is the part of the body shell on the front of your car that covers the
area where the air enters. The radiator grille can also be part of the bumper on some cars.
The radiator is connected to the shroud for the radiator. The shroud directs the air that
comes in through the radiator grille to the radiator only. This prevents the air from escaping
around the radiator and failing to cool the engine.
On newer cars, the radiator grille has been lowered to take advantage of lower hood lines,
brought about by an effort to increase fuel efficiency. Older cars had massive grilles, whereas
the cars now produced have smaller more aerodynamic grilles.
Driver's Side Mirror
The driver's side mirror is connected to the driver's side of the car's body. This mirror
is a very important device, not for adjusting your make-up. It enables you, with a slight glance
of the eye, to see places that you can't otherwise see without taking your eyes off the road.
The mirror is adjusted by the driver to suit the necessary visibility position (position
of the head). Sometimes the mirror must be manually adjusted outside the car.
The mirror is also often controlled from the inside of car by a series of cables. The cables
are connected to a "joystick" that allows you to tilt the mirror manually, or to
an electrical motor that allows you to tilt the mirror by pushing a button.
So if your mom, husband, wife, etc., is displeased with you for re-adjusting all the mirrors,
remind them that you're just being a safe driver!
Rear View Mirror
The rear view mirror is a wide rectangular mirror that you (the driver) use to view anything
behind the car. You don't have to take your eyes off the road to turn your head around.
On most cars, the rear view mirror has a "day/night" selection switch that tilts
the mirror inside its glass housing without tilting the exterior glass housing itself. The
switch tilts the mirror upward, about five degrees, to divert the majority of the light striking
the mirror up on to the headliner of the car. The light that you see when the mirror is on
the "night" setting is actually bouncing off the glass housing (a good reason to
keep it clean). The percentage of light reflected into your eyes in the night position, is
very small compared to the amount that would normally be reflected into your eyes in its normal
position.
Headrests
Headrests are a safety device and enhancement. If a headrest is properly positioned behind
your head, it can protect you from injury during a collision. Some safety conscious car manufacturers
have headrests for both front and rear seats.
Headrests can also be safety hazards if they are positioned improperly. A headrest that is
adjusted too high can obscure the driver's rear view. If a headrest is adjusted too low, during
the event of a collision, it can "chop" the driver or passengers in the neck, rather
than protect the head.
Rear-impact accidents occur frequently and are increasing with the greater density of today's
traffic. In rear end collisions, the car is suddenly accelerated forward, with the result that
the head of an occupant is snapped backwards over the seat back. This can cause a serious "whiplash"
injury to the neck. To prevent such injuries, some seats are fitted with head restraints. Many
of these, however, are not used as designed, because the user has to adjust his own head restraint
so that it is in the right position to protect them in a collision. In the United States, for
example, where nearly all head restraints are adjustable, field surveys have shown that 80%
of the head restraints are in the fully down position all the time. As a result, head restraints
are of hardly any benefit in an accident.
Roll Bar
The purpose of the roll bar is to protect driver and passengers from injury if the car rolls
over onto its roof. A series of tubes that are welded together into a contoured shape, and
then bolted directly to the frame members, or rails. Since frame members are located differently
on different types of cars, a roll bar is very unique to an individual car, and must be designed
for a specific car.
Although a roll bar is a very nice feature, it is not always practical, because there isn't
a place to mount it. Roll bars are usually put on convertibles as an aftermarket add-on piece.
A convertible provides no protection if it overturns.
Some cars have built-in "targa" roll bars. These are roll bars that are covered
up by body work; they appear to be part of the body. Targa roll bars are generally flat and
wide, instead of round like normal roll bars. Because they are wider, they are able to hold
up the overturned car. They also look nice, because they look like a body panel. They do reduce
rear visibility because of their greater width. Some targa roll bars are purely cosmetic, because
they have no frame inside. This type of roll bar affords you about as much protection as the
windshield, and so is not really a roll bar.
Most cars don't come with roll bars, but all race cars have roll bars. Roll bars themselves
are relatively inexpensive, but they usually require quite a bit of expensive installation
work. Some roll bars provide better protection than others.
If you have a tendency to exceed the speed limit along winding roads or go off roading, you
really ought to have a roll bar.
Rocker Panels
A rocker panel is a three or four inch piece of metal that runs along the bottom of the car
body underneath the doors. Rocker panels are usually coated with a rock proof protectant which
rubberizes the exterior surface before the car is painted. If you have mud flaps behind your
wheels, this protects your rocker panels, as well as your fenders and your doors. Rocker panels
are often made of chrome plating, and enhance the car.
Wheel Well
The wheel well is either plastic or metal. Metal wheel wells are usually part of the body
shell. Metal wheel wells strengthen the structure of the car because of their shape, and because
they are strongly welded to the body shell. Most rear wheel wells are made of metal.
Wheel wells are coated with a rock-proof, rubberized coating underneath, in order to prevent
the rocks kicked up by the wheels from damaging the metal and making a lot of noise when they
hit.
Often the front wheel wells are made of plastic. This is because it is harder to mount the
engine with the front wheel wells in place. Plastic wheel wells can be removed, and make it
easier to mount the engine during the manufacturing of the car.
Front Quarter Panel
The front quarter panel is composed of the body skin, or sheet metal, that runs from the
front corner of the hood to the front of the door. It is usually a separate piece that is welded
on in a few places. This makes it easy to replace if you get in a "fender bender."
Front quarter panels can usually be replaced relatively inexpensively.
Some newer vehicles use a rubber-like plastic for the fenders, which allows small impacts
to be absorbed without damage.
Chassis Cross Member
The chassis cross member is usually a heavy gauge piece of sheet metal that is bent into
a convoluted channel shape. It is mounted onto the bottom of the chassis, and keeps the transmission
firmly secured at the end where the drive shaft begins. On some cars, the cross member is removable.
On other cars, it is part of the body shell.
Drive Shaft Clearance Tube
The drive shaft clearance tube is a section of the floor pan. It is actually shaped more
like a tunnel than a tube. It provides clearance for the drive shaft, the universal joints,
and the rear of the transmission. The underside of the drive shaft clearance tube is coated
with a rubberized sound absorption coating that reduces road noise.
Only rear-wheel drive vehicles have drive shaft clearance tubes.
Transmission Tunnel
The transmission tunnel is a cone-shaped formation in the front of the floor pan. Its shape
duplicates the transmission, but it is a little bit bigger and provides about two inches of
clearance around the transmission. You won't find the transmission tunnel in front wheel drive
cars, because the transmission is on the side of the engine completely under the hood. Only
rear-wheel drive cars have transmission tunnels.
A manual transmission tunnel has a hole in it to allow the shift linkage to be worked from
inside the car. The shifter linkage goes through the transmission tunnel. A rubber boot on
the shifter linkage stops dirt, dust and exhaust fumes from entering the passenger compartment.
The rubber boot is mounted onto the transmission tunnel and fastened securely around the gearshift
linkage. This arrangement is not necessary with an automatic transmission, because the shift
linkage does not usually go through the transmission tunnel. The shift linkage in automatic
transmission usually goes in front of the firewall from the base of the steering column.
Rear End Tunnel
The rear end tunnel is a tube with a pumpkin shaped indentation in the center which provides
clearance for the drive shaft and the housing of the differential. It allows the rear end to
travel up and down with suspension motion; it clears the differential housing by a maximum
of three or four inches when the suspension is fully compressed. The rear end tunnel often
forms the front of the trunk floor. It is attached to the wheel wells on each side as well
as the floor pan and the trunk floor.
Springs
Springs all have one thing in common; they are made of specially formulated steel which is
tempered to prevent it from loosing the shape it is bent into when "sprung." For
this reason, a spring will compress or extend and then return almost entirely to it original
shape. There are two kinds of springs, leaf springs and coil springs.
Springs have life spans that are determined by the number of cycles they can withstand over
a certain period of time. Occasionally a spring will break on a car while it is being driven.
This doesn't usually lead to a collision, but if a spring breaks while you are driving , the
car will suddenly lurch downward-- you've got yourself a low-rider! The bottom of the car might
be damaged, or you might lose your muffler!
Leaf springs are made of individual springs, or plates. If you break one plate of your leaf-spring,
it won't be noticeable, but your car might begin to lean to one side or the other.
Coil springs, if they break, will suddenly drop the front or rear end of your car and impair
driving under the normal conditions of full suspension travel.
Usually the springs surround the shock absorbers, because space can be saved by putting the
shock absorber inside the spring. The spring on a MacPherson strut suspension rotates along
with the strut body itself; it pivots on a bearing mounted to the wheel well.
Some springs have adjustment dials mounted between them and their mounting points. This allows
the mechanic to increase the spring tension and the ride height, you desire. This type of spring
is usually used only in high performance cars, because it allows the raising and lowering of
suspension system's height. The suspension system is lowered for competitive events and then
raised afterwards. This way, the car can be driven normally and deal with road hazards such
as speed bumps.
Nuts and Bolts
Nuts are hexagon shaped metal objects with a threaded hole through them so that they can
be attached to bolts. Bolts are cylindrical objects with "threads" on the outside
of them which enable them to be threaded into nuts. The hexagon shaped end classifies a "bolt".
A "bolt" without an end is classified as a "lug" or "stud."
Most bolts have what is termed as a "right-handed" thread. This is a spiraling
thread. If you were inserting a right-handed threaded bolt into a threaded hole, you would
turn it clockwise. Some bolts have "left-handed" threads. When inserting this type
of bolt, you turn it counter clockwise.
There are many "grades" of nuts and bolts. Grades depend on the quality of the
materials and the tolerances observed during the manufacture of the nuts and bolts. The ends
of bolts and the faces of nuts are almost always marked with symbols denoting their quality
standards. Unfortunately, in recent years it has become apparent through various government
investigations, that unscrupulous individuals have been importing nuts and bolts with symbols
printed on them that falsely denote a higher quality bolt. In other words, these individuals
import and sell lead with gold stamped on it. This doesn't sound particularly dangerous, but
in the cases of certain airplane and amusement park incidents, it has been proven that such
a business deal, in conjunction with an innocuous object such as a nut or a bolt, can lead
to tragedy.
Nuts and bolts are often separated by washers. Washers have many shapes and sizes, but serve
one purpose. This purpose is to give the nut and the bolt a firm hardened surface for bedding
against. The parts that you put together with nuts and bolts are usually not as strong as the
nuts and bolts themselves. The washers allow the nuts and bolts to be fully tightened down,
providing a wider area to spread out the force of the tightening. Washers keep the nuts and
bolts from digging into the material when they are tightened. Washers shaped like a broken
section of a coil are called "lock washers." They are designed to prevent the nut
from rattling loose.
"Allen" bolts have socket heads, or a recessed hexagon shaped hole in the top.
You need Allen keys or wrenches to tighten or loosen the Allen bolts.
Glove Box
The glove box, or glove compartment, is a small storage cabinet in the dashboard of an automobile.
It is used to store small parts which fall off the interior, and usually a few forgotten parking
tickets. The smart motorist also keeps the following in the glove box: a flashlight, an air
pressure gauge, and a few paper towels.
Hood Release
The hood release is a small lever which is usually mounted under the dash. It is connected
to the hood latch by a cable. The hood latch has a safety feature which requires a second latch
to be released before the hood will open. This is to prevent accidental opening while driving.
Visor
The visor is a flat sunshade, usually movable. It is attached to the interior of the car
at the top of the windshield. Visors protect the eyes of the driver and passengers from the
sun's glare.
|
