![Hatch and wagon with pillar layout a](https://upload.wikimedia.org/wikipedia/commons/1/15/Hatch_and_wagon_with_pillar_layout_a.svg)
The pillars on a
car with permanent roof body style (such as four-door
sedans
A sedan or saloon (British English) is a passenger car in a three-box configuration with separate compartments for an engine, passengers, and cargo.
The first recorded use of the word "sedan" in reference to an automobile body occurred in 19 ...
) are the vertical or nearly vertical supports of its window area or
greenhouse
A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...
—designated respectively as the ''A, B, C'' and (in larger cars such as 4-door
station wagon
A station wagon ( US, also wagon) or estate car ( UK, also estate), is an automotive body-style variant of a sedan/saloon with its roof extended rearward over a shared passenger/cargo volume with access at the back via a third or fifth door ( ...
s and
sport utility vehicle
A sport utility vehicle (SUV) is a car classification that combines elements of road-going passenger cars with features from off-road vehicles, such as raised ground clearance and four-wheel drive.
There is no commonly agreed-upon definitio ...
s) ''D-pillar,'' moving from front to rear, in profile view.
Nomenclature
Car pillars are components that support the structure of an enclosed automobile body. This is similar to that of a house with pillars supporting the roof over the floor.
Car pillars are designed to stand in near vertical or inclined positions to support the roof.
The consistent alphabetical designation of a car's pillars provides a common reference for design discussion and critical communication. This is used by insurance companies to identify damaged components and
rescue teams employ pillar nomenclature to facilitate communication when cutting wrecked vehicles, as when using the
jaws of life
Hydraulic rescue tools, also known as jaws of life, are used by emergency rescue personnel to assist in the extrication of victims involved in vehicle accidents, as well as other rescues in small spaces. These tools include cutters, spreaders, ...
.
The A-pillars on each side of the windshield come up to be joined together by the header rail across the top of the windshield.
The B pillars are sometimes referred to as "posts" (such as a two-door or four-door ''post'' sedan).
Design
Body pillars are critical in providing strength to an automobile body. As the most costly body components to develop or re-tool, a vehicle's roof and door design are a major factor in meeting safety and crash standards.
Before safety standards, pillars were typically thin. The design of body pillars has changed with regulations that provide
roof crush
Roof crush is the failure and displacement of an automobile roof into the passenger compartment during a rollover accident.
Every year approximately 10,000 Americans are killed in rollover accidents, accounting for about 30% of all light vehic ...
protection. Standards in the United States were introduced in phases starting in 2009 that require enclosed passenger cars to be able to support from 1.5-times to 3.0-times the vehicle's unloaded weight on its roof while maintaining headroom (survival space) for occupants.
This has meant designing thicker roof pillars that not only provide sufficient strength, but also to incorporate padding and
airbag
An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a collision. It consists of the airbag cushion, a flexible fabric bag, an inflation module, and an impact sensor. Th ...
s.
However, thicker A-pillars block the field of vision and create
blind spots).
Some designs employ slimmer,
chamfer
A chamfer or is a transitional edge between two faces of an object. Sometimes defined as a form of bevel, it is often created at a 45° angle between two adjoining right-angled faces.
Chamfers are frequently used in machining, carpentry, fu ...
ed A-pillars on each side of the windshield to help improve driver vision and through the use of stronger
alloy steel
Alloy steel is steel that is alloyed with a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties. Alloy steels are broken down into two groups: low alloy steels and high alloy steels. The differe ...
.
The objective of this construction is to meet safety standards and offer crash protection.
One of the important design elements of modern cars is the A-pillar because its location and angle impact the shape of the front of the car and the overall shape of modern vehicles or what designers call "volume."
For example, more forward positioned A-pillars provide for increased interior room and make for less angle and visual difference between the hood and windshield.
This arrangement makes the side view of a car look aerodynamic.
The A-pillars that are positioned further back on a vehicle are most often found on rear-wheel drive and SUV models.
This arrangement provides a greater hood to windshield angle as well as achieving a bigger field of view for the driver, but at the disadvantage of encroaching on interior space.
In the case of the B (or center) pillar on four-door sedans, the pillar is typically a closed steel structure welded at the bottom to the car's
rocker panel and
floorpan
The floorpan is a large sheet metal stamping that often incorporates several smaller welded stampings to form the floor of a large vehicle and the position of its external and structural panels.
In the case of monocoque designs, the floorpan ...
, as well as on the top to the roof rail or panel.
This pillar provides structural support for the vehicle's roof panel and is designed for
latching the front door and mounting the
hinge
A hinge is a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation: all other ...
s for the rear doors.
As "perhaps the most complex of all the structures on the vehicle", the center or B-pillar may be a multi-layered assembly of various lengths and strengths.
Closed vehicles without a B-pillar are widely called
hardtop
A hardtop is a rigid form of automobile roof, which for modern cars is typically constructed from metal. A hardtop roof can be either fixed (i.e. not removable), Convertible#Detachable hardtop, detachable for separate storing or retractable ha ...
s and have been available in two- or four-door body styles, in sedan, coupe, and station wagon versions. Designs without a center or "B" pillar for roof support behind the front doors and rear side windows offer increased occupant visibility, while in turn requiring underbody strengthening to maintain structural rigidity. The need for stronger roof structures meant replacing the pillar-less designs with a rigid B-pillar such as the two-door
AMC Matador line. To continue capitalizing on the popularity of the design, General Motors broadened their definition of "hardtop" during the early 1970s to include models with a B-pillar although: "up to then, everybody thought a hardtop was a car without a center pillar." The "Colonnade" mid-sized General Motors models were so named because of their pillared structure designed to new rollover protection standards, but marketers continued to advertise them like the true hardtop predecessors. By the 1980s the full-size
Chrysler
Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automoti ...
was the last design without a B-pillar and with opening front and rear side windows.
The C-pillar is the rearmost on two- and four-door sedans and hatchback cars and has served as an opportunity for automobile designers "to introduce a little 'design flair' to what would otherwise be a fairly nondescript side view."
Most conventional C-pillars are rearward sloping, but reverse-angled have been used to differentiate their designs. Because many modern cars are similar in side view, the designs of the C-pillar have "become an area for stylistic whimsy."
Designs of the D-pillar typically found on station wagons and SUVs have also undergone a transition from function to more of a styling element. As crossover vehicles look similar, "the D-pillar is the only opportunity for any distinction."
Pillars are implied, whether they exist or not; where a design's
greenhouse
A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...
features a break between windows or doors without vertical support at that position, the non-existent pillar is "skipped" when naming the other pillars. Thus a two-door hardtop or a
three box designed coupé
A coupe or coupé (, ) is a passenger car with a sloping or truncated rear roofline and two doors.
The term ''coupé'' was first applied to horse-drawn carriages for two passengers without rear-facing seats. It comes from the French past parti ...
could have its rearmost pillar called the C-pillar even in the absence of a B-pillar. Conversely, additional doors, such as on
limousine
A limousine ( or ), or limo () for short, is a large, chauffeur-driven luxury vehicle with a partition between the driver compartment and the passenger compartment.
A very long wheelbase luxury sedan (with more than four doors) driven by a prof ...
s, will create additional B-pillars; the B-pillars are then numbered, B1, B2, and so forth.
In addition to the pillar nomenclature derived from viewing an automobile in profile, some older cars have a two-part
windshield
The windshield (North American English) or windscreen (Commonwealth English) of an aircraft, car, bus, motorbike, truck, train, boat or streetcar is the front window, which provides visibility while protecting occupants from the elements. Mo ...
or a split rear window, with the two halves separated by a pillar. Posts for
quarter windows (a smaller window typically between the front window and the windshield) are not considered a named pillar.
File:Automotive_C-pillar_typology.jpg, A photographic typology illustrating variations of the design of the C-pillar
File:1978 AMC Concord DL wagon blue 2014-AMO-NC-16.jpg, The B or center pillar between the front and rear doors on an AMC Concord
The AMC Concord is a compact car manufactured and marketed by the American Motors Corporation for model years 1978–1983. The Concord was essentially a revision of the AMC Hornet that was discontinued after 1977, but more luxurious, quieter, ...
station wagon
File:1969 AMC Ambassador limousine in Wisconsin side view mirrored.jpg, From left to right: A, B1, B2, and C-pillars, with small quarter glass
Quarter glass (or quarter light) on automobiles and closed carriages may be a side window in the front door or located on each side of the car just forward of the rear-facing rear window of the vehicle. Only some cars have them. In some cases ...
in both doors (AMC Ambassador
The Ambassador is an automobile manufactured and marketed by American Motors Corporation (AMC) from 1957 through 1974 over eight generations, available in two- and four-door sedan, two-door hardtop, four-door station wagon as well as two-door ...
)
File:A-pillar Blind-spot.JPG, A crash due in part to an A-pillar blind-spot
See also
*
Automobile design
Automotive design is the process of developing the appearance (and to some extent the ergonomics) of motor vehicles - including automobiles, motorcycles, trucks, buses, coaches, and vans.
The functional design and development of a modern mot ...
*
Automotive head-up display
*
Blind spot (automobile)
*
Driver visibility
A blind spot in a vehicle or vehicle blind spot is an area around the vehicle that cannot be directly seen by the driver while at the controls, under existing circumstances. In transport, driver visibility is the maximum distance at which the dr ...
*
Quarter glass
Quarter glass (or quarter light) on automobiles and closed carriages may be a side window in the front door or located on each side of the car just forward of the rear-facing rear window of the vehicle. Only some cars have them. In some cases ...
References
External links
"Art of Automotive C Pillars"€”Flickr photo group created 26 July 2005; webpage accessed 26 June 2022.
{{Automobile configuration
Automotive body parts
Automotive styling features
Vehicle safety technologies
sv:Kaross#A-stolpe