Vehicle Frame
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A vehicle frame, also historically known as its ''
chassis A chassis (, ; plural ''chassis'' from French châssis ) is the load-bearing framework of an artificial object, which structurally supports the object in its construction and function. An example of a chassis is a vehicle frame, the underpar ...
'', is the main supporting structure of a
motor vehicle A motor vehicle, also known as motorized vehicle or automotive vehicle, is a self-propelled land vehicle, commonly wheeled, that does not operate on rails (such as trains or trams) and is used for the transportation of people or cargo. The ...
to which all other components are attached, comparable to the
skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...
of an organism. Until the 1930s, virtually every car had a structural frame separate from its body. This construction design is known as ''
body-on-frame Body-on-frame, also known as ladder frame construction, is a common motor vehicle construction method, whereby a separate body or coach is mounted on a strong and relatively rigid vehicle frame or chassis that carries the powertrain (the en ...
''. By the 1960s, unibody construction in passenger cars had become common, and the trend to unibody for passenger cars continued over the ensuing decades. Nearly all
truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...
s, buses, and most pickups continue to use a separate frame as their chassis.


Functions

The main functions of a frame in a motor vehicle are: # To support the vehicle's mechanical components and body # To deal with static and dynamic loads, without undue deflection or distortion. :These include: ::*Weight of the body, passengers, and cargo loads. ::*Vertical and torsional twisting transmitted by going over uneven surfaces. ::*Transverse lateral forces caused by road conditions, side wind, and steering the vehicle. ::*Torque from the engine and transmission. ::*Longitudinal tensile forces from starting and acceleration, as well as compression from braking. ::*Sudden impacts from collisions. Types of frame according to their construction: * Ladder-type frame * X-Type frame * Offset frame * Offset with cross member frame * Perimeter Frame


Frame rails

Typically the material used to construct vehicle chassis and frames is
carbon steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, coba ...
; or aluminum alloys to achieve a more light-weight construction. In the case of a separate chassis, the frame is made up of structural elements called the ''rails'' or ''beams''. These are ordinarily made of steel ''channel'' sections, made by folding, rolling, or pressing steel plate. There are three main designs for these. If the material is folded twice, an open-ended cross-section, either C-shaped or hat-shaped (U-shaped) results. "Boxed" frames contain chassis rails that are closed, either by somehow welding them up or by using premanufactured metal tubing. C-Shaped By far the most common, the C-channel rail has been used on nearly every type of vehicle at one time or another. It is made by taking a flat piece of steel (usually ranging in thickness from 1/8" to 3/16", but up to 1/2" or more in some heavy-duty trucks) and rolling both sides over to form a C-shaped beam running the length of the vehicle. Hat Hat frames resemble a "U" and may be either right-side-up or inverted with the open area facing down. They are not commonly used due to weakness and a propensity to rust. However, they can be found on 1936–1954
Chevrolet Chevrolet ( ), colloquially referred to as Chevy and formally the Chevrolet Motor Division of General Motors Company, is an American automobile division of the American manufacturer General Motors (GM). Louis Chevrolet (1878–1941) and ou ...
cars and some
Studebaker Studebaker was an American wagon and automobile manufacturer based in South Bend, Indiana, with a building at 1600 Broadway, Times Square, Midtown Manhattan, New York City. Founded in 1852 and incorporated in 1868 as the Studebaker Brothers M ...
s. Abandoned for a while, the hat frame regained popularity when companies started welding it to the bottom of unibody cars, effectively creating a boxed frame. Boxed Originally, boxed frames were made by welding two matching C-rails together to form a rectangular tube. Modern techniques, however, use a process similar to making C-rails in that a piece of steel is bent into four sides and then welded where both ends meet. In the 1960s, the boxed frames of conventional American cars were spot-welded in multiple places down the seam; when turned into NASCAR "stock car" racers, the box was continuously welded from end to end for extra strength.


Design features

While appearing at first glance as a simple form made of metal, frames encounter great amounts of stress and are built accordingly. The first issue addressed is "beam height", or the height of the vertical side of a frame. The taller the frame, the better it is able to resist vertical flex when force is applied to the top of the frame. This is the reason
semi-trucks A semi-trailer truck, also known as a semitruck, (or semi, eighteen-wheeler, big rig, tractor-trailer or, by synecdoche, a semitrailer) is the combination of a tractor unit and one or more semi-trailers to carry freight. A semi-trailer a ...
have taller frame rails than other vehicles instead of just being thicker. As looks, ride quality, and handling became more important to consumers, new shapes were incorporated into frames. The most visible of these are arches and kick-ups. Instead of running straight over both
axle An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, beari ...
s, arched frames sit lower—roughly level with their axles—and curve up over the axles and then back down on the other side for bumper placement. Kick-ups do the same thing without curving down on the other side and are more common on front ends. Another feature are tapered rails that narrow vertically or horizontally in front of a vehicle's cabin. This is done mainly on trucks to save weight and slightly increase room for the engine since the front of the vehicle does not bear as much of a load as the back. Design developments include frames that use more than one shape in the same frame rail. For example, some pickup trucks have a boxed frame in front of the cab, shorter, narrower rails underneath the cab, and regular C-rails under the bed. On perimeter frames, the areas where the rails connect from front to center and center to rear are weak compared to regular frames, so that section is boxed in, creating what are known as "torque boxes".


Types


Full under-body frames


Ladder frame

Named for its resemblance to a ladder, the ladder frame is one of the oldest, simplest and most frequently used under-body, separate chassis/frame designs. It consists of two symmetrical beams, rails, or channels, running the length of the vehicle, connected by several transverse cross-members. Originally seen on almost all vehicles, the ladder frame was gradually phased out on cars in favor of perimeter frames and unitized body construction. It is now seen mainly on large 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. The vehicle's overall height will be greater due to the
floor pan 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 floorpa ...
sitting above the frame instead of inside it.


Backbone tube

Backbone chassis of the 1962 Lotus Elan A backbone chassis is a type of automotive construction with chassis, that is similar to the body-on-frame design. Instead of a relatively flat, ladder-like structure with two longitudinal, parallel frame-rails, it consists of a singular central, strong tubular backbone (usually rectangular in cross-section), that carries the power-train, and connects front and rear suspension attachment structures. Although the backbone is frequently drawn upward into, and mostly ''above'' the floor of the vehicle, the body is still placed on or over (sometimes straddling) this structure from above.


X-frame

This is the design used for the full-size American models of
General Motors The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...
in the late 1950s and early 1960s in which the rails from alongside the engine seemed to cross in the passenger compartment, each continuing to the opposite end of the crossmember at the extreme rear of the vehicle. It was specifically chosen to decrease the overall height of the vehicles regardless of the increase in the size of the transmission and propeller shaft humps, since each row had to cover frame rails as well. Several models had the differential located not by the customary bar between axle and frame, but by a ball joint atop the differential connected to a socket in a wishbone hinged onto a crossmember of the frame. The X-frame was claimed to improve on previous designs, but it lacked side rails and thus did not provide adequate side-impact and collision protection. This design was replaced by perimeter frames.


Perimeter frame

Similar to a ladder frame, but the middle sections of the frame rails sit outboard of the front and rear rails, routed around the passenger footwells, inside the rocker and sill panels. This allowed the floor-pan to be lowered, especially the passenger footwells, lowering the passengers' seating height and thereby reducing both the roof-line and overall vehicle height, as well as the centre of gravity, thus improving handling and roadholding in passenger cars. This became the prevalent design for
body-on-frame Body-on-frame, also known as ladder frame construction, is a common motor vehicle construction method, whereby a separate body or coach is mounted on a strong and relatively rigid vehicle frame or chassis that carries the powertrain (the en ...
cars in the United States, but not in the rest of the world, until the unibody gained popularity. For instance Hudson introduced this construction on their 3rd generation Commodore models in 1948. This frame type allowed for annual model changes, and lower cars, introduced in the 1950s to increase sales – without costly structural changes. The
Ford Panther platform The Ford Panther platform was an automobile platform that was used by Ford Motor Company from the 1979 to 2012 model years. Following the downsizing of the General Motors B-bodies and C-bodies by two years, the Panther platform marked the e ...
, discontinued in 2011, was one of the last perimeter frame passenger car platforms in the United States. However, the fourth to seventh generation
Chevrolet Corvette The Chevrolet Corvette is a two-door, two-passenger luxury sports car manufactured and marketed by Chevrolet since 1953. With eight design generations, noted sequentially from C1 to C8, the Corvette is noted for its performance and distinctiv ...
used a perimeter frame integrated with an internal skeleton that serves as a clamshell. In addition to a lowered roof, the perimeter frame allows lower seating positions when that is desirable, and offers better safety in the event of a side impact. However, the design lacks stiffness, because the transition areas from front to center and center to rear reduce beam and torsional resistance, and is used in combination with torque boxes and soft suspension settings.


Platform frame

This is a modification of the perimeter frame, or of the backbone frame, in which the passenger compartment floor, and sometimes also the luggage compartment floor, have been integrated into the frame as loadbearing parts, for strength and rigidity. The
sheet metal Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Sheet metal is one of the fundamental forms used in metalworking, and it can be cut and bent into a variety of shapes. Thicknesses can vary significantly; ex ...
used to assemble the components needs to be stamped with ridges and hollows to give it strength. Platform chassis were used on several successful European cars, most notably the
Volkswagen Beetle The Volkswagen Beetle—officially the Volkswagen Type 1, informally in German (meaning "beetle"), in parts of the English-speaking world the Bug, and known by many other nicknames in other languages—is a two-door, rear-engine economy car, ...
, where it was called "body-on-pan" construction. Another German example are the Mercedes-Benz "Ponton" cars of the 1950s and 1960s, where it was called a "frame floor" in English-language advertisements. The French Renault 4, of which over eight million were made, also used a platform frame. The frame of the Citroën 2CV used a very minimal interpretation of a platform chassis under its body.


Space frame

In a (tubular) spaceframe chassis, the suspension, engine, and body panels are attached to a three-dimensional skeletal frame of tubes, and the body panels have limited or no structural function. To maximize rigidity and minimize weight, the design frequently makes maximum use of triangles, and all the forces in each strut are either tensile or compressive, never bending, so they can be kept as thin as possible. The first true spaceframe chassis were produced in the 1930s by
Buckminster Fuller Richard Buckminster Fuller (; July 12, 1895 – July 1, 1983) was an American architect, systems theorist, writer, designer, inventor, philosopher, and futurist. He styled his name as R. Buckminster Fuller in his writings, publishing ...
and
William Bushnell Stout William Bushnell Stout (March 16, 1880 – March 20, 1956) was a pioneering American inventor, engineer, developer and designer whose works in the automotive and aviation fields were groundbreaking. Known by the nickname "Bill", Stout designed an ...
(the
Dymaxion Dymaxion is a term coined by architect and inventor Buckminster Fuller and associated with much of his work—prominently his Dymaxion house and Dymaxion car. Dymaxion, a portmanteau of the words ''dynamic'', ''maximum'', and ''tension''; ...
and the
Stout Scarab The Stout Scarab is a streamlined 1930–1940s American car, designed by William Bushnell Stout and manufactured by Stout Engineering Laboratories and later by Stout Motor Car Company of Detroit, Michigan. The Stout Scarab is credited by ...
) who understood the theory of the true spaceframe from either architecture or aircraft design. The 1951
Jaguar C-Type The Jaguar C-Type (officially called the Jaguar XK120-C) is a racing sports car built by Jaguar and sold from 1951 to 1953. The "C" stands for "competition". The car combined the running gear of the contemporary, road-proven XK120, with a li ...
racing sports car that won the
Le Mans 24 hours The 24 Hours of Le Mans (french: link=no, 24 Heures du Mans) is an endurance-focused sports car race held annually near the town of Le Mans, France. It is the world's oldest active endurance racing event. Unlike fixed-distance races whose w ...
twice, had a lightweight, multi-tubular, triangulated frame, over which an aerodynamic aluminum body was crafted. In 1994, the
Audi A8 The Audi A8 is a full-size luxury sedan manufactured and marketed by the German automaker Audi Audi AG () is a German automotive manufacturer of luxury vehicles headquartered in Ingolstadt, Bavaria, Germany. As a subsidiary of its paren ...
was the first mass-market car with an aluminium chassis, made feasible by integrating an aluminium space-frame into the bodywork. All Audi A8 models have since used this construction method co-developed with
Alcoa Alcoa Corporation (an acronym for Aluminum Company of America) is a Pittsburgh-based industrial corporation. It is the world's eighth-largest producer of aluminum. Alcoa conducts operations in 10 countries. Alcoa is a major producer of primar ...
, and marketed as the ''Audi Space Frame''. The Italian term ''
Superleggera Superleggera (Italian for ''Superlight'') is a custom tube and alloy panel automobile coachwork construction technology developed by Felice Bianchi Anderloni of Italian coachbuilder Carrozzeria Touring Superleggera. A separate chassis was st ...
'' (meaning 'super-light') was trademarked by
Carrozzeria Touring Carrozzeria Touring Superleggera is an Italian automobile coachbuilder. Originally established in Milan in 1925, Carrozzeria Touring became well known for both the beauty of its designs and patented superleggera construction methods. The bu ...
for lightweight sports-car body construction that ''only resembles'' a space-frame chassis. Using a three-dimensional 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. A skin is attached to the outside of the frame, often made of aluminum. This body construction is, however, ''not'' stress-bearing, and still requires the addition of a chassis.


Unibody

The terms "unibody" and "unit-body" are short for "unitized body", "unitary construction", or alternatively (fully) integrated body and frame/chassis. It is defined as: Vehicle structure has shifted from the traditional
body-on-frame Body-on-frame, also known as ladder frame construction, is a common motor vehicle construction method, whereby a separate body or coach is mounted on a strong and relatively rigid vehicle frame or chassis that carries the powertrain (the en ...
architecture to the lighter unitized / integrated body structure that is now used for most cars. Integral frame and body construction requires more than simply welding an unstressed body to a conventional frame. In a fully integrated body structure, the entire car is a load-carrying unit that handles all the loads experienced by the vehicle – forces from driving as well as cargo loads. Integral-type bodies for wheeled vehicles are typically manufactured by welding preformed metal panels and other components together, by forming or casting whole sections as one piece, or by a combination of these techniques. Although this is sometimes also referred to as a
monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...
structure, because the car's outer skin and panels are made load-bearing, there are still ribs, bulkheads, and box sections to reinforce the body, making the description
semi-monocoque The term semi-monocoque or semimonocoque refers to a stressed shell structure that is similar to a true monocoque, but which derives at least some of its strength from conventional reinforcement. Semi-monocoque construction is used for, among ot ...
more appropriate. The first attempt to develop such a design technique was on the 1922
Lancia Lambda The Lancia Lambda is an innovative automobile produced from 1922 through 1931. It was the first car to feature a load-bearing unitary body, (but without a stressed roof) and it also pioneered the use of an independent suspension (the front slidi ...
to provide structural stiffness and a lower body height for its torpedo car body. The Lambda had an open layout with unstressed roof, which made it less of a ''monocoque'' shell and more like a bowl. 1,000 were produced. A key role in developing the unitary body was played by the American firm the Budd Company, now ThyssenKrupp Budd. Budd supplied pressed-steel bodywork, fitted to separate frames, to automakers
Dodge Dodge is an American brand of automobiles and a division of Stellantis, based in Auburn Hills, Michigan. Dodge vehicles have historically included performance cars, and for much of its existence Dodge was Chrysler's mid-priced brand above P ...
, Ford,
Buick Buick () is a division of the American automobile manufacturer General Motors (GM). Started by automotive pioneer David Dunbar Buick in 1899, it was among the first American marques of automobiles, and was the company that established General ...
, and the French company,
Citroën Citroën () is a French automobile brand. The "Automobiles Citroën" manufacturing company was founded in March 1919 by André Citroën. Citroën is owned by Stellantis since 2021 and previously was part of the PSA Group after Peugeot acquired 8 ...
. In 1930,
Joseph Ledwinka Joseph Ledwinka (December 14, 1870 – November 26, 1949)''Buddgette'', January 1950 was an automobile engineer. Early life Joseph V. Ledwinka, a distant relative of Hans Ledwinka, was born in Vienna, and emigrated to the United States in 189 ...
, an engineer with Budd, designed an automobile prototype with full unitary construction.
Citroën Citroën () is a French automobile brand. The "Automobiles Citroën" manufacturing company was founded in March 1919 by André Citroën. Citroën is owned by Stellantis since 2021 and previously was part of the PSA Group after Peugeot acquired 8 ...
purchased this fully unitary body design for the
Citroën Traction Avant The Citroën Traction Avant () is the world’s first unibody front-wheel-drive car. A range of mostly 4-door saloons and executive cars, were made with four or six-cylinder engines, produced by the French manufacturer Citroën from 1934 to 1957. ...
. This high volume, mass production car was introduced in 1934 and sold 760,000 units over the next 23 years of production. This application was the first iteration of the modern structural integration of body and chassis, using spot welded deep stamped steel sheets into a structural cage, including sills, pillars and roof beams. In addition to a unitary body with no separate frame, the Traction Avant also featured other innovations such as
front-wheel drive Front-wheel drive (FWD) is a form of engine and transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitu ...
. The result was a low-slung vehicle with an open, flat-floored interior. For the
Chrysler Airflow The Chrysler Airflow is a full-size car produced by Chrysler from 1934 to 1937. The Airflow was the first full-size American production car to use streamlining as a basis for building a sleeker automobile, one less susceptible to air resistance ...
(1934–1937) Budd supplied a variation – three main sections from the Airflow's body were welded into what Chrysler called a bridge-truss construction. For the Chrysler Airflow, unfortunately, this method was not ideal – panel fits were poor. To convince a skeptical public of the strength of unibody, both Citroën and Chrysler created advertising films showing cars surviving after being pushed off a cliff.
Opel Opel Automobile GmbH (), usually shortened to Opel, is a German automobile manufacturer which has been a subsidiary of Stellantis since 16 January 2021. It was owned by the American automaker General Motors from 1929 until 2017 and the PSA Grou ...
was the second European and the first German car manufacturer to produce a car with unibody structure – production of the compact Olympia started in 1935. A larger Kapitän went into production in 1938, although its front longitudinal beams were stamped separately and then attached to the main body. It was so successful, that Soviet post-war mass produced GAZ-M20 Pobeda of 1946 copied unibody structure from Opel Kapitän. Later Soviet limousine GAZ-12 ZIM of 1950 introduced unibody design to automobiles with as long wheelbase, as 3.2 m (126 in). The streamlined 1936 Lincoln-Zephyr with conventional
front-engine, rear-wheel-drive layout In automotive design, a FR, or front-engine, rear-wheel-drive layout is one where the engine is located at the front of the vehicle and driven wheels are located at the rear via a drive shaft. This was the traditional automobile layout for most ...
utilized a unibody structure. By 1941, unit construction was no longer a new idea for cars, "but it was unheard of in the
merican ''Merican'' is an EP by the American punk rock band the Descendents, released February 10, 2004. It was the band's first release for Fat Wreck Chords and served as a pre-release to their sixth studio album ''Cool to Be You'', released the follo ...
low-price field nd Nash wanted a bigger share of that market." The single unit body construction of the
Nash 600 The Nash 600 is an automobile that was manufactured by the Nash-Kelvinator Corporation of Kenosha, Wisconsin for the 1941 through 1949 model years, after which the car was renamed the Nash Statesman. The Nash 600 was positioned in the low-pric ...
provided weight savings and Nash's Chairman and CEO,
George W. Mason George Walter Mason (March 12, 1891 – October 8, 1954) was an American industrialist. During his career Mason served as the Chairman and CEO of the Kelvinator Corporation (1928-1937), Chairman and CEO of the Nash-Kelvinator Corporation (1937-19 ...
was convinced "that unibody was the wave of the future." Since then more cars were redesigned to the unibody structure, which is now "considered standard in the industry". By 1960, the unitized body design was used by Detroit's Big Three on their compact cars (
Ford Falcon Ford Falcon is an automobile nameplate applied to several vehicles worldwide. * Ford Falcon (North America), an automobile produced by Ford from 1960 to 1970. * Ford Falcon (Argentina), a car built by Ford Argentina from 1962 until 1991. * Fo ...
,
Plymouth Valiant The Plymouth Valiant (first appearing in 1959 as simply the Valiant) is an automobile which was marketed by the Plymouth division of the Chrysler Corporation in the United States from the model years of 1960 through 1976. It was created to give t ...
, and
Chevrolet Corvair The Chevrolet Corvair is a compact car manufactured by Chevrolet for model years 1960–1969 in two generations. A response to the Volkswagen Beetle, it remains the only American-designed, mass-produced passenger car with a rear-mounted, air- ...
). After Nash merged with Hudson Motors to form
American Motors Corporation American Motors Corporation (AMC; commonly referred to as American Motors) was an American automobile manufacturing company formed by the merger of Nash-Kelvinator Corporation and Hudson Motor Car Company on May 1, 1954. At the time, it was the ...
, its Rambler-badged automobiles continued exclusively building variations of the unibody. Although the 1934
Chrysler Airflow The Chrysler Airflow is a full-size car produced by Chrysler from 1934 to 1937. The Airflow was the first full-size American production car to use streamlining as a basis for building a sleeker automobile, one less susceptible to air resistance ...
had a weaker than usual frame and body framework welded to the chassis to provide stiffness, in 1960, Chrysler moved from body-on-frame construction to a unit-body design for most of its cars. Most of the American-manufactured unibody automobiles used
torque boxes A vehicle frame, also historically known as its ''chassis'', is the main supporting structure of a motor vehicle to which all other components are attached, comparable to the skeleton of an organism. Until the 1930s, virtually every car had a ...
in their vehicle design to reduce vibrations and chassis flex, with the exception of the
Chevy II The Chevrolet Chevy II/Nova is a small automobile manufactured by Chevrolet, and produced in five generations for the 1962 through 1979, and 1985 through 1988 model years. Nova was the top model in the Chevy II lineup through 1968. The Chevy II ...
which had a bolt-on front apron (erroneously referred to as a subframe). American Motors (with its partner
Renault Groupe Renault ( , , , also known as the Renault Group in English; legally Renault S.A.) is a French multinational automobile manufacturer established in 1899. The company produces a range of cars and vans, and in the past has manufactured ...
) during the late 1970s incorporated unibody construction when designing the
Jeep Cherokee (XJ) The Jeep Cherokee (XJ) is a sport utility vehicle manufactured and marketed across a single generation by Jeep in the United States from 1983 through 2001 — and globally through 2014. It was available in two- or four-door, five-passenger, fro ...
platform using the manufacturing principles (unisides, floorpan with integrated frame rails and crumple zones, and roof panel) used in its passenger cars, such as the Hornets and all-wheel-drive
Eagles Eagle is the common name for many large birds of prey of the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. Most of the 68 species of eagle are from Eurasia and Africa. Outside this area, jus ...
for a new type of frame called the "Uniframe ..a robust stamped steel frame welded to a strong unit-body structure, giving the strength of a conventional heavy frame with the weight advantages of Unibody construction." This design was also used with the XJC concept developed by American Motors prior to its absorption by Chrysler, which later became the
Jeep Grand Cherokee (ZJ) The Jeep Grand Cherokee (ZJ) is the first generation of the Jeep Grand Cherokee sport utility vehicle. Introduced in 1992 for the 1993 model year, development of the ZJ Grand Cherokee started under American Motors Corporation (AMC) and was co ...
. The design is still in use in modern-day sport utility vehicles such as the
Jeep Grand Cherokee The Jeep Grand Cherokee is a range of mid-size SUVs produced by the American manufacturer Jeep. At its introduction, while most SUVs were still manufactured with body-on-frame construction, the Grand Cherokee has used a unibody chassis from the ...
. The unibody is now the preferred construction for mass-market automobiles. This design provides weight savings, improved space utilization, and ease of manufacture. Acceptance grew dramatically in the wake of the two
energy crises An energy crisis or energy shortage is any significant bottleneck in the supply of energy resources to an economy. In literature, it often refers to one of the energy sources used at a certain time and place, in particular, those that supply n ...
of the 1970s, and that of the 2000s in which compact SUVs using a truck platform (primarily the USA market) were subjected to CAFE standards after 2005 (by the late 2000s truck-based compact SUVs were phased out and replaced with crossovers). An additional advantage of a strong-bodied car lies in the improved crash protection for its passengers.


Partial frames


Subframe

A subframe is a distinct structural frame component, to reinforce or complement a particular section of a vehicle's structure. Typically attached to a unibody or a monocoque, the rigid subframe can handle great forces from engine and drive-train, and can transfer them evenly to a wide area of relatively thin sheet metal of a unitized body shell. Subframes are often found at the front or rear end of cars and are used to attach the
suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ring, in mathematics * Suspension (chemistry), small solid particles suspende ...
to the vehicle. A subframe may also contain the
engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...
and transmission. It is normally of pressed or box steel construction, but may be tubular and/or other material. Examples of passenger car use include the 1967–1981
GM F platform The F platform, or F-body, was General Motors' rear-wheel drive pony car automobile platform from 1967 until 2002. It was based partially on the GM X platform, which was used for compact applications instead of the sporting intent of the F-Body. Th ...
, the numerous years and models built on the
GM X platform (1962) The General Motors X platform (also called X-body) is an automobile platform designation that was used for compact cars with rear-wheel drive. Developed by Chevrolet, the architecture was produced from the 1962 to 1979 model years. During the ...
, GM's M/L platform vans (Chevrolet Astro/GMC Safari, which included an all-wheel drive variant), and the unibody
AMC Pacer The AMC Pacer is a two-door compact car produced in the United States by American Motors Corporation (AMC) from the 1975 through the 1980 model years. The Pacer was also made in Mexico by Vehículos Automotores Mexicanos (VAM) from 1976 until ...
that incorporated a front subframe to isolate the passenger compartment from engine, suspension, and steering loads.


See also

*
Bicycle frame A bicycle frame is the main component of a bicycle, onto which wheels and other components are fitted. The modern and most common frame design for an upright bicycle is based on the safety bicycle, and consists of two triangles: a main triangl ...
* Body-on-frame *
Chassis A chassis (, ; plural ''chassis'' from French châssis ) is the load-bearing framework of an artificial object, which structurally supports the object in its construction and function. An example of a chassis is a vehicle frame, the underpart ...
*
Coachbuilder A coachbuilder or body-maker is someone who manufactures bodies for passenger-carrying vehicles.Construction has always been a skilled trade requiring a relatively lightweight product with sufficient strength. The manufacture of necessarily ...
*
Locomotive frame A locomotive frame is the structure that forms the backbone of the railway locomotive, giving it strength and supporting the superstructure elements such as a cab, boiler or bodywork. The vast majority of locomotives have had a frame structure o ...
*
Monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...
*
Motorcycle frame A motorcycle frame is a motorcycle's core structure. It supports the engine, provides a location for the steering and rear suspension, and supports the rider and any passenger or luggage. Also attached to the frame are the fuel tank and battery. A ...
* C-channel


References


External links

*
What Is the A-Frame on a Car?

What Is Car frame?
{{CarDesign nav Automotive chassis types Automotive technologies Vehicle parts Structural system Structural engineering