A platform chassis is a form of vehicle frame / automobile chassis, constructed as a flat plate or platform, sometimes integrating a backbone or frame-structure with a vehicle's floor-pan.
A platform chassis is a form of vehicle frame / automobile chassis, constructed as a flat plate or platform, sometimes integrating a backbone or frame-structure with a vehicle's floor-pan.
A platform chassis is a separate chassis for a car or small vehicle. It is distinguished from other forms of chassis by being arranged as largely a single flat steel sheet, usually with additional box section stiffeners. [1]
Platform chassis developed after the ladder chassis or cruciform chassis designs in the 1930s, once car bodies began to be pressed from large steel sheets, rather than the chassis assembled from rolled channel sections. As a semi-monocoque they are still a form of body-on-frame construction, rather than a monocoque or unibody where the bodyshell and chassis are integrated into one component. Although both body and platform chassis are each made from similar pressed steel panels welded together, they were often bolted as the final two units and so may still be separable after construction.
Achieving sufficient rigidity is difficult with a pure platform and so they are usually extended vertically with some form of box or tube section. This can be either a perimeter frame (e.g. Renault 4) or a central spine (e.g. VW Beetle). Longitudinal rigidity is more critical than transverse rigidity and so this stiffening is mostly as front to back girders, rather than crosswise. The diaphragm sheet is usually pressed into shallow stiffening ridges as well, but these are mostly to stop drumming noise and are too minor to provide major structural strength.
Platforms are usually the full width of the car, but shorter and only span the length between the wheels. Suspension attachments for the wheels and the weight of the engine and transmission are carried on additional subframes beyond this. These subframes may be formed of box section tubes welded on to the chassis, deep-drawn box sections formed from sheet, or as separate subframes that are bolted in place.
Platform chassis have been used for both rear-wheel drive (Beetle) and front-wheel drive (Renault) layouts. However they keep the engine at the driven end, with a transaxle, rather than using the propeller shaft of the Hotchkiss layout of front-engine, rear-drive that was universal with chassis designs beforehand. This avoided transmitting the propeller shaft torque through the platform. Where a propeller shaft has been used, these have been for rare examples with four-wheel drive.
Attaching the suspension to a platform chassis requires independent suspension and encourages the use of suspension features such as torsion bars or trailing arms. As the chassis is in a single plane, it would be difficult to use a solid axle, without raising the entire platform above the axle line. It is also difficult to arrange spring attachments for springs such as half-elliptic springs requiring distance fore and aft of the axle line, or for coil spring or strut suspensions needing an attachment point raised vertically above the platform. Instead, springs such as torsion bars are used. Whether these are transverse or longitudinal, they lie in the horizontal plane of the platform and so can be worked in to such a chassis. Other torsion-based systems, such as twist-beam rear suspension, may be used as well for front-wheel drive cars with light rears.
The Volkswagen Type 1 Beetle used a platform chassis, with independent torsion bar suspension at each end. The 'Volkswagen', 'Peoples' Car' or 'KdF-Wagen' project began in 1933 and by 1934 Porsche had sketched out a design for a rear-engined, platform chassis car with four seats and torsion bar suspension. [2] A central stiffening tube provided much of the strength of the chassis.
This basic design proceeded through the pre-war Porsche Type 60, and several wartime military vehicles, before finally the first post-war mass-production Volkswagen Beetles of 1945. [3]
In 1936, Porsche adapted the developing KdF-Wagen 'domestic' car as a sporting car suitable for the auto trials organised by the NSKK. These were slow-speed competitions across off-road terrain and obstacles, which developed both driving skill and vehicle agility, in ways which were expected to be useful for military motoring. This Porsche Type 62 was an open-topped, open-sided four seater, still with rounded bodywork. Although it performed well in military trials at Münsingen, its appearance was considered to be 'too civilian'. [4]
Porsche continued to develop the Type 62 with such features as a rear portal axle to give increased ground clearance and the ability to move with infantry at a walking pace. The rounded bodywork was also replaced with ribbed flat panels, with doors, [lower-roman 1] and by the end of 1939 this had been accepted as the military Type 82 Kübelwagen. [6] The Kübelwagen was highly effective, in large part due to the light weight achieved by use of its platform chassis. It weighed only 1,510 lb, the same design weight as the road car, and was 200-300 lb lighter than its rival vehicles from Opel, DKW and Adler. [7]
A four-wheel drive version was also developed, again using the same platform chassis and basic layout, but under the civilian enclosed bodywork. This became the Type 87 Kommandeurswagen (Porsche Type 287) and was intended for use by senior field commanders. The central tube of the chassis pan was enlarged to give space for a propeller shaft and a powered front axle provided, with similar driveshafts as the rear axle. [7]
The Beetle powertrain comprised a rear-mounted flat-four engine with a longitudinal transaxle ahead of it. The rear suspension was by swing axles. The first 1945 civilian Beetle used a platform chassis which stopped short of the rear wheels and which had a central stiffening tube. This tube extended rearwards as a Y-shaped fork, which passed each side of the transaxle and to the engine mounts. The rear swing axles were also held at their outboard ends by flat plate trailing arms, which were pivoted on the ends of a crosswise tube, containing the torsion bars. At this time the rear shock absorbers were only single-acting, lever-type. [8]
The front suspension was provided by pairs of short trailing arms, again with transverse torsion bars mounted in two separate tubes, mounted ahead of the flat platform. [9] These torsion bars were stacks of flat strips, and the number of leaves was changed to vary the suspension stiffness, over the production of the Beetle. [10]
An advantage for the production of the vehicle was that controls such as the driver's pedals and brake piping, the gear stick and the handbrake which required connections to the engine or drive train could be installed onto the platform before the body was added. Even, until 1952, [11] the engine choke control and its Bowden cable were mounted on the central tunnel. Unlike most contemporary chassis-on-frame designs though, the steering column was mounted on the bodyshell and was not connected to the steering box on the chassis platform until the two were joined.
In the 35 year production history of the Beetle, the basic platform chassis remained largely unchanged, except for one change to the front suspension of the 'Super Beetle'.
From 1970, the new 1302 'Super Beetle' adopted MacPherson strut front suspension. [12] This increased front luggage capacity by nearly 50%, also due to a slightly lengthened front bonnet, but the upper mounts of the struts now coupled suspension forces into the inner wing panels of bodyshell rather than the platform: the chassis was now no longer a pure platform. The 1303 'Super Beetle' continued in production until 1975, although the Economy Beetle continued in parallel with it, still using the trailing arms and platform chassis. [13]
The platform chassis, and the large number of available VW Beetles, encouraged the use of the Beetle platform as a donor car for building kit cars. The most iconic of these was the dune buggy: a stripped-down Beetle chassis, with the simplest fibreglass 'bathtub' body on top of this.
The first production dune buggy, the Meyers Manx, used a shortened VW platform as a basis. The front of the chassis was cut off and replaced by a taller structure of welded square steel tube. This made the front end vertically stiffer and the suspension was replaced by one based on Chevrolet parts, although still with double trailing arms. The Meyers Manx was widely copied and most of these copies retained the full VW platform and VW front suspension.
Platform chassis were not significantly more or less safe than contemporary ladder chassis, although much less safe in an impact than a modern design with a monocoque integrated into a passenger safety cell. They had a tendency in serious accidents for the complete bodyshell to separate from the chassis, as did the ladder chassis. However with the platform chassis, this formed the floor of the passenger area, rather than the body tub, and had the seats mounted to it. The passengers could thus stay with their seats on the chassis, while the bodyshell tried to pass through them.
Modern developments of chassis materials, bodyshells materials and design, and also changes in drivetrain have given the platform chassis a resurgence. They are now in use for some electric and hybrid cars, such as the Tesla S.
An electric drivetrain (either hybrid or pure battery) does not require mechanical stiffness between an engine and final drive. The entire drivetrain can be mounted in a subframe at one, or increasingly both, ends.
Battery storage is required, and as the battery pack is heavy it is an advantage for stability to mount it in the largest flat layer, as low down as possible. The pack weight for a Tesla S is 1,200 pounds (540 kg) [14] As these are composed of 7,104 cells, packaged into 16 modules, [15] their overall shape is flexible and can be adjusted to best fit the vehicle. This makes the platform chassis a good way to carry it, with the batteries themselves either above or below the chassis platform, making them easier to access for exchange. [lower-roman 2]
A punt chassis is similar to the platform chassis, but in addition to the lower platform there are also deep raised sides. These give vertical stiffness, without requiring added stiffeners.
Punt chassis have often been used with armoured vehicles. The armoured outer bodyshell forms a robust monocoque which can serve double duty as the vehicle's chassis. Such armoured vehicles require all-wheel drive for off-road capacity with their weight, which many involve six or eight wheels, and so have often used a H-drive layout for the drivetrain. Rather than axles connected by a central propeller shaft, the two sides are linked fore-and-aft by driveshafts in the lower corners of the punt. This also allows greater useful space inside for crew or equipment. [16] [17]
The Volkswagen Beetle—officially the Volkswagen Type 1, informally in German der Käfer, 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, intended for five occupants, that was manufactured and marketed by German automaker Volkswagen (VW) from 1938 until 2003.
The Volkswagen Kübelwagen, was a light military vehicle designed by Ferdinand Porsche and built by Volkswagen during World War II for use by the German military. Based heavily on the Volkswagen Beetle, it was prototyped as the Type 62, but following improvements entered production as the Type 82.
The Volkswagen Schwimmwagen was an amphibious four-wheel drive off-road vehicle, used extensively by German ground forces during the Second World War. The Schwimmwagen is the most numerous mass-produced amphibious car in history.
A torsion bar suspension, also known as a torsion spring suspension, is any vehicle suspension that uses a torsion bar as its main weight-bearing spring. One end of a long metal bar is attached firmly to the vehicle chassis; the opposite end terminates in a lever, the torsion key, mounted perpendicular to the bar, that is attached to a suspension arm, a spindle, or the axle. Vertical motion of the wheel causes the bar to twist around its axis and is resisted by the bar's torsion resistance. The effective spring rate of the bar is determined by its length, cross section, shape, material, and manufacturing process.
The Volkswagen Type 3 is a compact car that was manufactured and marketed by Volkswagen from 1961 to 1973. Introduced at the 1961 Frankfurt Motor Show, Internationale Automobil-Ausstellung (IAA), the Type 3 was marketed as the Volkswagen 1500 and later as the Volkswagen 1600, in three body styles: two-door Notchback, Fastback and Variant, the latter marketed as the 'Squareback' in the United States.
In automotive design, an RR, or rear-engine, rear-wheel-drive layout places both the engine and drive wheels at the rear of the vehicle. In contrast to the RMR layout, the center of mass of the engine is between the rear axle and the rear bumper. Although very common in transit buses and coaches due to the elimination of the drive shaft with low-floor buses, this layout has become increasingly rare in passenger cars.
In automotive design, an RMR, or rear mid-engine, rear-wheel-drive layout, is one in which the rear wheels are driven by an engine placed just in front of them, behind the passenger compartment. In contrast to the rear-engined RR layout, the center of mass of the engine is in front of the rear axle. This layout is typically chosen for its low moment of inertia and relatively favorable weight distribution. The layout has a tendency toward being heavier in the rear than the front, which allows for best balance to be achieved under braking. However, since there is little weight over the front wheels, under acceleration, the front of the car is prone to lift and cause understeer. Most rear-engine layouts have historically been used in smaller vehicles, because the weight of the engine at the rear has an adverse effect on a larger car's handling, making it 'tail-heavy'. It is felt that the low polar inertia is crucial in selection of this layout. The mid-engined layout also uses up central space, making it impractical for any but two-seater sports cars. However, some microvans use this layout, with a small, low engine beneath the loading area. This makes it possible to move the driver right to the front of the vehicle, thus increasing the loading area at the expense of slightly reduced load depth.
A truggy is a type of high performance off-road racing vehicle that combines features from two older existing categories of off-road racing vehicles, trucks and buggies. The first truggies were built for racing in the SCORE and BITD off-road desert racing series, held in Mexico, California, Nevada and Arizona.
The Chapman strut is a design of independent rear suspension used for light cars, particularly sports and racing cars. It takes its name from, and is best known for its use by, Colin Chapman of Lotus.
A swing axle is a simple type of independent suspension designed and patented by Edmund Rumpler in 1903. This was a revolutionary invention in the automotive industry, allowing wheels to react to irregularities of road surfaces independently, and enable the vehicle to maintain a strong road holding. The first automotive application was the Rumpler Tropfenwagen, later followed by the Mercedes 130H/150H/170H, the Standard Superior, the Volkswagen Beetle and its derivatives, and the Chevrolet Corvair, amongst others.
An anti-roll bar is a part of many automobile suspensions that helps reduce the body roll of a vehicle during fast cornering or over road irregularities. It connects opposite (left/right) wheels together through short lever arms linked by a torsion spring. A sway bar increases the suspension's roll stiffness—its resistance to roll in turns—independent of its spring rate in the vertical direction. The first stabilizer bar patent was awarded to Canadian inventor Stephen Coleman of Fredericton, New Brunswick on April 22, 1919.
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 Volkswagen Type 181 is a two-wheel drive, four-door, convertible, manufactured and marketed by Volkswagen from 1968 to 1983. Originally developed for the West German Army, the Type 181 also entered the civilian market as the Kurierwagen in West Germany, the Trekker in the United Kingdom, the Thing in the United States (1973–74), the Safari in Mexico and South America, and Pescaccia in Italy. Civilian sales ended after model year 1980.
Rochdale cars were a series of mainly glass fibre bodied British sports car made by Rochdale Motor Panels and Engineering in Rochdale, Greater Manchester, England between 1948 and 1973. The company is best remembered for the Olympic coupé made between 1959 and 1973.
A subframe is a structural component of a vehicle, such as an automobile or an aircraft, that uses a discrete, separate structure within a larger body-on-frame or unit body to carry certain components, such as the engine, drivetrain, or suspension. The subframe is bolted and/or welded to the vehicle. When bolted, it is sometimes equipped with rubber bushings or springs to dampen vibration.
The Avenger GT was a kit car produced by Fiberfab. It was designed in California and manufactured in the United States and Canada for 12 years, from late 1966 until 1978.
Backbone tube chassis is a type of automobile construction chassis that is similar to the body-on-frame design. Instead of a two-dimensional ladder-type structure, it consists of a strong tubular backbone that connects the front and rear suspension attachment areas. A body is then placed on this structure. It was first used in the English Rover 8hp of 1904 and then the French Simplicia automobile in 1909.
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.
From 1931 to 1939, Daimler-Benz AG produced three cars with rear engine as well as a few prototypes. The production numbers remained quite low for each of these models, especially compared to the production of classical front-engine Mercedes cars.
The Volkswagen Typ 87, also known as the Kommandeurswagen, is a World War II, four-wheel-drive version of the Volkswagen Beetle. It was produced from 1941 to 1944 by the Volkswagen plant, primarily for high officers of the Wehrmacht. The Wehrmacht classified the Kommandeurswagen as leichter geländegängiger PKW, 4-sitziger, 4-radgetriebener Geländewagen Typ 87..
 | Wikimedia Commons has media related to Platform chassis . |
|volume= has extra text (help)