The chassis: the importance of what is not seen

There are two ways to look at or classify vehicles. The easiest will always be from the physical appearance and/or functional, which in a way it is the way in which we can distinguish the hundreds of cars available in the Spanish market. However, as tends to happen with everything, what is most important is often what is not seen: the chassis.

Although at the commercial level does not give the importance that really has, the chassis is the element of the car that really provides the car the rigidity and the personality that we offer during the driving.

How it all began

The first vehicles were produced, more than a hundred years, consisted of two separate elements that are coupled with each other. The top was the body, which was coupled, usually with screws, to a chassis independent on racks, commonly referred to as a frame or chassis rails.

This type of chassis gets its name from rack because it is a structure composed of spars or beams, which are placed longitudinally and transverse to form a lattice of rigid on which you are installing the rest of the mechanical elements of the vehicle and finally the body.

This independence between the two main parts of the vehicle allowed a certain freedom of combination between chassis and bodywork. In fact, at the beginning of the TWENTIETH century the most common was that many car manufacturers have agreements with several body shops independent to offer their customers various body styles to mount on your chassis independent. However, this possibility of choosing the body was reserved to the economies acaudalas.

Those middle-class families that could afford the luxury of buying a car, which one hundred years ago were rather small, they tended to resort to models are most modest that were sold with a single join between body and chassis.

In this regard, we can name the Ford Model T, which many consider as the first vehicle manufactured in chain. Actually it is not so although yes we can say that it was the first car that popularized it and took it for a manufacture in large volume. Well, even though between the Ford Model T manufactured, for example, in Detroit (Michigan), and the manufactured in Cadiz (Andalusia) there were several differences, we can assert that the coming out of the same factory were completely equal. In fact, they were so alike that at first they were made of a single body and a single exterior color. On the opposite end I can cite to the Rolls Royce Phantom IV, of which were produced only eighteen units and the eighteen had body other than.

despite its short run, the example of the Rolls Royce Phantom IV serves to explain the freedom of manufacturing with the chassis frame rails. All of them kitted out the same chassis and the same engine eight-cylinder in-line, but the fact that the mechanical parts were coupled on the frame was such that its location could be modified. This is so that despite having made only eighteen units, you can see three different types of fuel tank.

The freedom of design of the bodywork also allowed these eighteen Rolls Royce had a different design between them and are recognized by some peculiarity. For example, the three units that the government of Spain bought in 1952 are canopy by H. J. Mulliner, but which is built on the chassis 4AF18 is a convertible that is characterized by being the only one that had no doors suicide. Another peculiarity might be the fact that the unit with the rack 4BP7, property of the princess Margaret of England, had steering column located more low and front seats adjustable in height, that the sister of the queen of England would lead comfortably the Rolls Royce despite the meter and fifty five centimetres of height of the countess of Snowdon.

With the passage of time, the production chain allowed the manufacturers of passenger cars develop their own bodies and mount them on the chassis in the same factories, which resulted in a lower cost of manufacturing and the bankruptcy of the greater part of the mod independent. In fact, today there are very few occasions in which a manufacturer assigns to sell the rack of any of their cars to an external manufacturer. Interestingly in the world of industrial vehicles happens just the opposite, especially in regards to the bus or coach, where it is more typical that chassis and body are manufactured by companies that are totally unrelated to each other.

Another difference between passenger cars and large commercial vehicles is that while the latter are equipped with always separate chassis on stands, passenger cars have begun to use the chassis monohull, reserving the chassis rails for those vehicles that by their characteristics require a higher rigidity, as the great all-rounder “of truth”, as for example in new Mercedes-Benz a-class X. The last tourism manufacturing chassis rail was the Ford Crown Victoria, manufacturing of which ceased in 1992 in the united States and in 2011 in Canada.

The chassis monohull with self-supporting body

The word catamaran derives from the French word monocoque and means “a single shell” and gives its name to the constructive solution is used today for the manufacture of passenger cars and light commercial vehicles. The difference is basically in three aspects:

  • The mechanical elements of the vehicle are not attached to the chassis but which are integrated in the same.
  • The main elements of the structure of the body part of the chassis.
  • In this type of construction, the lower part receives the name of the platform.

despite being the most extended at present, the chassis monohull with self-supporting body was introduced already in Paris motor show of 1922 of the hand of the Italian manufacturer Lancia.

Regarded as the first great work of Vincenzo Lancia, the Lancia Lambda had a series of technical solutions never seen before and which could be considered nearly as premonitorias to the automotive world. The most important were:

  • The platform was considerably lower than usual because the tunneling transmission was not pinned under a rack of rails, but was integrated within the same chassis in which was the carrier of passengers, as is the case today, especially in the vehicles of propulsion rear.
  • main pieces to the side and rear of the body were integrated into the chassis itself.
  • the design of The chassis had in mind the shape and location of mechanical elements as important as the engine, the change, the direction, the fuel tank, the pipes that connected them, and a discreet electrical system. Let’s not forget that the first european car in the ride’s electrical system integrated was the Lancia Theta, 1913, which formed part of an installation of 6 volts manufactured by the us company Rushmore.

Another innovative element of the Lancia Lambda relative to the chassis of the vehicle was incorporation of the front suspension-independent in a vehicle manufactured in chain. I make this shade because it’s really the independent suspension was incorporated for the first time by the French manufacturer Dacauville in 1898.

The advantages of the new chassis of the Lancia Lambda, marked a tipping point in terms of the dynamics of the car and is that the rigidity of the structure of the car combined with the cushioning independent, and a lower center of gravity made the Lancia Lambda is a reference as to passenger comfort and grip to the road.

naturally, the technique has advanced much in the last hundred years, but the basic idea of construction from a chassis monocoque with self-supporting body is the one that prevails today in the manufacture of passenger cars.

Chassis semimonocasco

very minority, you can talk about vehicles with chassis semimonocasco as those that equip a chassis monocoque body is self supporting but that in some area of the chassis using a semibastidor by stringers.

This constructive solution very little extended can be found in vehicles like the McLaren MP4-12C or the very Opel Vectra, manufactured from a chassis monocoque body is self supporting but in the motor area, where more weight supports the chassis of a car, use a structure that could resemble a frame. In the case of the English model, the part of the body that could be called self-supporting is restricted to the side parts of the lower.

This type of construction should never be confused with what is called a sub-frame, which despite the name does not cease to be a piece bolted to the platform of a vehicle and which is used to hold or give robustness to a particular area subject to the greatest weight or torque. It is common to find a subframe to hold the engine block or the absorption system. Anyway, despite the name, the subframe is not a piece part of the chassis.

the evolution of The chassis monohull

As is clear from what has been said above, the introduction of the chassis monohull with self-supporting body limited the development of new projects by builders independent. However, this “freedom” creative was taken over by the own vehicle manufacturers.

Above I have said that the chassis monohull with self-supporting body formed of a single body from the welding of a car body on a bottom surface ques which we call platform. What I now is that both the platform and the vehicle body are also formed by pieces that are going soldier little by little, which allows manufacturers to use the same platform to mount different bodies or modifications of the same.

This allows manufacturers to have in their catalog of models that seem different but in reality are built on the same platform. For example the Lancia Thema I, Fiat Croma I and the Saab 9000 share platform and even part of the pieces of the body that make up the interior, but in no case can we speak of the same chassis. These three vehicles would have to be added to the Alfa Romeo 164, which shares with the previous platform but not any part of the body.

In this aspect, you can (and should) spinning very fine and determine that , before any structural difference, we must speak of chassis-different. With this I mean that vehicle so “the same” as the Peugeot 208 three-door and five-door share platform and almost all of the pieces of the body, but, for practical purposes, are two chassis different.

Needless to say, the main idea of that two or more cars share the maximum number of items produces a significant savings in the costs of production of a particular vehicle, savings that are rarely transferred to the customer.

Platforms arising

The evolving technique and the ability of manufacturers to lead to production of minor changes in the platforms allowed the development of new products adapted to the demands of the customers. For example, on the same platform in effect you can enter the modifications necessary for the launch of the market to different vehicles, as it happened at the beginning of the 80’s with the Renault 9 and Renault 11. Both cars had basically the same platform, showing differences only in the rear of the same.

however, on the basis of a platform effect, the modification of the distance between the axles required a greater degree of technology and, therefore, a higher cost due to that an increase in this parameter adversely affects the rigidity of the entire structure, unless that introduction of reinforcing elements. This was not impediment so that there would be manufacturers who dared to do so although, in principle, this type of modification is observed primarily in high-end vehicles.

For example, when in 1965, came on the market the Mercedes Benz W108 was launched parallel to the Mercedes Benz W109, with ten more inches of distance between axes and a body that absorbed that increase in length in the central area of the passenger compartment. Being puntillosos one cannot speak of the same platform or the same body, and, by both, or a lot less same-chassis monocoque body is self supporting. However, to be honest, the only modifications observed in the W109 with respect to the W108 were fair and necessary to grow the passenger compartment, those ten centimeters, so that talk about a new platform or new body would also be unfair.

As expected, in terms of are more popular and cheaper, cany technical improvement or construction, you enter a large manufacturer ends up being adapted by the rest of the builders. For example, the Lancia Delta III launched in the year 2008 using the same platform as the Fiat Bravo II although the distance between the axes of the first to be 2700 mm and the second as “only” 2600 millimeters.

Platforms “evolved”

I Put quotation marks around this concept, because sometimes you can call equivocal. What is more usual is that the term “evolved” in reference to a platform to be used by the same manufacturer when you want to say that on an existing platform introduces a number of improvements in order to increase the robustness of the set or to adapt the platform for the introduction of new technologies. An example of the use of platform “evolved” can be, for example, the Citroen Saxo, that equates the same as the Citroën AX suitably reinforced.

modular Platforms

In a relentless struggle for the resource optimization, the manufacturers are forced to develop platforms that can be used for the development of the greatest number of vehicles possible. Add to that the fact that currently the future of the automotive passes through the electrification of their groups-drive and that a platform designed exclusively for a vehicle with internal combustion engine is not ready to host an electric thruster. This forces manufacturers to design platforms, the most versatile possible that they are able to serve as a basis for the development of the widest range of combinations between bodies and groups thrusters but always with the minimum of amendments, and, therefore, investment.

An example, perhaps the best that we have right now, is the Volvo’s Scalable Product Architecture, better known by the SPA, which debuted in the year 2014 with the launch of the second generation of the Volvo XC 90 and currently serves as a base for vehicles as disparate as the Volvo S90L or the new Volvo XC 60.

it is True that at this point many people will have the temptation of compare this platform for Volvo with a platform evolved, or derived, . The difference between these latter and the modular platform Volvo is the Swedish manufacturer has managed to design a platform in which it is possible to modify its physical parameters (length, width, and battle) in order to adapt it to the different current models and future does not mean a new investment on the part of the mark of Göteborg. In addition, this modular platform is ready for:

  • Vehicles front-wheel-drive or all-wheel drive.
  • Vehicles with manual change or automatic change.
  • Vehicles with combustion engine or hybrid.
  • electric Vehicles (coming soon).

The Swedish manufacturer is so convinced of the benefits of the modular platform that its next product, the Volvo XC 40, will be manufactured on a new modular platform called CMA and that will be the match point for the development of a whole new range of compact models and small.

Platforms, “peculiar”

Even if you put the example the example of the modular platform of Volvo as the most complete and versatile there is in the market, I would like to explain the particularity of the platform modular Small Wide Fiat.

The origin of this platform is to be found in the platform that debuted in the year 2005, the Fiat Punto 199 and that also provided the basis for the Opel Corsa D. In the beginning or even the manufacturer spoke modular platform although already in his time in efforts to clarify which would be the basis for different models. In fact his name was Small Common Components Systems (SCCS), something that could be translated as small system common components.

by the time this platform was modified to give rise to models that appear to be so antagonistic as the Fiat Doblò or the Fiat Line. In 2008, the the Alfa Romeo MiTo premiered a chassis produced from a platform SCCS evolved built with lighter material and resistant, on the never came to make any of the generations of the Fiat Punto. In any case, this platform only allowed the development of chassis to front wheel drive vehicles and with changes with the architecture manual, which were either conventional clutch pedal, clutch driven or dual-clutch (remember that in this last type clutches are also out of the change).

has also given the case of an involution of this platform. Although it may seem paradoxical, there is a simplified version of the platform SCCS that has been the basis for the development of the chassis of the Fiat Punto marketed in emerging countries and for the Tata Indica and Tata Indigo.

In the year 2012, the platform SCCS received a new evolution (a word text of the press releases from Fiat Auto Spa) and received the name of Small Wide, or simply B-Wide, in reference to the commercial sector for which it was developed. This new platform because of the modular architecture, allows the Dutch group (formerly Italian) to manufacture vehicles with front-wheel drive or full and the possibility of riding in them automatic changes with converter of pair.

The first vehicle to mount the platform Small Wide was the Fiat 500L, but currently also serves as the basis of models that are as different as the Jeep Renegade, Fiat.

As you can see, sometimes two vehicles may be more similar than commercially seem. In any case, the reason of this article was to explain and make them understand the differences between chassis, frame and platform, words that are commonly confused and used incorrectly.

You may be interested to