Basic elements of a passenger car

3.1.1 General Description 

For a mechanical unit to be called a car, its design shall include certain elements, systems and mechanisms.

Basic elements of the car (shown in the Figure 3.1):

• Body 
• Engine 
• Chassis 

Figure 3.1 Basic elements of the car 

3.1.2 Body

In case if the design provides that the car body is a load-bearing element, then other parts and assemblies are installed on it. An engine with a gearbox is installed in the engine compartment, the suspension is connected to the sides (directly or via a sub frame - more about this in Chapter 6), and the wheels that support the car through pneumatic tires are connected to it. The space for passengers is equipped with cladding elements. The dashboard, steering wheel, and seats are installed. All these elements are sheathed with leather (depending on the value of the car specifications).  

3.1.3 Engine

This is the heart of the whole car. The energy of the combusted fuel is converted into rotation (mechanical work) inside the engine. Then it is transmitted to the wheels via the transmission, and the wheels, in turn, by pushing off the road, give motion to the entire car. Internal combustion engines (ICEs) are mainly used in cars. They are distinguished according to the kind of fuel, which is used for obtaining the sacred energy conversion, namely: diesel, gasoline or gas. Also, an internal combustion engine can be installed on a car along with an electric motor. In this case the car is called a vehicle with a hybrid system. The internal combustion engine and the electric motor on such vehicles work in turn or simultaneously, depending on the driving mode. It can also happen that the motor is installed exclusively, powered by rechargeable batteries.

3.1.4 Chassis

This is a set of units, elements and car control systems. It includes chassis, transmission, brake system and steering.

3.1.5 The concept of "platform"

For information

Every now and then we hear the following phrases from various specialized media: "The car is built on such and such platform..." or "Such and such a platform is the basis of..." The concept of “platform” is quite extensive. In two words we can say that this is the floor pan, the cross-member, which separates the engine compartment from the passenger compartment, all load-bearing elements and body overlays for the installation and fastening of suspension elements and a powertrain (engine + gearbox). In a broader sense, a platform is a set of basic elements, components, structural and technological solutions of a car. 

The set of components that are included in the platform is not standardized, so it may differ from manufacturer to manufacturer (but the basic set almost always remains unchanged - see above). The so-called modular platforms have appeared in the modern world. Thus, each platform consists of several modules that can be combined with other modules without spending hundreds of millions for inventing something new.

Figure 3.2 Example of a unified body platform, which is designed for several models.

Where did this "platform" come from? The fact is that a load-bearing body is the most complex and expensive element of a car's design to develop. 

This is due to the fact that the incompatible has to be combined in the car body, namely: it must be light so that the engine power is sufficient for its transportation, and strong enough to save the lives of passengers and the driver in case of an accident. In addition, it must be of certain shape, content and purpose. Therefore, in order to somehow reduce the value of the car, while designing and manufacturing it manufacturing companies came up with the lower part of the car body (this very platform) that shall be used as a “cloned” part, that is, several models can be created on one platform.

Figure 3.3 Example of a unified body platform with chassis elements and engine.

Thus, nowadays one platform can be used as a floor pan for two or more cars of different classes - from golf class to crossover. We came up to the point that some companies enter into contracts and partnerships in order to use ready-made platforms for the production of car models under various names. On the one hand, it seems to be a trickery. But on the other hand, it is a completely justified attempt to unify cars as much as possible and, as a result, to reduce the cost of their production and subsequent maintenance. However, in case if one says that two cars are built on the same platform, this does not mean that the cars are structurally identical - the suspension design and geometric parameters may differ radically.

3.1.6 Transmission

This is a set of elements and mechanisms that transmit rotation from the engine to the wheels. It includes clutch, gearbox, drive shafts with joints and drive gear with differential.

3.1.7 Chassis

These are wheels, a suspension by means of which these wheels are attached to the car body. Chassis consist of springing elements (for example, springs) and damping elements (shock absorbers), as well as axle beams (if they are continuous*), a frame or part of the body.

*  The term "continuous axle" will be described in section 5.4 "Drive gear and differential. Purpose, device and types"

3.1.8 Steering and braking system

These are mechanisms and systems that are designed for controlling a car - change the direction and speed of movement. In case of failure of any control system or any of the elements of these systems, the movement of the vehicle is prohibited, unless on a tow truck.

3.1.9 Vehicle interior controls

When you get inside any car, you find yourself in a space filled with switches, indicators, levers and parts that are common in all passenger vehicles.

Figure 3.4 Controls inside the car.

Main controls that are located in the passenger compartment will be described in order in this chapter, using the example of the Figure 3.4 above.

3.1.9.a Instrument panel 

The information about the state of all car systems is indicated on the instrument panel: how fast the car is moving, at what revolutions the engine is running, which gear is engaged, what is the temperature of the engine coolant, the level of fuel in the fuel tank, etc. In case if the vehicle is equipped with an on-board computer, it is possible to display information about instantaneous fuel consumption, daily mileage, approximate mileage until the next refueling, tips about car maintenance and many more useful data.

3.1.9.b Steering wheel 

The rotation of the steering wheel is transmitted to the steering mechanism, which, in turn, turns the steered wheels in the corresponding direction via the steering gear. Buttons for remote control of additional systems are installed on the steering wheel of modern cars, namely: multimedia (audio system/radio), cruise control, on-board computer control, etc., depending on the wishes of the buyer and the imagination of the automaker.

3.1.9.c Ignition lock or recent trend - button for turning on the ignition and starting/stopping the engine 

The key in the lock can be switched to several positions, each of which has a specific purpose. In one position, the power of all auxiliary electrical systems is turned on. That is, electricity is supplied to all consumers - from the audio system to the interior lighting and the operation of window regulators (usually this position is called ACC), and the steering wheel is unlocked. If you turn the key further - to the ON position - the engine ignition system will be switched on and self-diagnosis of all vehicle systems starts (this usually takes 2-4 seconds). 

Unlike the ignition lock, the button has no fixed positions. Often, you need to press the button and release it within 1-2 seconds in order to turn on the ignition. Press the button a second time and hold it in order to start the engine until it starts. In premium segment cars it is not necessary to hold down the button to start the engine. It is enough to press it briefly after turning on the ignition. 

Some manufacturers, who pay tribute to sports, install a separate ignition switch and a separate engine start button (“hello” from Porsche).

3.1.9.d Multipurpose understeering switches 

These switches are empowered to control the exterior lighting system, direction indicators, wipers and washers. Sometimes additional functions appear on the switch levers - it all depends on the philosophy of the developer.

3.1.9.e Pedal assembly 

In case if the gearbox is automatic (hereinafter referred to as the automatic gearbox), then there are two pedals: a brake pedal (left) and an accelerator pedal (right). In case if the gearbox is mechanical (hereinafter referred to as the manual gearbox), then to the left of the brake pedal, you can also find the clutch pedal.

3.1.9.g Central control panel (in slang – “beard”) 

Typically, this panel contains switches and controls for the ventilation, heating and air conditioning system (if such is provided by the specifications). Also, as a blueprint, car manufacturers place the head unit of the audio system (slang name - "head") with all controls and switches on this panel. The screen of the multimedia system is also mounted here. It, in combination, can display information from the navigation system (depending on the vehicle configuration).