For millions of passengers, the metro remains the fastest and most predictable way to travel around the metropolis, but few people think about the complex engineering system hidden behind the doors of the cars. When we lean on handrails or glance at advertising posters, a colossal mechanism is working beneath us, combining heavy industry, precision electronics and automated control systems. Understanding that what exactly are we driving?, helps to better navigate emergency situations and appreciate the work of engineers who ensure our safety every minute.
Metro rolling stock is not just a set of interconnected bodies, but a single organism, where each unit performs a critical function. From the traction motor system to the pneumatic doors and air conditioning systems, all elements must work in perfect synchronization. In this article we will analyze in detail the internal structure of the car, the types of trolleys used and the principles of operation of the safety systems that make the subway one of the most reliable modes of transport.
Many people mistakenly believe that subway cars are the same all over the world, but this is not true. Depending on the year of manufacture, country of origin and line capacity, technical specifications may differ radically. For example, control system in older models it can be completely manual, while the newest trains are controlled by artificial intelligence without the participation of a driver. The differences even extend to the track width and type of current collection, making each park unique.
Typology of rolling stock: from “E” to “Moscow”
The history of the development of the metro has given rise to many modifications of cars, which are classified by letter designations. These letters indicate the generation of equipment, dimensions and technical solutions. In Russia and the CIS countries, the most common types of cars are E, D, 81-717/714 and the newest series “Moscow” and “Baltiets”. Each generation marks a step forward in comfort and energy efficiency.
Old models such as the famous type E, were distinguished by a characteristic “corridor” type design with vestibules and had exclusively a rheo-contactor control system (RKSU). This meant that high-power resistors were used to regulate the speed, which dissipated enormous amounts of heat. Efficiency of such systems was relatively low, and acceleration and braking were accompanied by characteristic jerking and loud humming.
⚠️ Attention: In old carriages of type “E” and “D”, it is strictly forbidden to lean on the doors while moving, since the locking mechanisms of the vestibule may not withstand the pressure of the mass of passengers during sudden braking of the train.
Modern cars, such as the 81-765 "Moscow" series, are high-tech complexes. Applied here asynchronous traction, allowing energy to be returned to the network during braking. The bodies of such cars are made of stainless steel or light alloys, and the interior is devoid of sharp corners for safety. The transition between cars became through, which radically changed the distribution of passenger traffic within the train.
- 🚇 Type “E” cars are classics of the Soviet metro, produced from 1963 to 1969, distinguished by the presence of vestibules.
- 🚇 Series 81-717/714 - the “workhorse” of the post-Soviet space, is being massively modernized to modern standards.
- 🚇 Type "Moscow" (81-760/761/763) - a completely low-floor car with a through passage and asynchronous motors.
- 🚇 “Baltiets” (81-775/776/777) is the latest development with improved ergonomics and climate control system.
The differences between the types concern not only the appearance, but also the internal layout. In new models, the number of seats has been reduced in favor of a larger storage area, which speeds up alighting and boarding. Ventilation system replaced by full climate control, maintaining the set temperature regardless of the heat in the tunnel or on the surface.
Chassis and bogies: the basis for stability
The foundation of any car is the chassis, represented by bogies. They carry the weight of the body with passengers and ensure movement along the rail track. The subway uses two-axle bogies, which are divided into motor and trailed ones. The motor trolley is equipped with traction electric motors that transmit torque to the wheelsets through a gearbox.
The design of the subway trolley is much more massive than that of railway cars, due to the need for frequent acceleration and braking. Spring suspension here it is performed in two stages: primary (between the axle box and the bogie frame) and secondary (between the bogie frame and the body). This allows you to dampen vibrations and ensure smooth running even at rail joints.
Particular attention is paid to wheel pairs. The wheel profile has a special ridge shape that holds the car on the rails. However, even with an ideal profile, there is a risk of derailment when making sharp turns. To prevent this it is used comb lubricator - a device that supplies special lubricant to the wheel flange before entering a curve.
| Parameter | Motor trolley | Trailed trolley |
|---|---|---|
| Availability of engines | 2 or 4 traction motors | None |
| Power transmission | Through gear transmission | Not applicable |
| Weight | Significantly higher (up to 8-9 tons) | Below (about 4-5 tons) |
| Brake pads | Disc or pad | Mostly disk |
The most important element of the chassis is the axle box, in which the axle of the wheelset rotates. Inside the axlebox there are rolling bearings that require constant temperature control. Overheating of axle box can lead to jamming of the wheelset and a serious accident, which is why modern cars are equipped with hot-box control (HBC) sensors that transmit data in real time.
If you hear a lot of clunking or grinding noise from your wheels when driving around a curve, this may indicate a faulty comb lubricator or a worn wheel profile.
Electric traction and control systems
The heart of the metro is electrical energy. The cars are powered by a contact rail (third rail), which carries 825 volts of direct current. Current collection is carried out using a special device - a current collector (runner), which slides along the surface of the rail. Current collection system must ensure reliable contact even with vibrations and contamination.
Speed and traction control have come a long way in evolution. If previously a rheo-contactor system (RKSU) was used, where the current was regulated by turning resistors on and off, now the thyristor-pulse (TISU) and asynchronous systems dominate. In TISU, the current is regulated by changing the pulse width, which saves energy and ensures smooth acceleration without jerks.
The asynchronous drive is considered the pinnacle of the evolution of traction systems. It uses AC motors, the frequency of which is controlled by an inverter. This makes it possible to implement a recuperation mode: when braking, the engine operates as a generator, returning energy to the contact network. Energy efficiency of such compositions is 30-40% higher than that of older models.
⚠️ Attention: The contact rail is under deadly voltage. It is strictly prohibited to drop any objects (phones, keys) onto the path. Trying to reach the object yourself can result in electric shock even without direct contact with the rail.
The cable network of a carriage is a complex web of wires connecting all systems. The fire safety of the composition depends on the state of the cable insulation. In modern cars, cables are laid in special boxes and have a sheath that does not support combustion. Diagnostic system Constantly monitors leakage currents and circuit integrity.
Pneumatics and brake systems
Traffic safety in the subway is impossible without a reliable braking system. The basis here is pneumatics - compressed air, which powers the brake cylinders. A compressor installed under the car body pumps air into the main tanks. The pressure in the system is usually about 7-8 atmospheres.
Combined braking in the metro. The main work is performed by electrodynamic brakes, which reduce speed due to the operation of the engines in generator mode. When the speed drops to a minimum (usually about 5-10 km/h), the pneumatic pads or disc brakes, which finally stop the train. This scheme allows you to significantly save the life of brake pads.
One of the key features is the presence of auto brakes. If the train's brake line pressure drops (for example, when a coupling breaks or doors are opened while moving), the brakes are automatically applied. This safety principle, preventing the movement of a train with a faulty braking system.
☑️ Checking the brake system by the driver
Sandboxes mounted on trolleys play an important role in winter. They feed sand onto the rails in front of the wheels, increasing traction. Without this, when braking on a wet or icy section of the track, the wheels could simply slide along the rail (skid), increasing the braking distance significantly.
Interior, doors and comfort systems
The interior space of the car is designed taking into account high passenger capacity. Modern models use anti-vandal coating on seats and walls. LED lighting provides uniform light without flickering, and new compositions introduce dynamic lighting that changes color temperature depending on the time of day.
Doors are the busiest mechanism in a carriage. They open and close hundreds of times a day. The door drive can be pneumatic (older models) or electric (newer). The electric drive is quieter, more reliable and allows you to implement the “anti-clamp” function when the door opens back if there is an obstacle. Locking system doors are rigidly connected to the traffic control system: until the doors are closed and locked, the train will not move.
Ventilation and air conditioning systems in the metro operate under extreme conditions. In summer, the temperature in the tunnels can reach 30-40 degrees due to heat generation from train braking. Powerful refrigeration units on the roof or under the body must cool the air by passing it through filters. In winter, the heating system operates, often using heat from electrical equipment.
- 🚪 Leaning-sliding type doors are the most common and ensure tightness.
- 🚪 Screen type doors - used in some systems, they open into the interior.
- 🚪 Video surveillance systems - cameras in each car transmit the flow to the cabin and the dispatcher.
- 🚪 Information boards - dynamically show stations and transfers.
Particular attention is paid to fire safety. Interior finishing materials should not emit toxic substances when burned. Smoke detectors are installed in the cars, and automatic fire extinguishing systems are installed in the engine room. Emergency communication communication with the driver or dispatcher is available to passengers through special intercoms.
Why does the wind blow in the subway?
The wind in a subway tunnel is created by a piston effect. A moving train, like a piston in a cylinder, pushes air in front of itself and sucks it in behind. The speed of this air flow can reach 10-15 m/s, which feels like a strong wind on the platform.
Automation, signaling and train control
The movement of trains in the metro is regulated by a sophisticated automation system. The driver does not choose the speed arbitrarily - he follows the indications of traffic lights and signals from the ALS (automatic locomotive signaling) system. If the driver passes a prohibitory signal, the ALS system will automatically apply emergency braking. This security guarantee, excluding the human factor.
In modern systems such as CBTC (Communication Based Train Control), movement is controlled via radio. The computer knows the exact location of each train and calculates the optimal speed and intervals. This makes it possible to reduce intervals between trains to 90 seconds or less. The driver's cabin in such systems is often closed by a partition, since the train moves in automatic mode.
Communication between cars and with the dispatcher is carried out through a radio channel and wire lines. The tunnels contain special leaky-cables that emit a radio signal along the entire length of the path. This ensures continuous communication even deep underground. Digital protocols data transmissions allow telemetry to be transmitted about the state of all train systems in real time.
⚠️ Attention: The use of powerful radio transmitters (walkie-talkies, signal amplifiers) in the metro can interfere with the operation of communication and train control systems, so their use is strictly regulated.
The supervisory control system completes the picture. The dispatcher's console displays the schedule of all trains on the line. Any deviation from the schedule, delay at the station or technical malfunction is immediately visible on the screen. The dispatcher has the ability to remotely control traffic lights and, in some cases, the speed of trains.
A modern metro is not just transport, but a single information and control complex, where each car is a smart network node that constantly exchanges data with the control center.
Car maintenance and life
After the end of the working day, the cars are sent to the depot - specialized repair and maintenance enterprises. Here, a daily inspection (TO-1) is carried out, which includes checking the brakes, doors, pantographs and oil level. More in-depth diagnostics are carried out after certain runs.
Wheel pairs undergo regular turning on machines. The wheel profile wears unevenly, and dents and flat spots appear. Turning restores the ideal profile, which reduces noise and vibration. If the wheel is worn to the maximum size, it is replaced with a new one.
Overhauling a carriage is a process that lasts several months. The car is completely disassembled down to the frame. Cable insulation is changed, body elements are digested, and new electrical equipment is installed. In fact, after a major overhaul, the carriage gets a second life and can run for another 10-15 years.
The service life of a metro car is on average 30-40 years, but with high-quality modernization it can be extended to 50 years or more. However, economic efficiency often dictates the replacement of older trains with new, more energy-efficient models that pay for themselves through energy savings.
How does the driver know where to open the doors?
The driver is guided by special markings on the platform (usually yellow triangles or light indicators) and by instrument readings in the cab. In Automatic Operation (ATO) systems, the train itself stops at a predetermined point within a few centimeters, and the doors open automatically when a signal is received from the platform.
Why can't you take photos with flash on the subway?
The camera flash can blind the driver, especially in a dark tunnel or when exiting it. Blinding the driver while passing a traffic light or approaching a station can lead to an emergency. In addition, some metros have restrictions on professional filming without permission.
What to do if you dropped something on the path?
Under no circumstances try to get the item yourself! This is deadly. You must immediately contact the station duty officer or any metro employee. They will stop train traffic in the area and remove the item using a special insulated tool.
Does the metro have a backup power source?
Yes, life support systems (ventilation, lighting, communications) and control systems have backup power from batteries. In the event of a complete shutdown of the external current, the batteries will be enough to operate the emergency systems for several hours to evacuate passengers from the tunnel.
Why do carriages sometimes “jerk” when starting?
This is typical for RKSU (resistor-contactor) systems, where switching resistor stages causes current surges. In modern cars with asynchronous drives, acceleration is absolutely smooth. Jerking can also be a sign of wheelset slipping (slippage) when accelerating on wet rails.