The LiAZ-677, launched in 1967, became a symbol of Soviet public transport and a primary means of transportation for millions of citizens for decades. This high-floor transport giant, developed by the Likinsky Bus Plant, was created taking into account strict requirements for cross-country, maintainability and capacity in harsh climates. The engineers set the task to create a universal machine capable of working both on the central streets of Moscow and on the broken roads of remote villages, which determined its design features.
The body of the wagon layout with a load-bearing structure of tubular profiles provided the necessary rigidity and durability, allowing the car to withstand colossal loads during peak hours. The engine located under the floor of the rear of the cabin and the automatic transmission made the control relatively easy for the driver, despite the dimensions of the vehicle. It is the combination of a reliable, though not without flaws, hydromechanical transmission and a powerful diesel engine that allowed this model to dominate the country's roads for more than thirty years.
History of creation and stages of modernization
Development of the new city bus began in the late 1950s, when it became obvious that the existing models of the ZIL-158 and LiAZ-158 can no longer cope with the growing passenger traffic. The designers were tasked with increasing capacity and improving dynamic performance, while maintaining ease of maintenance. Prototype that received an index Liaz-677The first bus line was launched in 1967, marking the transition to a new generation of Soviet buses with automatic transmission.
During the production process, the model was constantly improved. The first versions were equipped with a ZIL-130 engine with a capacity of 150 hp, but it soon became clear that this was not enough to fully load. Therefore, in the 1970s, an upgrade was carried out during which the car received a more powerful engine. ZIL-375JA5 11 litres. This allowed to improve acceleration and the ability to overcome protracted climbs with full load.
Significant changes have affected both the external appearance and the management system. If the early modifications had a characteristic "humpback" roof above the driver's cab and a windshield of two parts, the thin versions received a more streamlined shape and a single windshield. Also, the air drive system of the doors and the location of storage platforms changed, which directly affected the speed of boarding and disembarking passengers during rush hour.
The evolution of design
LiAZ-677 went from angular shapes of the 60s to more smooth lines of the 90s. Particular attention was paid to increasing the glazing area for better lighting of the cabin.
Technical characteristics and power unit
The heart of the legendary bus was a carburetor V-shaped eight-cylinder engine, developed on the basis of truck units. This engine, known for its thrust and unpretentiousness to fuel quality, worked in tandem with a two-speed automatic transmission. This bundle ensured smooth running, which was critical for standing passengers, but required the driver to have certain skills for economical driving.
Hydromechanical transmission GM-3 later GM-4 It consisted of a hydrotransformer and a planetary gearbox. The hydraulic transformer allowed to move from place without jerks and softened the impact loads on the transmission when changing gears. However, this system had its drawbacks, the main of which was high fuel consumption, especially in the urban cycle with frequent stops.
⚠️ Warning: Operation of hydromechanical transmission requires constant monitoring of oil level and temperature. Overheating oil in hot weather could lead to system failure and immobilization of the bus.
The LiAZ-677 braking system also deserves a special mention. It was completely pneumatic, with two circuits and energy accumulators for the parking brake. Braking efficiency was ensured by drum mechanisms on all wheels, although a loaded car required a considerable distance to stop completely, which drivers had to consider when maneuvering.
Body and passenger compartment device
The design of the body was based on a load-bearing frame welded from steel pipes of rectangular cross-section. This scheme allowed to evenly distribute the loads and eliminate the need for a heavy frame, which had a positive effect on the total mass of the vehicle. The sheathing was made of steel sheets, which were often corroded during operation, especially in places where moisture and reagents accumulate.
The interior of the cabin was organized as utilitarianly as possible. The high floor, due to the placement of aggregates under it, required passengers to overcome three stages at the entrance. The seats were located on the sides and were made of hard plastic or plywood with dermatine upholstery, which ensured ease of sanitary treatment, but did not add comfort on long trips.
The ventilation system in the basic version was represented only by opening windows and hatches in the roof, which in the summer turned the cabin into a stuffy room. Heating was carried out due to the heat of the engine, but often it was not enough to warm up the entire volume of the cabin in severe frosts. Lighting was provided by plafonds operating from the onboard network with a voltage of 12 or 24 volts, depending on the modification of electrical equipment.
Typical malfunctions and operational problems
Despite its legendary reliability, the LiAZ-677 model had a number of characteristic "diseases" that repair services regularly encountered. One of the most common problems was leaking oil from the engine and gearbox through the glands and gaskets, which quickly lost elasticity under the influence of high temperatures.
The pneumatic system responsible for the operation of doors and brakes, also often failed. The cuffs of the pneumo cylinders dried up and cracked, leading to air leaks and failure of mechanisms. Drivers had to constantly monitor the pressure gauge readings and, if necessary, pump up the pressure with a compressor or eliminate fistulas on the spot.
- 🔧 Frequent engine overheating in summer due to radiator pollution and insufficient efficiency of the cooling system.
- 🔧 Wear of the squeezers and bushings of the front suspension, leading to backlashes and deterioration of handling at high speed.
- 🔧 Corrosion of thresholds and bottom of the body, especially in regions with active use of deicing reagents.
- 🔧 Failures of the generator and starter due to vibrations and moisture entering the electrical circuits.
To eliminate these faults, regular and high-quality technical inspection was required. The mechanics had to be highly skilled, since the design of the machine, although simple by modern standards, required precise adjustment of many components, such as the carburetor, ignition interrupter and brake mechanisms.
Table of basic technical data
In order to fully understand the scale and characteristics of this vehicle, it is advisable to consider its basic parameters in a consolidated form. These figures are averaged for the most massive modification of the LiAZ-677M, which was produced in the 1970s and 80s.
| Parameter | Meaning | Unit of measurement |
|---|---|---|
| Length | 10545 | mm |
| Width | 2500 | mm |
| Height. | 2870 | mm |
| Mass in curb | 6450 | kilogram |
| Capacity (total) | 80-100 | man. |
| Maximum speed | 70 | km/h |
| Fuel consumption | 35-45 | l/100 km |
As can be seen from the table, the dimensions of the bus allowed it to be quite roomy, but the high fuel consumption was a significant economic factor. In the conditions of the planned economy of the USSR, this shortcoming was compensated by the low cost of diesel fuel and spare parts.
To save fuel, experienced drivers used inertia and tried to avoid sharp accelerations, given the inertia of the heavy car.
Cultural Importance and Heritage of the Model
The LiAZ-677 became not just a vehicle, but a real cultural code of an era. Its recognizable silhouette, the characteristic sound of the engine and the specific smell of the cabin (a mixture of diesel, engine oil and rubber) were imprinted in the memory of several generations. This bus was filmed in dozens of Soviet films, it appeared in literature and anecdotes, becoming an integral part of the cityscape.
In the 1990s, when the country’s economy was experiencing a deep crisis, it was the unpretentiousness of LiAzikov that allowed transport enterprises to continue their work. The lack of alternatives and the ability to repair the machine "on the knee" from improvised materials extended the life of these machines far beyond their estimated resource.
Today, finding a live specimen in regular operation is almost impossible. However, enthusiasts and museums of technology are actively engaged in the restoration of preserved samples. For many collectors, the restoration of the LiAZ-677 to factory condition is a matter of preserving history and respect for the work of Soviet engineers and workers.
⚠️ Attention: When restoring historic buses, it is important to use original parts or quality analogues, so as not to disturb the historical authenticity of the exhibit.
Comparison with modern analogues
Comparing the LiAZ-677 with modern low-floor buses, one can see a tremendous progress in the field of comfort and ecology. Modern machines are equipped with air conditioning, USB charging, navigation systems and meet strict environmental standards. Euro-5 and higher. The noise and vibration levels are minimized, and the entrance to the cabin is adapted for people with limited mobility.
Nevertheless, it should be noted that the repairability and survivability in extreme conditions, the old LiAZ gave a head start to many modern "Europeans". The simplicity of the design allowed for field breakdowns with a minimal set of tools, whereas a modern bus with its sophisticated electronics often requires specialized diagnostic equipment.
☑️ What the mechanics checked daily
In the end, the model bus LiAZ-677 fulfilled its historic mission, having worked several decades to wear. It became a bridge between the era of post-war recovery and the time of mass motorism, leaving an indelible mark in the history of domestic engineering.
What was the maximum speed of LiAZ-677?
Technical documentation indicated a maximum speed of 70 km / h, but in reality buses rarely reached speeds above 50-60 km / h due to the heavy weight, engine wear and safety restrictions.
Why does the LiAZ-677 have such a high fuel consumption?
High consumption (up to 45-50 liters per 100 km) is due to the use of an old carburetor engine of large volume, heavy load-bearing structure of the body and frequent stops in the urban cycle.
When did the LiAZ-677 model stop?
Serial production of the main model was curtailed in 1994, but the assembly of the remaining machine sets and capitally restored bodies continued at various enterprises until the mid-2000s.
What kind of gearbox was on the LiAZ-677?
The bus was equipped with an automatic hydromechanical transmission (HMP) model GM-3 or GM-4, which had two gears forward and one back, which was a progressive solution for the time.