MAZ 251 buses and complete sets of models
The lineup of MAZ 251 buses contains various configurations, the models are formed by adding three characters after the main model name, for example, the MAZ 251062 package includes a Mercedes-Benz engine with a power of 360 hp. and a manual transmission from ZF with a 6-speed gearbox.
MAZ-251 was designed on the basis of high-tech units and assemblies foreign production... In terms of its equipment and design, the bus today has no analogues in the CIS. The high-floor tourist airliner of increased comfort has been produced at the Minsk Automobile Plant since 2005. All the details of the cabin equipment have been thought out for the convenience of passengers, so that even long trips do not become tiresome.
A distinctive feature of MAZ 251 is the outer body panels made of fiberglass, which are absolutely not subject to corrosion. The model has an attractive and modern appearance that does not get lost over time.
Main advantages:
- modern powerful air conditioning system;
- comfortable seats;
- individual folding tables;
- soft suspension for comfortable movement even on rough roads;
- kitchenette with refrigerator;
- dry closet.
Buy MAZ 251 by affordable price you can in the AUTOTECHKOM company.
Characteristics of MAZ 251
Overall dimensions, mm) 11985/2500/3355
Number of seats: 47/45
Fuel tank: 500l.
Equipment
- Independent 30kW Webasto liquid engine heater used for engine preheating and interior heating
- Independent air heater for driver's cab 2.0-2.2 kW (Webasto or Eberspacher)
- Lincoln automatic centralized lubrication system
- Anti-lock braking system ABS
- Traction control system ASR
- Tachograph
- Conditioner CC200 Webasto
- STARCOOL kitchen: boiler, sink, microwave, heating unit, refrigerator
- Audio-video system "Actia VideoBus" car radio CD, DVD-player, 2 monitors 14 "with holder and arm or 1 monitor 14" without holder and arm, guide microphone, driver microphone
- Dry closet aircraft type "PLACO ESMMI" with a refrigerated chamber, Holland
- Tinted glass units
- Roof fans, 2 pieces
- Imported driver's seat ISRI 6860/875 on air cushion with automatic height control and heated seat cushion and backrest with seat belt
- Adjustable, center-shifting passenger seats with footrest and folding table
- Floor covering "Avtolin"
- Thermal and noise-insulating ceiling covering
- Anti-corrosion treatment of the bottom and hollow cavities
- Lighting technology HELLA
- Mekra exterior mirror set
- Imported tires
- Melvia carpet runner
- Driver's berth equipped with an independent air heater and a communication device with the passenger compartment
- Sides, roofs, luggage and engine compartment lids made of fiberglass panels
- Individual ventilation and lighting units for passenger seats
- Curtains on the back and side windows
What will be held in Belarus in the summer II European Games, now everyone is talking here and everywhere. All areas are involved in the preparation process, and automotive production was no exception. The Games Directorate ordered from Minsk Automobile Plant special tourist buses made on the basis of model 251062. The lot is rather big - 75 pieces, and the first samples have already been delivered to the customer.
Why "tourist" MAZs are better than ordinary ones - we were the first to see.
MAZ 251062 is the flagship model of the Minsk Automobile Plant, which is designed to carry passengers on long-distance routes. The design of the bus provides a high level of comfort and safety.
The "heart" of the model is a 360-horsepower Mercedes-Benz ОМ 457 LA (Euro-5) turbodiesel, which is paired with a 6-speed manual transmission ZF 6S 1901 BO (or ZF 6S 1911 BO). The acceleration time of a bus with a rated load to a speed of 60 km / h is no more than 20 seconds. The maximum kinematic speed is 133 km / h (usually limited depending on the destination of the bus).
The cabin of a 12-meter liner can accommodate 44, 47 or 49 comfortable passenger seats. Individual airflow and lighting panels are provided above the passenger seats. The interior height of the passenger compartment in the middle aisle is 2100 mm. Volume luggage compartment- 7.3 cubic meters
The basic equipment includes an air conditioning unit, a kitchen, a microwave oven, a refrigerator, two LCD monitors, a driver's sleeping compartment, and a dry closet. The electronically controlled air suspension guarantees a smooth and smooth ride.
According to the website in the press service of the Minsk Automobile Plant, out of the batch of buses ordered for the European Games-2019, the State Enterprise Minsktrans will receive 18 units, the remaining 57 cars will be regional carriers (9 units each - Brest, Minsk, Mogilev; 10 units - Vitebsk, Gomel, Grodno). We were able to inspect one of the first buses for 47 passengers, which was preparing to be handed over to the "oblast" - the car got, as they say, in cellophane.
The buses ordered for the European Games-2019 for regional centers have their own characteristics, said Oleg Smolyanko, Deputy Head of the Passenger Equipment Sales Department of OAO MAZ... In the cabin: completely new passenger seats, they have a more modern design, two-tone colors and better finishing materials; made LED illumination of the steps and the central aisle; each row has USB sockets (for two gadgets on each side); an electronic clock with a temperature function appeared on the ceiling in the central aisle.
By moving the air conditioner closer to the center of the bus, the air flow will now be more evenly distributed.
At the driver's workplace, the new compact gearshift lever immediately attracts attention. The fact is that this version of the bus uses a gearbox with a ZF Servoshift servo drive and a cable shift. The innovation has already been appreciated by the factory drivers - now it has become much more convenient to drive the bus.
In addition, its complete set includes: a multifunctional terminal for the driver "Azimut"; digital tachograph; intercom of the driver's berth; voltage converter with 12 V socket; imported driver's seat with seat belt; guide seat; independent air heater for driver's cab and sleeping compartment 2.0-2.2 kW; wear-resistant floor covering; carpet; tinted double-glazed windows; Lincoln automatic centralized lubrication system.
New in the exterior - LED running lights are now installed on all MAZ 251062 buses in standard configuration(previously combined with fog lights).
Gray color - customer's choice. Generally speaking, a plant can manufacture a bus at any colors, but most often they choose either white or gray.
The MAZ 251 bus was presented to the general public in August 2004. The presentation took place at the Moscow Motor Show. The auto giant began mass production of the model the following year. Today, it is MAZ 251 that is considered to be a high achievement of the Belarusian plant and a striking representative of the line of passenger vehicles of the auto brand.
Features and benefits of MAZ 251
Today's coach bus Maz 251 represents the second generation of the model. It is designed on the basis of high-tech systems, components and assemblies foreign production... Among its advantages, professionals and passengers note:
- the presence of high-quality air conditioning;
- ergonomic seats;
- comfortable individual tables;
- soft suspension;
- the presence of a refrigerator and dry closet in the cabin.
Purchase of the MAZ 251 bus
LLC "AUTO-TRANS", official dealer MAZ has been presented on the Russian car market for more than 8 years. Through a wide retail network, Russians are offered to purchase the well-proven MAZ 251 buses. They are reliable, durable, and maintainable. Spare parts are always in the company's warehouse.
SPECIFICATIONS| Options | Index |
| Overall dimensions, mm | 11990/2550/3820 |
| Base, mm | 6060 |
| Wheel track (front / rear), mm | 2093/1825 |
| Outside turning radius, no more, mm | 12500 |
| Step height above the road level, mm | 380 |
| Floor height at aisle level, mm | 1440 | 7000 | 11000 |
| Full weight, kg | 18000 |
| Number of seats | 44-49* |
| Nominal capacity, people | 44-49 |
| Maximum speed, km / h | 134 |
| Engine | Mercedes-Benz OM457LA (E-5) |
| Engine power, kW (hp) | 265(360) |
| Transmission | MCP ZF 6S1901 BO with intarder (6st.) |
| Front / rear axle suspension | independent / dependent pneumatic with telescopic shock absorbers |
| Main bridge | rigid beam with double spaced transmission |
| Brake system | pneumatic with ABS system/ ASR |
| Volume fuel tank, l | 500 |
| Wheels | disk, 8.25x22.5 |
| Tires | 295 / 80R22.5 |
| * - without kitchen installation |
EQUIPMENT
| Independent 30kW Webasto liquid engine heater used for engine preheating and interior heating |
| Independent air heater for driver's cab 2.0-2.2 kW (Webasto or Eberspacher) |
| Lincoln automatic centralized lubrication system |
| Anti-lock braking system ABS |
| Traction control ASR |
| Digital tachograph |
| Air conditioner CC200Webasto |
| Kitchens: boiler, sink, microwave oven, heating unit, refrigerator |
| Audio-video system, car radio CD, DVD-player, 2 monitors 14 "with holder and arm or 1 monitor 14" without holder and arm, guide microphone, driver microphone |
| Dry closet |
| Tinted glass |
| Roof fans |
| Imported driver's seat on a pneumatic cushion with automatic height control and heated seat cushion and backrest with a seat belt. |
| Adjustable, center-shifting passenger seats with footrest and folding table |
| Guide seat |
| Floor covering "Avtolin" |
| Thermal and noise-insulating ceiling covering |
| Anti-corrosion treatment of the bottom and hollow cavities |
| Lighting technology HELLA |
| Mekra exterior mirror set |
| Faworit "AZO" carpet runner |
| Driver's berth equipped with an independent air heater and a communication device with the passenger compartment |
| Sides, roofs, luggage and engine compartment lids made of fiberglass panels |
| Individual ventilation units and lighting of passenger seats |
| Curtains on the back and side windows |
| Electric curtain of any glass |
| Painting with Helios polyurethane enamels |
ADDITIONAL EQUIPMENT ACCORDING TO THE CUSTOMER
DIMENSIONS
INTRODUCTION
For my course project, I chose the MAZ 231 bus. The uniqueness of the promisingMAZ 231 lies in the possibility of its application both on intercity and on suburban routes. With a car length of 12 m, 51 seats can be installed in the cabin. The suspension of the new Minsk liner is made completely dependent, that is, it is less expensive to manufacture and easier to maintain (there are two in the front and four in the rear).
However, newMAZ 231 is quite suitable for "long-distance" transportation. For example, the sample shown in Moscow was equipped with soft comfortable seats with high-quality finishes, armrests and tilt-adjustable backrests. Comfort blocks were placed above the passengers' heads, luggage racks for small hand luggage stretched along the entire cabin, and on the windows one could see curtains, which were difficult to do without on long-haul flights. On request, the bus can be equipped with air conditioning and a video system.
In the same time, salon MAZ 231 it is also designed for the fact that on some suburban routes some passengers can ride while standing. Thus, its total passenger capacity is 80 people.
Although Russia still continues to produce and register vehicles that meet environmental standardsEuro-3 , the new Minsk bus was originally designed immediately for the standardEuro 5 , which is currently in force in Europe. To achieve these standards, one of the most modern serial turbodiesels was installed in the engine compartment of the liner - an in-line 6-cylinderMercedes-Benz OM926LA ... From its 7.2-liter volume, the designers managed to remove 326 hp. Considering that the rest of the aggregate "filling"MAZ 231 also consists mainly of imported components
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The exterior of MAZ 231 is made in full accordance with the tendencies prevailing in Europe. What's more, the exteriorMAZ 231 made in the same vein with other modern buses of the Minsk Automobile Plant, and this is one of its strengths.
The driver's workplace is also arranged in the spirit of modern ideas: on both sides of dashboard located control keys for various systems, the seat and steering column are adjustable in a wide range. The cabin floor rises several centimeters above the rest of the cabin floor, which protects the pedal assembly from water flows during washing and from dirt in slushy weather. The only surprise is that the MAZ 231 gear lever is installed in the old fashioned way next to the driver's seat, while in Europe it is now increasingly placed right on the dashboard, to the right of the steering wheel. Yes, and the algorithm for switching transmission stages, judging by the scheme, is not the most familiar, as if specially made backwards. The bus would also benefit from more stylish exterior mirrors. in general, both the ergonomics of the driver's workplace and visibility are at a very high level.
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Section 1.
Comparative analysis of buses MAZ 231, MAZ 251, MAZ 152
The MAZ-251 bus from the Minsk Automobile Plant is designed to transport passengers over long distances. Tourist bus 251 series received the prize of the visitor's sympathy and was recognized as the best tourist bus at the international exhibition MIMS-2004. The concept of the tourist bus MAZ-251 is based on the use of fiberglass body panels in the structure, which significantly reduce the weight vehicle... The use of glued-in tinted plastic glasses in a tourist bus of the Minsk Automobile Plant, which are made using all modern technologies and materials, ensures the tightness of passenger transport, increases the rigidity of the body. The general style of this tourist bus is also determined by the use of modern lighting fixtures.
Equipped modern engine MAN D 2866 LOH 28, with Euro 3 environmental safety class, MAZ tourist bus generates 360 power Horse power, this is an excellent indicator. It is capable of a speed of 134 km / h, this property allows MAZ-251 to reach its destination faster. Excellent indicators of speed and power make MAZ-251 competitive in the world market. The MAZ-251 cabin can comfortably accommodate 44-49 (depending on the configuration) people, for each of whom there is a comfortable seat. According to experts, the MAZ bus is not inferior to foreign counterparts either in the level of passenger comfort or in high-quality technical equipment.
The MAZ-152 bus is actually the only alternative on the territory of the former Soviet Union to the outdated Ikarus-250 for motor vehicles engaged in intercity and tourist transportation. The bus is designed using most of the components and assemblies used on trucks MAZ.
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The body of the bus is all-metal, wagon-type, bearing. The sides and roof are made of solid-drawn galvanized steel sheet, the front part is made of fiberglass. Glasses - glued, which has a positive effect on the rigidity of the body. Has two sliding doors. On the MAZ-152A bus, the rear door has been moved to the wheelbase. The front door and the rear door are equipped with an electropneumatic drive of the same design. In the pneumatic system of the drive of each of the doors, a distributor, an electronic control unit, and emergency door opening valves are installed. The pressure in the pneumatic systems is regulated by a pressure reducing valve, which is installed near back door... To ensure the required trajectory of the door movement, a rod is installed, which is hinged at one end on the lower part of the door, and at the other on the bus frame.
MAZ-152 buses are equipped with soft seats with a backrest angle adjustment mechanism, a footrest adjustment mechanism and a lateral seat offset mechanism. The seat cushion and backrest are fixed to the frame. The aisle side seat frame is bolted to the floor. The backrest angle adjustment mechanism allows the backrest angle to be changed within 15 °. To change the angle of inclination of the backrest, it is necessary to move the handle to the limit in the direction indicated by the arrow, tilt the seat to the desired angle and release the handle. When the handle is released, the seat locks in any intermediate position.
Inside the MAZ-152 bus there are soft seats with armrests. The angle of inclination of the backrest and the distance between the seats in width are adjustable. The salon is equipped with individual lighting and ventilation systems, air conditioning, dry closet, refrigerator, mini-kitchen, audio and video systems. The number of seats is 43-47 (MAZ-152) and 39-45.
The buses can be equipped with both YaMZ engines and engines manufactured by MAN and Mercedes. The buses operating in Minsk are powered by YaMZ-7601 engines developing 300 hp. and 1275 N * m.
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comparison table technical characteristics
| SPECIFICATIONS | MAZ-231 | MAZ-251 | MAZ-152 |
| Engine: | Daimler OM 926LA (Euro-5) | MAN D 2866 LOH 28 (Euro-3), Mercedes-Benz OM 457 LA (Euro-5) | Mercedes-Benz OM 501LA |
| Engine power, kW (hp): | 240(326) | 265(360) | 260(354) |
| Transmission: | Mechanical ZF 6S-1701, automatic ZF6HP | ZF 6S-1701 BO mechanical with intarder | ZF |
| Front / middle / rear axle suspension: | Dependent, pneumatic, 2 pneumocylinders, 2 shock absorbers | Independent / dependent pneumatic with telescopic shock absorbers | Dependent spring |
| Main bridge: | ZF with hypoid final drive | Rigid beam with double spaced transmission | |
| Wheels: | 8,25*22,5 | Disc 8.25 * 22.5 | Disc 8.25 * 22.5 |
| Tires: | 295 / 80R22.5 | Tubeless 295 / 80R22.5 | 295 / 80R22.5 |
| Base, mm: | 6180 | 6060 | 6000 |
| Overall dimensions, mm: | 12000/2550/3100 | 11990/2550/3820 | 11985/2500/3323 |
Comparison table of weight and load distribution
Scheme of the MAZ-231 bus
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The experience of operating buses shows that on uneven roads
average speed drops by 35 - 40%, fuel consumption increases by 50 - 70%, overhaul mileage decreases by 35 - 40%. At the same time, the productivity of road transport decreases by 32 - 36%, and the cost of transportation increases by 50 - 60%. To this should be added the losses caused by the overexpenditure of metal, fuel, rubber and additional labor costs. To reduce these losses, you can either improve the roads, which is expensive, or improve the car's suspension, which is even more expensive, but in terms of thousands of cars it turns out to be cheaper.
However, even roads with a flat surface impose very stringent requirements on the suspension. After all, the speeds are constantly growing, and the requirements for the handling and stability of cars and road trains are becoming more stringent.
The characteristics of the suspension affect many of the performance of the car: ride smoothness, comfort, driving stability, durability, both of the car itself and of a number of its assemblies and parts. In heavy road conditions it is the suspension capabilities, and not the engine power at all, that determine the average and maximum speeds movement.
Suspensions with steel springs are no longer always able to fit into the requirements imposed on them, while pneumatic elastic elements have a high energy intensity in the main operating range and with large deflections, which means they provide a decrease in the vibration amplitude, a decrease in the amount of energy absorbed by shock absorbers, simplify adjustment; at the same time, in suspensions with steel elastic elements, a progressive characteristic is achieved only due to a strong complication of the structure; ease of automatic regulation of stiffness and dynamic suspension travel in accordance with loading conditions, which allows you to get more smooth running and improve other performance; with the same dimensions of the elastic element, the suspension allows for a high degree of unification for vehicles of different carrying capacity with a significant difference in the size of the sprung masses; pneumatic elements have an extremely high durability unattainable for steel elastic elements.
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Reducing the stiffness of the suspension improves the smoothness of the vehicle during low-frequency vibrations, most noticeably reducing body acceleration, as well as body and wheel movements.
Based on the comparative table of the technical characteristics of MAZ 231, MAZ 251 and MAZ 152 buses, I propose to improve the air suspension of the MAZ 231 bus, which will increase such characteristics as smooth running, comfort, driving stability, durability.
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At the end of August 2004, the first Belarusian tourist bus MAZ 251 came out of the gates of the bus production of the Minsk Automobile Plant. The new bus MAZ 251 was developed by MAZ designers. This is a model of a foreign manufacturer not assembled from an import kit. Such a stage took place in the life of the Minsk Automobile Plant ten years ago. This is a completely in-house development. The first thing that attracts attention is the modern design of the body and lighting technology. The bus is a representative of the second generation of buses of the AMAZ Branch of the MAZ RUE. It is more expensive than buses of the first generation, however, it is significantly cheaper than European counterparts, while it was created on the basis of reliable and high-tech units and assemblies of foreign production. In fact, the bus has no analogues in the CIS in terms of modern design and basic equipment. A distinctive feature of the bus is the outer body panels made of fiberglass, which are not afraid of corrosion. The bus is distinguished by a serious and very modern appearance, the use of a large number of modern design solutions in the transmission and chassis, a large list additional equipment... The MAZ-251 bus is a high-floor bus, as it is customary to call it a “one and a half” bus with a high level of comfort. It is intended for use on long-distance intercity routes, international flights, for the transportation of tourist groups. Comfortable seats, a powerful air conditioning system, soft suspension, a mini-kitchen, a refrigerator, a dry closet, a comfortable sleeping bag for the driver-shift - all this allows you to travel by bus of almost any distance.
The bus has a four-row layout along the entire length of the passenger compartment. On the left there are 12 pairs of seats, on the right - 5 pairs of seats each before and after the second door. Access to the salon is opened by two sliding doors, and the second is disguised as a side panel and does not protrude beyond the lower window line. The body of the bus is of a wagon type, carrying. The body frame is welded from box sections. Frame blanks - galvanized rectangular pipes - are fixed on a large sheet in special conductors. This is how the sidewalls, floor and ceiling are welded. On the slipway, they are combined into a single whole. At the same time, the frame beams have a rather complex shape, providing the body shape conceived by the designers. The wheel arches and part of the floor are sewn up with stainless steel sheets. The sides of the MAZ-251 bus are made of glass-plastic panels, which are least susceptible to environmental influences. They are attached to the frame with glue. The front and rear parts are also made of fiberglass and are fixed to the frame with glue and rivets. Bumpers - removable, also made of fiberglass. The roof is clad with steel sheet, resistance-welded to the frame. Paint - multicomponent polyurethane. They mix it in their own laboratory. The color is selected at the request of the customer.
Glasses are glued into the openings without a joint, which has a positive effect on the rigidity of the body. The windshield and rear windows are made of three-layer glass and are glued into a swarm of glass with a plastic panel. Side and rear windows and door windows are made of heat-absorbing tempered glass and glued into the openings. The driver's window consists of several glued-in glass, one sliding in polyamide guides and one glued with electric heating threads. MAZ-251 has two sliding doors. The doors are equipped with a pneumatic rotary drive with an emergency opening valve. The door leaves are made of aluminum profiles. The driver's cab is entered through the front passenger door. The bus is provided with a blocking of movement when the doors are open, which is deactivated by a button with a symbol (B) on the front panel in the driver's cab. The doors are equipped with a system that prevents passengers from being trapped. The "insect-like" mirrors of the bus are from Mekra. They can be folded against the windshield if necessary. On the left and right brackets there are one main mirror and one additional on the left, two additional on the right. The mirror system provides excellent visibility, including areas near the front of the bus.
The MAZ-251 buses have soft passenger seats with fabric upholstery. The passenger can adjust the angle of inclination of the backrest, armrest, footrest at his discretion. Each passenger is provided with an additional handle, a net for storing maps, magazines and newspapers, as well as a folding table with a cup holder. Luggage racks are located above the passengers. Their lower part contains individual control units for passenger seat lighting, ventilation, and radio equipment. At the second door there is a convenient dry closet with a toilet, sink, lighting. There is a mini-kitchen next to the stairs of the second entrance: there is a refrigerator up to the second door above the dry closet, behind the second door there is a table, a microwave oven, and a coffee maker. Under the ceiling in the front of the bus, as well as at the second door, there are screens of a video system with a DVD player. The driver's workplace is quite spacious, not separated from the passenger compartment, which is typical for all intercity and tourist buses. The controls are located at an optimal distance and do not overlap. There is a dashboard in front of the driver. A tachometer, a speedometer, two brake pressure gauges, oil temperature and pressure indicators, fuel level in the tank, and battery charging are located behind the glass on a single panel. There are three groups of control lamps located above and on the sides. The steering wheel is of the optimal diameter, pleasant to the touch and externally. There are two under the steering switches - one controls the external lighting devices, the second - the wipers. There are three floor pedals on the floor - clutch release, accelerator control and brake system. To the right of the dashboard are the door opener buttons, the interior lighting switch, and the sunblind control button.
Below are four control panels. This is an electronic tachograph, control units for an audio system, an air conditioner and a DVD video system, an information system rum and a hazard warning light button. To the left of the dashboard there is a buzzer, a heating control knob, control buttons for the body tilt system, ceiling ventilation system, switches for heating windows, mirrors, interior and driver's cab lighting, interior heaters. Both to the left and to the right of the dashboard are the deflectors for the heating and ventilation system of the driver's cab. There is also a timer for controlling a liquid heater, buttons for controlling an automatic transmission, a lever parking brake, main light switch, body lowering switch, air heater regulator, emergency switch. Beneath the high floor of the passenger compartment, there is an impressive luggage compartment, accessible through large lifting side covers. Its volume is an impressive 10.5 cubic meters.
Also under the floor behind the second door is a sleeping compartment for the driver-shift driver. It is equipped with a lamp, heating, and also has a telephone for communication with the driver. The heating system is three-circuit (two-circuit was used on MAZ buses of the first generation). The bus uses fluid energy from the engine cooling system to heat the air in the bus. The first circuit of the heating system, which heats the driver's workplace, consists of a tap through pipelines. The air is directed through the air duct system to the air inlet box, and from there through the air vents on the front panel to the windshield and into the niche at the feet of the driver, as well as through the air ducts in the control panel. In addition, an independent air heater is installed to heat the driver's workplace. The heater has two radiators and two fan drives. Air is taken from the driver's cab. Ventilation of the driver's workplace is carried out through the driver's cab heater when heating is turned off with air intake from outside the bus. The heating system that heats the interior of the bus consists of a tap through pipelines, convectors and heaters. The heaters have one radiator and one fan drive. Natural ventilation is carried out through two Parabus hatches, as well as forced through two roof fans.
In the body of the MAZ-251 bus, a rooftop air conditioning unit from the well-known Webasto company is integrated. It is located on the front of the bus roof. Prepared air of the required temperature is supplied through air ducts to each passenger seat. The airflow intensity can be adjusted by each passenger at his own discretion. The engine compartment is located in the rear overhang of the bus, which is typical for all large tourist buses. Power unit is attached to the bus frame on four supports (two front and two rear). The front and rear legs are of the same design. Each support consists of a shock absorber bolted to a frame bracket. Engines of German companies MAN and Mercedes-Benz are installed on the MAZ-251 model. The six-cylinder MAN is a motor from the well-known D28 series. The MAN D2866 LOH28 engine meets the Euro-3 environmental standards and develops 360 hp. The Mercedes-Benz engine - OM501LA series - has a capacity of 353 hp. and also meets Euro-3 standards. In the near future, there will also be modifications with engines in the Euro-4 and Euro-5 versions. MAZ-251 has electronic system engine control. When you press the accelerator pedal, the sensor of its position is triggered and sends a signal to the control electronic module. The bus is equipped with an engine brake flap, which serves to increase the life of the main braking system, being the mechanism of the auxiliary braking system. When the engine is running, the damper is installed along the exhaust gas flow, when the engine brake is applied, it is perpendicular to the gas flow, creating a certain back pressure at the outlet. At the same time, the fuel supply is turned off using a pneumatic cylinder connected to the engine stop bracket.
The fuel supply system of the engine is of a split type. It consists of a fuel tank, low fuel lines and high pressure, coarse filter, fuel booster pump, fine filter, high pressure fuel pump and injectors. The buses can be equipped with Webasto liquid heaters. They are designed to preheat the engine, which makes it easier to cold start the engine, as well as for long-term maintenance in automatic mode thermal state of the switched off engine, the interior of the bus and the driver's seat. The pre-heater is supplied with fuel via separate fuel lines from the main fuel tank. The cooling system is liquid, closed, with forced circulation of the coolant, designed for the use of low-freezing coolant. The optimum temperature of the coolant in the system with the engine running (80-95 ° C) is automatically maintained by thermostats and fan performance. The radiators for the engine cooling and intercooling system are located at the top of the engine compartment, just above the engine. The fan is hydraulically driven and electronically controlled. The pump is a high pressure gear type. The pump converts the rotary motion of the input shaft into the energy of the working fluid flow. The air intake for the cooling system is located at the rear on the left side of the bus.
The clutch for the MAZ-251 bus is supplied by Sachs. It is frictional, one disc, with a diaphragm spring. The driven disc has a torsional vibration damper. The clutch is equipped with hydraulic drive with pneumatic reinforcement. MAZ-251 is equipped exclusively mechanical boxes gears of the German company ZF. The gearbox of the ZF 6S-1701 BO model is six-speed, synchronized in all gears, except for the reverse. The “mechanics” drive is mechanical, it is a chain of intermediate shafts. An effective hydraulic retarder is connected in series with the gearbox, which saves the standard brakes, allowing you to comfortably and safely overcome long slopes. As befits a modern tourist bus, the MAZ-251 has an electronically controlled Knorr-Bremse air suspension. The "electronic" suspension includes four floor level sensors, two blocks of control valves, control keys and directly air bellows, combined under the command of the control unit. The driving rear axle of the German production MAN HY-1336-B07 is installed on MAZ-251 buses. The location of the central gear is traditional - no offset to the port side. In the gearbox, the torque is transmitted by gears with hypoid engagement. Rear suspension dependent, has four air bellows, two floor level sensors, four hydraulic shock absorbers. The rear axle is fixed on two lower and two upper jet rods.
The front axle of the bus consists of two wheel-hub assemblies fixed on pivots. They, in turn, are mounted on separate metal arms. That is, the bus has a front independent suspension, as on all modern tourist liners. It gives the bus a smooth ride and high cornering reliability at high speeds. The front suspension has one air spring, one floor level sensor and one shock absorber for each half. MAZ-203 is equipped with disc wheels with tubeless tires of dimension 295/80 R22.5. The width and height of the profile are slightly larger than in city buses. Increasing the width makes the tall bus more stable and the profile height optimized for comfort. Depending on the customer's preferences, the bus is equipped with Michelin XZA 2 Energy 152 / 148M tires or Continental 295/80 R22.5 152 / 148M tires. Tire pressure: two front wheels - 8.5 bar; four rear wheels - 7.5 bar. The dehumidifier of the MAZ-203 bus has a special outlet for pumping tires from pneumatic system. Spare wheel located just behind the front bumper on the hinged holder.
The steering of MAZ buses of the second generation was created with the expectation of using a modern integral-type steering mechanism. In the driver's cab there is a safety steering column, adjustable in height and tilt. Rotation and force applied to the steering wheel by means of two cardan shafts and the bevel gear is transferred to the steering gear. The bevel gear consists of two bevel gears. The steering mechanism is connected by a bipod and a steering rod to the wheel kingpin. The hydraulic booster system is powered by a pump supplied with the Mercedes-Benz engine. Since the front suspension of the bus is independent, the steering linkage is six-link. The steering mechanism of the German company ZF is based on the same principle of transferring rotation and changing the gear ratio as in the usual mechanism with the transmission "screw - ball nut - rack - toothed sector". However, in the integral mechanism, the rack is simultaneously the piston of the hydraulic booster and divides the steering mechanism into two cavities filled with fluid. Thus, it combines the functions of a mechanism that changes the gear ratio and a hydraulic booster cylinder. Moreover, there is no need for a separate installation of the latter, and at the same time the design of the steering rods is simplified. Such a device is demanding on the production technology, however, it greatly simplifies the design and layout of the steering, and also does not require maintenance at all for 800-900 thousand kilometers.
The buses are equipped with working, parking, spare, auxiliary braking systems and a stopping brake, as well as terminals for monitoring and diagnosing the pneumatic system and supplying other consumers with compressed air. Working brake system affects the braking mechanisms of all wheels of the bus. The service brake system is equipped with anti-lock braking system(ABS). The rear contour can be equipped with an additional anti-slip control (ASR) at the request of the customer. The parking and spare brake systems act on the rear axle brakes, which are actuated by spring-loaded brake chambers. The drive of the spring energy accumulators is pneumatic, double-circuit. The parking brake system acts as a reserve brake. It is designed to brake the bus in the event of a complete or partial failure of the service braking system. The holding brake acts on the brakes on the rear axle. When the parking brake is turned on with the button located on the instrument panel, or automatically when any of the doors of the bus is opened, air under pressure is supplied to the brake chambers of the rear axle.
Secondary braking system (engine brake) - with remote control a flap in the exhaust system and a pneumatic drive for shutting off the fuel supply. In addition, a retarder is installed behind the gearbox - a very effective brake-retarder that helps when driving on long descents and long braking. The brakes of the MAZ-251 bus are disc brakes from the well-known Knorr-Bremse company. The brakes are powered by diaphragm-type brake chambers on the front axle, and on the rear axle - by brake chambers that contain spring-loaded accumulators. Naturally, the bus is equipped with a modern 4-channel anti-lock braking system from Knorr-Bremse. It includes 4 sensors and the same number of modulators, as well as an electronic control unit. The system prevents the wheels from locking when braking on slippery or uneven surfaces, helping the driver to effectively slow down the bus without losing control of the trajectory.
The buses have a 24-volt electrical system, which is made using a single-wire connection diagram. The minus is the frame of the bus, connected to the minus of the batteries. A distinctive feature of the electrical equipment system is that the connection of wiring harnesses and the connection of a significant part of its products is carried out using plug connections.
The switching unit is located behind a cover in front of the front left wheel. The switching unit contains fuses, intermediate relays, turn signal relays, a wiper impulse relay, a starter relay and diode assemblies, the designation and purpose of which are indicated on the unit. On buses in special niches of the body, two dry-charged rechargeable batteries of the 6ST-190A type are installed. For ease of maintenance, they are fixed on a base with a slide. The generators are from the German company Bosch. There are two of them, both of 140 A. taillights and license plate lights. Interior lighting includes bus interior lighting, driver's workplace lighting, doorway lighting and engine compartment lighting. All buses of the second generation have modern "spot" lighting technology with round diffusers. In the headlights of the low and high beam, as well as in the “fog lights”, 70 W H7 halogen lamps are installed. All taillights are equipped with 21W lamps and parking lights buses are designed for a power of 4-5 watts. The interior luminaires are T5 fluorescent lamps with a power of 13 W each.
For the safety of passengers in the event of a fire hazard, MAZ buses can be installed automatic system fire extinguishing of the engine compartment. In general, the finishing materials for the passenger compartment and the engine compartment in particular have been selected to be fire-resistant. With proper care of the finishing materials and the absence of stains from fuels and lubricants the bus completely burns out in more than forty minutes.
The fire extinguishing system is based on the use of flameless powder with the addition of special inhibitors that extinguish the flame when the powder charge is fired. The device is triggered if the flame enters through the fire-resistant cord or an electrical signal is generated by the emergency button. It also triggers when the temperature in the engine compartment rises to 170 ° C. The fire extinguishing aerosol is ejected outward in a stream. The flame draws in the cloud containing the inhibitors and the combustion stops. Two aerosol generators are located in the engine compartment, another one in the fluid heater compartment. In this case, it is forbidden to open the hatches of the engine compartment within 5 minutes after the system has been triggered to prevent the resumption of combustion.
MAZ-251 is a modern comfortable tourist airliner for sightseeing trips and long-distance passenger transportation. The modern layout and the choice of the main units made it possible to create an easily controlled and comfortable car for passengers. Equipping the bus only with engines of high environmental standards has a positive effect on the environmental situation. Passengers will note a good modern interior, an excellent heating system and a powerful air conditioning system. Each passenger has his own lighting shade, individual ventilation, pockets, handles, a table with a cup holder. The design of the second generation MAZ buses is attractive and solid, and especially the MAZ-251 bus.
The driver's workplace is also convenient - good visibility, informative devices, an additional stove, convenient location of all controls. However, there is a certain shortage of niches and shelves for things in the driver's cab. While one driver is driving the bus, the second can comfortably rest in a comfortable sleeping compartment under the floor of the passenger compartment. The bus is designed in accordance with European standards, EEC directives and UNECE regulations. Serially produced models have the “Vehicle Type Approval” certificate.
©. Photos taken from publicly available sources.
