Hinged buses and bus trains are usually operated in large cities with heavy traffic. Therefore, the traction and speed properties of bus trains should be at the level of single buses. Among the 13 indicators of traction and speed properties that assess the dynamics of the road train, the most important are maximum speed, acceleration during acceleration, time and path of acceleration to maximum speed, acceleration time on the path of 400 and 1000 m. road trains. The A70132 diesel bus and the A701 electric bus were selected as the object of the study when working with the trailer. A comparative assessment of these buses on the indicators of traction and speed properties. It was found that the use of electric buses to create a bus train is problematic in view of the lack of traction in the area of high loads due to the acceleration of the bus. However, for a bus with diesel there is a significant reserve of traction in lower gears, due to the operation of the torque converter. The efficiency of using such a bus train when working on urban routes, where there is a limit on the maximum speed at 50 km / h. If the speed increases to 70 km / h, the use of a bus train consisting of a bus A70132 and a trailer with a total weight of 16,000 kg becomes inefficient. To increase the speed, it is necessary to either increase the power of the bus engine or activate the trailer.

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Currently, the National Guard of Ukraine and other power structures of the state are actively working on the acquisition of subdivisions with modern weapons, including armored vehicles. For objective reasons, such work cannot be done in a short time, therefore, the BTR-70 armored troop-carrier, developed and adopted in the seventies of the last century, is still in operation in significant numbers. An analysis of the design of the armored troop-carrier indicates that its power plant has structural features that do not fully meet modern approaches to the design of such weapons and, moreover, the vehicles have practically exhausted their assigned resource. However, the experience of operating the BTR-70, including in the combat zone, testifies that the potential capabilities and maintainability inherent in its design make it possible to use the armored troop-carrier even after the end of its intended resource, although the aforementioned complicates and increases the cost of operation. One of the ways to solve this problem is the modernization of the power plant of the armored troop-carrier, in particular, the replacement of gasoline engines with modern diesel engines and the improvement of the transmission design. In the course of the study, traction and speed properties of the armored vehicle in the standard configuration and when equipped with two D245.30E2 engines and Deutz engines are calculated and estimated. As a change in the design of the transmission, the option of replacing the standard gearbox with a gearbox with an overdrive is considered. It was found that equipping an armored personnel carrier with modern diesel engines in both cases leads to a significant increase in traction properties and an improvement in the fuel efficiency of the vehicle. However, due to the fact that the crankshaft speed of diesel engines is approximately 25-30 % lower than the corresponding frequency of gasoline engines, the maximum speed of an armored personnel carrier with diesel engines is limited by the design of the transmission and is about 70 km / h. This does not meet modern requirements for machines of this type, therefore, as an option; it is proposed to install a step-up reducer (divider) at the inlet of the gearbox. In this case, it is possible to reduce the gear ratio of the transmission in higher gears and, accordingly, increase the maximum speed of the armored troop-carrier on paved roads.

The article considers the issue of choosing a gearbox for the modernization of the BTR-70 by replacing two gasoline engines with two diesels. The object of research is the fuel economy of the BTR-70 car with different gearboxes when replacing two gasoline engines with two diesels. The purpose of the work – to determine the type and gear ratio of the transmission, which provides the best fuel efficiency of the car. Research method - mathematical modeling. When replacing a gasoline engine with a diesel of a different power and a different speed range, it is necessary to determine the gear ratio so as to provide the car with the required level of speed properties in the specified operating conditions with minimal fuel consumption. Due to the fact that the modernization of the BTR-70 involves the replacement of the engine and transmission, the further search for the gearbox was carried out on the basis of analysis of existing structures by the maximum torque of the engine. A five-speed and eight-speed MAZ gearbox and a six-speed Mercedes-Benz G 85-6 / 6.7 gearbox were used for analysis. Taking into account the fact that at a given coefficient of drag  = 0.03 the car can move only in direct gear, then for all gearboxes the fuel characteristics of steady motion will be the same as the control fuel consumption, which was 30 l / 100 km. In terms of fuel consumption during the acceleration of the car and the average kilometer fuel consumption when driving on paved roads, preference should be given to a car with a Mercedes-Benz G 85-6 / 6,7 transmission and only when driving in difficult road conditions, preference should be given to the car with 8-speed MAZ-5335 transmission. KEY WORDS: CAR, ENGINE, FUEL ECONOMY, TRANSMISSION, GEAR RATING, SPEED, COMPARATIVE EVALUATION