YAG-7 family trucks. Last prewar
It must be recalled that all existing serial trucks developed by the YAZ had a lot of common features. Their design dates back to the I-3 project, which was based on foreign ideas from the mid-10s of the 20th century. As a result, such machines were not perfect and did not meet current engineering requirements. In this regard, at the end of the thirties, the YAZ design bureau was engaged in the development of a fundamentally new machine, suitable for full operation in the foreseeable future.
New concept
Work on the new truck project started at the very beginning of 1938 of the year. Developing the achieved success, the designers of the YAZ began to work on the machine with a payload at the level of 7 t. However, it immediately became clear that the project would again face the problem of engine selection. To obtain the desired traction and ride characteristics, an 110-120 horsepower engine was required, but such products were not available in our country at that time.
Truck YAG-7. Figure Bronetehnika.narod.ru
Since the beginning of the thirties, the development of a family of promising diesel engines under the general name "Kocju" was conducted. By 1938, NATI developed a new model of this line - the MD-23 engine with a power of at least 110 hp, and it was proposed to be used on a new Yaroslavl truck. However, such an engine still needed refinement and was not ready for mass production. It was possible to launch the assembly of trucks with MD-23 only in 1939 year.
Not wanting to waste time, YAZ design bureau made a principled decision to create a “universal” truck project. It was proposed to create a chassis platform suitable for installing the MD-23 and capable of carrying 7 tons of cargo. In anticipation of the finished diesel, a “transitional” version of such a machine with a less powerful gasoline engine and 5 and load-carrying capacity should have been developed. Thus, the Yaroslavl Automobile Plant could master the production of a new five-ton, and then go on to produce a seven-ton truck.
A gasoline engine truck with a reduced payload was designated YAG-7. The second car with a diesel engine MD-23 called YAG-8. Such indexes can cause certain questions. The fact is that the figure in the name of the Yaroslavl truck usually indicated its payload in tons.
Given the future modernization of production facilities, engineers have introduced a number of new solutions to the new project. However, at the time of the construction of an experienced truck, the necessary technologies were missing. Because of this, YAZ was forced to seek help from other automobile plants. In particular, the elements of the frame of new design and some other units were performed at the Moscow Plant them. Stalin.
New design
In terms of its architecture, the YaG-7 differed little from its predecessors, but completely new units were used in its design. So, the frame was now assembled not from channels, but from forged parts from 7-mm steel sheet. The YAZ did not have the necessary press, and therefore stamping was sent from Moscow. The strength of the frame met the requirements of the project YG-8.
In front of the frame of the YAG-7, they placed the ZIS-16 carburetor engine with the HP 82 power. The inline six-cylinder engine was equipped with a carburetor MKZ-6 and had a liquid cooling. For new trucks, an improved tubular radiator was developed, but for technological reasons, the project used a serial cellular. Together with the engine, the ZIS company supplied a two-plate dry clutch. Especially for the YaG-7 in Yaroslavl developed a new four-speed manual gearbox. It was similar to existing products from the VMS, but differed in gear ratios. From the box there was a drive shaft connected to the main transmission of the driving rear axle.
In the YAG-7 transmission, a demultiplicator was provided to compensate for the lack of power in the ZIS-16 engine. The YAG-8 unified truck with a higher power diesel engine did not need such a device, but could save other transmission units.
The main transmission of the rear axle was built on new components, but its general parameters have not changed. Thus, spur spur gears were replaced with chevron gears, and conical spur gears gave way to conic gears with a helical tooth. Gear ratios were determined taking into account the characteristics of the future YG-8.
The chassis has received a front steering axle with single wheels and a driving rear axle with a gable. The suspension was built on longitudinal leaf springs, but now they were attached to the frame and axles with rubber supports. The pneumatic brake system with vacuum booster was redesigned. An advanced serial steering mechanism was used on the front axle, but the large steering wheel had to be retained.
Of great interest was the exterior of the experienced YAG-7. Machines of the new models were to receive a metal cab with a “fashionable” appearance. However, she had problems. YAZ could not manufacture such a product and could not order it on the side. Therefore, during the construction of the prototype machine, a ready-made cab from the GMC T-series 1936 of the year was used. Old identification marks were removed from the cab and they put their own. In the future, the possibility of borrowing the cabin from one of the serial domestic trucks was not ruled out.
In finished form, the YAG-7 had a metal hood with neat outlines with a vertical grille and horizontal louvers at the sides. Upper hatches this time absent. On the sides of the hood were installed wings, made at the same time with the steps under the doors. The all-metal cabin accommodates a control post and two passenger seats. Under the seats installed tank capacity 175 l. The cabin had front glazing with a central pillar and lifting windows in the doors.
As a cargo platform, a simple flatbed of wooden and metal parts was used. The front and rear sides were fixed, and the side could recline. In the future, the possibility of using YAG-7 and YAG-8 as a base for special equipment or a dump truck was not excluded.
The full length of the YG-7 truck was 6,7 m, width - 2,5 m, height - 2,32 m. The base and gauge corresponded to the previous YAZ technology. Curb weight - 5,3 tons, load capacity - 5 tons. Estimated speed on the highway reached 50-52 km / h. A prospective YAG-8 car with a MD-23 diesel engine should have similar dimensions and mass, but should have a higher payload capacity - 7 tons.
Prototypes and development
The development of new cars took several months, because of which the construction of two experienced chassis was able to start only in 1939 year. The assembly of two prototypes was completed in early November, and immediately after that they went to Moscow. Two samples were to become exhibits of the exhibition dedicated to the 15 anniversary of the Soviet automotive industry. After the end of the exhibition the car was sent to NATI.
Tests at the same time passed two cars of different types. First of all, YAG-7 itself was launched in the configuration of an onboard truck. The second prototype differed slightly reduced base and was a dump truck. This version of the car received its own name YAS-4.
The YAS-4 was distinguished by a reinforced frame with hinges for a lifting body. For the rise of the body was responsible hydraulic system, the pump which was driven by the propeller shaft. The machine was completed with a rectangular all-metal welded body. Bulk cargo was discharged through the opening swinging tailgate. As in the case of the previous dump trucks, the installation of new equipment led to the weighting of the machine and a reduction in capacity - to 4500 kg.
Over the following months, specialists from YAZ and NATI carried out the necessary tests and confirmed the calculated characteristics of the equipment, and also revealed ways of the required refinement. The design office of the plant was engaged in the improvement of the project.
10 March 1940 of the Year Sovnarkom adopted a resolution on the modernization of the Yaroslavl Automobile Plant. Before 1942, it was planned to build a number of new workshops, with the help of which the company would be able to produce a wide range of new products of various kinds, including engines and transmission units. A modernized plant could master the full production cycle. Until the end of the reconstruction, the YAZ design bureau had to develop new truck projects designed to be launched into the series with YaG-7.
Sad final
Unfortunately, after testing the spring 1940, traces of the experienced YAG-7 and YAS-4 cars are lost. At the same time there are fragmentary information about the continuation of work on the YAG-8 project. A prototype of such a machine was completed at the very end of 1941 of the year, but there are no exact data on it. In particular, it is not known whether the automakers were able to equip it with the originally planned diesel engine.
However, the diesel YAG-8 already had no prospects. It was planned to produce diesel engines of the Koju family at the Ufa Motor Plant, but by this time the enterprise had been transferred aviation industry. They did not look for a new platform for the production of diesel engines. Thus, the YAG-8 was left without real prospects and after the tests had to go for disassembly. In the future, based on the YAG-8, it was supposed to develop the YS-5 dump truck, but this project remained on paper.
Modernization of production facilities was delayed and by the beginning of World War II was carried out only partially. However, the Red Army and the national economy have not risked remaining without heavy trucks. The assembly of the YG-6 machines in the base and modified versions continued until the 1942 year, when the YAAZ was left without ZIS engines.
By releasing YAG-6 trucks, the Yaroslavl Automobile Plant did not stop engineering design. In 1941-42, new designs were created based on the YAG-7 platform. In particular, the possibility of equipping this car with American engines was being worked out. Procurement of engines abroad in theory also allowed to put in the series an updated version of the diesel YG-8. Moreover, YAAZ even managed to get a certain number of GMC-4-71 engines and test them on production trucks.
However, all these works did not make sense. At the turn of 1942 and 1943, it was decided to reprofile the Yaroslavl Automobile Plant. Now he had to collect not trucks, but tracked artillery tractors developed by NATI. In 1943, the first batch of I-11 type trucks rolled off the assembly line. In the future, they were repeatedly upgraded and built a large series.
Yaz returned to the subject of trucks after the war. In 1946-47, completely new types of equipment appeared, developed without extensive use of existing ideas and solutions proposed in previous projects. In fact in stories factory began a new era.
Yaroslavl Automobile Plant developed and built trucks of different models from the mid-twenties. Almost all such projects were created by deep modernization of old ones, and only in the late thirties the company was able to create a completely new platform. Unfortunately, the circumstances were such that these cars did not reach mass production. The creation and launch of production of a fundamentally new line has shifted by several years.
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