At the beginning of 1932, the Yaroslavl State Automobile Plant No. 3 launched mass production of YAG-10 trucks - the first domestic vehicle with a three-axle chassis and a carrying capacity of 8 tons. This development made YAGAZ a real industry leader, but its designers did not rest on their laurels. Soon, a new truck with special capabilities was developed - YAG-12. This car was the first in many ways. YAG-12 was the first four-axle vehicle in our country and the first showed a carrying capacity of 12 tons. This was an outstanding achievement by the standards of the global automotive industry.
Experienced YAG-12 at the factory site. Photo Bronetehnika.narod.ru
During that period, the command of the Red Army showed great interest in trucks with an increased number of axles. So, it was on the initiative of the Red Army that new three-axles were developed, including the Yaroslavl YaG-10. In addition, the military in 1931 tested an all-wheel drive four-axle vehicle of British design and became interested in such technology. This interest resulted in a new order for YAGAZ.
New project
After the completion of development work on the YAG-10 machine, the load on the YAGAZ design bureau was sharply reduced. However, the engineers did not rest and began to fulfill the new army order. The military wanted to get a truck with an unusual wheel arrangement 8x8, due to which it was planned to get an increase in cross-country ability on rough terrain and off-road.
In the early thirties, such trucks were being developed in several leading countries, and the command of the Red Army considered this a cause for concern. Thus, YAGAZ had to create a fundamentally new car in the shortest possible time and reduce the gap with foreign leaders in the industry. The plant got an excellent opportunity not only to catch up, but also to get ahead of foreign competitors.
View to the port side. Drawing "Technique - for youth"
The head of the new project was A. S. Litvinov, who already had extensive experience in the development of trucks. A promising car from a certain time bore the designation YAG-12 - "Yaroslavl Truck". The numbers indicated the calculated carrying capacity of the machine.
The customer demanded that the truck be presented as soon as possible, and for this reason, the YAGAZ Design Bureau decided to build a new YAG-12 based on the existing YAG-10. It was planned to use proven design solutions and borrow various units. At the same time, it was necessary to use completely new components and introduce non-standard ideas.
For example, its own concept of a four-axle truck with four-wheel drive was formed. The use of four pairs of wheels made it possible to reduce the specific pressure on the ground, and the all-wheel drive provided an increase in tractive effort. Abroad, these opportunities were most often used separately: in some projects, middle-class cars with improved cross-country ability were offered, while others provided for an increase in carrying capacity. The team of A. S. Litvinov decided to perform two tasks at once and get outstanding performance.
Four bridges
The new YAG-12 truck was supposed to resemble the serial YAG-10 to a certain extent. It was proposed to use an elongated frame made of channels, assembled on rivets. Its rear part was reinforced with additional profiles. In front of the frame was placed the power unit, behind which was the cabin. The rest of the frame was given for the installation of the cargo area. It was proposed to place a front bogie with a pair of axles under the engine and the cab on the frame. The two rear axles were under the body.
Front view. The characteristic units of the front axles are clearly visible. Drawing "Technique - for youth"
The car needed a more powerful power plant. An American-made Continental 22R gasoline engine with a capacity of 120 hp was chosen for use on the YAG-12. The multi-plate dry clutch and the Brown-Lipe 554 gearbox were taken from the serial YAG-10. The box had 8 forward gears and 2 reverse gears. There was a band parking brake on the output shaft of the box.
Behind the gearbox, under the rear wall of the cab, there was a self-developed YAGAZ transfer case. The drive of the main gears of the four axles was organized using a set of cardan shafts. The shafts from the transfer case went to the gears of the second and third axles. Two more shafts departed from them to drive the extreme axes.
The rear bogie was borrowed from an existing three-axle truck. It included two bridges with gears based on spur gears. The design of gearboxes and axle housings remains the same. The same was true for the suspension. The rear bogie retains the existing vacuum booster braking system. A mountain stop was installed on the crankcase of the fourth axle to fix the machine on the slopes.
View to the starboard side and stern, noticeable frame structure and the location of the units. Figure Denisovets.ru
The front bogie has been designed from the ground up. Two main gears with bevel gears were rigidly installed on the machine frame. From them departed short transverse cardan shafts connected with open-type hinges of equal angular velocities. This made it possible to provide drive to the front wheels, as well as to make both front axles steerable. Earlier calculations showed that a four-axle vehicle with the proposed layout needs several steerable wheels, and this problem was solved. The front axles were controlled using a modified steering gear from Ya-5. It was connected to the wheels of the second axle, which interacted with the first axle through longitudinal rods.
Despite the difference in drive design, both bogies had a similar suspension. Shoes with longitudinal semi-elliptical springs were suspended under the frame. The ends of the springs were connected to the CV joint housings (on the front axles) or to the axle bodies (on the rear axles). A characteristic feature of the applied chassis was some reduction in unsprung mass, which made it possible to increase the carrying capacity.
It is worth noting that YAGAZ designers had to work on non-trivial tasks in the absence of proven solutions. This led to a serious complication of the transmission: it had 9 cardan shafts, 18 hinges and more than 40 bearings at once. In this regard, special schemes had to be transferred to production along with other documentation to control the directions of rotation of shafts and other components.
On wheels, the YAG-12 truck was unified with the existing equipment. The front bogie had single wheels, while the rear was equipped with gable wheels. The rims were borrowed from serial equipment. The rear wheels could be equipped with removable track chains of the Overroll type.
The layout of the power plant, transmission and chassis. Drawing Bronetehnika.narod.ru
Additional devices were connected to the transfer case. So, under the front part of the body was placed a winch with the possibility of issuing a cable forward or backward. Also, the car was equipped with its own compressor for pumping the wheels. Constant pumping, however, was not used.
The engine compartment of the new car was covered with an oversized hood, created on the basis of existing products. As before, there was a honeycomb radiator in the front. Above provided a cover with rectangular hatches, on the side - lifting sides with shutters. A ready-made serial-type cab with three seats for the driver and passengers was used. Under the common seat was a fuel tank for 164 liters of gasoline. A new wing of increased length appeared on the sides of the hood and cockpit. Its rear part served as a footrest.
The cargo platform was made in the form of a side body. It was taken from the serial YAG-10, but slightly shortened. The front wall of the body was rigidly mounted, the rest could be reclined and fixed with locks. A spare wheel and a toolbox were transported under the front of such a body.
YAG-12 on trials. Photo Bronetehnika.narod.ru
The fundamentally new chassis has had a minimal impact on the dimensions of the truck. The length of the YAG-12 increased to 6, 6 m, the width did not exceed 2.4 m, the height was less than 2, 8 m. The curb weight of the car was 8 tons. The estimated carrying capacity on the highway is 12 tons, on rough terrain - 8 tons. Thus, the gross weight of the truck reached a record 20 tons. The engine of sufficient power allowed it to reach speeds of up to 45 km / h, as well as overcome various obstacles. Fuel consumption - 52 liters per 100 km.
Car for the holiday
The development of the YAG-12 project was completed in the middle of the summer of 1932. Soon thereafter, Yaroslavl State Automobile Plant No. 3 began producing the necessary parts and then assembling a prototype. It took about three months to assemble the prototype. Perhaps the construction of a complex machine could take longer, but the automakers decided to present it for the next anniversary of the October Revolution. There was some lag behind the schedule, but in recent days the situation was corrected, and in the late evening of November 5, the experienced YAG-12 started up and drove off for the first time.
The first test for the car was a trip to Moscow to participate in festive events. By the evening of the next day, a convoy consisting of a single YAG-12 and several serial YG-10s was in the capital. On November 7, Yaroslavl-made cars passed through Red Square. Soon, the equipment was shown to the military and political leadership of the country. The military leaders highly appreciated the new development for the army and gave the go-ahead for the continuation of the work.
After the holiday, the experienced YAG-12 went to the Scientific Automobile and Tractor Institute for testing. Over the next few months, scientists and engineers tested the machine and established its real capabilities. Designed running characteristics and lifting capacities have been confirmed. In addition, the capabilities of the equipment on the off-road were determined. A truck with a payload could climb a slope with a steepness of 30 °, cross ditches with a width of 1.5 m and fords with a depth of 0.6 m. The car moved in snow with a depth of 500 mm and could overcome obstacles of a similar height. The use of Overoll tracks significantly increased the cross-country ability.
Truck tests on a slope. Photo Bronetehnika.narod.ru
The YAG-12 was also tested as an artillery tractor. With the help of a towing device and, in some situations, a winch, she could carry any domestic weapons, including large calibers. In the back, it was possible to transport ammunition and calculation.
Plans and reality
In general, the promising four-axle heavy-duty YAG-12 truck suited the customer in the person of the Red Army command. Minor modifications and fine-tuning were required to improve technical and operational characteristics. As part of the fine-tuning, it was planned to build and test seven new prototypes. After the completion of the improvement, the machine could find application in various fields - both in the army and in the national economy.
The main customer of the new technology, as it was believed in 1932-33, was to be the Red Army. She needed cars in the configuration of flatbed trucks, but the possibility of creating other modifications with other equipment was not excluded. A car with a carrying capacity of 12 tons could become a vehicle for people, solid, bulk or liquid cargo, or a tractor for implements or other trailers.
An additional front axle makes trenching easier. Photo Bronetehnika.narod.ru
In the interests of the national economy, it was also proposed to build various modifications of the YaG-12. Together with the truck, dump trucks, tank trucks, etc. could serve in civilian structures. A proposal to create a double-decker bus with increased capacity was considered. Previous Yaroslavl trucks managed to become the basis for buses, and the new car also had a high potential of this kind.
However, all these plans did not come to fruition. The situation around the YAG-12 project and the entire direction of heavy trucks changed dramatically in the same 1933 year. After passing the tests in NATI, the only built four-axle truck was handed over to one of the military units in Saratov for further testing in the army. On this, his trace is lost. How long and how the YAG-12 was used in the new location is unknown. Information about his further fate is also lacking. Apparently, at some point, the experienced truck was decommissioned and disassembled.
Soon after the transfer of the prototype truck for military trials, the command of the Red Army decided to abandon the further development of four-axle vehicles. Such a technique had great prospects and confirmed them in practice, but at that time it did not look optimal. New machines of the YAG-12 type were more complex and more expensive than the existing ones, which could complicate their mass construction. As a result, it was decided to abandon the eight-wheeled chassis in favor of existing and produced three-axle designs.
Model of the YAG-12 truck at the Moscow Polytechnic Museum. Photo Wikimedia Commons
Past and future
Work on the promising YAG-12 truck with an unusual wheel arrangement and unique technical characteristics did not last too long. The design of the new machine started at the beginning of 1932, and the decision to stop the work was made before the end of the next 1933. It should be noted that by this time only the Yaroslavl State Automobile Plant had managed to develop and build its own version of a four-axle truck. Other enterprises either did not deal with this topic at all, or could not advance beyond preliminary study.
The closure of the YAG-12 project had a great impact on the further development of Soviet automotive and special equipment. They returned to the topic of four-axle heavy-duty vehicles and high cross-country ability only in the mid-fifties. At the same time, the Yaroslavl Automobile Plant did not participate in the development of new samples - by that time he was entrusted with the construction of trucks of a less daring look.
The YAG-12 truck project took its place in the history of the domestic automotive industry. He confirmed the ability of our enterprises to develop the most daring and promising new technology projects. However, he also showed that not all such developments can find application in a specific period of time in the conditions characteristic of him.
