The history of technology, especially the military Soviet period, has many glorious pages. Designers of the Minsk Automobile Plant, who worked in the department of wheeled tractors, which over time became a separate MZKT plant, made a significant contribution to the writing. Remarkable and today a unique creation was the tractor MAZ 7907.
Historical background
In response to the creation by the American experts of the MX intercontinental missile, the launch mass of which was almost 90 tons, the leadership of the USSR Ministry of Defense decided to develop an analogue. Such an answer was the RT-23 Molodets rocket, according to NATO code SS-24 Scalpel weighing almost a hundred tons. A transport and launch container with a rocket inside weighed one hundred and five tons. Its length was almost twenty-three, and its diameter was two and a half meters. The design dimensions of the launcher were: length - 32 m, height - more than 5.5 m.
But to create a rocket is not enough, a cargo with such a mass and of such dimensions still needs to be transported along the roads, and sometimes without them.
Since the special division of MAZ already had extensive experience in designing heavy trucks, this plant received an order for the manufacture of a wheeled vehicle with a carrying capacity of more than 100 tons.
The result of two years of work of the enterprise’s specialists, whose chief designer was Dr. B. L. Shaposhnik, Hero of Socialist Labor, laureate of the Lenin and State Prizes of the USSR, became the unique MAZ 7907.
Specifications
This project is called “Tselina-2”. The first was an MAZ 7906 eight-axle tractor with a lifting capacity of 150 tons.
The MAZ 7907 (24x24) tractor was developed for two years. And in 1985, two samples were collected for sea trials. The curb weight of the conveyor was 66 tons with a carrying capacity of 150 tons. The estimated maximum speed on the highway (hard and smooth surface) is 40 km / h. In tests with a prototype launcher, the conveyor showed a speed of 25 km / h.
Impressive overall dimensions of the tractor. Its length was more than 28 meters, width - 4.7 m, and height - almost 4.5 meters. The width of the wheel track, and the front and rear, was more than 3.3 m, and the clearance was 465 mm. The radius of rotation of the chassis is 27 meters. The base of the front and rear bogies is not the same - 9.065 and 9.22 m. The distance between the axles of the wheels is 1.75; 1.8 or 1.855 m.
Twelve pairs of driving wheels VI-207 of domestic production had dimensions of 1660 x 600-635 mm. That is, the diameter of the wheel was the height of the average person. How small are the people next to this monster MAZ 7907, the photos from the report on the transportation of the boat demonstrate very clearly.
Design features
To provide such an impressive carrying capacity, all MAZ 7907 wheelsets had to work at full load without hanging the wheels on dirt roads. Therefore, in addition to the suspension design, a power hinge on bearings with one degree of freedom was provided in the ridge-type frame, which retained rigidity in the horizontal plane. That is, the platform was two-link on two six-axle bogies that could move in a vertical plane relative to each other at an angle of up to 8 °.
To ensure the maneuverability of such a long base, eight of the twelve pairs of wheels turned. These were the first and last four pairs. Moreover, two rotation options were provided. In the first, eight wheels turned in one direction, and eight - in the opposite direction. In the second, the turn was synchronous - the so-called “crab” movement or sideways.
Powerplant MAZ 7907
MAZ of such carrying capacity and power required an engine with special characteristics. The tractor was equipped with a three-shaft gas turbine engine GTD 1000T FM with a capacity of 1250 liters. from. Kaluga Engine Plant, which is now called State Unitary Enterprise "Plant named after V.Ya. Klimova. " The engine was mounted on the front console of the frame under a three-seater cabin with three windshields.
Many people call the engine tank, although the plant specifically created modifications of the base engine for missile carriers, including MAZ 7907. Fuel consumption in the literature open for public access is indicated only for tank engines, and for the GTD-1000TF with a capacity of 1100 liters. from. it is 235 g / hp * h, and for the GTD-1250 at 1250 liters. from. - 225 g / hp * h. Given that a tractor could travel one hundred kilometers at maximum speed in four hours, then it took about one and a half tons of fuel to spend on it.
The VSG-625 alternator installed in the engine block fed the TE-660-24 electromechanical transmission units and air-oil-cooled synchronous electric motors installed inside the frame, separately for each wheel.
Oil radiators and electric control units were located under parallel covers at the rear of the chassis.
Advantages and disadvantages
Compared with the previous MAZ conveyor, the 7906-twelve-axle tractor had significant advantages. The best were the handling, soundproofing of the cab, higher manufacturability and survivability, since the mobility of the installation was maintained even if the eight-wheel drive was damaged.
But the MAZ 7907 tractor had shortcomings as well. The electromechanical transmission was characterized by low efficiency and low efficiency. In addition, the heavy machine had low passability on soft soils and insufficient acceleration dynamics, increased axial load.
The design required serious improvements, although prototypes of missile carriers were tested successfully. Perhaps the shortcomings would have been eliminated over time, but the Cold War ended and the disarmament phase began, strategic missile forces became unnecessary.
MAZ 7907 in action
Unique conveyors remained at the factory site, but one of the tractors underwent a kind of test drive, which, however, confirming the declared characteristics, ended in disrepair for him.
After ten years of oblivion, in the summer of 1996, it was necessary by land to deliver a pleasure boat 40 m long and weighing 90 tons to its destination. And besides, the owners loaded building materials into the bow compartment, so as not to spend money on their delivery. It was discovered after loading that the centering of the vessel was violated, and I had to urgently load the stern. As a result, the total weight of the vessel was approximately one hundred tons.
For almost two months, the MZKT specialists prepared the equipment for work. The subframe that existed for attaching the TPK was redone. Now it was the lodgment for the bottom of the pleasure craft. We launched a gas turbine, checked the electric motors of the wheels. Four engines did not work. One hundred and seventy tons of total mass traveled on twenty wheels. As stated when creating the tractor with serial number 7907.
MAZ passed under its own power more than 200 km at a speed of about 20 km / h. Only when crossing the bridge over the Berezina River, not designed for transporting such a mass, the four-axle MZKT-79091 with a winch and aft mast took over part of the cargo, raising the stern of the boat above the platform.
When unloading, truck cranes and a tractor in reverse were driven directly into Lake Naroch. The electric transmission did not pass the test of water. I didn’t reach MAZ 7907 back under its own power, it was delivered by a factory tractor.
Inverted History Page
Ten years later, one of two missile carriers at the factory training ground was assembled. The result was such a monumental monument in a museum exposition on the territory of the Minsk Wheel Tractor Plant. Unfortunately, today there were no problems for the solution of which such a powerful equipment as the MAZ 7907 would be needed.
Photos of a unique car are not so common. The sad moments of decline and destruction and black-and-white photographs are now almost twenty years ago, which depicts the path from the Berezina River to Lake Naroch - that’s all. But they are enough to show the power of the tractor and the power of thought of Minsk designers, headed by B. L. Shaposhnik, for whom this project was the last.