The experience of the Great Patriotic War has clearly shown that the troops need armored personnel carriers capable of delivering infantry units to the battlefield, providing protection from bullets and shrapnel and possessing high mobility. In service with the Soviet Army during the war years and after its end, only American armored personnel carriers, received under Lend-Lease and well-proven in operation, were consisted. The German experience of using such machines did not go unnoticed either.
K-75 armored personnel carrier in its original configuration. An awning is installed above the troop compartment
Immediately after the creation in 1947 of the Design Bureau of Engineering and Tank Equipment as part of the TsPII SV im. D. M. Karbyshev (later - Design Bureau of the Engineering Committee of the SA, or OKB IV) under the leadership of A. F. Kravtsev, a number of combat tracked amphibians were designed - the K-75 armored personnel carrier, the K-73 self-propelled amphibious installation (ASU-57P), the K-90 amphibious tank and the K-78 armored personnel carrier. This work went on almost simultaneously with the creation of the K-50, K-61 and K-71.
Placement of the power plant and transmission units in the K-75 housing
When developing new models of armored vehicles A. F. The rich experience gained during the operation and improvement of armored and automotive vehicles in OKDVA conditions was very useful to Kravtsev. In the Far East, special difficulties arose when restoring equipment - the lack of special, often short-lived, tank units and assemblies affected. Therefore A. F. Kravtsev and his designers tried to make extensive use of units and assemblies already mastered by the domestic automotive industry, tested in operation and produced in large quantities. Much attention was paid to the low cost and simplicity of the design, as well as the convenience of its operation.
In the design of the open-type tracked armored personnel carrier K-75, units and assemblies of the M-2 artillery tractor, as well as trucks, were widely used.
K-75 armored personnel carrier in its original configuration. The removable mounts for the awning on the sides of the hull are clearly visible
The prototype of the armored personnel carrier was manufactured in 1949 at the Military Repair Plant No. 2 GBTU (Moscow) according to the design documentation of the Design Bureau of the Engineering Committee of the SA, developed in accordance with the TTT, approved on December 31, 1948 by Marshal of the Engineering Troops M. P. Vorobiev.
The K-75 hull was made waterproof, which made it possible for it to stay on the water and cross the rivers with the help of additional traction (motorization means, poles, oars and a rope).
The armored personnel carrier was divided into three sections: motor-transmission (MTO), control and landing.
K-75 armored personnel carrier in its original configuration
K-75. View of the troop compartment. For the landing of personnel, two doors served in the stern sheet of the hull.
Tests of K-75 afloat
The MTO, located in the bow of the hull at the starboard side, housed the engine, its systems and transmission units. The armored personnel carrier was equipped with a two-stroke, four-cylinder compressorless liquid-cooled YaAZ-204B diesel engine with a capacity of 140 hp. (according to the plant) [1], borrowed from the M-2 tractor. The power system consisted of two fuel tanks (located along the starboard side of the MTO), distribution valves, a manual fuel pump, coarse and fine filters,the fuel supply pump and pumps - injectors of the engine cylinders. The total capacity of the fuel tanks was 220 liters. Air supply was carried out through two inertial oil air cleaners connected in series with a multicyclone filter. The cooling system included a radiator, a centrifugal pump, a twelve-blade fan, a thermostat, a tank with a steam-air valve, and a pipeline.
BTR K-75 control scheme
The transmission of the armored personnel carrier consisted of the following units: dry single-plate clutch of the YAZ-200 truck; three-way five-speed (with one reverse gear) gearbox YAZ-200; the main gear, which is a pair of bevel gears with a gear ratio of 1, 07; onboard multi-disc dry friction clutches with single-acting band brakes and final drives. The connection of the drive shaft of the main gear with the secondary shaft of the gearbox was carried out using a gear coupling.
At the ends of the driven shaft of the main gear, there were side clutches with band brakes, which were the control mechanisms of the armored personnel carrier. They were controlled using levers and a linkage system in such a way that when the levers are turned off, the friction is first turned off, and then the brake is tightened.
K-75 with a load of 2 tons forcing the river. Vuoksi 350 m wide
Transporter K-61 comes ashore from K-75 in tow
The drive gear was connected to the semi-axle through toothed couplings, and the driven gear was mounted on the same shaft with the drive wheel of the caterpillar.
Above the control compartment and MTO there was an armored * roof with two hatches, which were closed by armored covers.
In the control compartment, located in the bow of the hull at the left side, there were the seats of the driver and the gunner-radio operator, an inspection hatch, observation devices, control drives, instrumentation, batteries, a radio station and ammunition for a machine gun.
The airborne compartment provided for the placement of a landing in the amount of 16-20 people or a cargo weighing 2 tons. For the paratroopers there were crossbars with soft seats, which were removed when transporting goods. The dismounting of motorized riflemen and their landing in the K-75 armored personnel carrier was carried out through the hull open on top and the aft door. To protect personnel from the effects of precipitation, an awning could be mounted on the troop compartment.
The K-75 armored personnel carrier overcomes the moat
Driving on a slope
Turn in place by 360"
Overcoming a ditch 2 m wide
Climbing 38 'with a load of 2 t
Descent from the rise 38 'with a load of 2 t
Driving on arable land
Overcoming a vertical wall with a height of 0.7 m
The main weapon of the armored personnel carrier was the 7, 62-mm machine gun SG (SG-43), which was installed in the sockets that were on the body of the vehicle and provided circular fire. The main location of the machine gun was the swivel of the standard field machine mod. 1943. A basket for a box with a tape was attached to the swivel on the right, and a sleeve outlet body was attached to the left, to which a sleeve catcher was attached from below. Machine gun ammunition was 1000 rounds, loaded in four belts. In addition, the armored personnel carrier housed 12 F-1 grenades in two modes (six in each).
The armor protection of the K-75 armored personnel carrier was bulletproof. The upper and lower frontal hull plates were made of 13 mm thick armor plates having an inclination angle of 50 °, and 6 mm thick, located at an angle of 70 °. 12-mm side and 10-mm aft armor plates were installed vertically. The bottom was 3 mm thick.
Low height (1.5 m) made it easier to camouflage the K-75 on the ground
The undercarriage of the K-75 armored personnel carrier included drive wheels with cast toothed rims, track chains, consisting of 95 small-link tracks 300 mm wide. The tracks were connected to each other using floating pins that worked without lubrication. The upper branches of the caterpillar tracks were supported by guide skids. The tension of the caterpillar chain was carried out by turning the crank of the idler wheel (sloth). The idler roller was interchangeable with track rollers and was attached to the crank pin. The armored personnel carrier had ten welded road wheels with rubberized rims, five on each side. The rear road wheels were additionally supported by shock absorbers from the ZIS-154 bus. The torsion bar suspension consisted of torsion shafts and their brackets.
The car used single-wire electrical wiring (with the exception of emergency lighting devices). The nominal voltage in the network was 12 V. The electrical equipment of the machine included 6-ST-128 rechargeable batteries, a G-500 electric generator and a ST-25 starter.
For radio communication, the BTR K-75 was equipped with a 10RT-12 radio station.
Armored personnel carrier K-75 moves on virgin soil
In the period from September 9 to September 28, 1950 (in accordance with the order of the Minister of War of the USSR No. 00172 dated August 19, 1950), in the area of Brovary, Kiev region, comparative factory tests of a prototype of the K-75 tracked armored transporter took place. They were held according to the program approved by the Deputy Minister of War Marshal of the Soviet Union V. D. Sokolovsky and Minister of Transport Engineering Yu. E. Maksarev. The test commission was headed by Colonel-General of Tank Forces P. P. Poluboyarov. OKB IKSA was represented by engineer-colonel A. F. Kravtsev.
The purpose of the tests was to determine the compliance of the tactical and technical characteristics of the prototype with the specified requirements, the reliability of the operation of all mechanisms, the ease of maintenance and repair of units and assemblies in the field by the crew, the placement of troops, other military cargo, as well as the maintenance of the machine gun and sighting devices.
During the tests, the prototype of the K-75 armored personnel carrier passed 1997 km, and the mileage at night was 796 km.
Transporting 16 fighters
Based on the test results of the prototype of the armored personnel carrier, the commission stated that in terms of the main indicators, it meets the tactical and technical requirements approved by the chief of the Engineering Troops on December 31, 1948. At the same time, the following positive qualities of the K-75 were noted:
- The armor plates of the hull of the prototype of the K-75 tracked armored personnel carrier, in accordance with the order of the Minister of the USSR Armed Forces, were replaced with sheet steel of the ST-3 brand.
- the armored vehicle is manufactured using serial units of the automotive industry, which greatly simplifies its design and reduces the cost of serial production and repair;
- due to its low height (1.55 m), the armored personnel carrier can be easily camouflaged on the ground;
- in wooded areas, due to its small width, the armored personnel carrier is distinguished by good maneuverability and speed;
- the vehicle has bulletproof armor (side - 12 mm) with a relatively low weight (7, 8 tons without troops and cargo);
- an armored personnel carrier, possessing buoyancy, can cross water obstacles using additional thrust.
At the same time, the prototype also had a number of design flaws, the main of which were:
- insufficient speed of movement on a cobblestone highway and unpaved roads;
- insufficient power density;
- insufficient capacity of the troop compartment.
K-75 armored personnel carrier in final configuration with armament. 1950 g
According to the commission, due to the presence of these shortcomings, the K-75 armored personnel carrier in its current form cannot be adopted by the Soviet Army.
One of the important conclusions from the test results of the K-75 prototype was that it was confirmed that it was possible to create a simple in device, cheap and mass-produced, reliable tracked armored personnel carrier in operation using units of the automotive industry.
Therefore, given the importance of developing such a machine and adopting it for service, the commission recommended the manufacture of two improved prototypes of the K-75 tracked armored personnel carrier with the following basic requirements:
- an increase in the maximum and average speeds of movement;
- an increase in the capacity of the troop compartment up to 24 people;
- Ensuring the convenience of deploying troops and their weapons.
- increasing the reliability of the armored personnel carrier - with a guaranteed service life of up to 3000 km:
- the ability to independently cross water obstacles using a simplified water propulsion system.
During the revision of the K-75, according to the test results, the design of the aft armor plate of the hull was changed. Instead of two doors for the landing of personnel, one
However, for unknown reasons, the construction of two modified models of the armored personnel carrier did not take place. But the experience gained by the developers of the K-75 was not in vain. It was used in subsequent machines created at the Design Bureau of the Engineering Committee of the SA under the leadership of A. F. Kravtseva.
Later, the K-75 tracked armored personnel carrier was transferred to the Military-Historical Museum of Armored Weapons and Equipment (Kubinka settlement), where it is currently kept.
Characteristics of an experienced armored personnel carrier K-75
Length, mm ……………………………………………….5370
Width, mm …………………………………………….2756
Height along the body, mm ……………………………… 1550
Weight without cargo and landing, kg ………………………… 7820
Specific ground pressure, kgf / cm2:
- without cargo …………………………………………… 0, 415
-with cargo …………………………………………….0, 528
Track, mm ……………………………………………..2425
Ground clearance along the bottom, mm ………………… 400
Max, overcome ascent and descent ………… 34 '
Max, side roll …………………………………..27 '
Height of overcome vertical
walls, m …………………………………………………..0, 7
Speed, km / h:
- on the highway …………………………………………… up to 40
-on the ground ………………………………………… up to 36, 6
Minimum turning radius
(along the front edge of the outer wing), m ………… 4
The width of the ditch to be overcome, m ……………….2, 25
Cruising range for fuel, km:
- on a highway of average quality …………………..216
- on unpaved country roads ………. 170
