The Second World War showed how important floating transport vehicles can be when crossing rivers and reservoirs with defensive structures on them. They allow "from the wheels", without special engineering training, sometimes under enemy fire, to quickly transport manpower, ammunition, artillery, sometimes with tractors, over a water barrier, and pick up the wounded on the way back. Thus, a new type of military equipment was born - wheeled and tracked transporters, amphibians. They began to be widely used in the American and British armies since 1942, first in the Pacific Ocean, later in Europe during the landing in Sicily, in Normandy, during the crossing of the Seine, Weser, Meuse, Rhine rivers and numerous lakes and canals
Overseas prototype
Under Lend-Lease, American-made floating vehicles began to arrive in the Red Army in mid-1944. This allowed our troops in the Vistula-Oder operation, when crossing the Svir and Daugava rivers, to solve complex combat missions with significantly less losses than when using conventional and henchmen ferry facilities. It became clear that in the future, amphibious vehicles will find widespread use in the army as an effective and reliable landing craft.
In preparing the plans for the post-war technical re-equipment of the Soviet Army, the development of large waterfowl trucks with a carrying capacity of 2.5 tons was also planned. However, there was no experience in creating such machines in our country, therefore, it was impossible to do without careful study and reasonable copying of foreign analogues.
To create a large floating vehicle, a three-axle vehicle was needed, capable of transporting across a water barrier, with a reliable entry into the water and access to the shore, landing units of up to 40 people with weapons and ammunition, military cargo weighing up to 3 tons, 76, 2- and 85-mm artillery systems with service staff, etc. The Allies had such a car - the American GMC - DUKW - 353, which entered service in June 1942.
American amphibian GMC - DUKW - 353
GMC layout - DUKW-353
GMC - DUKW-353 was developed by Marmon Herrington on the basis of aggregates and chassis of 2, 5-ton three-axle army off-road vehicles (ATP) GMC - ACKWX - 353 (1940) and GMC - CCKW - 353 (1941). The body of the car and its contours were made by the naval architecture firm Sparkman and Stephen from New York.
The existing frame of the car with the chassis was placed in a water-tonnage hull - a pontoon-type boat. The chassis was made according to the classic three-axle scheme, which became standard for army vehicles: in front was a gasoline 6-cylinder engine with a capacity of 91.5 hp. The afloat was provided by a water propeller, which was located in the stern of the hull in a special tunnel. Maneuvering on the water was carried out using a water rudder installed immediately behind the propeller.
In the aft part of the hull there was a winch with a drum 61 m long. It was intended to facilitate loading artillery and vehicles into the cargo compartment. The winch operated conveniently during self-pulling of the machine, but only during the backward stroke.
In theory, the cable could be pulled forward and through the cargo compartment and the guide bracket on the nose of the car. But this method was used very rarely.
In September 1942, a centralized tire pressure control system was installed on the machine. It made it possible to reduce the pressure from normal 2.8 kgf / cm2 (driving on paved roads) to 0.7 kgf / cm2 on soft soils (for example, sand). Due to the deformation (flattening) of the tire, the contact area of the tread with the ground increased, which reduced the total pressure on the ground. This, in turn, increased the vehicle's cross-country ability. It is believed that these were the first cars in the world with a tire pressure control system on the go. However, even before the war, a similar system was developed in Germany and used on small-scale 4x4 cars, for example, the Mercedes Benz G-5 or Adler V40T.
In total, 21,247 GMC vehicles - DUKW-353 were produced from March 1942 to May 1945. Combat losses (on all fronts) amounted to 1137 units. In the USSR, 284 vehicles were delivered under Lend-Lease in 1945 (data for 1944 are not available).
Table 1. Technical data of the amphibian GMC - DUKW-353
Carrying capacity, kg:
on land - 2429;
on the water - 3500.
Total weight (with driver and cargo), kg - 8758.
Dimensions (LxWxH), mm - 9449 x 2514, 6 x 2692.
Clearance, mm - 266.
Turning radius on the ground, m - 10, 44.
Maximum travel speed, km / h:
on paved roads - 80, 4;
on the water - 10, 13 (without cargo - 10, 25).
Loading platform area, m2 - 7, 86.
Soviet response
Tests of the amphibious GMC - DUKW-353, which were carried out in the USSR in October 1944, did not confirm some parameters of the machine (see table 1). So, the maximum speed on land was 65 km / h, not 80, 4 km / h, on water - 9, 45 km / h. The steep slope of 27 ° declared by the company was never taken, and the total weight of the car with cargo and the driver was 9160 kg.
After testing, Soviet engineers began to create their own large floating vehicle. It was supposed to be developed at the Moscow Automobile Plant. Stalin (ZiS), which by that time, in the spring of 1946, had already built a three-axle 2.5-ton ZIS-151 all-terrain truck. It turned out to be not the most successful, but in terms of external parameters, dimensions and kinematic scheme of the chassis, it was close to the American GMC - DUKW-353. But the plant was overloaded with the development, fine-tuning and mastering of the production of new cars and combat vehicles of the first post-war generation (ZIS-150, ZIS-151 (BTR-152), ZIS-152, etc.) and therefore refused this work. He suggested that the branch should take up this task. The branch was the then unfinished Dnepropetrovsk Automobile Plant (DAZ), which was supposed to produce ZIS-150 trucks as a backup plant.
Truck ZIS (ZIL) -150
By May 1947, K. V. Vlasov, a former chief engineer of the Gorky Automobile Plant (GAZ), was appointed director of the plant, and the 42-year-old engineer V. A. Grachev, who had previously been successfully developing cross-country vehicles at Gorky, became the chief designer of DAZ. car factory. Grachev was always drawn to the military theme, so in 1948 he took up this interesting and complex work with enthusiasm, on his own initiative, despite the lack of personnel. There was especially a shortage of designers - motorists and qualified specialists to work in the experimental workshop, which bears the bulk of the work.
Chief Designer of DAZ Vitaly Grachev
In addition, the plant continued to be built, not all workshops and services were fully formed. Also, work continued on the modernization of the ZIS-150 - GAZ-150 "Ukrainets", on the original semitrailer to it under the radar "Thunder", on the AK-76 truck crane.
DAZ-150 "Ukrainian"
Vitaly Grachev introduces L. Brezhnev to the first car of Dnepropetrovsk DAZ-150
But despite all this, work on the future large amphibian began at the end of the same 1948. First, the prototype - GMC was thoroughly studied (two cars were brought to the plant, one of which was dismantled "to a screw"). Through long road trips and sailing along the Dnieper, we discovered the strengths and weaknesses of the "American". At the same time, the designers were "tested" and introduced to the machine "from the inside". To do this, on weekends in the summer of 1949, the whole team sailed along the Dnieper, went to the shores and islands.
At GMC I liked:
- good for such a machine body hydrodynamics;
- well-chosen propeller;
- moderate own weight;
- quite soft springs;
- precise work of the clutch.
Discovered and disadvantages:
- inconvenient loading of equipment onto the cargo platform through the rear high side, which did not fold back;
- insufficient engine power;
- unreliable tire air supply heads;
- insufficient maneuverability on the water;
- constant roll to the left side due to the gas tank located there.
All this helped to formulate, together with the military, the final terms of reference for a large floating three-axle vehicle:
- approach on soft soils with an inclination of up to 20 ° to a water barrier up to 1 km wide of any depth with amphibious groups of up to 40 people with weapons and ammunition or with other cargo;
- crossing of landing groups to the unequipped opposite shore at a speed of at least 8.5 km / h;
- reliable exit from the water to a sandy or clay bank with a steepness of up to 17 °;
- further continuous advance into the depths of the enemy's territory along different roads at a speed of up to 60 km / h.
It was also supposed to provide fast and convenient loading (using its own winch) for crossing the 76, 2-mm ZIS-3 cannon, 85-mm D-44, ZPU-4 and 37-mm anti-aircraft guns with calculations (one installation each), light wheeled tractors GAZ-67, GAZ-69 (one at a time), and in the presence of a flat coast with dense soil and the absence of waves and strong winds - crossing 3.5 tons of cargo (100-mm cannon BS-3, 152-mm howitzer D-1 with calculation, medium wheeled tractor GAZ-63 without cargo).
Loading of 76, 2-mm cannon ZIS-3 on BAV using ramps
The vehicle was supposed to be equipped for towing a 30-ton raft on the water, and when used as a self-propelled ferry (without going ashore) - for ferrying amphibious groups of up to 50 people with standing weapons, self-propelled guns SU-76M, tracked tractors AT-L.
Gradually, the ideology of the layout of the new machine was formed, which received the DAZ-485 brand. In the bow compartment of the hull, closed on top by a riveted aluminum deck with three sealed hatches for access to the engine compartment, there was a 6-cylinder ZIS-123 engine (from the BTR-152) with a power of 110-115 con. forces. In addition, two 120-liter gas tanks were installed on the car (the GMC had one for 151.4 liters). The frame of the car was borrowed from the ZIS-151. It was significantly strengthened, additional cross-members, attachment points for driveshaft supports, a winch, and a propeller were introduced.
Behind the engine compartment there was an open double cabin of the crew with controls and control devices. In front and on the sides, the wheelhouse was closed with a folding glass, on top - with a removable tarpaulin. In winter, the cabin was heated. The cushions and backrests of both crew seats were floatable and served as life-saving appliances.
The tonnage thin-walled hull, as well as the three-blade propeller, increased by 25 mm in diameter, were simply copied from the "American" in the absence of experience. Therefore, externally, these two machines were very similar, especially on the front of the hull. But the layout of the domestic machine was slightly changed: the winch with a cable was placed in the middle of the hull, which made it possible, by releasing the cable back, to quickly and more efficiently run the load onto the platform through the hinged sealed tailgate (which was not the case at GMC). At the same time, the loading height decreased by 0.71 m, and the platform area increased to 10.44 m2 (in GMC - 7.86 m2). Also, at the rear of the platform, a crane could be installed, capable of working afloat. It was also planned to transport two metal quick-release ladders for loading wheeled vehicles. The car was equipped with a wide range of equipment: navigation (up to an aviation compass), skipper (anchor and hook), rescue equipment, there was an electric siren and a search light.
General plan of the amphibian DAZ-485
General view of the amphibian DAZ-485
Most of the work on the machine was devoted to the development of a centralized tire pressure control system. It was seen as the key to solving the problem of the high cross-country ability of a floating car. After numerous tests and improvements, the system was made. With a decrease in air pressure in tires on the off-road, the pressure of the wheel on the ground decreased by 4 - 5 times, the number of contacting lugs increased approximately 2 times and the track became better compacted, its depth decreased and, accordingly, the resistance of the soil to the wheels decreased. Accordingly, the average speed of movement on soft soils has also increased. But most importantly, the traction reserve of the car increased by 1, 5 - 2 times while driving on snow, sand, arable land. And the larger this stock, the higher the vehicle's cross-country ability. It was at that time in the USSR at DAZ that a decisive and revolutionary step was taken in the matter of a sharp increase in the cross-country ability of wheeled vehicles on soft soils and off-road conditions, which brought them closer in this indicator to tracked vehicles.
It was also of great importance that, unlike GMC, in the event of a tire damage, the compressor could maintain the pressure in the tire longer, and the process itself was monitored by the driver. For example, after five shots with 9-mm bullets (10 holes), the tire pressure reached normal after 8 minutes. after the shelling and further remained constant. Inflating the tires with air "from zero" (completely deflated wheel) took 16 minutes. Whereas at GMC - 40 minutes. The development of such tires was carried out by the Research Institute of the Tire Industry, the lead designer for them was Yu. Levin. And one more thing about the tires, or rather the location of the spare tire in the body. Since the domestic tire came out heavier than the American one, it was decided to place it horizontally on board the car in a special niche under the winch. As a result, the tire (weight about 120 kg) was located much lower than the American analogue (about 1.3 m from the ground, on GMC - 2 m), which greatly facilitated its replacement.
DAZ-485 in the yard of the plant
The moment of installing the spare wheel on the car
Propeller view
First sample
The detailed design of the car began at the beginning of 1949. They worked like in a war - 10-12 hours each, with enthusiasm. The work was well stimulated financially, and most importantly - morally. The team was in love with the future car. The main difficulties fell on the shoulders of the head of the body bureau B. Komarovsky and the leading designer for the body S. Kiselev. They went through a good school at the Gorky Automobile Plant and arrived at GAZ together with V. Grachev. They were the ones answering V. Grachev's question "Can we design such a building ourselves?" answered: "Yes, we can!"
The engine bureau was headed by S. Tyazhelnikov, the transmission bureau - by A. Lefarov. The road test laboratory was headed by Yu. Paleev. Engineer Colonel G. Safronov was the observer from the Engineering Committee of the Soviet Army.
Head of the body bureau B. Komarovsky
The design of the DAZ-485 was carried out throughout 1949. As the drawings were released, they were immediately given to the workshops of the plant, without waiting for the release of all the papers. Two vehicles were immediately laid down. The greatest difficulty was caused by the production of the case. Its panels were hand-nailed on wooden blockheads. Slipways were built to weld the panels, and baths to test the tightness. In the winter of 1950, full-scale production of prototypes began. At the same time, at the request of V. Grachev, scientists and specialists of the Gorky Shipbuilding Institute calculated its stability, controllability and buoyancy on the DAZ-485 model. They turned out to be normal.
Stability is the ability of a floating machine, unbalanced under the influence of external forces, to return to a position of equilibrium after these forces cease to act. Stability allows the car to enter the water with a roll and trim, float on a wave, tow another (of the same type) car, provides the team (crew) with the ability to move inside the car.
Buoyancy is understood as the ability of a machine to float on water with the required load and maintain a certain draft at the same time. It is known that a body made of materials whose specific gravity is less than the specific gravity of the water displaced by this body always floats. This is the law of Archimedes, known to all.
Stability types of floating vehicles
One of the experienced amphibians on testing
From left to right: ch. designer V. Grachev, test driver A. Chukin, designer A. Sterlin, military representative I. Danilsky
By mid-August 1950, the first car was assembled. We put it on the run in the late afternoon and, unable to resist, went to swim on the Dnieper. From the shore, the American amphibian GMC illuminated it with its headlights. It was an enchanting sight: the GMC floating car seemed to pass on its baton to a newcomer.
The machine "took shape" immediately: no special errors were found, an efficient and sufficiently reliable machine did not need any serious alterations in the future. It was the style of V. Grachev's work - to make fundamentally new machines "off the beaten path" (or "hit the bull's-eye", as the designer himself said). And that is why he did the first trips and swims himself, sitting behind the wheel, he was used to receiving information from someone else's hands.
Ease of use was appreciated from the outset, especially the tailgate and the winch located in the center of the machine. In general, this was the case in domestic practice when the car behaved no worse, but much better than the prototype: higher cross-country ability, better driving dynamics, convenient loading, greater ground clearance.
