The Mazur D-350 was the main Polish tracked artillery tractor (registration number UAK 5419) from the late 1950s. About 1,000 were manufactured and it was used also by Czechoslovakia and exported abroad, based on many elements from the T54A tank manufactured in Poland. It remained in service until the fall of USSR.

Work on the Polish artillery tractor project started in 1956 at the Łabędy Mechanical Works, using components from the T-54A tank, license-produced at the same plant. The final tractor was approximately 75% unified with the T-54A tank with two prototypes built i 1957 as ACS Mazur D-300. In 1958 two improved models were tested and the production approved, which ran until 1960 or 1961 depending on the sources. While final assembly was at Łabędy, along with the body, drivetrain, and road wheels, both the chassis and suspension came from Huta Stalowa Wola, the engine from PZL Wola.

This tractor had solid performances and compared well with Soviet tracked tractors built at the same tume, but still, production was discontinued due to the unification of artillery tractors within the Warsaw Pact forces. In short USSR twisted arms for the mass adoption of its own ATS-59 tractor, which in the end was manufactured in Poland under license. Comparative trials by the Soviets argued the ATS-59 was superior in most respects.

Development

Some of the most important military vehicles used to support combat missions were tracked artillery tractors, best for towing heavy guns and howitzers and transport their ammunition on difficukt terrains far from roads and in adverse conditions of snow, sand or mud impassable to trucks. It was a tactical asset already recoignized by USSR already after the end of the civil war, which manufactured series of tracked tractors for the need of the artillery until 1945.

World War II the Polish Army used the same Soviet tractors, such as the JA-12, S-65, and S-80 Stalinec, but also the lend-lease HD-7W, the Caterpillar D-7, and occasionally the German RSO and SdKfz 9 Famo or Opel Maultier catpured on the late stage of the war. This was a jungle, and a nightmare to maintain. So in the 1950s, work commenced on a unitary artillery tractor, domestically designed SG-10 half-track tractor, based on the Star 20 truck. However, greenlight was never given for production as it proved unsuccessful.

All these different types of tracked artillery tractors that were used simultaneously caused a chaos for maintenance and repairs, which were soon impossible due to the lack of spares. Still, there was an enormous demand for artillery tractors and in 1947-48 it was impossible to get a new-built artillery tractor as Polish industry was just rebuilding at this point. The problem was partially solved by the introduction of the Polish-made FSC Lublin 51 (license-built GAZ-51) and Star 20 and 21 trucks.

Still, they appeared unsuitable for towing heavy guns and howitzers, being wheeled and underpowered. The half-track chassis was preferred as a solution, especially since Poland was well experiences with them, having licenced Citroen and Unic or domestic models of half-tracks already before the war and manufacturing German components for half tracks during the war. Ultimately, this project was stopped, but by the mid-1950s, the idea was revisited, this time a fully-tracked chassis.

In 1958, licensed production of the first-generation T-54A main battle tank was acquired by Poland, to provide its own army while being under the Soviet standard. Production started at the Łabędy Mechanical Plant. Seeing the potential of this platform, the idea soon emerged to create an artillery tractor using the same parts, and preparations for a Polish design called the Mazur D-300 started. There were two waves of prototypes.

The first in 1957 were called D-300 but trials revealed scores of problems, so this led after corrections to a second wave, heavily modified in early 1958. This time, trials revealed few issues and after corrections were assigned and next trials performed, it was accepted as the D-350 for production, which started at the end of the same year. "Mazur", loosely translated as "rustic".

It was based on three-quarters of the T-54A tank components produced in Łabędy, allowing standardization of parts, for seamless delivery to the military, easy repairs, taining and reduced production costs. As said above, production only lasted for two years (1960-1961) with approx. a thousand Mazurs (disputed number) rolling off the assembly lines until the Poish Army was forced to adopt instead the Soviet ATS-59, from 1962 in its place.

Production

Design work began in 1956 at Łabędy Mechanical Works based on the chassis and drivetrain of the T-54A tank under license (acqired on July 15, 1955). The first two prototypes developed in 1957 as ACS Mazur D-300 had 75% commonality, leading in 1958 to a second aves of prototypes in 1958, perfected and subjected to a very intensive testing. They were approved for production under the designation Mazur D-350. Individual components were manufactured at multiple plants, as seen above, chassis and suspension at Huta Stalowa Wola, engines at PZL Wola, body, drivetrain, and wheels in Łabędy also the final assembly, and production went into full swing in 1959 or 1960, lasting until 1961 with circa 1,000 Mazur D-350 tractors produced until replacement by the ATS-59.

Design

The Mazur D-350 was a high-speed tracked tractor, prime mover for the Polish heavy artillery, 1937 ML-20 howitzer (152 mm) and 1931/37 (A-19) heavy field gun, 122 mm and in some cases, the KS-19 100 mm AA and radar trailers. Its towing hook could pull a maximum of 12.5 T, albeit its trailer could reach 25 t.

The Mazur D-350 artillery tractor was 5.8 meters long, 2.9 meters wide, and 2.7 meters high with a maximum weight of 13.5 tons, 12.5 t empty. The layout was simple like Soviet comparable tracked tractors with the engine relocated forward (as the drive sprojects) unlike on the standard T-54A, under bonnet, followed by a fully enclosed metal cabin large enough for eight men, two forward and the remainder seated on two benches at the rear, with four doors and windows. Next was the flatbed and cargo area at the rear with payload of up to 12.5 tons. The was a folding back plate and arches to mount a tarpaulin.

The Mazur could tow a trailer or gun weighing up to 25 tons. Power-wise it had the same twelve-cylinder W-54 diesel engine de-rated to 350 hp, from the T-54A, an engine reworked to produce more couple and towing power, rather than keeping a good speed. Road speed observed on trials was still of 53 km/h on road, with a range of 490 km also on flat with cargo and trailer. The speed went down to 25 kph on average off-road and range down to 200 km when used on diffiult terrain. Apart the driver seating forward, a co-driver, there were up to seven gun crew seated in the cab with their own equipments. The cab was heated up by the engine in winter. In troop mode, the Mazur could carry eight more men seated on benches in the flatbed at the rear.

The tracked chassis comprised 5 roadwheels, front drive sprocket, idlers at the rear, four return rollers per side. The doubles roawheels, stamped, had rubber rims, and compbined with single pin tracks. The Suspension used torsion bars like for the original T54. The PZL Wola W-54 Engine was a 4-stroke V12 diesel with a power output of 350 hp at 1.800 rpm hence te name of the vehicle, coupled with a transmission which was manual, with 5 forward, 1 reverse. The Power to weight ratio was 25.9 hp/t at combat load and 11.5 hp/t with 2 t cargo and 15 t towed load. It had a Ground clearance of 0.46 m, could climb a wall 0.5 m tall, gap a trench 2.5 m wide and climb a 30° gradient, or 35° slope and ford 0.8 m.

Protection was light, it was edsentially a softskin, unarmed vehicle apart the personal carried, without NBC system or smoke system. The cargo capacity was 5 t on rear flatbed on road, 3.5 t capacity off road and the towing capacity 25t for a full trailer on road, 15 t towed load on road and 10 t towed load off road. The front Winch had a 17 t capacity with 80 m cable.

Users

Poland: c700 vehicles
Czechoslovakia: 218 vehicles
Rep. Dem. Vietnam: 50 vehicles

Mazur D-350 specifications
Type	Full Track, bonnet and cab
Lenght	5,81 m
Width	2,89 m
Height	2,69 m
Total weight	13.5 tonnes
Payload	25 tons
Crew	2 cabin, +8 troops
Propulsion	V-54 diesel, 261 kW/1800 rpm
Transmission	Manual, 5 forward, 1 reverse.
Suspension	Torsion Bar, Tracks
Speed (road)	53 km/h flat, 25 kph cross country
Range	490 km
Armament	None (Towing Vehicle)
Production	1,000
Manufacturer	Huta Stalowa Wola, PZL-Wola, Bumar-Łabędy

The D-350 in Service

The D-350 Mazur tractor shared a lot of components with the T-54/55 used in the Warsaw Pact , easing maintenance and repair. The Polish army used it at first for towing the 122 mm A-19 guns. For its undisputed quality, it was dubbed by is crews "Gomulka's Revenge". Production started in 1959 and in addition to Poland, Czechoslovakia obtained 218 units delivered in the early 1960s.

A third of the tractors were exported, to Czechoslovakia and North Vietnam, the rest used by the Polish Army, and after 1979, many were still listed in the inventory of untouched stocks dating back a decade later due to the large adoption of the ATS-59 instead. In the early 1990s, Mazur tractors were still around at the Dobre nad Kwisą military unit. When used by the Poles, it was dubbed a "high-speed tracked tractor" for heavy artillery units, primarily the 152 mm model 1937 (ML-20) howitzer and 122 mm model 1931/37 (A-19) heavy field gun. In some cases it was also used for towing the 100 mm KS-19 anti-aircraft gun or trailers with radar equipment, a role kept until the 1980s in some units.

Mazur artillery tractors remained in service with the Polish Army until the late 1970s and of those sold to Czechoslovakia in the early 1960s (according to Czech reports, 218 delivered as "Gomułka's revenge"), others were sold to the North Vietnamese Army (Democratic Republic of Vietnam 50 from Poland in the 1970s) used by them during the Vietnam War.

Mazur artillery tractors withdrawn from the army were used by the railway, including rescue trains and forestry services or other roles, notably in winter where their tracks were well useful. One, used for towing the 152 mm model 1937 howitzer (serial number 3520730, registration number UAK 5422) was transferred to the Polish Army museum in the spring of 1986 from Unit 5575 in Głogów, 5th Pomeranian Artillery Brigade and had been preserved to this day in working conditions. At least one tractor of this type was converted to a firefighting version.

Gallery

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Links and sources

E Gajkowski Na poligonie i na defiladzie wyd. Horyzonty Warszawa 1975
Ciągnik artyleryjski Mazur, „Raport - Wojsko Technika Obronność” nr 02/2017, s.70
Jerzy Modrzewski (red.): Encyklopedia techniki wojskowej. Warszawa: Wydawnictwo Ministerstwa Obrony Narodowej, 1987.
Sławomir Drążkiewicz, Ciągnik artyleryjski SG-10, "Poligon" nr 1/2008, s.6
Andrzej Kiński. 70 lat pancernego Bumaru-Łabędy. „Wojsko i Technika”. Nr 7/2021. s. 9. Warszawa.
Andrzej Kiński. Zmodyfikowane podwozie gąsienicowe do moździerza Rak i wozów dowodzenia - nowa propozycja Huty Stalowa Wola. „Wojsko i Technika”. Nr 5/2021. s. 12. Warszawa.
POL - D-350 Mazur w serwisie forum.valka.cz
Albert Grandolini: Armor of the Vietnam War (2). Asian forces. Concord Publications, 1998
E Gajkowski Na poligonie i na defiladzie wyd. Horyzonty Warszawa 1975
Mały Modelarz 10/1976, Ciągnik artyleryjski Mazur, „Raport - Wojsko Technika Obronność” nr 02/2017, s.70
Jerzy Modrzewski (red.): Encyklopedia techniki wojskowej. Warszawa

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