T-55 Model 1958
Instead of manufacturing the uparmed T-54M (Obiekt 140), the Soviets selected the T-55 (Obiekt 155) to replace the T-54B. The T-55, although closely resembling the T-54, was in fact a substantially redesigned tank with many internal and external differences. Externally, the T-55 used a new turret, similar in shape to the T-54A turret, but without the prominent roof-top "mushroom" ventilator dome, and as a result, two enlarged "D" roof panels. Internal improvements include the new V-55 engine, increase of ammunition to 43 rounds, and other features. Unlike the T-54B, the T-55 dropped the loader's 12.7mm DShK antiaircraft machine gun. This version had the initial stages of the PAZ chemical/radiation protective system. The T-55 was accepted for service in the summer of 1957 and placed into production in the USSR on 1 January 1958.
The T-55A was primarily developed to incorporate a new antiradiation lining and the full PAZ/FVU chemical filtration system. The T-55A finally dispensed with the fixed, hull-mounted machine gun. One of the major internal additions was the use of a plasticized lead sheeting for antiradiation protection. This was evident externally due to the use of an enlarged driver's hatch and enlarged combings over the commander's and loader's hatch to accommodate the new material. The Polish version is sometimes called the T-55A(P) by other armies which use it, such as the former East German NVA. Originally, the T-55 and T-55A did not carry the 12.7mm DShK antiaircraft machine on the turret, as had been typical of the T-54. DShK machine gun was retrofitted.
T-55A Model 1970
Beginning in 1970, T-55A tanks began to receive a new turret fitting for the 12.7mm DShK antiaircraft machine gun. The revival of the turret antiaircraft machine gun resulted from the growing importance of NATO antitank helicopters, as evidenced by the appearance of the AH-1G Cobra with TOW antitank missile shortly after the end of the Vietnam war. This upgrade was later adopted on the T-62M in 1972. Besides its use on new-production T-55A tanks, this feature was retrofitted on earlier T-55 and T-55A tanks as well. This version is sometimes called T-55M or T-55AM in NATO. Two different machine gun fittings were used. On vehicles with the larger antiradiation hatch collars, a collared mounting was used. In the late 1970s, a low-cost export type was produced, with a simpler collar and a hatch arrangement than was used on the T-62M.
T-55, T-55A Model 1974
Beginning in 1974, T-55s began to be retrofitted with the KTD-2 (kvantoviy tankoviy dalnomer) laser range finder as part of a fire control upgrade. This was mounted immediately above the main gun in an armored box. It is not clear whether these initial rangefinder modifications included the more elaborate Volna fire control upgrade.
T-55K Command Tank
The T-55K is fitted with two additional radios (originally an R-112 and R-113; later an R-123 and an R-124), an additional AB-1P/30 generator for the radios, and a special 10-meter aerial carried in a tube at the hull rear. To accommodate the added equipment, the T-55K had the hull SGMT machine gun deleted, and it carried six fewer rounds of ammunition. Eventually, at least three versions of the T-55K were developed. The Kl and K2 versions both carry two R-123 or R-123M and an R-124; the T-55K3 carries one R-130M, an R-123M, an R-124, and a 10-meter antenna. Variants based on later chassis are designated accordingly: T-55AK, T-55MK, etc.
The Poles build their own version of the T-55 command vehicle, called the T-55AD. This vehicle differs from the Soviet type in that it is fitted with a slight rear turret bulge to accomodate the added communication equipment.
OT-55 Flamethrower Tank
This is an engineer flamethrower tank based on the basic T-55, called OT-55 or TO-55. This version can be distinguished by the large pig's head mantlet over the ATO-200 barrel. The ATO-200 flamethrower uses a unique revolver system fitted with 12 charges to ignite the flammable liquid. A total of 460 liters of flamethrower fuel is carried, with 35 liters used in each burst. The ATO-200 can fire at a rate of 7 bursts a minute and has a maximum range of 200 meters. The maximum effective range of the system is 200 meters, with the stream having an intial muzzle velocity of 100 meters per second.
The TO-55 is fitted with the same D-10 gun as a normal tank but carries considerably fewer rounds of ammunition. The distribution of the OT-55 is not known, but it probably equips special combat engineer tank regiments, rather than being used in normal tank regiments.
T-55 Engineer Tanks
In 1959, a portion of the new production T-55s were modified to accept the PT-55 mine-roller. These versions are externally identifiable by the attachment fittings on the hull front. The PT-55 mine roller weighed 6 to 7 metric tons and was fitted to the tank only when in mine clearing operations. Shortly afterwards, additional fittings were developed for th BTU and BTU-55 bulldozer blades. The BTU-55 was an improved and lightened type (1.4 versus 2.3 tons) and was eventually the more common of the two.
Romanian T-55 Variants
TR-580 -This Romanian derivative of the T-55 uses a lengthened hull and a new suspension system with spoked wheels. It has also been called the TR-77, which may be an export designation.
TR-85 - This drastically modified Romanian version of the T-55, with a new German diesel engine and a completely redesigned suspension. The turret, although resembling the T-55 was in fact, completely new. This vehicle has been called the TR-80 and TR-800, which may be export designations.
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