Know Your Steel: The M-84 tank

Hunter1911: F   Hello tankies,
Welcome to our "Know Your Steel" series of articles. The following article is something new, some interesting facts about a fairly "modern" vehicle.

Hope you will enjoy this article.   The M-84 tank The M-84 is based on the Soviet T-72 but with several modifications. It was built under licence acquired from the USSR. The licence itself was bought by the Yugoslavian government for 39m dollars or 1000 manufactured tanks. At the time Yugoslavia was not permitted sell, modify or enter into other coproduction without USSR’s permission. Interesting fact; the acquired documentation for production of this vehicle consisted of 120 000 A4 pages for the prototype series, with manufacturing plans being 200 000 pages of documentation. The weight of the documentation was over 20 000kg!     The prototype First prototype was made in April 1983, and was mostly made out of imported components. First prototype party consisted out of five tanks which were later disassembled and used as training dummies for future production. First true test of local production were the zero series of 10 tanks made in 1984. In the next three years 370 tanks were made, and since of 1988 (after the development of the new engine and adapting the concept of improved protection, with the authority of General Command, the tank was designated M-84A. Up until the outbreak of the War in Yugoslavia, the mass produced version were the M-84A, [80 delivered to JNA (Yugoslav People's Army), with 150 M-84AB series made and delivered to Kuwait. (The M-84AB comes with the new SUV-M-84 computerized fire-control system, including the DNNS-2 gunner's day/night sight, with independent stabilization in two planes and integral laser rangefinder. It also comes with the TNP-160 periscope, TNPA-65 auxiliary periscope, and DNKS-2 day/night commander's periscopes, as well as the TNPO-168V driver's periscope. Furthermore, the M-84AB is fitted with new gyrocompass, communication and intercom systems).   Production cost of the tank was 700 000 dollars, of which labour costs were 74%, 18% materials and 8% imported materials and components. By the late 80s production capacity was 150 vehicles a year.   T-72M was characterized by a series of good qualities which reflected in its small size of 41t,  good armour protection and a gun of 125mm calibre. A series of compromises between traditionally contradicting requirements were made; manoeuvrability – armour protection – firepower at which each requirement received equal significance. Red Army introduced the T-72 into operational use during mid-70s and it carried the characteristics of that period. In some fields the T-72 had flaws for which the 80s technology had a reply. The Yugoslavian engineers had built in a new fire control system, enhanced V-46 engine, new fire extinguishing system, as well as many additional enhancements. Some flaws were not possible to be smoothened without compromising the initial design of the T-72, hence retaining the ammunition storage (22 shells) in the rotating transporter below the turret. The main idea was to get an almost new tank based on the T-72 and without compromising the basic layout and tactical – technical characteristics. The main difference between the T-72 and M-84 is the firepower. Although the same gun model was retained, an entirely domestic fire control system was implemented (SUV). Probability of hit at distances from 1.700m to 2.100m was raised from 50% to 60%. For manufacture of this new tank,  production of 150 new material types was introduced, spread over 240 factories and with over a 1000 outsourced work organisations. The tank was built in numerous variants: basic M-84, enhanced M-84A, export variant the M-84AB, as well as the command variant the M-84ABK. In mid 90s an engineering variant was developed, the M-84AI. In total the production halls made 650 vehicles. Largest number goes to the basic variant the M-84(370). Since 1989, variants with more powerful, 1000 HP engine, new smoke screen box schedule and reinforced armour were in production - the M-84A.     Tactical and technical characteristics Main weapon of the M-84 tank is the 2A46 125 mm gun of 50 calibre length or 6.250mm. The weapon in combination with the domestic SUV (domestic fire control system) has 60% probability of hitting a target over 2m tall at ranges of 2.100m, and a 2.5m tall target at distance of 2.500m. The gas cylinder positioned in the middle of the barrel is shielded with a thermal coating that minimizes deformation of the barrel from high temperatures and ensures it is cooled at the same rate during rapid firing The M-84 differs from most western tanks in that it does not have a human loader; it instead utilized a mechanical auto-loading device to load rounds into the main gun. The auto-loader is operated by the gunner who selects the ammo type and instructs the auto-loader when to load the round. The M-84 auto-loader differs from the T-64 and T-80 basket auto-loader, in that it has both propellant and projectile stored horizontally. The carousel rotation is limited to 1 direction only. In normal operation, the cassette loader takes 6 seconds to load a round. However, it can take up to 15 seconds to load a round if the round desired is a 355 degree turn of the carousel away. There have been rumours that the auto-loader has eaten the hands of gunners, and fed them into the main gun breech, but this is impossible. The gunner would have to put his hand into the breach, after pushing the gun load button. Most likely, the source of this urban legend goes back the very first auto-loader models that were integrated into the T-62 as well as the unprotected hydraulic loading mechanism of the BMP-1 where a uniform could get snagged with moving parts and result in injuries. In the case of an auto-loader failure, the TC has 2 manual cranks, one of which is attached to a bicycle chain, to rotate the carousel, and hoist the ammunition elevator. However, this is painstakingly slow, taking over 1 minute to complete the loading of a single round. Fortunately the auto-loader is very simple, and extremely reliable.         Firepower element is also affected by the quality of ammunition. The gun uses two types of the sub-calibre projectiles: BM9 and BM12 (local designation M-88), the OF-19 HE-FRAG projectile (local M86P1) and the 3BK14 HEAT round. Combat usage experiences have confirmed the effectiveness sub-calibre projectiles against armour equivalent to 350mm of homogenous steel at ranges of 2.000m. High-explosive anti-tank 3BK14 round has a possibility of penetrating homogenous steel armour of 500-550mm at distances up to 4.000m. Initial velocity of the projectile is 900m/s, its total mass being 19kg. Although usage of modern armour, combined with reactive armour gives an advantage to the armour over the HEAT projectile.     OF-19 HE-FRAG is intended for use against live force and fortified positions, and in case of high emergency for use against other tanks.   Of the secondary weaponry the M-84 has at its disposal the 7,62mm M-86 machinegun, which can effectively engage targets up to range of 800m (600m for individual targets). Its practical rate of fire is 250 rounds per minute. Battle compliment consists of 2.000 rounds consisting of five types of ammunition with: standard, light, heavy, tracer and armour piercing - incendiary round. The turret carries Zastava M87 12.7mm mount with effective range versus air targets of 1.500m, 2.000m for ground targets and 800m for light armour. Practical rate of fire is 150 rounds a minute, with battle compliment of 5 rows with 60 bullets each. Vertical field of engagement is -5 to +75 degrees.   Croatian Army M-84A4   Fire control system [Sustav Upravljanja Vatrom (SUV)] is modular with independent stabilization in two planes and integral laser rangefinder. It also comes with the TNP-160 periscope, TNPA-65 auxiliary periscope, and DNKS-2 day/night commander's periscopes, as well as the TNPO-168V driver's periscope. Three work modes are available: Manual (firing at immobile targets from the spot), semi-stabilised (firing at mobile and immobile targets from the spot), and stabilized firing at mobile and immobile targets on the move). System is ready for use in 0.5 – 2 min after ignition, at temperatures of -40 up to +50   For a measure Fire control system’s aberration at 1000m equals the surface of an A4 paper.   Fire control system [Sustav Upravljanja Vatrom (SUV)] provides:   Stabilization of the gun and the machinegun while on the move. Guidance of the gun and the machinegun on horizontal and vertical plane. Possibility for the commander to prioritize the targets for the commander. DNKS-2 day/night vision. Target distance calculation and weather condition determination. Input of the ballistic data manually or automatically for the calculation of ballistics and leading the shot. Emergency turret rotation from the driver’s side in case of emergency.     Powerpack The base M-84 engine is a 12-cylinder water-cooled V46-6 diesel engine, rated at 574 kW. The improved M-84A has a more powerful, V46-TK 735 kW (1,000 hp) engine. With maximum fuel capacity (1,200 litres) the tank's range is 450 km, and with external fuel tanks, this range can be extended to 650 km. The Croatian-made variants have enhanced power plants. The M-84A4 Sniper model has a German-built 820 kW (1,100 hp) engine, while the M-84D has an 895 kW (1,200 hp) engine, the most powerful of all M-84 variants. The M-84D also has greater fuel capacity (1,450 litres). The tank can ford 1.2 meters of water at any time or up to 5 meters with a snorkel.   The vehicle sports mechanical transmission with seven forward and one reverse gear. Tank uses tracks 580 mms wide, with 4.280 length of contact with the ground. Each track has 96 segments. Each side has 6 double bogie wheels and 3 return wheels supporting tracks in opposite direction. Vertical movement limit of suspension is 280mm, with independent torsion bars and doubled shock absorbs on 1st, 2nd and 6th wheel.   Armour protection Concept of armoured protection was taken from the T-72M, that is T-72M1 for the M-84A, but the process was improved during the production period. M-84 body is made from welded, hardness steel, rolled panel set at 22 degrees angle. Upper glacis panel is 231mm thick, made from the composition of: hardness steel panel 60mm, glass-ceramic 105mm, hardness steel 50mm, the M-84A had received an additional hardness steel panel of 16mm thickness, recognizable for 2 “ribs” in front of the driver’s hatch. Side panels are 80mm thick, 70mm around the driver-transmission compartment. Turret ring is protected by additional steel girders. Tank’s flank and the suspension area are protected by hard impregnated rubber, which provides additional protection against HEAT projectiles.   Turret is casted, with uneven thickness, with maximum being 410mm, with the M-84A variant a segment 130mm of thickness. Angle of the turret front is 35-40 degrees which makes the protection equivalent to homogenous armour of 550-600mm of thickness (due to the trajectory distance of the projectile after penetration). Low profile of the vehicle also attributes to its protection, the M-84 being among the lowest MBTs around. Its body profile surface being 35% smaller than that of an Abrams M1, and the turret being 45% smaller. Based on certain assessments, vehicle’s front provides 550mm of armoured protection against kinetic projectiles, and 550-650mm against HEAT projectiles, with turret providing 350-450mm versus kinetic weapons and 450-550 versus HEAT weapons. Reactive armour was developed based on Russian solutions (T-64BV, T-72AV/B and T-80BV). The M-84 is a bit less protected versus kinetic weapons, compared to its anti-HEAT protection.   M-84(M) with reactive armour.   Even though the development of the armour had started in early 90s, the development was completed by 1998 and labelled KAO M-99. Its characteristics remind of Russian and Ukranian solutions. KAO M-99 is modular, with dimensions of 152x305x65mm, mass of 6kg, of which 350g is explosive. Depending on the type of the projectile, attack angle, distance of ERA armour compared to the basic armour and other factors, the penetration reduction is 25% for kinetic weapons, and up to 80% for HEAT projectiles.       The vehicle can take on slope approach at 30 degrees and side slope at 25 degrees. With additional preparation it can ford through water obstacles up to 5m of depth and 1.000m in length. It can take on a trench of 2.8m in width, and a vertical obstacle up to 0.85m.   Additional equipment consists of collective NBC device, 12 smoke box discharges. Additionally part of the equipment are the underwater kit, and the self-hunkering kit. Tank also possesses automatic fighter extinguisher with 14 sensors. Coms system is a radio device of 20W VV and 20km of reach (15km during movement). Mine plow can also be mounted on the vehicle. The command tank variants have an additional power generator for accumulator relives during large energy consumption times, in cases of main engine being offline. Three men crew (gunner, driver and commander) is armed with automatic pistol M-84 Skorpion and defence hand granates M-75. The commander and the gunner have additional armament in form of M-70A automatic rifle.