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Chrysler M-1 main battle tank


Written by Sakhal

The 1st August 1963 the North American and German governments signed an agreement for the joint development of a tank called MBT-70. Each country formed its own work team and quickly they began to work on the new tank, being completed the first prototypes in 1967. The MBT-70 had many notably advanced characteristics, among them a crew of three men (commander, gunner and driver) who were all of them accommodated in the turret, being this possible thanks to the installation of an automatic loader for the main weapon. The suspension could be adjusted in accordance to the tactical situation and the 1500-horsepower engine provided a top speed of 71 kilometers/hour. The standard equipment comprised an NBC (Nuclear-Biological-Chemical) warfare system, lights for night vision and a snorkel for deep fording. The prototypes were armed with a 152-millimeter cannon/launcher for the MGM-51 Shillelagh anti-tank missile, a 20-millimeter anti-aircraft cannon and a co-axial 7.62-millimeter machine gun, besides smoke launchers at each side of the turret.

Then, the development program began to have problems, not only because of the rise in the cost of the tank, but also because Americans and Germans did not agree regarding the main armament. While the former wanted the 152-millimeter cannon/launcher and their Shillelagh anti-tank missile, the latter preferred a 120-millimeter cannon. Eventually, in January 1970 the whole program was cancelled and the Germans continued with the development of their Leopard 2 main battle tank. The Americans gave then a push to the MBT-70, renamed Austere XM803, but in the late 1971 the Congress eventually cancelled the project.

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The MBT-70 prototype developed during the 1960s.

Development program of the M-1

The Army insisted in having a tank for the incoming 1980s and thus a new group of specifications was ellaborated. In January 1973 the United States Secretary of Defense approved the document for the development concept, and so the contacts with the industry of defense began. The 28th June 1973 contracts were awarded to two private companies which had expertise in the design and construction of tanks: the Chrysler Corporation (which had started this activity shortly before the Second World War, with the M3 medium tank, and was then producing the M60 series) and the Detroit Diesel Allison Division of the General Motors Corporation (which had built the prototypes for the MBT-70/XM803 program). These companies had to create prototypes for a program denominated XM-1.

Both companies presented proposals for tanks weighing around 50 tonnes, with suspension of torsion bar type, armed with the M68 105-millimeter cannon and the Bushmaster 25-millimeter chain cannon as co-axial weapon. General Motors proposed a tank propelled by one or two Diesel engines, whereas Chrysler left open the choice of engine, indicating that it could be either a Diesel engine or a gas turbine, despite this latter was not liked. But both proposals showed something clearly: that it was not possible to obtain the desired protection levels within the limit of the initially specified weight.

Meanwhile, the engineers of the Tank Command of the United States Army were working to solve this problem. In March 1973 it was clear that laminated and spaced composite armor, placed on the proper angle, offered the best possibilities. Even so, it would be necessary to increase the total weight of the tank. It became clear as well that the original cost limit per unit would have to be revised upward, from 400,000 to 500,000 dollars. This was favorably compared with the estimated cost of 611,000 dollars per unit of the cancelled XM803. The contracts for Chrysler and General Motors were awarded at 69 and 87.9 millions of dollars, respectively, which should cover the cost plus the profits of the development, manufacture and trials of the prototypes.

When both companies completed their projects, a great surprise arose. Despite the Tank Operation Group of the United States Army having shown firm opposition to the utilization of a gas turbine, the chief of the Chrysler project team, doctor Philip Lett, chose this engine. He adduced as justification the higher power, the smaller size, the lesser power loss, the lesser noise levels, the absence of smoke and the easier start up at low temperatures. He had to prove his decision, but the Avco Lycoming AG-1500 gave as result a very good engine. Albeit it was more expensive to produce than the AVCR-1360 variable-compression Diesel engine specified by General Motors, which was an improved version of that offered for the M60A3 and the M60AX private project, the gas turbine would demonstrate that it was less expensive to maintain. In fact, there was very little difference of costs between both engines, considering the expected service life of each.

Other factors that affected the two prototypes were the availability of Chobham armor (newly developed in United Kingdom) and the decision of removing the Bushmaster cannon from the specification, as a consequence of a later analysis of the combats of the Arab-Israeli War of 1973. The Bushmaster had been initially specified due to its capability of destroying lightly armored vehicles, but it was seen that in practice the crews invariably resorted to the main cannon to destroy such targets. Besides, the removal of the Bushmaster would grant additional space for storing the ammunition of the main cannon.

The two prototypes, along with test wheel ensembles, were delivered to the Aberdeen Proving Ground in the late 1975. Starting February 1976 they were submitted for trials which would last until the 7th May, performing both tanks in accordance with the specifications. At this point, a third competitor appeared: a version of the Leopard 2, armed with a 105-millimeter cannon and modified to comply with the American specifications. The German tank would be tested in equal conditions against the American prototypes, despite its much higher price. In fact, it was the price what threw the Leopard 2 away from the competition, for this tank complied more than enough with the specifications.

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The Leopard 2 "Austere Version" which competed against the American prototypes.

The choice between the two XM-1 prototypes was made in July, but kept secret for the time being. It was leaked, however, that General Motors had won the contest with an offer valued at 208 millions of dollars, against one of 221 millons offered by Chrysler, for producing 110 tanks in 1979 and another 352 in 1980. At this time, the Army had decided to adopt the turbine engine, but installed in the General Motors tank, so it proposed to simply change the engines without passing again through a complex selection process. But the Secretary of Defense would not allow this.

But there was also another complication. It had been anticipated that in the future it would be necessary to install a more powerful main cannon, which would require to redesign the turret. Hence, the decision of awarding the initial contract was delayed until November 1976. Meanwhile, both competitors took advantage of the opportunity and presented projects again fitted with both engine types. The 12th November it was announced that the offer presented by Chrysler, of 196 millions of dollars, had been selected against that of 232 millions presented by General Motors. The price of Chrysler's offer had been greatly increased due to the higher installation cost of the turbine engine, but Chrysler had been able to limit these costs through better calculations, and hence his model would be put into serial production.

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Chrysler XM-1 prototype armed with the M68 105-millimeter cannon, 1976.

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The first preseries exemplar left the factory in February 1978. The Lima Army Modification Center started in 1979 the construction of the first 110 series exemplars, being delivered the first two tanks to the Army the 28th February 1980. The initial number of series exemplars was estimated to be 3312, with a cost of 4900 millions of dollars. After ten years of development and 400 millions of dollars (of 1972), the United States Army was to receive its first third-generation main battle tank. The new tank received its name after General Creighton Abrams, a former chief of armored units who later became chief of the Army's High Staff.

Two years later the Detroit Tank Arsenal, close to complete the production of the M60, prepared its production lines for the M-1, while Chrysler sold its tank manufacturing division to the General Dynamics Corporation, leaving behind a business in which the company had been very influential during 40 years. The order from the Army reached 7251 exemplars to be delivered before the end of the 1980s, and the production, initially of 30 exemplars per month, was increased to 60 in 1982 and reached 70 in the late 1983.

Characteristics of the Chrysler M-1

The first units were armed with the M68 105-millimeter 51-caliber cannon (American version of the British Vickers L7 produced uncer licence), like the M60A1, but this was just a temporary weapon until a decision were taken about a new main weapon. The alternatives were the German 120-millimeter smoothbore cannon or the British rifled cannon of the same caliber. To make things further complicated the M-1 would take elements from the German tank, specially developed for United States under a memorandum signed in 1974. The hull and the turret of the M-1 were built with the new Chobham armor developed by the British, and which allegedly protected against both projectiles and missiles. The crew comprised four men accommodated following a conventional layout: the driver in the fore part of the hull and the other crew members in the turret, with the gunner and the commander in the right part and the loader in the left part.

Besides the 105-millimeter cannon, the M-1 had a 7.62-millimeter co-axial machine gun, a 12.7-millimeter anti-aircraft machine gun installed in the commander's cupola and another 7.62-millimeter machine gun installed in the loader's hatch. The tank carried fifty-five 105-millimeter projectiles, a thousand of 12.7-millimeter cartridges and 11400 7.62-millimeter cartridges. The cannon was stabilized in two axes, allowing to fire it with success while the tank was on movement. The gunner would select a target, then use the laser rangefinder to determine the distance and finally press the firing button; at the same time, the ballistic calculator would carry out the operations and adjustments required to ensure a direct hit.

chrysler_m-1_main_battle_tank.jpg

M-1 series tanks effectuating fire with their M68 105-millimeter 51-caliber cannon, American version of the British Vickers L7.

Fuel tanks were separated from the combat compartment by armored bulkheads as well as the largest part of ammunition, which could be accessed through sliding doors and was covered by soft safety panels on the upper part. The suspension was one of torsion bar type made of titanium and steel, with rotatory shock absorbers which allow a vertical movement of 38 centimeters. The M-1 could move cross country at a speed of 48 kilometers/hour and accelerate from 0 to 32 kilometers/hour in six seconds, becoming so a difficult target in the battlefield. Propulsion was granted by an AGT-1500 1500-horsepower turbine developed by Avco Lycoming which could be fed with gasoline, Diesel fuel or kerosene; for this, the driver just had to change a selector in his control panel.

According to the manufacturers, the engine would not require a full revision before the tank had traveled 19000 or 20000 kilometers, which was a notable progress in relation to other existent engines. In counterpart, the fuel consumption was very high, about 450 liters per 100 kilometers (in road, twice than the Leopard 2). So, the smaller size of the engine was in practice outweighed by the vast amount of fuel that the tank had to carry: 1908 liters. The engine was coupled to an Allison X1100 automatic transmission which had four speeds forward and two backward. It was a derivative of that initially developed for the M60 and included hydrostatic/regenerative power steering. Great consideration was given to reliability and maintenance, and it was said that the whole engine could be removed in less than thirty minutes for being replaced.

In the development of the Chrysler M-1 eight main subcontractors worked: the Government on the armament, Avco Lycoming on the engine, Cadillac Gage on the turret and the stabilization system, Control Data Corporation on the ballistic computer, Detroit Diesel Allison (General Motors Division) on the transmission, Hughes Aircraft Corporation on the laser rangefinder and Kollmorgen Corporation on the auxiliary optics of the gunner. The M-1 was provided with an NBC (Nuclear-Biological-Chemical) warfare system and a complete night vision equipment for the driver, the gunner and the commander. The fire control system was of similar complexity than that of the M60A3, with incorporated weather and cannon status sensors to improve the chances of hitting the target at the first shot.

It was intended that the tanks produced from 1984 were armed with a version of the Rheinmetall 120-millimeter 44-caliber smoothbore cannon (which equipped the Leopard 2, in service with the West German Army from 1979-80) produced under licence in United States, designated M256 and fitted with a breech of new type. The version armed with the new cannon, designated M-1E1, weighed 55.9 tonnes and could carry 40 projectiles.

Specifications of Chrysler M-1

Crew: 4

Armament: One M68E1 105-millimeter 51-caliber cannon; one 7.62-millimeter co-axial machine gun; one 7.62-millimeter machine gun in the loader's hatch; one 12.7-millimeter machine gun in the commander's cupola; six smoke launchers in each side of the turret

Ammunitions: 55 x 105-millimeter cannon; 1000 x 12.7-millimeter machine gun; 12400 x 7.62-millimeter machine gun

Armor: Chobham type

Lenght (with the cannon aiming forward): 9.61 meters

Lenght (hull): 7.92 meters

Width: 3.66 meters

Height (to the top of the turret): 2.84 meters

Weight (in order of combat): 54.5 tonnes

Ground pressure: N/A

Engine: Avco Lycoming AGT-T 1500 HP-C flex-fuel turbine, developing 1500 horsepower at 3000 revolutions per minute

Power/weight ratio: 27.52 horsepower/tonne

Maximum speed (in road): 72.4 kilometers/hour

Maximum speed (in countryside): 48 kilometers/hour

Maximum operational range (in road): 440 kilometers

Maximum surmountable trench: 2.74 meters

Maximum surmountable step: 1.22 meters

Maximum surmountable slope: 60 percent

Maximum sideward slope: 40 percent

Maximum fording (without preparation): N/A



Categories: Tanks - Cold War - 20th Century - [General] - [General]

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Website: Military History

Article submitted: 2019-02-26

Article updated: 2019-02-26


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