Bernardini X1/A1/A2

     Notes: These light tanks are a radical rebuild of the World War 2-era M3A1 Stuart, with a new suspension, new diesel engine, new turret, heavier armament, and a new fire-control system.  (One has to look hard to see their M3A1 roots.) These were adopted by the Brazilian Army in the early 1970s since their Stuart progenitors were getting a bit long in the tooth, and 77 were delivered total, of X1s, X1A1s, and X1A2s.  They have never been offered to the international market. The X1-series were used until the early 1990s, though in the mid-1980s, they were at first supplemented, then replaced by better vehicles in the mid-1980s.

X1

     The X1 were based on heavily-modified M3 and M3A1 Stuart chassis.  The Brazilian Army went through a process to weed out the still-usable chassis from those that were too far gone to continue as military vehicles.  The Stuart chassis was modified with a new vertical volute suspension derived from that of the M4 artillery tractor which was more shock-absorbing. This suspension worked because it was related to the suspension already used on the M3 and M3A1. The frontal armor, in addition to applique, was given increased slope. The sides of the tank were given a moderate slope. The original engine was replaced with a Scania-Vabis DS-11 A05 CC1 diesel, with 256 horsepower. The hulls were extended slightly in the engine compartment to seat the new engines. The turret of the Stuart was completely shafted in favor of a new turret called the BT90; the turret ring had to be widened by 200 millimeters to accommodate the turret. This turret was armed with a licensed copy of the same French low-recoil 90mm gun that armed the EE9 Cascavel armored vehicle. (The designers decided to not go with the H90 turret of the EE9 because they wanted the turret to have more armor, though lessons learned from the H90 turret went into the design of the BT90.) Communications were brought up to date, and the fourth crewmember could now operate as a loader. The driver has a hatch on the front left side, and the commander and loader have hatches on the turret deck.  The gunner uses loader's hatch.

     Some 52 X1s were produced.  Some of these were further modified into other members of the X1 family, including one into the X1A1.  It is still somewhat of a mystery as to the fate of the X1 prototype; however, it is probable that the X1 prototype was modified into the prototype of the XLF40 MRL system, which was not proceeded with. X1s based on the M3 differ slightly from those based on the M3A1; those based on the M3 have flat rear plates, while those based on the M3A1 have curved rear plates.

X1A1

     The X1A1 began as an update program to the X1, but as what became the X1A2 ran concurrently with the X1A1 program, the X1A1 reached only the prototype phase and was not proceeded with. The X1A1 is a stretched X1, primarily to allow for more ammunition stowage.  A third bogie was added, replacing the massive idler wheel of the M4 artillery tractor’s suspension, and the vehicle increased in length by 0.8 meters. The new suspension was a sort of hybrid between the suspensions of the M4 artillery tractor and the M4 Sherman MBT. The longer hull allowed for a larger fuel tank. The turret was fitted with a longer bustle to carry more ammunition. While many deficiencies were fixed in the X1A1, lengthening the hull causes a new problem – the width of the tracks remained the same, and the ground pressure of the treads therefore increased, making the X1A1 difficult to steer as the tracks dug more into the ground. This problem was later fixed in the X1A2 design.  The X1A1 was not proceeded with.

X1A2

     The X1A2 incorporated the features of the previous two vehicles, including the stretched length of the X1A1.  However, unlike the X1 and X1A1, the X1A2 is a new-build vehicle, with the experience gained in producing the X1 and X1A1 allowing Bernardini to design a new hull. Improvements have been made in the turret and hull armor, night vision has been added, a laser rangefinder has been installed, and air conditioning is provided. The engine is also more powerful, replaced with a Scania-Vabis DS-11 A05 CC1 turbocharged diesel uprated to 280 horsepower to cope with the added weight, and the fuel tanks are larger. The transmission was replaced with an Allison CD-500.

     The main gun is replaced with a more powerful 90mm gun that has more flexibility in ammunition and is low-pressure, and, along with a beefier muzzle brake, has much reduced recoil. This gun is a Brazilian copy of a French gun which was itself a copy of a British Cockerill Mk 3 gun. It should be noted that while the EC-90 was capable of firing APFSDS rounds, internal stowage in the X1A2 was such that there was no room for the carriage of APFSDS rounds, and the muzzle brake used on the main gun did now allow the use of a discarding-sabot round. Rough rangefinding was done with a graticule, but then the gunner switched to a coincidence/laser rangefinder. The loader position has been removed, with the commander working as a loader. The chassis lengthening and improvements were carried over to the X1A2, and rearranged ammunition stowage allowed more rounds to be carried.  The X1A2 was also given a new name, the Carcara, after a Brazilian jungle bird. Some 24 X1A2s were built between 1979 and 1983, but only 10 entered active service, with the remainder going directly into storage or to museums and monuments.

X1/60 HVMS

     In the early 1980s, Ecuador wanted to upgrade their M3A1 Stuarts with a new gun and engine.  They looked to X1 that Brazil had made out of their M3s and M3A1s, but wanted something better still.  Negotiations centered around the fitting of an Israeli 60mm L/70 HVMS autocannon and a Detroit Diesel 6V53T diesel engine (a variant of which powers the famous M113 series).  The 60mm HVMS was considered by Ecuador since it had better antiarmor performance than any of the guns at that time manufactured in South America, and the 6V53T engine because it was a mechanically simpler design with slightly better performance (260 horsepower) than the X1’s Scania-Vabis engine, and it could be hooked up to an automatic transmission. Such a conversion would have given the Ecuadoreans a vehicle with better antiarmor performance than any vehicle in South America at the time and with more ample ammunition carriage than a vehicle with a larger-caliber gun.

     It is believed that possibly as many as 30 of Ecuador’s M3A1s were in good enough shape for the conversions.  Unfortunately, the Ecuadorean government had other ideas; they had over the years been steadily cutting the defense budget and by the time negotiations took place in 1984, the MoD had already bought 32 EE9 Cascavels and there was no funding for the conversion project. The argument was also made that the Cascavels were new vehicles while the conversion project used 40-year-old hulls. The Ecuadorean M3A1s were eventually scrapped.  The idea of mating a 60mm HVMS gun to a South American tank, however, later appeared in Chilean M4s.

     It should be noted that in addition to the X1 series, the Brazilians retained some 100 stock M3 and M5 Stuarts, and these were not replaced until the mid-1980s.  X1 and X1A1 variants were phased out in the 1990s and scrapped.  X1A2s are maintained in working order by civilian employees of Bernardini and kept in a reserve role, but they were quickly supplanted by the superior M41C tank in Brazilian service.

*Floor armor AV is 3Sp.