39b BAI-M & BA-3:
The Izhora plant Design Bureau led by N. I. Dyrenkov launched, in early 1932, at its own initiative, a study for a new model designated BAI (BroneAvtomobil Izhorskij). This took place after some experience was gathered on the "Ford Timken" D-13 armoured car chassis. This vehicle featured a 6×4 chassis developed from a marriage between a rear Timken truck axle with a short Ford A chassis. In parallel, the BA-27M (Russian Vehicle
Note 38b) was also developed. In the end, this model was the starting point of the BA series of heavy armoured cars, which will encompass, until 1941, the BAI, BAI-M, BA-3, BA-6 (Russian Vehicle
Note 39) and BA-10 (Russian Vehicle
Note 39a).
The BAI had a welded body assembled from 4-8 mm (0.16-0.31 in) thick armour plates attached in 10 points to the chassis. The rear part of the Ford Timken original chassis was shortened by 400 mm (15.7 in), the bureau managing to provide a more compact design compared to the previous D-13. The BAI towered 3.86 m (12.6 ft) above the ground. The fighting compartment floor was lower than the front part of the vehicle. This solution helped reduce the overall height and subsequently applied to all the Soviet medium armoured vehicles which were built in the 1930s. The BAI had three doors, two on the sides and one at the stern. The driver had a hinged armoured hatch with viewing slot in the front hull, and others were located in the side doors. Above the driver and hull-gunner (co-driver), another hatch was placed, used for ventilation and air surveillance. The commander was located in the small turret, sitting on a suspended canvas belt. He had a set of three hinged armoured covers with slits in the turret, with armour flaps.
The armament consisted of a 37 mm (1.47 in) Hotchkiss (PS-1) QF light gun and and 7.62 mm (0.3 in) DT machine gun installed in the frontal slope of the turret. Another DT, installed in a ball mount, was manned by the co-driver in the front hull. Ammunition consisted of 34 gun rounds stored in canvas pockets inside the turret and 3024 cartridges stored in 48 discs, packed in racks, installed on the side walls of the fighting compartment, while others and tooling took place in additional stores under the floor. The BAI had a Ford 40 hp engine with a crash gearbox and dual drive. The motor block was protected by an armoured hood with shutters for radiator ventilation. The chassis frame was reinforced by a cross bar under the front suspension.
The spare wheels, mounted after the front wheels, could rotate freely. This allowed them to play the role of additional rollers on soft ground. To further improve all-terrain performance, the BAI’s tires could be equipped with snow tracks on the rear axles, the operation being done in 8-10 minutes by two crew members. They were stored on the rear mudguard when not in use. This system was so successful that it became a Red Army standard for armoured cars.
In the summer of 1938, the armour repair base number 6 in Bryansk fitted a BAI body on the new GAZ-AAA chassis. The new 1937 frame had the rear shortened by 300 mm (11.8 in). The front axle was strengthened and the course amplified for better off-road performances, while the roadwheel tires were replaced with bulletproof ones. The electrical and other mechanical parts also came from the GAZ-AAA, and an additional 18 liter fuel tank was added. Although shorter, the BAI-M was heavier (4680 kg vs 3860 kg). Top-speed values remained unchanged, whereas the range was doubled (286 km vs 140 km). The BAI-M was first tested at the NIBT range in January-March 1939, on a 3120 km (1940 mi) course, including 33 km (20 mi) on snow, and entered service in October 1939. By the summer of 1940, the upgrade of the entire fleet had been completed. Most vehicles were sent sent to the Far East, remaining there until 1945 as part of the Trans-Baikal and Far Eastern military districts, facing Japan, a quiet affectation. The remainder were mostly destroyed in the summer of 1941, and at least one was captured and reused by the Germans.
The BA-3 was an improved model, following an 1932 army specification asking for a model equipped with the T-26 turret, and its high velocity 45 mm (1.77 in) 20K gun (60 rounds), allowing excellent antitank capabilities. The armament was completed by a coaxial DT machine-gun and another in the front compartment co-driver ballmount. The Izhora plant chose to radically improve the BAI design, lengthening the rear part of the hull by 50 cm (1.64 ft) to cope with the extra top-weight of the new T-26 turret. The ring was also reinforced, as was the entire rear compartment.
The riveted armour was also thickened and the engine compartment received extra exhaust vents, as the GAZ engine proved prone to overheating. It was also remarkable that it was tested and equipped with spare chained tracks for its rear wheels, for a quick conversion into a half-track.
Cross-country speed proved less than 35 km/h (21.7 mph) and the engine also overheated badly, imposing better cooling and a reinforced front suspension, which were added on the next series. Production was part of the 1st Five Year Plan and was partly assumed by Vyksunskij (Gorki Works), the first series based on the US-based Ford-Timken truck chassis converted into a 6×4, and later production vehicles received a new Russian-built GAZ AAA chassis. When the production ended in 1935, 180 have been delivered to the Red Army.
The BA-3 Zhd was a "kit" especially designed for railways in 1936, which saw very limited production with the improved BA-6ZD. This consisted in hydraulic jacks mounted on the front and rear to lift it in position, and six adapted metal wheels to be installed over the tires. This operation was performed in just 30 minutes.
When the war broke out in 1939, the 7th, 8th, and 9th Brigades, half equipped with BA-3/6s, were sent to the Far Eastern border with Japanese-controlled Northern China. The dry and flat steppe helped these heavy armoured cars and their 47 mm (1.77 in) gun gave excellent results against Japanese tanks at Khalkin Gol. However, they proved vulnerable even to the Japanese 13 mm (0.51 in) heavy machine-guns. Some were delivered to the 6th and 8th Armored Cavalry Battalions of the Mongolian Revolutionary People’s Army, which also took part in various operations in this sector against the Japanese.
Others took part in the invasion of Poland in September. Later on they took part in the "Winter war" campaign against Finland, showing good mobility in the snow with their "half-track kits". Many were easily destroyed by Finnish antitank rifles and other lighter expedients, and a dozen were captured. They were later pressed in service as the BAF-A (BA-3) and BAF-B (BA-6) (Finnish Vehicle
Note 21a) and fought on until late 1944. The Russian models were still frontline during the summer of 1941.
However, like the BA-10, they were gradually phased out during the Great Patriotic War in favor of the new generation of mass-produced light scout tanks, like the T-60/T-70. The BA-6 was also exported to Turkey. Some sources speak of 60 delivered in 1939.