Although the Belgian armed forces were generally very pleased with the capabilities of the existing T-13 B1 and B2s, there were obvious issues with both models of the tank destroyer. Since the original Vickers artillery tractor was not designed to carry a gun, it was faced with a common vehicle design problem called 'weight creep', which in essence is the gradual accumulation of weight every time a new feature or capability is added to the design. This led to the first model T-13s being underpowered, somewhat unstable as a gunnery platform, and prone to mechanical malfunctions because of overloading and wear and tear. Full weight was 4,5 tons for a 51 hp gasoline engine. Much more important however was the vulnerability of the three man crew. Exporting fully assembled designs was too expensive a solution to field a tank destroyer in adequate numbers, especially with the Belgian economy performing rather poorly because of the worldwide
Great Depression and the resulting drop in foreign demand for industrial products. In 1936 a new vehicle was imported from Vickers; an export version of the
Vickers-Carden-Loyd Light Dragon Mk. IIB artillery tractor, equipped with an 88 hp
Meadows 6 cylinder gasoline engine and a "crash" type gearbox. The general design of the vehicle was almost identical to the
T-15 Light tank already in service with the Belgian armed forces, which was also designed and produced by the Vickers company. The suspension was made out of Horstmann suspension resting on
bogies with two rubber-lined wheel sets per bogie. The drive sprocket was in the front, the
idlers were placed in the rear, with three return rollers. Steering was again a combination of declutching the drive to one track and braking to increase the turn. The bigger track area, the inclusion of return rollers and the bigger and more powerful engine convinced the Belgian armed forces that this platform would be superior in the tank destroyer role. Also, since the Familleheureux factory, a vehicle and tractor company, was already producing the license built Vickers utility tractor, the decision was taken to buy a license for production at this company instead of directly acquiring all vehicles from the UK. This would allow for a larger and more economical production run compared to the T-13 B1/B2 version. The definitive T-13 B3 was structurally very different from the earlier B1 and B2 versions, with the B3 suffix obviously chosen to play down the fact that a new tank destroyer was being produced rather than a variant of the older systems. The chassis of the T-13 B3 was bigger, with, apart from the redesigned turret, a box-on-box like appearance. The gun was no longer pointed rearwards as in the first two versions. Armor was only slightly upgraded to 13 mm armored steel on the frontal surfaces and 7 mm steel on the sides, still insufficient to cope with anything but small arms fire and blast and shrapnel damage. However, the chassis was big enough to accommodate the four man crew without the need for the side armor panels, which also allowed the gun to traverse 360° without lowering the (still very low) level of armor protection for the crew in the process of gun laying. The rear remained open, since the vehicle was still meant to be a light tank destroyer. The most important and obvious difference was the bigger and more powerful engine, which allowed for greatly reduced wear and tear and a rather more stable gun laying platform, and above all for better manoeuvrability in the field. Top speed for the T-13 B3 was increased to 56 km per hour or even 65–70 km per hour, a speed reached by commander A. Modera in 1940. The armament, apart from lay out and sighting systems, was left untouched, although more ammunition could be carried. Range was increased: from 240 km for the B1-B2 versions to 400 km for the B3 version. Total weight became 5.08 tons.
Production Given the need for the Familleheureux company to set up production after acquiring a Vickers licence in 1936, delivery of the first production T 13 B3s did not commence until 1938. After the Second World War broke out in September 1939, production was stepped up so as to equip as many army units as possible. Since acquiring its first T-13 B3s, the Belgian army was finally satisfied with the resultant tank destroyer and kept on ordering. Production of the B3 ended at the start of the
Battle of Belgium, after a total of 250 to 255 units were produced at Familleheureux. Together with the earlier B1 and B2 production, this made, in theory, a total of 303 to 311 T-13 vehicles. However, a few dozen of these T-13s were still at the factory in the process of being outfitted when war broke out. About two dozen others were on their way to being delivered to new units, but since there was no more time for driver, gunner or maintenance crew training they ended up being used as reserve vehicles for units already equipped with the T-13 or as spare part hulks. In total, it seems that only about 220 T-13 B1/B2/B3s were actually fielded with operational units. This made the T-13 the most numerous armored tracked vehicle in the Belgian armed forces inventory. ==Deployment and operational history==