USSR (1936-41)

Armored Bridge Layer – 1 Built

The origins of armored bridge laying vehicles can be traced back to the First World War, when fascines (bundles of wood) were used by Allied tanks to be able to cross trenches and German anti-tank ditches. After the war, the idea of trench crossing systems based on tank chassis settled and the Soviets started to develop such vehicles which led, for example, to the CT-26 (ST-26), a bridge-laying tank based upon the T-26 light tank. When the T-28 medium tank was taken into production in 1933, it also proved to be a valuable base to test new designs and technologies, like mine crawlers, but also bridge tanks, one of them being the ИТ-28 (Инженерный Танк: Engineering Tank IT-28).



A clear view of the IT-28. Photo: SOURCE

Development

The development of the IT-28 was started in 1936 by the Научном авто-тракторном институте (abbreviated НАТИ, NATI: Scientific Auto-Tractor Institute). Work went slowly and it was 4 years later, in March 1940, that the tank could be equipped with the prototype bridging system. Only one T-28, carrying serial number 1638, was assigned to be converted. The conversion took place at the Kirov factory No. 100 located in Leningrad. The main and the two secondary turrets were replaced by an armored superstructure. After completion, it was sent to the testing range and designated IT-1.



The IT-28 beside the factory. These pictures provide a good comparison between the size of the tank and the bridge. Photo: aviarmor.net

Design

The space freed by the removal of the two secondary turrets was used to enlarge the crew compartment. However, two machine guns were fitted in ball mounts in the hull, roughly on the same place as the original turrets. On top of the enlarged hull, two extensions were placed to which two arms were attached. The bridge was carried, raised, and lowered by these two arms. These arms could be turned backward in case the bridge was not attached. To do so, a power transmitter was placed between the engine and the arms. The two-track bridge had a length of 13.3 meters. Both tracks were attached together by steel beams and had a total width of 3.5 meters. The weight of both chassis and bridge combined was 29 metric tonnes which was one tonne heavier than a serial production T-28.



Note the spikes at the end of each track so it would have a better grip. Source: Eksmo Publishing

The main turret was replaced by an armored eight-sided superstructure and two winches were placed on top. The winches were attached to the back of the bridge via a pulley located near the arms. With these winches, the bridge could be pulled forward. After that, the arms could be pointed to the ground and, by loosening the winches, gravity pulled the bridge to the ground until the last bar rested on the slight slopes on the arms. At this point, the winches had to be detached by the crew. Then, the arms could be lowered more, the bridge would lay on the ground and the vehicle could drive backward removing the hooks from under the bridge. After that, the arms were turned backward to ease travel.

Picking up the bridge was a bit more difficult to perform. Although it was basically the reverse system, the winches could not pull the bridge further than the position of the pulleys. When the bridge reached that point, the arms were slightly raised, so the bridge could slide down by the force of gravity, while the winches would be slowly loosened again.



The front and the back of the vehicle. Source: en.valka.cz