Monday, 10 August 2015

More on Tank Bunkers

I posted some photos of dug-in tanks used as bunkers before, but not many details about them. Here are some more details about the various tank components that were dug in around Leningrad. As you remember, the tank park on the Leningrad front was very colourful, and this is reflected in this document.

"In BT-2 turrets with dual machineguns that still had a mantlet, no changes were made. Where there were no mantlets, a successful combination was used (fig. 38) designed by Red Armyman Sidorov, nicknamed Sidorov's Mantlet. In this case, the DT mount from a 45 mm gun mantlet was used. As no more than 100 pillboxes could be made if we only used DT machineguns, a simple mantlet for the Maxim machinegun was made and has proven itself worthy (fig. 39).

Pillboxes made from old tank turrets at UNI make powerful fortifications. There is the "YuL" type for 45 mm guns and "VS" type for 76 mm guns and larger (fig 40-41).

Machinegun turrets are attached to a turret ring and installed on top of a blockhouse (fig. 42), but artillery turrets are installed on a special welded metal frame (fig. 43). Starting with a simple blockhouse on top of a ditch, we gradually perfected the design until we arrived at the method shown in fig. 44: turrets (machinegun and cannon) are placed on a blockhouse that is installed on top of a dugout where the crew lives. A more detailed description would be excessive. Let us focus on some characteristic cases:
  • A turret with a 152 mm gun needed to be installed (fig 45). This took 1950 man-days. 
  • Same with a turret with a 85 mm gun.
Both of these projects consumed 36 cubic meters of concrete with an internal volume of 9 cubic meters, which was too small for the crew to operate and supply shells. Additionally, the ammunition magazine was protected by only wood and stone. These problems were considered when installing 76 mm KV turrets, and the design was changed (fig. 46). Here, the above defects were corrected, each turret took 43 cubic meters of concrete with an internal volume of 25 cubic meters. Construction of each bunker with a dugout for the crew took 2000 man-days.

Lastly, a design made of stone and wood due to a lack of concrete in Leningrad (fig. 47).

When using the turrets in the winter, there is one downside that is also observed in other structures, but to a lesser extent. Condensation gathers on the inside.

The turret is cooled externally. Inside, it contains warm moist air that rises from the basement or from the breath of the crew. The turrets are covered with frost or moisture on the inside, which seeps into the turret traverse mechanism and freezes, locking the turret in place. This effect is accelerated by snow on the outside that melts.

Measures were taken to protect our turrets from the above problems.
  1. The turret and its platform are always kept clear of snow and water.
  2. The turret ring is covered with a warm cover made from sacks reinforced with felt.
According to our calculations, a turret needs a 5 cm thick cover. When the covers were applied, the condensation stopped. Special desiccant packets also helped (see fig. 53).

Fig. 46. "VS" type artillery pillbox with a reinforced concrete base and ammunition magazine.

Fig. 47. 

Report of an artillery pillbox with an armoured KV-4 type turret, built by 125th OSB from September 29th to October 8th, 1942

Photo #8. KV artillery pillbox with a 76 mm L-11 gun.
Photo #9. KV artillery pillbox with a 76 mm ZiS-5 gun.

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