Engines of the Red Army in WW2

Note new combat weight saving track style and modern horn but old-style periscopes

KV-1s Heavy Tank

First production series with combat weight saving road wheels, early fall of 1942

KV-1s "skorostniy" Heavy Tank

Though successfully fighting the German advance in the first year of the Russian-German war, the heavy and clumsy KV tank was about to loose his armour advantage against the upcoming German armament in summer 1942.
A new improved KV had to be designed, lighter and thus faster in combat, the KV-1s (s=skorostniy=fast).
The reduction in weight was to be achieved by reducing the armour strength and ammunition storage by fielding a revised cast turret.

Trials with the new engine V-2K with 650hp already began in March 1942 in accordance with the design of a completely reworked transmission.
In July/August 1942 two KV-1S preseries vehicles were tested.
These had a combat weight of 42.3 tonnes and a top speed on the road of astonishing 43.3 km/h (the KV-1 barely reached the factory requirement of 35 km/h. 15-20 km/h was more realistic).
The KV-1s was still armed with the 76.2mm ZIS-5 gun albeit of improved design with parameters now equalling the F-34.
In July altogether 52 KV-1S had been manufactured.
In late August 1942, the first series-production KV-1S reached the Red Army.
In September 1942, the mass-production for the KV-IS was launched and followed by instructions to again increase the ammunition complement from 90 to 114, which increased weight to 43.4 tonnes.
A total of 180 KV-IS was built in that month, the highest-ever monthly output of this model.

Aside from the already mentioned principal changes in design, the KV-1S was also the first KV series tank that received the long-desired commander's cupola.
The hull of the KV-1S can be identified by the angled engine deck - introduced to safe weight.
The introduction of the new transmission finally led to a significantly enhanced reliability of the whole drivetrain and powertrain.
The shape of the new cast turret was now ballistically even better than the late KV-1 types.
The turret now also mounted two hatches to enter or leave the vehicle for the three-man turret crew.
Furthermore planned improvements, such as an even better commander's cupola could not be introduced until the KV-1S production came to an end in August l943 after some 1,300 tanks had been accomplished.