Soviet tank building appeared as one straight continuous line. The opening of the archives showed that there were many deviations from it, small and large branches leading to dead ends. The story of Nizhniy Tagil's "new medium tank" indexed Object 140 is well known today. The label "unfortunate" firmly stuck to it, given by the tank's creator himself.
Leonid Nikolayevich Kartsev wrote in his My Fate - Nizhniy Tagil in 1991:
"After several sleepless nights I wrote a letter to the Central Committee of the CPSU and Council of Ministers asking to cancel the project... The project was cancelled. I wasn't even punished. I still felt guilty regardless. 10 million rubles went down the drain!"
|Object 140 at the Uralvagonzavod Museum of Armoured Vehicles
Kartsev blames this on his inexperience as a chief designer.
"Evaluating my actions and thoughts in hindsight, I understand that the main cause of the mistakes was my inexperience and desire to get to a result quickly no matter what."
Kartsev became the chief tank designer at Uralvagonzavod in 1953 at the age of 30. He gained experience during the Great Patriotic War and Armoured Vehicle Academy, but he had nearly no experience as an individual tank designer. How such a person became a chief designer is a different story, but KB-520 had already produced such famous tanks as the T-54A, T-54B, and T-55 by the time work on the Object 140 ceased in June of 1948.
It seems that years spent on the Object 140 left their mark on Kartsev and his design bureau. Kartsev wrote in 1991:
"The work on Object 140 was not in vain. The ideas and solutions put into this tank were used again in subsequent tanks. Combination fuel tanks and ammo racks were used on subsequent tanks starting with the T-55. The 100 mm rifled gun developed for the Object 140 became the foundation for the 115 mm smoothbore gun later used on the T-62. When we were starting designing the Object 140, designer A.A. Bakhirin suggested using aluminium road wheels. S.M. Braginsky, the chief running gear designer, was opposed, since he deemed them unreliable. The blueprints were put into production without his signature. Despite his pessimistic outlook, they worked reliably. Running gear with these wheels was used in many prototypes and finally went into production on the T-72.
In November of 2003, 50 years after work on the Object 140 started, the workers of the Ural Design Bureau of Transport Machinebuilding (the new name of KB-520) got the chance to reevaluate the design and experience gained while working on the Object 140. A special conference was held that evaluated the new technical solutions developed during the creation of the Object 140. The result of the conference was a description of the original technical solutions and their expected performance, as well as issues that arose while working on the tank.
The hull was a progressive and original design. It formed the shape of a cone around the turret. This allowed the hull to meet the seemingly contradictory requirements for a narrow wheel base and a wide turret ring. The turret ring diameter grew by 434 mm, i.e. the diameter was now 2250 mm compared to 1816 mm on the T-54. The sides were going to be stamped in one piece (without additional splash protection) from a special variable thickness rolled plate. The upper portion was 57 mm thick and the lower portion was 80 mm thick. In the rear section the upper side was interrupted by the sloped 30 mm thick engine compartment roof. The hull shape turned from a cone into a hexagon.
|Object 140 at the Uralvagonzavod Museum of Armoured Vehicles. The restored engine compartment roof can be seen.
An engine deck made from a light aluminium alloy was used for the first time. The stamped arc-shaped turret ring foundation gave the hull sufficient rigidity and solved the problem of deformation as shells hit the front of the turret. In addition to the stamped variable thickness sides, the sloped roof armour was only 30 mm thick, which helped further reduce the weight of the tank.
A lack of dovetail joints was a drawback. This would lead to a low lifespan of the hull under fire.
There is an opinion that such a hull would be difficult to produce, as only the Izhora factory was capable of rolling variable thickness armour. However, in 1955-1959 the Mariupol branch of TsNII-48 and Moscow branch of TsNII-100 developed a process that would allow variable thickness rolled steel to be produced at Azovstal, Kuznetsk and Magnitogorsk metallurgical plants, and the Novo-Tagilskiy metallurgical plant.
- Enlarged turret ring
- Turret shape
- Sloped turret platform
- Stamped sides
- Light alloys
- Partial recirculation of hot gases due to the proximity of the ejector exhausts and radiator intakes and poor direction of gas ejection straight up from the ejectors into the radiators.
- Lack of a drainage compensator in the hydraulic pathways, leading to high sensitivity to coolant leakage when the engine was running, which led to a reduced lifespan of the engine.
- Use of an ejection cooling system, which was less efficient than a fan based one and reduced temperature more slowly when engine output decreased. This had a negative effect on the tank's mobility and increased heat pressure on the engine.
|Heating system diagram.
"The layout of the Object 140 with a lower and smaller engine compartment with improved power characteristics of the engine demanded a radical redesign of the V-54 engine and complete change of all components of the engine and gearbox.
The high temperature cooling system of the engine and transmission did not allow for sufficient cooling of the components and assemblies in the engine compartment. The effectiveness of the cooling system had to be increased due to the need to place the transmission air and oil radiator in the engine compartment (and thus increase its size and weight) and increased back pressure upon engine release to 0.4 kg-seconds per square centimeter (compared to 0.1 on the V-54).
Such a radical amount of design changes in all assemblies could only be justified by a radical improvement in tactical-technical characteristics of the tank, reliability and ease of maintenance of the engine compartment, and possibility to use the chassis for the creation of various types of engineering and special vehicles (with secondary equipment powered by the main engine) and potential to supercharge the engine. It was not possible to do this on the Object 140 due to its layout.
Positive solutions in the engine design include:
- Ammunition racks/fuel tanks that increase the amount of fuel protected by armour as well as ammunition capacity.
- Use of a highly effective heating system including a space heater for the crew."
Transmission and controls
The Object 140 used a mechanical two-shaft planetary gearbox with a friction clutch. The gearbox functionality was rationally designed, which made it very small and light. The gearbox provided the desired spectrum of speed and power, including reverse. Drawbacks include a lack of adjustable gears on the drive shaft to allow for shock-free shifting between the 4th and 3rd gear. This led to breaking of gear teeth.
|Fuel system diagram.
|Torsion bar and road wheel.
- Ability to increase suspension travel from 140 mm on the T-54 to 242 mm.
- Reduction in suspension rigidity, which would provide for a smooth drive when coupled with the shock absorbers.
- Use of hydraulic shock absorbers resulted in an increase of energy volume compared to the T-54, although the increase was insufficient due to the reduced suspension rigidity.
- The use of soft bump stops (conical springs) was supposed to reduce the shocks on the hull.
|Hatch for ejecting spent shell casings. Despite being included in the design, it was not installed on the prototype.
"Overall, the decision to stop working on the Object 140 in 1958 was the correct one, since the design had several strategic mistakes build into it, although some of them were solvable. It's possible that trials could be continued for some time to gain experience."