Monday 16 August 2021

Object 140: A Promising Loser

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.

Object 140 at the Kubinka tank museum, early 2000s. The engine deck is missing.

Later, in July of 1957, director of Uralvagonzavod I.V. Okunev and chief of the armoured forces Colonel-General P.P. Poluboyarov agreed that:
"The use of a hull with curved variable thickness sides that offers different protection to different areas of the vehicle provides the optimal combination of high armour protection and the necessary internal space."

The Ministers of Transport Machinebuilding and Defense Production had no objections either, despite a projected 20-30% increase in cost of production compared to a T-54 hull.


The turret used a stamped dome-shaped roof, with the exception of the front, where the slope remained sharp in order to improve protection. This shape provided as much internal space as possible, which allowed the height of the front of the turret to be reduced.

The turret  of the Object 140 was considerably lower than that of the T-54, by 87 mm. This was done by lowering the trunnions and sloping the walls as highly as possible. This reduced the required armour footprint and saved on weight. 

Remains of the engine.

The use of a hull and turret with the aforementioned technical solutions solved the issues of layout of the turret and fighting compartment according to department #5 chief V.I. Vasilyev and designer V.D. Tumasov. The tank could have a more powerful gun while reducing the silhouette of the turret and vehicle overall and still increasing the space allotted to each crew member.

The hull and turret heights in the middle of the vehicle allowed the crew to function properly and service the armament. The height in other places was reduced as much as possible. In the rear the roof sloped downwards and dropped by 80 mm in the rear. The turret platform sloped downwards at an angle of 7 degrees 30 minutes from horizontal.

The sloped sections of the hull allowed for sufficient clearance of the gun at maximum gun depression even with lower trunnions than on the T-54.

Overall view of the T-64 (Object 140) tank.

The following solutions were used on later projects:
  • Enlarged turret ring
  • Turret shape
  • Sloped turret platform
  • Stamped sides
  • Light alloys

The Object 140 used a TD-12 (8D12U-1) 4-stroke V-shaped 12 cylinder V-2 type diesel engine. It was developed by a group of designers led by Ye.I. Artemyev and produced at the Barnaul Engine Factory. Its gross horsepower was 580 hp (426 kW) at 2100 RPM, size of the cylinder piston group D/S was 150/180 (186.5 mm). It consumed 238-248 grams of fuel per kWh or 175-182 grams per hp per hour. The engine weighed 1000 kg compared to the 895 kg V-54 engine in the T-54 tank.

Cutaway of the T-64 (Object 140) tank.

The engine was located in a very original configuration: perpendicular to the tank and slanted (the left cylinder block was tilted by 7 degrees from horizontal), shifted towards the left of the tank. The engine rested on three foundations: two (upper and lower) on the left side of the hull, one on the right side near the gearbox. The upper foundation was linked to the rear plate via a shock absorber, the lower was attached to a base welded to the floor. The foundations were installed with a special device so that the engine did not have to be realigned when it was removed and reinstalled.

The method of installation required the upper and lower engine casings to be redesigned as well as the driveshaft, accessory linkages, lubrication system, cooling system, and several accessory mountings. Three large hatches and several small ones were cut in the floor of the tank to allow for the engine compartment components to be installed and adjusted.

Cutaway from the top.

The engine and transmission compartment layout was also original. The engine and transmission were located in a separate compartment in the rear. The cooling system, including the oil and water radiators with two vertically positioned ejectors (instead of cooling fans) were located in a separate compartment in front of the engine and transmission.

When driving underwater the cooling compartment could be flooded since the air cooling system was sealed. All that was needed was the installation of a special watertight cover on the hatch separating the two compartments.

Cooling system

The Object 140's cooling system was radically different from the T-54A's. It consisted of two vertical ejectors that ran 4.5 cubic meters of air per second through the oil and water radiators, compared to 5.5 cubic meters per second with fans. As mentioned above, the airflow was sealed. To compensate for reduction in air circulation, the maximum acceptable temperature had to be increased to 110 degrees for the water and 115 degrees for the oil. The surface area of the radiators also had to be increased to 72.6 square meters (54 square meters on the T-54A) for the water and 24 square meters (11.4 on the T-54A) for the oil radiators.

Engine compartment cutaway diagram.

The measures taken to improve cooling turned out to have been insufficient. The performance of the ejectors had to be improved.

Additional heat dissipation was required for the transmission oil system, as the stock radiator did not provide the necessary heat transfer from the gearbox into the general oil system for the transmission and planetary turning mechanisms. At the design stage it was assumed that the gearbox radiator and airflow around the final drive casings will allow them to work for long periods at oil temperature no higher than 130 degrees.

The additional heat exchanger had to be mounted outside of the hull after the tank was finished.

Engine installation.

The Object 140's cooling system drawbacks include:
  • 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.
However, the ejection system was in vogue and was considered very promising. VNII-100 and the GABTU insisted on its use.

Oil and fuel systems

The oil system of the Object 140 used the same components as the T-54A, but the fuel system used many original solutions.

Special fuel tanks were used that could also hold new high power ammunition. This was the first instance of combination fuel tanks and ammunition racks in the world. This allowed the increase of ammunition storage by 47% and fuel capacity by 33% compared to the T-54A.
Tank floor under the engine compartment. Despite what some say, there are not that many hatches here.

Aluminium alloys were widely used. The fuel tanks and fuel lines were made from the AmTs aluminium-manganese alloy.

Fuel was consumed from fuel tanks in sequence (the T-54A consumed fuel in parallel). This improved the reliability of the fuel system in case one or more fuel tanks were damaged. It also reduced the amount of spilled fuel and reduced the difficulty of replacing a fuel tank during repairs since all fuel did not have to be drained. It was also easier to find and get rid of leaks in the fuel system.

The decision to use the AmTs alloy for fuel tanks was poor, since they deformed from static and dynamic pressure.

Heating system

The Object 140 used a highly efficient heating system. The exhaust fumes ran over a special section of the oil tank, which reduced the time required to prepare the engine to start in winter.

The heater was equipped with a fan that was powered by an electric motor. The heater heated the fighting compartment, improving crew comfort.

Heating system diagram.

The two-stage air cleaner used in the Object 140 was the traditional variety. The first stage consisted of a cyclone device, the second had two cassettes with wire traps. Unlike the multicyclone cleaners with tangential air intake used in the T-54A, the Object 140's air cleaners had a plug-type intake. This allowed the air to run through more cycles and reduce the intake resistance.

Overall conclusions made on the engine compartment of the Object 140 by lead designer of department #2 E.B. Vavilonsky and acting chief of department #9 V.I. Harlov was as follows:
"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.

The installation of the gearbox on hoops that aligned with the planetary turning mechanism mounts and linkage to the engine using a half-hoop with a cylindrical base that rested on the drive shaft of the gearbox made it nearly unnecessary to calibrate the gearbox. The alignment of the gearbox and engine drive shafts was guaranteed by the precise finish of the surfaces.

The joining linkages allowed the gearbox to be installed and removed without removing the turning mechanism or engine. The engine could also be removed without removing the gearbox or turning mechanisms. These design solutions were quite progressive.

Turning mechanism and final drive.

The planetary turning mechanism coupled with the final drives was a precursor of final drive gearboxes. A drawback of this design included the drive sprocket that required the removal of the final drive cover to uninstall.

The aforementioned drawbacks of the gearbox and planetary turning mechanisms could have been resolved during trials and post-trial revisions.

Running gear

The Object 140 used small pitch tracks with an open metallic joint as on the T-54 tank. The new 700 by 368 mm road wheels with external solid tires consisted of two stamped aluminium disks held together with bolts. The T-54 used cast steel wheels 810 by 423 mm. The bearings were analogous to those used in the T-54.

Torsion bar and road wheel.

The Object 140 had idlers with tensioning mechanisms that were the same as those used on the T-54 and T-55 tanks. However, a new element was introduced: return rollers. The rollers were installed on ball bearing in pairs and held on the side of the tank with bolts. Surviving blueprints show two types of return rollers: with rubber rims and fully metallic.

The Object 140 was equipped with a torsion bar suspension, telescoping shock absorbers, and bump stops. Six torsion bars per side were included. Each wheel had its own torsion bar and suspension arm. The first and last wheel on each side had a shock absorber. Sprung bump stops were installed for these wheels.

Two variants of road wheels.

The second and fifth wheels had rigid bump stops welded to the side of the tank, the third and fourth had no bump stops. The torsion bar was linked to the suspension arm on one side and to the suspension arm mount on the other side. Torsion bars from the left and right sides were not interchangeable.

The Object 140 used telescoping hydraulic shock absorbers with 145 mm of travel and 1800 cubic centimeters of fluid capacity (transformer oil).

Return roller.

The following was said about the running gear of the Object 140 tank.

Stamped aluminium alloy wheels were used for the first time on tanks of this type, which allowed a significant reduction in weight.

The reduction of the road wheel diameter allowed the use of six road wheels per side to better spread out the weight.

Return rollers were used for the first time on Soviet medium tanks. This led to increased mass, but also improved efficiency of the tracked drive, higher average speed, and less shocks on the fenders.

Shock absorber.

The use of a suspension arm with a large (355 mm) fulcrum allowed the following:
  • 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.
All of these solutions (except telescoping hydraulic shock absorbers) were later used on new armoured vehicles.

In addition to those already mentioned, the Object 140 had a mechanism for ejecting spent shell casings (just in the design, not implemented on the prototype), unified automatic fire suppression system, atomic protection system, and thermal smoke system later used on the T-55, T-62, and T-72 tanks.

Hatch for ejecting spent shell casings. Despite being included in the design, it was not installed on the prototype.

The head of the UKBTM, Chief Designer V.B. Domnin, made this conclusion:
"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."

Original article by Aleksey Hlopotov.

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