How the USSR compared the Chieftain's technology with domestic tanks
During the Iran-Iraq War, Iran deployed British Tanks Chieftain tanks delivered to Tehran under military contracts. One of them was captured by the Iraqi army and was soon shipped to the USSR. For Soviet designers and military specialists, this was a rare opportunity to see an example of British post-war tank design firsthand. The captured Chieftain was not only disassembled and thoroughly examined, but also tested at a proving ground, allowing for a comprehensive assessment of its combat and operational qualities.
In addition, special attention was paid to analyzing the technical solutions of British engineers and the tank's production technology, as well as comparing these data with Soviet vehicles. And, it must be said, while the results weren't shocking, many aspects were of great interest to Soviet researchers.
Analysis of the technological feasibility of the tank design
Various processing methods were used in the production of the Chieftain Mk.5P tank.
Casting. The upper frontal hull plate, turret base, transmission housings, and track links are cast. Sand casting is the primary method for casting large components. The transmission housing casting precision eliminates the need for end-face machining. All cast components are high-tech.
Hot stamping. The weight of the stamped forgings for the Chieftain Mk.5P tank is 5500 kg, which is 33-45% lower than that of domestic tanks. The weight accuracy coefficient is 0,58 versus 0,52-0,55. Let's consider the tank's road wheel as an example. It is welded and consists of a stamped disc (from 10 mm thick sheet) and a ring made from flexible rolled steel. The road wheel's design is simple and technologically advanced.
The production of these roller blanks requires a 630-ton press and bending rolls, while the production of road wheels for domestic tanks requires a 30000-ton hydraulic press, a 16-ton MPCh hammer, and a KPS-1000 ring-rolling mill. The unique design of the final drive carrier assembly is noteworthy, as its use reduces metal consumption by 75 kg per vehicle.
The use of band brakes and spring suspension in the Chieftain Mk.5P tank almost completely eliminates the need for unique forging and stamping equipment (10- and 16-ton hammers, KPS 1000 ring-rolling mills). This type of processing reduces the metal consumption per vehicle by 2,3 tons compared to a domestic tank.
Heat treatment.The labor intensity of heat treatment is somewhat lower due to the smaller number of parts being processed, and heat pressing work is due to the simple configuration of the bottom and a smaller number of parts subject to heat treatment, straightening, and stamping.
Cold stamping. The volume of cold stamping work required to produce the Chieftain Mk.5P tank is relatively small. The cold stamping process is somewhat more labor-intensive due to the use of corrugated brass plates for the heat-dissipating radiators (in domestic tanks, they are flat).
A Chieftain Mk.5 at the Kubinka Museum
The oil tanks are stamped and welded. They are made of 2mm-thick aluminum alloy and are similar in design to domestically produced ones. It should be noted that the use of aluminum alloys in domestic tank construction is limited due to their larger bending radii, the need for intermediate annealing, and their tendency to crack in weld zones during operation.
A distinctive feature of the Chieftain Mk.5P tank is the use of brass, a material that is in short supply in domestic tank construction, for the manufacture of pipelines. Pipe bending radii are standardized, and the pipeline shapes are simple, making high-performance machine bending practically possible anywhere.
Mechanical processing. The study of machining technology was primarily conducted on transmission components, as they are the most characteristic and complex. While the design of most transmission components differs significantly from that of domestically produced transmissions, it is largely similar to that of similar domestically produced components. For example, although the carriers used on the tank are prefabricated, the profiles of the slots for the pinion gears are more technologically advanced, and the mating surfaces for the pinion gears are produced using fine milling. The carrier design eliminates the need for machining of the complete assembly.
It's worth noting the absence of numerous holes in domestic transmission components intended for gear lubrication. The planetary gear shafts are attached by riveting and subsequent grinding, rather than using fasteners as is done on domestic vehicles.
The vast majority of the parts in question are not ground, but rather fine turning is used as the final machining operation. All shaft-type parts lack grinding wheel exit grooves. Grinding of the ends and necks is performed simultaneously with grinding of the fillet, significantly reducing the tooling requirements and machining labor.
The gear tooth ends are free of chamfers. Burrs and sharp edges are removed using a melting process. The transmission housing design is technologically advanced. There is virtually no machining of the end surfaces for the bolts. The parting surface is finely milled instead of ground, ensuring a tight seal without the use of gaskets.
A large number of threaded connections are made without a hex key on the bolt head. Rotation is prevented by a single milling cut in a groove machined into the component being fastened.
Assembly and welding production. The hull and turret are joined by welding. All welded parts, except for cast ones, are flame-cut from sheet metal. The length of the weld seams is somewhat greater than on domestic tanks, but the cross-section of the seams themselves, and therefore the mass of deposited metal, is smaller. There are significantly fewer welds on the exterior and interior of the hull and turret than on domestic tanks.
The widespread use of welded studs instead of bolts for fastening instruments, units, cables, and pipelines is of interest. This fastening method significantly reduces the weight of welded parts, simplifies the welding fixtures required to ensure accurate center-to-center dimensions, and facilitates installation, allowing for necessary adjustments without the need for additional parts or fittings.
Cast parts feature bosses with threaded holes instead of the welded studs. It's common practice to insert a cutting tool through the studs into the armor components to which they are welded when drilling holes, which allows for a reduction in the height of the mounted equipment components protruding above the armor surface.
The significantly reduced volume of assembly and welding work is also explained by the extensive use of bolted connections instead of welded ones. Bolted fastening is also used for large components, such as spring-balanced suspension bogies and fenders.
Assembly and installation production. The tank's design is technologically advanced in terms of assembly, installation, and electrical installation. This is partly due to its large internal volumes and the absence of an automatic loader. The tank makes extensive use of materials such as anaerobic resins for locking components and sealing threaded and flanged connections.
The engine unit is designed as a single unit, including the engine, fans, radiators, and cooling and air cleaning system piping. This design allows for the assembly of these components in parallel with the overall assembly, significantly improving maintainability.
The use of flexible cables instead of rigid ones in the control system significantly reduces the labor intensity of their installation. The use of industrially manufactured cables instead of prefabricated cables reduces the space occupied by cable runs and reduces labor costs.
Protective coatings. The range and surface area of metal coatings are significantly smaller than those on domestic tanks. The paint coatings on the horizontal surfaces of the hull and turret contain abrasive particles, creating a rough surface to increase wear resistance and improve traction on the crew and troops' boots.
Output. The Chieftain Mk.5P tank's design is technologically advanced thanks to the extensive use of non-metallic and anaerobic materials, the use of bolted components instead of welded, the simple design of welded, stamped, and cast parts, and the ease of installation of flexible control linkages. The tank's relatively low labor intensity is explained by the absence of an automatic loader and its large internal volume.
Sources:
"Analysis of the Manufacturability of Tank Design." V.N. Domostroev, V.S. Podolsky. "Questions of Defense Equipment," Series 6, Issue 6 (112)
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