Category: Cold War British MBT Prototypes

Cold War British MBT Prototypes Has Own Video

Straussler Main Battle Tank

Post author By Andrew Hills
Post date March 25, 2022
5 Comments on Straussler Main Battle Tank

Straussler Main Battle Tank. Illustrations by the Glorious Pavel Carpaticus funded by our Patreon Campaign.

United Kingdom (1960)
Main Battle Tank – None Built

Nicholas Peter Sorrell Straussler (1891* – 1966) is perhaps most famous for designing the inflatable floatation screen for tanks such as the M4 Sherman, commonly referred to as a ‘Duplex Drive’ or DD tanks.

Born in Hungary in 1891*, at a time when it was still Austria-Hungary, he had, as a young man, come to the United Kingdom in 1910 or 1911. He may have found work during World War One in one of the hundreds of ordnance factories supporting the war effort. Certainly, he was demonstrating his engineering skills when he filed his first patent in January 1911 for a rotary engine.

(*His UK death certificate indicates a date of birth which could be 1892)

Early Engineering Work

After the First World War, he remained in the UK and applied for British nationality, marrying Edith Arbib in 1923. His engineering skills quickly found purpose and, by 1928, he was running the firm of Folding Boats and Structures Ltd. He was also designing small scout cars both with and without armor, both for domestic use and for export. He was finally naturalized as a British citizen in February 1933.

Clipping from a pre-war advert for the Vickers ‘Straussler’ folding boats.
Source: Pinterest

He would eventually open a small workshop in Brentford, West London, and produced a variety of unusual-looking but highly effective designs in partnership with the Alvis motor company, which proved to be both effective off-road and ruggedly reliable, gaining him some limited production contracts. He continued with armored vehicle design work, operating as Straussler Mechanization Ltd. until it entered voluntary liquidation in 1941 and its assets sold off in 1942. He would marry a second time in 1944 to a woman twenty years his junior, Josephine Vassie, and produce one child, Roderick, in 1945. They divorced or separated in around 1958.

A complicated private life aside, his most famous contribution to the war effort was to build on his work on Folding Boats and create an erectable canvas screen and outboard motor, tested on a Tetrarch light tank in July 1940. By the spring of 1942, this unusual arrangement was accepted as part of the general solution to solve the problem of how to get tanks ashore for an amphibious assault. The Infantry Tank Mk.III, better known as the ‘Valentine’, was equipped with these screens as well. Later, by 1943, the Valentine was replaced as the primary vehicle for ‘Strausslerisation’ using a floatation screen by the Sherman.

That development was a successful addition to the Allied arsenal in WW2 and, clearly, Straussler was keen that this development see wider adoption.

Designing the Ultimate Tank

After World War Two, Straussler continued work as an engineer and was, at some point, inspired to try and design a new type of vehicle. This was to combine two of his areas of design expertise, a screen for helping vehicles cross water, and a highly flexible suspension system allowing for a wide range of movement from track units and wheels alike to improve mobility.

Key features of the main battle tank design were to reflect what he felt were the fundamentals that would be needed from an “ideal” tank, specifically:

A vehicle as small and light as possible with a low profile.
Screen around the tank to allow it to be amphibious in water.
As small a crew as possible.
The largest possible primary “heavy caliber” armament, which would be loaded, aimed and fired automatically.
As much ammunition as could be carried.
The ability to mount alternative or additional weapons as may be required or desired.
Simple suspension system, allowing for ease of movement cross-country with low ground pressure and allowing the vehicle to operate on wheels or on tracks equally, including the braking system.
Suspension units mounted or unmounted by means of the vehicle’s own power.
Simple driving mechanism.
Easy access.
All-round visibility.
A crew compartment distinct from the main gun and engine provided with its own ventilation.
Easy maintenance with a simple and reliable design.
Width of 3,150 mm.
Railways loading width.
Height “below that of a normal man” – 1,700 mm.
700 – 800 hp engine.
28 – 32 hp/ton. (28.4 – 32.5 hp/tonne)
2 speed gearbox.
Wheel speeds of 80 km/h.
65 km/h on tracks.

“There is no Tank either projected or existing which has only a few of the features of the ‘Straussler’ let alone all the large numbers of highly desirable properties which are assembled in a single device. There is nothing in any of the design features which are mechanically, technically, or operational of doubtful or of difficult nature and which cannot be designed, and manufactured by any competent organisation to produce a highly successful tank”

Nicholas Straussler

Layout

The whole tank was to be divided into three basic compartments. The front compartment housing the crew, behind this was the ammunition compartment, and at the rear, the engine compartment and fuel.

The outline for Straussler’s MBT shows a compact design with the crew area at the front. The weapon system is mounted in the center and the engine compartment at the rear.
Source: The Tank Museum Bovington, modified by the author

The tank was to be of a very low profile, with the gun projecting directly out of the front of the well sloped glacis and with a flat roof to a slowly sloping back. On each side of the vehicle would be two pairs of track or drive units, consisting of four double rubber-tired road wheels on a common frame able to rotate around a central pivot and around which was a track. At the rear of the tank would be a large and permanently affixed electrically-driven and steerable propeller system to provide propulsion in the water for the tank when floating. To aid in crossing a water obstacle, the tank would also have a large fabric screen that could be installed and easily erected. When not in use, this was to be held in a “perimental trough” (a recess running around the outside of the tank) and sealed with a rubber gasket.

Each track unit was designed to be fitted with a pair of large cantilevered spring leaf units, providing cushioning on the move. Braking was to be provided within the unit as well, in the form of 8 large disc brakes, constituting a pair per track unit. Further, because of the electrical drive system, electrical braking could be employed as well, providing an easy and simple method to control the speed of the tank. The 600 mm wide track itself was not particularly important to Straussler, although he did suggest the use of a “spring leaf” type of track, as it was cheap and light and could resist the sort of sideways forces imparted on a track during turning using its flexibility.

The middle compartment, designed to house the ammunition, had within it a cage which was rigidly attached to the breech of the gun, which projected through the front of the tank, through the crew space, and into this section. Ammunition would be loaded through the roof via a large trap-door style hatch into the middle compartment. Likewise, in order to refuel or access the powerplant, another hatch was on top of the hull over the rear section as well.

Date

Sadly, there is no date on Straussler’s design for this low profile main battle tank. The design can, however, be roughly dated by some of the technology within it. For example, the ‘perimental trough’ mentioned by Straussler is similar in description and purpose to a patent design granted to Straussler in 1947. That design was for a collapsible screen, as before, for imparting buoyancy on an armored vehicle. However, this was to be fitted into an armored box around the vehicle to prevent damage, instead it would be a permanent ‘trough’ into which such a screen could go on a purpose-designed vehicle.

An armored protective enclosure for an integrated collapsible waterproof screen allows an armored vehicle to carry a permanently fitted screen protected from damage.
Source: British Patent GB623427 of 1947.

A second clue is the use of the folding propeller at the back of the tank. In March 1942, Straussler filed a patent in the United Kingdom for this design shown on a Valentine tank with a wading screen clearly in place. Although filed in 1942, this design was not granted a patent until 1945.

The folding rear propeller to move a floating tank in the water.
Source: US Patent: 2398057 of 1946 from British Patent GB487622.

A further clue is found in the name itself ‘Main Battle Tank’. The term itself originated after WW2 and was first used around 1957. These three clues combined would imply a date of design of not earlier than around 1957 and perhaps as late as 1965 or so.

Armor

Armored side skirts could be fitted to enhance the protection of the vehicle and especially to protect the drive units. However, no other mention of armor is included in his letter accompanying the design and the drawing itself shows no implicit thickness of armor either. Based solely on the drawing, it can only be inferred that protection was to be very light and this would be in keeping with a planned weight of just 25 tonnes. Given the low weight, a relatively low level of protection could be expected and the vehicle would have to rely for its primary protection on its low profile. At just 1.7 m high, allowing it to be easily concealed or camouflaged, the armor, or lack of it, would leave the vehicle highly vulnerable to even just cannon fire.

Crew

Just two men were supposed to operate this vehicle according to Straussler’s design, specifically a commander and a driver. Access for them was by means of a large hinged “trap-door” arrangement on the roof of the tank, with one for each man. Each man would sit in the forward section of the hull, on the right, sitting upright alongside each other. This meant only their compartment would need forced ventilation.

As well as telling the driver where to go and operating the radio to receive their own instructions, share combat information etc., the commander was also tasked with firing the primary armament. Aiming and loading were done automatically as the primary sight (a telescopic periscope) for the gun was placed on the roof between the driver and commander’s positions. The sight could be shared so that, in theory, both men would be able to aim the main gun.

Armament

The ‘ideal’ characteristics for a main battle tank, as outlined by Straussler, had to include the largest possible primary armament which could be carried. For this vehicle, Straussler proposed a 120 mm gun, although he does not mention if it were to be rifled or smoothbore. Considering a probable design date of the mid to late 1950s and his British experience, this would strongly suggest a rifled gun as a logical assumption.

Straussler had proposed that guns should be loaded, aimed, and fired automatically and that the tank should carry as many rounds as possible. However, his design principles included the smallest possible size characteristics as well, and the result was that just 31 shells could be carried inside in the “shellcage”. With a predicted firing rate of up to 12 rounds per minute (one every 5 seconds), this meant a continuous barrage of fire of just 2 ½ minutes if firing took place without a break. The automatic loading system was to be driven by an independent electrical motor moving new shells into the breech and the casing from spent shells out of the breech. As the gun was fixed in a side-mounted gimbal, it could move in both traverse and elevation, both of which were controlled via a hydraulic motor by the commander.

Front cross-section of the design, showing the angled position of the loading system and eccentrical position location of the main armament in the front left of the hull. The gimbal mount is to the side of the gun, shown without a blue outline.
Source: The Tank Museum, Bovington modified by the author

With the original drawing removed, the positioning of the loading system is even clearer.
Source: Author

Possibly, the most unusual part of the armament plan for the vehicle was the position of the main gun. The basic layout of the vehicle and the protrusion of the gun from the front implies a centrally ( or close to center) mounted gun, as this is commonly seen on numerous other vehicles of a roughly similar design, from the Jg.Pz. 38 t and Jagdpather, to the Swedish S-tank. However, this is not the case at all. Close examination of the drawings show that the gun was in fact offset to the front left, meaning that both of the crew were sequestered inside not only the front ½ of the vehicle, but also the front right of that third.

An advantage of this layout was that it obviated the problem of the mounting of the gun being too far back. As such, when the gun elevated, depressed or traversed, it would leave a large ‘track’ in the frontal armor which had to be empty to allow gun movement. Given the arrangements, this ‘hole’ in the front armor would not leave any weakness in protection for the crew, who would be separated by both a lateral and transverse bulkhead, meaning that all the barrel might need was some kind of flexible canvas shroud to prevent water ingress. The gun itself was rigidly fixed to the “shellcage” of 31 rounds and automatic loading mechanism. The drive motors were fixed at an angle, causing the shells to be carried at around 25º to 30º to the vertical in the center, directly behind the crew compartment. The drive motor was inside the right sponson. If the gun rotated or traversed, this angled arrangement would prevent fouling.

Primary armament for the design, loaded and mounted centrally, along with the optional rockets on the roof.
Source: The Tank Museum, Bovington modified by the author

As well as the 120 mm main gun, 4 machine guns were also to be carried, of either a ‘heavy’ (i.e. 0.50 caliber) or ‘light’ (i.e. 0.303” or 7.62 mm caliber) type. These machine guns would be placed in a pair of turrets, with one on each side of the front of the tank’s hull, mounted on top of the mudguards over the tracks. These turrets would be rotated, aimed, and fired remotely from inside the tank, although this would seriously occupy the crew inside, who already had plenty to do. Nonetheless, the position of these twin machine gun turrets would, in theory, allow for a level of protection across a wide arc on both sides as well as to the front, although how these were to be aimed was not explained by Straussler.

Engine, Steering, and Propulsion

The vehicle was to make use of a hybrid-type of drive system, whereby an engine drove an electrical generator which, in turn, drove electric motors to drive the tracks and provide the vehicle’s propulsion.

Straussler wanted a multifuel engine, i.e. one which could run on petrol or diesel or any available fuels. This type of engine could be the ‘normal’ kind of piston-driven engine or the Wankel type of engine as an alternative system. The Wankel type engine consists of a single triangular piston with curved faces with reciprocates within a roughly ‘8’-shaped cylinder. They are commonly known as rotary engines and have seen commercial use in some sports cars but were, and still are problematic for some issues like lubrication. The advantages, however, offered by a Wankel engine would have appealed to Struassler, not only because of the larger proportional size to weight and power output characteristics, but also because this type of engine produced a more uniform torque than a ‘normal’ type of piston engine as well as less vibration.

Nonetheless, this desire or at least the consideration of a Wankel type motor harkened back to Strausssler’s work decades earlier and his 1911 patent for an engine of exactly that type.

Straussler’s rotary engine design of 1911. Note that this image has been digitally cleaned.
Source: British Patent GB1611.

This engine would drive a single generator which would then drive the electrical motors. One motor was provided for each track. With four tracks, that meant four motors. In his design submission, Straussler does not expressly detail the use of the motors, but this sort of system would have allowed the driver to vary the electrical current being supplied to each track in order to provide turning forces as well as providing redundancy from damage. For example, even if one track unit on each side was damaged by enemy fire and the motors stopped working, as long as there was at least one operational motor and drive unit on each side, then not only could the vehicle still move under its own power, but it could also turn. With a fixed gun, not being able to turn meant not being able to fight, so providing this kind of redundancy with 4 tracks was a rational and logical step. What it also meant was that the vehicle would be able to neutrally steer around the center of the four units by powering one side one way and the other side the opposite direction.

Straussler’s MBT with engine in the rear compartment, large air intakes above and folding propeller system at the rear.
Source: The Tank Museum, Bovington, modified by the author

The system had other advantages in common with some other hybrid designs, namely in the layout of the vehicle. Lacking the need to have the engine and gearbox mechanically connected (as this system did not need a gearbox) to the final drives, it meant that it would create a more efficient internal volume unencumbered by rotating shafts and differentials, etc. Instead, the engine and generator could be simply connected by electrical cabling to the motors. Each motor would then drive one wheel within each track unit, so that, of the four double rubber-tired road wheels, the lead wheels on the front track units would be powered and so would the rearmost wheels on the rear track units.

Improved Mobility on Land and Water

The intention of Straussler was to have the tank as capable of moving on wheels as it was on tracks. This was not new, in the sense that the concept had been around for decades, most famously with wheel-cum-track machines, and the reason was exactly the same. Tracked vehicles tend to be better off-road, especially on a soft surface, as the tracks spread the load on the ground and gain more traction, whereas wheeled vehicles are better on hard surfaces, like roads. With less weight moving around, there was also less wear and tear.

In order to change between wheels and tracks, Straussler envisaged a hydraulic jacking system, whereby the center 2 pairs of rollers on each side could be lifted. By doing this, it would transfer the weight of the vehicle to be borne by the large driven rollers at opposite ends of each side. The tracks, once removed, could then be gathered up and stowed on the tank, as it would be driving on just the four driven rubber-tired road wheels.

When in the water, propulsion would be provided by both the tracks and by the electrically driven propeller at the back, which could be both steered as well as raised, so it did not foul with obstacles under the vehicle when not in use. When traveling in the water, the fabric screen would be erected from its collapsed position in the trough around the outside edge of the tank. The screen would neither make the tank taller than it had been beforehand, nor wider or longer. It would, in fact, only serve to displace enough water to provide the buoyancy the tank needed whilst floating in the water. The closest vehicle showing how this might have looked in real life if it had ever been made, is the Swedish S-tank.

Screen used on the S-tank followed Straussler’s basic floatation principle and method for tanks. Note how the design has to be modified to go around the barrel – something his MBT design circumvented by mounting the screen on the roof.
Source: Pinterest

Of note during the transit of the tank through water by this method is that Straussler envisaged that it could be used as a transporter too. Specifically, he stated that between 15 and 20 men could be accommodated on the roof, enough to form a small assault party to seize a structure or other without the need for boats.

This was not the only potential use for the roof space either. Quite why Struassler thought that adding a rocket launcher might add value to his design is unclear, although his inspiration perhaps might stem from something like the ‘Calliope’ system. He declined to outline what sort of rockets or other items might be mounted. It is possible, therefore, that he was thinking of this type of chassis for being the basis for vehicles like a bridge layer, but he declined to elaborate on the comment. Be it for rockets or men, the roof was available for transport, but hopefully not at the same time for safety reasons.

Suspension

The most complicated part of Struassler’s design was not the unusual gun mount, vehicle layout or even the roof-mounted screen and rockets. Instead, it was the suspension and this, perhaps more than anything else, is the primary defect of the design.

Nicholas Straussler was undoubtedly a talented engineer and had paid a lot of attention to vehicle suspension before WW2. In 1935, he filed a patent for a centrally pivoted system with separate sprung wheels as outriggers on each end and secondary sprung wheels underneath to provide tension and spread ground pressure.

Straussler’s patented suspension system from 1935. Note that this image has been digitally cleaned.
Source: British Patent GB453200

Straussler’s 1935 patent suspension shown on his 10-tonne V-4 design before WW2. The amount of movement from the front and rear wheels is readily apparent during this movement of the vehicle by a crane.
Source: Pinterest

The lineage of thought from this 1935 design to his MBT design is readily apparent with a close examination of the drawing provided. The same basic system was maintained, with a central pivot (dark blue) on a longitudinal frame (orange) and with a pair of large wheels (yellow) at each end of the beam. Around these wheels would go the track (green), but this design provided track tension and springing slightly differently. Instead of the coil springs as used in 1935, this design clearly made use of long leaf springs (light blue) linking the large wheels via their pivoting sub-frame (pink). With that long spring leaf above the central pivot, there was a single return roller (light orange) mounted centrally, directly above the pivot for the whole unit. Directly below this central pivot was another addition to his 1935 idea, and second tensioning wheel (light orange) and one which also served to provide track tension, as it was attached to another spring leaf (light blue) which was shorter than the top one but also attached to the sub frame for the main road wheels. In this way, whichever way the entire unit rotated during passage over the ground, this wheel would be pushed down against the track, providing tension and contact of the track with the ground. Likewise, when the hydraulic system was used to rotate the track units, it would be done to put one end of the unit in contact with the surface, presumably a road. With or without the track units fitted, this would serve to elevate the tank somewhat.

However, despite the seemingly advantageous nature of this suspension, Straussler chose not to patent it.

The complex suspension and track unit from Struassler.
Source: The Tank Museum, Bovington, modified by the author

In ‘wheel-mode’ for road-marching, the track units hydraulically rotated with or without tracks. The vehicle would be elevated by this process, as identified by the change in ground level shown in by the red arrows.
Source: The Tank Museum, Bovington, modified by the author.

Conclusion

This vehicle was far from Straussler’s last design for anything, let alone military items. By the late 1950s, Straussler had retired from running a business but not from inventions. Living in Geneva, Switzerland, he continued to produce designs including a folding boat and a folding motorized tricycle, amongst other things. He returned to England and died in London in 1966, aged 75, leaving a long history of inventions and his folding screen floatation system as his defining legacy.

The Straussler MBT, however, was not one of them. The design was not going to get any interest from the authorities who, at the time, would have been building more conventionally designed vehicles, such as the Chieftain. The concepts in inherent amphibious capacity were useful ones, but not essential and the light armor and unusual suspension were perhaps just a step too far for the authorities to engage with. Likewise, the roof-mounted rockets were an unnecessary addition and added nothing to the fightability of the design and in fact detracted somewhat from the otherwise clever idea to have the roof plate serve as a means of transport for troops over a water obstacle.

Perhaps the cleverest part of the design is the hardest to see in the side view – the loading system. The British were not advocates at the time of automatic loading systems, let alone one mounted in the manner Straussler designed, but the ability to mount the gun in this way would have provided the vehicle with the ability to deliver substantial firepower quickly against an opponent, creating the effect of more than one conventional tank for less than half the crew.

It is hard to assess Straussler’s design as being perhaps a step too far as an invention and this perhaps is reflected in the lack of a patent submission for what was a novel layout and could quite rightly have received legal protections. Straussler was certainly no stranger to the process and maybe it is the fact that he did not specifically try and protect this layout that indicates that even he felt it had serious limitations too. The design today is in the files in the archive of The Tank Museum, Bovington, a mostly forgotten idea from one of the foremost engineering freethinkers of his generation.

Straussler Main Battle Tank. Illustrations by the Glorious Pavel Carpaticus funded by our Patreon Campaign.

Straussler Main Battle Tank specifications
Dimensions (L-L-W-H)	~4.50 (hull), ~6.80 (over gun), 3.15, 1.70 m
Weight	25 tons
Crew	2 (driver, commander/ gunner)
Engine	700 – 800 hp multifuel or Wankel type with electric drive. Propellor for propulsion in the water.
Speed	65 km/h (on land using tracks), 80 km/h (on land using wheels)
Armament	Fully automatic 120 mm gun with 31 rounds 4 machine guns in a pair of remotely operated turrets

Sources

British Patent GB1622, Rotary Internal Combustion Engine, filed 21st January 1911, granted 21st September 1911
British Patent GB453200, Improvements in or relating to wheel suspensions for endless track vehicles, field 4th March 1935, granted 4th September 1936
British Patent GB623427, Improvements in buoyancy imparting means for vehicles, filed 10th December 1946, granted 17th May 1949
England and Wales Marriage Registration Index, 1837-2005, Page 746, Volume 1A.
England and Wales Marriage Registration Index, 1837-2005, Page 801, Volume 1A.
England and Wales Death Registration Index 1837-2007, Page 268, Volume 17.
England and Wales Death Registration Index 1837-2007, Page 701, Volume 5C.
England and Wales Birth Registration Index, 1837-2008, Page 530, Volume 1A.
Fletcher, D. (2020). Strausslers and Alvis. https://www.keymilitary.com/article/strausslers-and-alvis

Cold War British MBT Prototypes Has Own Video

Vickers Mk.7/2

The Vickers Mk.7/2 Main Battle Tank. Illustrated by Andrei 'Octo10' Kirushkin.

United Kingdom (1984-1986)
Main Battle Tank – 1 Built

Despite the progressive weakening of the Soviet Union in the 1980s, the prospect of a nuclear war in Western Europe was perhaps just as likely in that decade as anytime during the Cold War. The significant quantitative advantages that the Warsaw Pact had in tank terms had led to a serious rethinking in NATO as to how to increase the survivability and fightability of their own tanks. That redevelopment had been assisted in no small amount by the British development of a new type of armor called Chobham. This new generation of tanks had left some designs out in the cold and one of those was the Vickers Valiant or Vickers Mk.4. The Valiant failed to receive orders and was seriously damaged in a transportation accident. Its biggest problem, however, was considered to be the relatively low mobility, as the emphasis of the design had been on acceleration and torque rather than top speed.

With the design a failure and the need for a new successful product, the firm of Vickers was spurred at the end of the Valiant project to combine its own Universal Turret concept with a new high mobility hull and was considering its own options for a Valiant 2. When the hull for Valiant was ruined in an accident and with significant money already spent by Vickers and its partners, it needed a new option.

The solution to both a new hull and the mobility problem was found in the form of the West German Leopard 2 hull and mating the Vickers Universal Turret to that hull produced a very capable vehicle known as the Vickers Mk.7/2. The market being eyed was, once more, the lucrative Middle Eastern one.

Vickers Mk.4 / Valiant during early trials. Source: Vickers

A model of the Vickers Mk.7 MBT with 120 mm L11A5 rifled gun. Note the position of the smoke grenade launchers is on the turret cheeks. Source: Janes

The work on the Vickers Mk.7 built on the experience and knowledge of the engineers at the British firm of Vickers. That company, which had nearly a century of tank building experience was based in Newcastle-Upon-Tyne in the northeast of England. They had some export success with the Vickers Mk.3 and some failure in the form of the Mk.4 – better known as the Valiant. The success of the Valiant though was a Universal Turret concept. This turret could fit a variety of tanks through the use of a universal coupling, a design that also permitted the Vickers Shipbuilding 155 mm howitzer turret to fit a variety of vehicles. With the new Chobham-based armor package, this turret also offered a choice of guns that could be fitted, such as the RO L7 and L11 105 mm and 120 mm rifles and the Rheinmetall 120 mm smoothbore. The turret was a state of art design with modern optics, fire control, and armor, so adding this turret to the existing hull of the Leopard 2 provided a vehicle arguably better than the Leopard 2 or any other NATO tank then in service. From the Leopard 2 addition to the turret, the name was given as ‘Mk.7/2’.

An array of contemporary NATO tanks left to right: Chieftain, Challenger, Leopard 2, M1 Abrams and the Vickers Mk.7/2. Source: Pinterest

Layout

The Vickers Mk.7/2 followed a conventional tank layout, with the driver in the front of the hull, the turret roughly centrally, and the engine in the back. The hull was identical to that of the Leopard 2. The turret was large and rectangular with vertical sides and an angled front made from flat panels. The gun, located centrally on the front of the turret, was flanked by a pair of smoke dischargers when it was on the Valiant. These would later be moved to the rear sides of the turret. On the roof were two circular hatches for the commander on the right, and the loader on the left. A rectangular sight was provided on the front right of the turret roof for the gunner who, in keeping with British general tank-layouts, was located on the right, in front of the commander. All 3 turret crew were positioned on a turntable that rotated with the turret and which was supported on steadying rollers as opposed to the conventional turret-basket concept. The floor of this rotating platform was covered with non-slip aluminum plating and also contained the ready-ammunition stowage.

The final crew member, the driver, was located in the hull on the front right, with an ammo rack to his left. The driver lay in a reclining position with automatic controls and steered by means of a wheel with a conventional accelerator and brake pedals.

Vickers Mk.7/2 outside the Vickers Scotswood Road plant, Newcastle-Upon-Tyne. In the background is Scotswood Bridge. The unusual angular structure just to the left of the image is the turret testing building. Source: Vickers

Unveiling

Early ideas of using the upgraded Universal Turret from the Valiant project (repaired after the accident) had been looking for a new hull with improved mobility. Initially, Vickers had considered the existing Challenger 1 hull which would mean a joint Venture with Royal Ordnance Factory Leeds where it was made. At this time, however, ROF Leeds and Vickers were direct rivals competing for the same markets so this concept proved untenable. The German firm of Krauss-Maffei in Munich however, was much more receptive and, at the time, a hull with no weapons was not subjected to export controls meaning that, from the German point of view, that they could effectively be selling Leopard 2 hulls to countries where the government had export bans in place for a whole tank.

Work on the Mk.7 began in 1984 after trials of the Valiant elicited interest in the advanced turret with a goal to demonstrate the tank in the summer of 1985. The vehicle was unveiled on time in June 1985 and was set for Middle East demonstrations shortly thereafter.

Optics

A tank that is blind is worse than useless and modern optics are essential to the survivability and fightability of any vehicle. The optics for the Mk.7/2 were concentrated, as would be expected, in the turret.

The commander was provided with a slightly raised cupola consisting of 6 fixed x1 magnification non-reflecting Heliotype viewers. Sighting for the commander was provided by the French SFIM VA 580-10 2-axis gyro stabilized panoramic (360 degrees) sight. This sight had various magnification modes, x2, x3, and x10 and incorporated an nd-YAG-type laser rangefinder. In addition to this is a PPE Condor-type 2-axis gyro-stabilised image intensifier (Phillips UA 9090 thermal sight) displayed on a 625-line television monitor for both gunner and commander alike.

Commander’s station inside the Vickers Universal Turret here mounted on the Leopard 2 hull as Mk.7/2. Source: Foss and McKenzie

The gunner had a x10 magnification Vickers Instruments L31 telescopic laser sight with Barr and Stroud LF 11 nd-YAG-type laser rangefinder fitted with a projected reticle image (PRI) for ranging. In addition to this, he was provided with a Vickers Instruments GS10 periscopic sight for target acquisition. The loader was provided with a single AFV No.10 Mk.1 observation periscope.

Gunner’s station inside the Vickers Universal Turret here mounted on the Leopard 2 hull. Source: Foss and McKenzie

Tracks and Suspension

The tracks and suspension for the Mk.7/2 were identical to those on the Leopard 2, as this was the hull on which the Vickers Universal Turret was placed. As such, suspension was provided by means of torsion bars for each of the 7 road wheels and 4 return rollers. Additional rotary shock absorbers were fitted to wheel stations 1, 2, 4, 6, and 7, and the 635 mm wide track was made by Diehl and fitted with removable rubber pads with rubber-bushed end connectors.

Vickers Mk.7/2 during cross-country trials at Bovington. Source: Vickers

Automotive

The automotive elements of the Vickers Mk.7/2 were dependent on the engine and transmission of the Leopard 2 main battle tank. This meant that the power was provided by the German MTU MB873 Ka-501 12-cylinder 4-stroke turbocharged diesel engine delivering 1,500 bhp and a Renk HSWL 354/3 hydro-kinetic planetary gearbox containing all of the gear change and steering and providing 4 forward and two reverse gears. The top speed was 72 km/h. In the event of a failure of the automatic gear, the transmission could be used in manual mode with a single forward and reverse gear.

Vickers Mk.7/2 during trials at Bovington showing the power of the German MTU engine on the cross-country course. Source: Vickers.

Armor

The Federal Republic of Germany (‘West Germany’) had received Chobham technology via the Americans after the British had shared it with them so it had come full circle to now have a German tank with the British Army and now a British turret to try and meet an export market in the Middle East. The hull armor was identical to that of the Leopard 2, with Chobham-type armor across the frontal arc on top of a rolled homogeneous steel armored base. The Valiant had saved a lot of weight using the unconventional approach of an all-welded-all-aluminum-alloy armor hull. Now, with the larger Leopard 2 hull in steel, the weight had gone up but, likewise had the engine power to move the vehicle

The turret was also a steel base structure and, although the exact makeup was never released, it should be borne in mind that the Valiant (or Mk.4, as it was originally) was based on the technology from the Mk.3. The Mk.3 had moved from an all-welded steel turret to a partially cast one to improve ballistic protection. Despite this switch, it appears that, in order to accommodate the blocky sections of Chobham, Vickers returned to an all-welded steel structure. This would be different to the Challenger 1 then coming into service – this had a complex steel half-casting covering part of the roof, sides, and all of the front to which rolled homogeneous armor was welded to complete the structure followed by the Chobham packs to complete the external appearance. Chobham armor covered the whole front of the turret and the sides to approximately ⅔ of the way back, at which point they became hollow boxes for storage around the rear corners. In the center of the turret at the back was the large and effective nuclear, biological, and chemical warfare air filtration system made by Westair Dynamics. Mounted externally, the unit was easy to access, making replacement and maintenance easier and consisted of a multi-stage high-efficiency filtration process and worked to create an overpressure inside the tank which served not only to keep gases out of the tank but also to evacuate fumes from the weapons.

An automatic fire fighting system, the Graviner Firewire CO2-based (could be switched for other gases, like Halon) was fitted to the Valiant, and an automatic fire fighting system from the Leopard was simply used on this Mk.7.

Firepower

The Universal Turret’s enormous selling point was not only the coupling allowing it to be mated to a wide variety of the most common tank hulls in the world’s armies at the time, but also the choice of different guns on offer. The Valiant had started with the reliable Royal Ordnance L7A3 105 mm rifled gun but this was quickly switched out for the L11A5 120 mm rifled gun. When it came to the Mk.7/2 tank, there was no option for the 105 mm gun as no potential buyer would have wanted one, as this was now the age of the 120 mm gun for NATO tanks. If the purchaser did not want the very capable L11A5 rifle, they could also choose the Rheinmetall 120 mm smoothbore which had been approved for the German Leopard 2 and the American M1A1 Abrams. With probably the most reliable hull in the world at the time (the Leopard 2), and this turret featuring some of the most advanced fire control of any vehicle, the addition of the best tank gun available in NATO and armor to match any contemporary, the Mk.7/2 was a true world-beater. Exports of this tank would technically and potentially mean that the UK was selling tanks as good as, or better than its own and those of its allies.

Ammunition storage for the 120 mm Rheinmetall smoothbore ammunition amounted to 44 rounds (20 in the hull front, 15 in the turret bustle, and 9 in the ready rack in the turret). With the British 120 mm L11A5 rifle storage was listed as being reduced to just 38 rounds. The reason for the low amount of stowage is unclear, as with this turret, the smaller Vickers Valiant was able to store 52 rounds and the turret was unchanged stowage-wise. Fifteen in the turret, plus an additional 20 in the hull rack next to the driver would make 35 meaning just 3 rounds in the ready rack instead of 9.

Vickers Mk.7/2 MBT being put through its paces during trials. Note the smoother sides of the turret with the permanently incorporated Chobham armor packs and the grenade launchers now moved back. Source: Pinterest.

The elevation range for both of the guns was identical at -10 to +20 degrees. Loaded manually, the rate of fire was given as 10 rounds per minute (1 every 6 seconds). A Vickers muzzle reference system (MRS) on the end of the barrel added additional information into the computer system and the barrel was clad in a thermal sleeve to reduce distortion.

The fire control system and gun stabilization system was an all-electric system developed by Marconi. This system had a built-in laser rangefinder and a brand new ballistic computer to improve the chances of a first-round hit against static and moving targets as well as for supporting firing on the move. This system used the SFCS 600 computer derived from the GCE 620 system installed on the Vickers Mk.3 with some improvements known as the Marconi Radar Systems Centaur 1 system.

Vickers Mk.7 during firing trials at Lulworth sporting a two-tone camouflage scheme. Source: Vickers.

The RO L11A5 120 mm gun made by Royal Ordnance, Nottingham, was 7.34 m long and weighed 1,782 kg. It featured improvements over the earlier designs by using a forged upstand for the muzzle reference system and featured a smaller volume and lighter fume extractor than the L11A2. As a result of these changes, the gun was out of balance, so 7.7 kg of additional weights had to be added to counterbalance it normally.

Secondary armament included a single 7.62 mm Hughes chain machine gun mounted coaxially with the main gun and a second 7.62 mm machine gun (L37A2) in a remote-control mount next to the commander’s cupola on the roof. In total, 3,000 rounds for these could be carried. Both of these weapons were interchangeable with a variety of commercially available 12.7 mm machine guns.

The Vickers Universal Turret as it would later be advertised for the Mk.7/2 fitted with the Rheinmetall 120 mm smoothbore gun. Note the storage for 15 rounds in the turret bustle. Source: Lobitz.

Fitted with the British L11A5 rifled gun, firing trials were conducted in Egypt in 1985. In total, 43 rounds of Armor-Piercing Discarding Sabot (APDS) ammunition were fired at targets 2.6 m high between 1,100 m and 2,600 m, achieving a total of 32 hits – 74.4% accuracy. A second set of 40 shells (26 APDS and 14 Practice) were fired at the 2.6 m high stationary target between 1,100 m and 3,000 m, achieving 33 rounds on target – 82.5 % accuracy.

When the firing trials were repeated against a mix of stationary and moving targets using both gunner and commander’s stations to control the firing, a total of 65 APDS rounds were fired at ranges from 1,100 m to 2,370 m. In total, 37 rounds hit the target – 56.9 % accuracy.

A rate of fire of 6 rounds in just 43 seconds could be achieved using High Explosive Squash Head (HESH) ammunition (8.4 rounds per minute). In perhaps one of the most peculiar firing trials ever asked of a tank, the Egyptian team had the Mk.7/2 driven up an 18 deg ramp, brought to maximum elevation (20 deg.) and fired. The purpose was to test the strength of the coupling between the hull and the turret and firing an APDS shell to provide the stress. The British team expressed strong concerns about this test, not from the point of view of the coupling but because they really had no idea just how far an APDS round would go fired in this way even if the backdrop was the vast expanse of the Egyptian desert. Nonetheless, the round was fired, the coupling survived, and seemingly no random camel herd discovered the true range of a maximum elevation 120 mm APDS shell.

Vickers Mk.7/2 (labeled just as the Mk.7) combines the Vickers Universal Turret with 120 mm gun options and the proven German Leopard 2 hull. Note that this is an early image as the smoke grenade launchers are still on the turret cheeks. They were later moved to the rear sides of the turret.

Markets

The market for the Mk.7/2 was a large one: Egypt. Egypt had been trying hard to modernize its military and, in particular, its outdated tank fleet. Mated to the Leopard 2 hull, the Mk.7/2 had been finished and formally unveiled in the summer of 1985 and evaluated for reliability and other parameters. Late on in that summer, the combined Vickers and British Army demonstration team led by Peregrine Solly and the Mk.7/2 were shipped out to Egypt for a very rigorous examination of everything including reliability, ease of maintenance, mobility, and firing.

The driving assessment showed it to have a range of 263 km cross country with an average speed of 55 km/h and a top speed of 80 km/h. On soft sand, just 151 km were driven, but it is noteworthy that the area selected was impassable by any Egyptian vehicles then in service. There, the Mk.7/2 managed to traverse the ground albeit at a reduced average speed of just 39.4 km/h. A further 274 km were then driven off-road, where it was still able to reach a top speed of 80 km/h and an average speed of 60.3 km/h.

Vickers Mk.7/2 being put through its paces in desert terrain. Source: Vickers

Trials in the scorching 35° C Egyptian desert took place between 5th September and 1st October 1985 operated by both British and Egyptian crews. Firing trials showed the fire control system to be very good and that the MTU engine was easy to remove and maintain. Whether Egypt was ready to place an order is not known, but the Mk.7/2 had certainly made a good impression of itself. When the German government closed the chances of exporting the Leopard 2 hull, so ended the project and all chances of a contract with Egypt.

Termination

The tank had proven to be an effective combination of firepower and mobility. With the proven 120 mm British gun and the option to switch relatively easily to the German 120 mm gun if desired, and combined with the latest generation of optics, this tank was a fearsome opponent. With the Leopard hull, the tank gained a proven and reliable chassis and engine with the mobility found lacking on the Valiant but the project was just not going to happen. At the time, the export of an unarmed hull was not covered by German government export restrictions on arms, but by exploiting this loophole Krauss-Maffei could, in effect, circumvent the restriction to put a German-hulled tank into the hands of a nation which might other not be able to obtain the Leopard 2. It would also mean that countries that could buy the Leopard 2 could also buy this version which was better in many ways and also outside of the control of the German government. Virtually, at a stroke of a pen, the project was thus killed, the German government canceled the export of tank hulls, and lacking their own alternative, the Vickers Mk.7/2 was dead. A somewhat ignominious end to probably the best tank of the day.

Conclusion

The Valiant had not been a success and had died in ignominious circumstances only to be reborn as the Mk.7. The early plan to mate this excellent Universal Turret with the hull of the Challenger 1 to make the Mk.7 had failed due to competing business interests with ROF Leeds. Ironically, Vickers acquired ROF Leeds in 1986, when it won the contract for the Challenger Armored Repair and Recovery Vehicle. At the same time, Vickers had also taken over design authority from Royal Armament Research and Development (RARDE) at Chertsey. Yet this had come too late for the Mk.7 and, with the availability of the Leopard 2 hull, the chances for a second Mk.7 had appeared as the Mk.7/2. This was a world-leading design and yet, thanks to the German government pulling the plug on export licenses for the hull, this too failed. With no more options and no contracts for other vehicles, the attention for a market for the turret shifted from European and Middle Eastern eyes to South America. The technology of the Vickers Mark 7/2 turret seems to have been merged with that of the Vickers Mark 4 turret in order to create two brand new turrets for Brazil’s new MBT by Engesa, the Osório, which would also meet a similar ignoble end despite promising beginnings. The Mk.7/2 marks a true lost opportunity for a truly world-class vehicle.

The Vickers Mk.7/2 Main Battle Tank. Illustrated by Andrei ‘Octo10’ Kirushkin.

Vickers Mk.7/2
Crew	4 (driver, gunner, loader, commander)
Dimensions	10.95 m long (with gun), 9.77 m (gun to the rear), 7.72 m (hull length only), 2.54 m high (turret roof), 2.99 m (top of commander’s sight), 3.42 m wide (without side armor packs, 4.945 m of track on the ground.
Ground Clearance	0.5 m
Weight	55,000 kg
Engine	German MTU 873 12-cylinder diesel engine delivering 1,500 hp at 2,600 rpm
Speed	80 km/h top speed on a good surface. Up to 60.3 km/h cross country(road). Very soft sand 39.4 km/h.
Suspension	Torsion bar
Armament	L11A5 120 mm rifled main gun, coaxial 7.62 mm or 12.7 mm machine gun, roof-mounted remote-control 7.62 mm or 12.7 mm machine gun. Rheinmetall 120 mm smoothbore.
Armor	steel base hull and turret with Chobham armor arrays across frontal 60-degree arc.
For information about abbreviations check the Lexical Index

Sources

Cold War British MBT Prototypes

Vickers Mk.7

The Challenger 1-based Vickers Mark 7 mated the turret of the Vickers Mark 4 with the new hull. Illustration by Andrei 'Octo10' Kirushkin

United Kingdom (1984-1986)
Main Battle Tank – None Built

The Newcastle-based firm of Vickers Defence Systems had been building tanks on Tyneside for decades but had struggled in the 1980s to find markets for its tanks. With the unveiling of the Chobham armor technology in 1976 and Vickers being brought into the committee on its use, they obviously wanted to make use of this latest protection technology for their own tanks to try and meet the new export markets. The first attempt to move beyond the otherwise very competent Mk.3 design was the Mk.4, later reworked and known as the Valiant. The Valiant was a solid design with several significantly advanced features such as the all-aluminum hull and brand new fire-control system. When the Valiant failed to receive any orders, plans were put in place to upgrade the mobility aspect of the vehicle, but the hull was lost to an accident leaving just the turret needing a new body. A solution proposed was to use the already in production Challenger 1 hull for this to create a brand new tank – the Vickers Mk.7.

The British Challenger 1 MBT. Source: Mark Nash Photography

The background

The Mk.7 started life as a goal to combine Chobham armor technology with the experience gained in the production of the Mk.3. The first attempt had been the Mk.4, a new turret made from cast steel with Chobham armor and an all-aluminum hull. That project was let down very early by the RO L7A3 105 mm gun which, despite being an excellent gun in its own right, was simply inadequate for the modern battlefield with a new generation of Soviet tanks like the T-72 fielded and exported in increasingly large numbers. The Mk.4 turret, therefore, was redeveloped quickly to be a ‘Universal’ Turret, one with a carefully designed mounting able to take the L7A3 105 mm, the L11A5 120 mm, and even the German 120 mm smoothbore. In this way, it could appeal to both first-world armies who wanted a 120 mm gun and also to an export market where a 105 mm gun might be considered a cost-effective alternative. The vehicle was quickly rebranded as the Valiant.

Vickers Mk.4/Valiant during early trials. Source: Vickers

The Valiant had also included a state-of-the-art suite of fire control making it a very potent machine for delivering firepower on the battlefield. Its drawback had been an automotive one and despite plans in hand for an improved version, an accident wrecked the hull.

Slipping off a low loader, the Valiant fell onto its side and rolled on the roof, causing damage to the optics and causing irreparable damage to the hull. Source: arrse.co.uk

With the loss of the Valiant hull, ideas for improvements based on the Valiant’s automotives had to be shelved, as there was no budget to design and build a new hull. Instead, the work was done to salvage the turret, repair the optics, and hunt for a new hull with hopefully some improved mobility.

The first candidate for this new hull was that of their direct opposition, the Challenger I hull of ROF Leeds. Their proposed marriage would have been the first instance of the Vickers Mark 7, but it never got further than a proposal.

Optics

The optics for the Universal Turret were state of the art for the time. Firstly, the commander was provided with a slightly raised cupola consisting of 6 fixed x1 magnification non-reflecting Heliotype viewers. Sighting for the commander was provided by the French SFIM VA 580-10 2-axis gyro stabilised panoramic (360 degreesdegree) sight. This sight had various magnification modes, x3 and x10 and incorporated ana Nd-YAG-type laser rangefinder. In addition to this was a PPE Condor-type 2-axis gyro-stabilised image intensifier (Phillips UA 9090 thermal sight) displayed on a 625-line television monitor for both gunner and commander alike.

Gunner’s and commander’s stations inside the Vickers Universal Turret. Source: BAE

The gunner had a x10 magnification Vickers Instruments L30 x10 telescopic laser sight with Barr and Stroud LF 11 Nd-YAG-type laser rangefinder fitted with a projected reticle image (PRI) for ranging. In addition to this, he was provided with a Vickers instrumenta Vickers instruments GS10 periscopic sight for target acquisition. The loader was provided with a single AFV No.10 Mk.1 observation periscope. The driver’s optics consisted of a single wide-anglewide angle episcope in the centre-front of the hull

Firepower

The Universal Turret was able to mount a choice of main gun with the two primary options being the British 120 mm L11A5 rifled gun or the German 120 mm smoothbore from Rheinmetall with ammunition storage in the hull, turret bustle, and with a ready rack in the turret basket.

Elevation for the main gun was limited to -10 to +20 degrees and, loaded manually, the rate of fire was given as 10 rounds per minute (1 every 6 seconds) with the British 120 mm gun. A Vickers muzzle reference system (MRS) on the end of the barrel added additional information into the computer system and the barrel was clad in a thermal sleeve to reduce distortion.

The fire control system and gun stabilisation system was an all-electric system developed by Marconi. This system a built-in laser rangefinder and a brand new ballistic computer to improve the chances of a first-round hit against static and moving targets as well as for supporting firing on the move. This system used the SFCS 600 computer derived from the GCE 620 system installed on the Vickers Mk.3 with some improvements known as the Marconi Radar systems Centaur 1 system.

The Vickers Universal Turret as it would later be advertised for the Mk.7/2 fitted with the Rheinmetall 120 mm smoothbore gun. Note the storage for 15 rounds in the turret bustle. Source: Lobitz

The RO L11A5 120 mm gun, made by Royal Ordnance, Nottingham, was 7.34 m long and weighed 1,782 kg. It featured improvements over the earlier designs by using a forged upstand for the muzzle reference system and featured a smaller volume and lighter fume extractor than the L11A2. As a result of these changes, the gun was out of balance so 7.7 kg of additional weights had to be added to counterbalance it normally.

Secondary armament included a single 7.62 mm machine Hughes chain gun mounted coaxially with the main gun and a second 7.62 mm machine gun (L37A2) in a remote-control mount next to the commander’s cupola on the roof. In total 3,000 rounds for these could be carried. Both of these weapons were interchangeable with a variety of commercially available 12.7 mm machine guns.

Layout

The turret was large and rectangular with vertical sides and an angled front made from flat panels and with the gun located centrally on the front of the turret. On the roof were two circular hatches for the commander on the right, and the loader on the left. A rectangular sight was provided on the front right of the turret roof for the gunner who, in keeping with British general tank-layouts, was located on the right, in front of the commander. All 3 turret crew were positioned on a turntable which rotated with the turret and which was supported on steadying rollers as opposed to the conventional turret-basket concept. The floor of this rotating platform was covered with non-slip aluminium plating and also contained the ready-ammunition stowage. The turret sat on the Challenger 1 hull which was conventionally arranged with the driver in the front, fighting compartment in the middle on top of which the turret sat, and engine compartment in the rear.

Armor

The turret was a steel base structure and, although the exact makeup was never released, it should be borne in mind that the original Valiant (or Mk.4 originally as it was) was based on the technology from the Mk.3. The Mk.3 had moved from an all-welded steel turret to a cast one to improve ballistic protection and, although the technology for the Mk.4 followed much of the lessons from the Mk.3, it appears to have switched back to an all-welded turret in order to accommodate the block-like Chobham armor packs on top. This would be in contrast to the Challenger 1, then coming into service, which used a front half made from a complex steel casting and welded rear portions with the Chobham packs over the front and sides.

Chobham armor covered the whole front of the turret and the sides to approximately ⅔ of the way back, at which point they became hollow boxes for storage around the rear corners. In the centre of the turret at the back was the large and effective nuclear, biological, and chemical warfare air filtration system made by Westair Dynamics. Mounted externally, the unit was easy to access making replacement and maintenance easier and consisted of a multi-stage high-efficiency filtration process and worked to create an overpressure inside the tank which served not only to keep gases out of the tank but also to evacuate fumes from the weapons.

The hull used heavy sections of Chobham across the front and sides with the driver sat recessed within the armour at the centre-front of the tank. Spaced armour covered most of the upper sections of the hull and all this combined to make the Challenger 1 one of the best protected tanks of the era.

Tracks and Suspension

The tracks and suspension for this vehicle were identical to those on the Challenger 1, with 6 large road wheels, each on a swing arm. Each wheel had a rubber tyre and ran on steel tracks fitted with removable rubber pads. The suspension was an improvement over the torsion bars of the Valiant and consisted of hydropneumatic units.

Automotive

Power for the vehicle was provided by the Rolls Royce CV12 26-litre diesel engine located in the rear of the hull. Producing 1,200 hp and delivering it through a David Brown TN37 automatic transmission with 4 forward and 3 reverse gears. As the complete Challenger 1, the vehicle had a top speed of 56 km/h and with the new turret would be around the same weight so likely a very similar performance as well.

The Rival and the Name

At this time, around 1983, Vickers Defence systems was a direct rival to the Royal Ordnance Factory Leeds which was producing the Challenger 1 MBT. The Challenger 1 was just entering service with the British Army as the replacement for the Chieftain. Both the Valiant and Challenger 1 had already been rivals during British Army trials in 1982 and, despite more capable the fire control system of the Valiant, the Challenger had won out. Vickers were left needing a new foreign market for the tank and a new hull. Asking for a joint partnership with ROF Leeds to use the Challenger 1 hull when ROF already had the Challenger in production and were seeking overseas orders was simply not viable and, understandably, the project ended before it even began. When the solution appeared in the form of the Leopard 2 hull being made available from the German firm of Krauss-Maffei, the turret found a new lease of life as the Mk.7/2, implying that Mk.7 was just to be the original Valiant turret/Challenger hull combo or that Mk.7 was the general ‘fit the Valiant turret onto an MBT platform’ project name.

Vickers Mk.7/2 outside the Vickers Scotswood Road plant, Newcastle-Upon-Tyne. In the background is Scotswood Bridge. The unusual angular building just to the left of the image is the turret testing building. Source: Vickers

Given that when the Mk.7/2 was unveiled, it was identified as the Mk.7, it is logical to assume the latter and that the ‘2’ was added retrospectively.

It is with some irony perhaps that in Egypt, in 1985, the Mk.7/2 was tested against the rival Challenger 1 and the fire control system once more proved itself to be superior to that of the Challenger 1, which was suffering from issues with firing on the move and engagement speed.

As it turned out, the Egyptians bought neither the Mk.7/2 nor the Challenger 1, and less than a year later Vickers Defence Systems bought the ROF Leeds plant and with it the rights to Challenger 1 and was awarded contracts for the Challenger-based Armoured Repair and Recovery Vehicle (C.A.R.R.V.).

Vickers Mk.7/2 (labeled just as the Mk.7) combining the Vickers Universal Turret with 120 mm gun options and the proven German Leopard 2 hull. This is an early image of the turret as the smoke grenade launchers are still on the turret cheeks. They were later moved to the rear sides of the turret. Note the VFM Mk.5 in the background. Source: Unknown

At the same time, Vickers also acquired tank-design authority from Royal Armament Research and Development (RARDE) at Chertsey. Vickers, by 1986, therefore had all of the cards with the exception of the superior turret from the Valiant – that was repackaged and sold off to Brazil for their EE-01 Osorio. Instead of simply trying to get the British Ministry of Defence to replace Challenger 1 turrets with the Valiant Universal Turret as envisaged in 1984, Vickers had other plans.

Conclusion

In 1986, just a year after taking over ROF Leeds, Vickers submitted a completely unsolicited plan to the MOD for a new tank to replace the Challenger 1. At a time when the Challenger 1 was brand new in service, this was certainly a bold move. Development of the Challenger 2 was to start thereafter and a working prototype was ready by the end of 1989. The Challenger 2 was a completely new tank despite sharing a name and general shape with the Challenger 1 and built-in much of the preceding years’ worth of knowledge gained by Vickers. Development of the Challenger 2 finally gave Vickers the Chobham-armored tank they had wanted and started nearly a decade earlier.

Resolving the key problems with the Challenger 1, the Challenger 2 more than anything else perhaps best illustrates the potential Vickers had offered way back with the Valiant but which had been lost. The Valiant turret with the Challenger 1 hull would have resolved the fire control issues with the Challenger but it did not really resolve the mobility problem. The Mk.7/2 on the other hand, resolved the mobility problem but was stymied by the fact that the German government limited exports of the Leopard 2 tank hull. Having suggested using the Valiant turret on the Challenger 1 and being rejected, Vickers had simply moved on to a design to replace the Challenger so that, when they took over control, changing the turret on the old hull would not suffice. Instead, the new tank would improve on the old one in all areas.

The Challenger 1-based Vickers Mark 7 mated the turret of the Vickers Mark 4 with the new hull. Illustration by Andrei ‘Octo10’ Kirushkin

Specifications
Crew	4 (driver, gunner, loader, commander)
Propulsion	Rolls Royce CV12 26-litre diesel engine producing 1,200 hp
Speed	56 km/h (road)
Range/consumption	190 km (118 mi)
Armament	L11A5 120 mm rifled main gun, coaxial 7.62 mm or 12.7 mm machine gun, roof-mounted remote-control 7.62 mm or 12.7 mm machine gun. Rheinmetall 120 mm smoothbore.
Armor	Welded steel and Chobham
Suspension	Hydropneumatic
Production	None built

Sources

Ground Defence International #69. November 1980
Ground Defence International #70. December 1980
Janes. (1985). Arms and Artillery. Janes Defence Group
Ogorkiewicz, R. (1983). Vickers Valiant. Armor Magazine March-April 1983
Lobitz, F. (2009). Kampfpanzer Leopard 2. Tankograd Publishing, Germany

Cold War British MBT Prototypes Has Own Video

Vickers Mk.4 Valiant

United Kingdom (1977-1985)
Main Battle Tank – 1 Built

The Chieftain tank replacement?

The final decades of the Cold War saw a generational change in Western tanks as they faced off against the armies of the Warsaw Pact across Central Europe. The Soviet-led forces were dominated by tanks such as the T-55, T-72 and variants of both, and there were continuing concerns over even newer Soviet tanks with improved armor and firepower. The Western tank armies of NATO were dominated by an older generation of tanks in a long and slow process of improvement and replacement: the British wanted a replacement for the Chieftain, the Americans were replacing the aged M60 with the new M1 Abrams, and the Germans were replacing the Leopard I with the Leopard II. Much of that Western generational change from tanks based on steel armour had come about as a result of the British development of a new type of armor, announced in June 1976 as ‘Chobham’. A whole new level of protection for Western tanks promised to provide a true qualitative edge in protection over their Soviet contemporaries. With this new armor, and a need for a replacement for Chieftain urgently required, there was a clear opportunity for a large and lucrative contract for a new main battle tank for the UK, and potentially for export.

Vickers Mk.4 Valiant (Ground Defence International No.70 December 1980)

Based in Newcastle-Upon-Tyne in the northeast of England, engineers at the British firm of Vickers, with decades of tank building experience, were, at this time, developing a new ‘conventional’ tank for the export market: the Mk.3. Using the availability of this new Chobham armor, they applied that knowledge to their Mk.3 to produce one of the first of this new generation of tanks moving away from tanks reliant solely on steel armor, analog fire control and ranging to a new era of enhanced protection and digital fire control. Originally simply referred to as the Mk.4, it soon gained a much more marketable name, the Valiant.

Vickers Mk.3 MBT – a conventional tank reliant on steel armor was the apex of conventional steel tank design for Britain with good mobility and excellent protection on the turret. The arrival of Chobham provided a qualitative step-change in protection available to tanks. (Source: Foss and McKenzie)

Vickers Mk.4/Valiant during early trials. (Source: Vickers)

Layout

The Valiant followed a conventional layout with the driver in the center of the front of the hull, the turret roughly central, and the engine in the back. On top of the hull was the large rectangular turret with vertical sides and an angled front made from flat panels. The gun, located centrally on the front of the turret, was flanked by a pair of smoke dischargers, and on the roof were two circular hatches for the commander on the right, and the loader on the left. A rectangular sight was provided on the front right of the turret roof for the gunner who, in keeping with British general tank-layouts, was located on the right, in front of the commander.

Unveiling

Work on the Valiant began in earnest at the end of 1977 and progress began on manufacture from March 1978 through November that year and the initial turret was finished in September 1979.

A working prototype was being put through mechanical trials in June 1979, meaning it had taken less than 2 years to go from drawing board to the testing ground. Those automotive trials ended in September with some problems identified and the vehicle was returned to the factory for modifications in December. There, it was taken apart and thoroughly examined and the improvements started. Reassembled and improved, it was ready for unveiling to the British Army as a potential replacement for the aging Chieftain.

Vickers Mk.4 Valiant during early trials. Note the single periscope for the driver. (Source: Vickers)

When the British Army received this tank in March 1980 at Bovington Camp in Dorset, it was faced with a tank unlike anything it had seen to that point. Gone was the highly sloped casting of the Chieftain to try and deflect incoming shells. Instead, this was replaced with a very rectangular turret made up of a series of flat faces, the defining characteristic of a tank made with Chobham technology and a general shape for which this new Western tank-generation would exploit.

Trials of this new tank began immediately to check for automotive performance and firing trials over their course. The formal public unveiling took place at the British Army Exhibition at Aldershot in June 1980 along with its formal new name ‘Valiant’. This new development was made possible by the formulation of an international sales consortium with Societe de Fabrication d’Instruments de Mesure (SFIM) (responsible for the panoramic stabilized commander’s sight), Vickers Instruments (gunners, telescopic, and unitary sights), Marconi Radar UK (gun stabilization and fire control), Philips and Odelft of Netherlands (panoramic stabilized thermal imager), and Simrad of Norway (laser range finders for the commander and gunner) each of whom invested financially in the project.

With these new partners, the redevelopment of the turret unveiled in 1980 was progressed and manufacture commenced at the Elswick, Works of Vickers, in 1981 followed by a demonstration of the finished product in the British Army Exhibition at Aldershot in 1982. British Army trials were completed by late 1982 after the tank had covered over 4,500 km of automotive and operator trials with few problems.

Still bearing ‘Trade Plates VRM 447 BB’, the Valiant, with turret reversed is put through its paces. The single periscope for the driver dates these images to 1982.

British Army officers inspect the Valiant during trials. (Source: GDI)

Following the 1982 unveiling, a promotional video was created at Long Valley, Aldershot, with the vehicle painted in a very-non-standard camouflage scheme for dramatic purposes. The goal was not to show some new style of camouflage, but simply to be noticed despite the non-military emulsion paints used and not to be confused with the Chieftain 900 project: an armor and mobility upgrade option offered for the old Chieftain.

Fitted with the L11A5 120 mm rifled main gun and sporting a very fancy non-standard camouflage, the Valiant is put through its paces at Long Valley, Aldershot. (Sources: Janes)

The Chieftain 900 shows little resemblance with the Valiant hull although the general shape of the new turret led to a desire to visibly differentiate the Valiant. (Source: fighting vehicles.com)

Optics

The commander was provided with a slightly raised cupola consisting of 6 fixed x1 magnification non-reflecting Heliotype viewers. Sighting for the commander was provided by the French SFIM VA 580-10 2-axis gyro stabilised panoramic (360 degree) sight. This sight had two magnification modes, x3, and x10 and incorporated a Nd-YAG-type laser rangefinder and had been added to the design in 1979 following a tour of the plant by Derek Rile and Patrick Michon of SFIM as part of their UK-wide sales tour. In addition to this was a PPE Condor-type 2-axis gyro-stabilised image intensifier (Phillips UA 9090 thermal sight) displayed on a 625-line television monitor for the gunner and commander alike.

The gunner had a x10 magnification Vickers Instruments L30 x10 telescopic laser sight with Barr and Stroud LF 11 Nd-YAG-type laser rangefinder fitted with a projected reticle image (PRI) for ranging. This was mounted coaxially with the main gun, directly on the rotor for the gun eliminating mechanical error. In addition to this, the gunner was provided with a Vickers Instruments GS10 periscopic sight for target acquisition mounted on the roof. The loader was provided with a single AFV No.10 Mk.1 observation periscope. The driver was well equipped with optical equipment too, including his own image intensifier, a PPE Badger Jenno viewer.

Through the clever use of electronics, the commander could access the imagery from both the gunner’s 2-axis gyro-stablised day-sight (and independently operate it), as well as the driver’s optics. Originally, the driver was provided with just a single wide-angle AFV No.44 Mark 2 modified periscope, but this was supplemented by the end of the 1982 trials with an additional periscope on each side of the original. The range of the night vision was limited to 1,200 m for the gunner and commander and 500 m for the driver.

Tidworth 1982. The Vickers Valiant strikes an imposing image next to the shorter Chieftain. (Source: asrrse.co.uk)

Tracks and Suspension

The original tracks and running gear from the Vickers Mk.3 were changed out in December 1979 for a wider track on which the Mk.4 was running by March 1980. Running on six large rubber-tyred road wheels, similar to those on Chieftain, each wheel station was, however, attached to a trailing arm connected to a torsion bar. Additional secondary torsion bars were mounted inside the trailing arms for the arms of wheel stations 1, 2 and 6. During operation over particularly rough terrain, these secondary bars could be released to provide additional shock absorption. In addition to this, stations 1, 2, and 6 also had hydraulic shock absorbers. With the adoption of the Universal Turret for the 120 mm gun and the additional weight this brought about an improvement whereby all wheelstation-trailing arms were fitted with the secondary torsion bars. Later this type of suspension was changed to a hydrogas suspension system on a vehicle designated as Valiant 2.

The track, like that of the Mk.3, was a manganese steel single connector type. It was 558 mm wide, having replaced the original 520 mm wide track from the Vickers Mk.3 and provided additional ground contact on which to spread the weight of the vehicle, reducing ground pressure to between 0.81 kg/cm2 and 0.83 kg/cm2. On its return run, the track was supported by 3 small rubber-tyred return rollers. Each side of the tank required 98 track links, each of which was fitted with a removable rubber pad to reduce road damage. Interestingly, Vickers’ own performance figures for the Valiant in its later form state a ground pressure of 0.92 kg/cm2 with a wider body (explained by the switch to wider side skirts with improved protection), a longer gun length (explained by the switch to a 120 mm gun), and a faster top speed (explained by the switch to the German MTU engine). All these modifications added weight and is the likely explanation as to why this ground pressure figure is higher.

Jimmy Nichol, Geoff Newcomb, and Brian Dillon from Vickers take a break during testing at Aldershot. (Source: Vickers)

Automotive

The emphasis on the maneuverability of the Valiant was not to focus on top speed, but on acceleration. This meant an emphasis on the available torque from the engine. Trials were done using the derated Rolls Royce CV12TCA Condor diesel engine delivering 1,000 hp at 2,300 rpm to roughly match the very similarly sized General Motors 12V71T diesel engine delivering 915 hp at 2,500 rpm which was also tried. Ideally, the goal was the use of the Condor delivering its normal power output of 1,200 to 1,500 hp. There was sufficient space in the engine bay for engineers at Vickers to also contemplate the use of the German MTU 872 1,200 hp diesel engine. Operating with the RR Condor at 1,000 hp, the vehicle was capable of 51 km/h on the road with a range of 380 to 603 km depending on weight and engine from a fuel tank holding just 1,000 liters. Later figures state 1,150 liters. Vickers’ performance figures for the Valiant give the top speed as 70 km/h presumably quoting a top speed for the most powerful engine option.

The 17.41 liter RR Condor engine made at the Rolls Royce plant in Shrewsbury was a V12 (60 degrees) diesel engine with a 135 mm bore and a stroke of 152 mm with a low compression ratio and turbo-chargers. The V12-1200A, as used on the Valiant, weighed just 2,638 kg complete with water-filled radiators and coolant and rated at 1,000 hp was eventually selected to power the Challenger MBT, Chieftain 900, the Indian Vijayanta and even a re-engined Chieftain project.

The engine was matched to an automatic gearbox with mechanical speed gear as well as a centrifugal clutch as the TN12-1000 gearbox. The TN12-1000 was developed from the one used on the Chieftain and Mk.3 providing gear-change efficiency improvements. The TN-12-1000 cross-drive transmission was produced by Self-Changing Gears Limited, Coventry, and weighed 1,361 kg, the same as the earlier TN-12 but was able to handle greater torque, specifically 3,660 Nm compared to 2,509 Nm of torque on the TN-12. The TN-12-1000 was also used in the Chieftain 900 and was able to manage engines up to around 1,200 gross hp.

This system provided 6 forward and 2 reverse gears. The important change was the elimination of the torque converter which reduced wasted torque from the power system, allowing for up to 150 hp of power available which would otherwise be wasted.

The vehicle was also fitted with an electrohydraulic differential which provided ease of steering and braking for the driver who, like on the Mk.3, steered using a very simple yoke system instead of tiller bars. The steering, by means of handlebars, little different to a bicycle, used a twist-grip throttle control, a simple handle for the brakes, and a button which served as an override for the gearchange to prevent the gearbox from the automatic change down for improved performance for example during cornering or when firing on the move.

The Valiant being put through its paces and providing a view of the Chobham armor packs fitted to the sides of the turret as well as the NBC pack at the back. The two corner sections are simple stowage bins. (Source: GDI)

Armor

Underneath the square-cut appearance lay a tank similar to the Vickers Mk.3. The regular armor of the Mk.4 provided protection against small arms and cannon fire but was insufficient to protect against direct fire from Soviet tanks, unsurprisingly, as without the Chobham, it weighed just 30 tonnes. The primary way in which this weight was kept so low was the use of an all-welded all-aluminum alloy armor for the main structure of the hull. The type of alloy used was developed from 7039 series aluminum armor produced by Alcan Specialty and Aerospace Limited of Birmingham, England to produce a material more resistant to corrosion, ballistically stronger, and with better resistance to stress. Chobham technology had been made available to Vickers by the Ministry of Defence when it was announced in 1976 and two company directors from Vickers served on the Chobham Armour Committee, so they were well aware of its potential.

The turret, on the other hand, was primarily made from steel with the Chobham armor packs added across the front and sides. The adoption of aluminum for the hull differed from the Mk.3, which had a conventional all-welded rolled armor steel hull. The turret itself followed on internally from the lessons of the Mk.3 using a cast steel front to produce a good ballistic shape which could not be matched in aluminum, and then with steel sections welded to the sides and rear in much the same fabrication manner as that used on Chieftain. It is not known, however, if when the turret was modified to take the universal mounting if this form of cast/weld steel was retained or if there was a switch to an all-welded steel plate turret underneath to simply manufacture.

With the addition of the Chobham armor, the appearance was changed, as was the weight, an additional 16.3 tonnes, with the likelihood that in the future, as armor technology improved, more weight could be added. Across the frontal 60-degree arc (30 degrees from centerline each direction), the Valiant, with this new armor, offered ballistic protection above that of the then in-service 56-tonne Chieftain, a design which had started in the 1950s.

An important additional consideration for the tank was the ‘future battlefield’ of the 1980s and 1990s seeing a potential large-scale use of nuclear or chemical weapons. Crew protection, therefore, was supplemented by a built-in nuclear, biological, and chemical warfare air filtration system made by Westair Dynamics and located on the back of the turret. This NBC filter system was mounted externally which made replacement and maintenance easier and consisted of a multi-stage high-efficiency filtration process and worked to create an overpressure inside the tank which served not only to keep gases out of the tank but also to evacuate fumes from the weapons.

Inside the vehicle was the Graviner Firewire CO2-based automatic fire fighting system, although these CO2 cylinders could be switched for an alternative gas like Halon if required.

The turret design itself had the same diameter ring as that of the Chieftain and was supported on a ball race with a semi-type basket. The turret crew were situated on a turntable that rotated with the turret.

Firepower

The Valiant, using a clever design, was able to offer a choice of guns with either the tried and trusted Royal Ordnance L7A3 105 mm rifled gun or, in a new mounting in the Universal Turret, with the L11 120 mm rifled gun. In order to potentially fulfill the NATO need for a common 120 mm smoothbore gun, the Rheinmetall 120 mm gun could also be fitted, a gun finishing development for use in the M1E1 and Leopard 2 at the time. When it first appeared, the Valiant mounted the 105 mm gun, but this was quickly exchanged for the superior L11A5 120 mm rifle instead. The advantage of the Universal Turret mounting being that the main gun could be removed in one piece from the front of the turret through the trunnions without having to remove the turret. This was achieved by using a wide-diameter gun rotor with pre-loaded trunnion bearings and extended cradle bearings. Not only did this allow for different guns to be mounted easily but also for good stability and thereby accuracy from the gun.

Alec Keiler, Tony McNally, Robin Lyon, and John Codling from the Vickers team taking a break during testing of the Valiant on Ridsdale Ranges. Note the VRM is now VV001. (Source: Vickers)

Loaded manually, the rate of fire was given as 10 rounds per minute (1 every 6 seconds). A Vickers muzzle reference system (MRS) on the end of the barrel added information into the computer system and the barrel was clad in a rigid thermal sleeve (a patented Vickers design) made from a material called Fibrelam Vickers developed with Ciba-Geigy of Duxford. This sleeve reduced distortion and was used on the Valiant, the Mk.7 vehicle and even had a 105 mm gun version for the Mk.3. That sleeve was thoroughly tested at Fort Halstead by the Royal Armament Research and Development Establishment (R.A.R.D.E.) and found to offer a significant improvement in reducing barrel sag in hot weather.

Basic outline of the Patented Vickers thermal sleeve made from Fibrelam. (Source: US Patent US4628713(A))

The fire control and gun stabilization system was an all-electric system developed by Marconi. This had a built-in laser rangefinder and a brand new ballistic computer to improve the chances of a first-round hit against static and moving targets as well as for supporting firing on the move. This system used the SFCS 600 computer derived from the GCE 620 system installed on the Vickers Mk.3 with some improvements, known as the Marconi Radar systems Centaur 1 system.

The Centaur 1 fire control system (FCS) was a state of the art solid-state system designed specifically for Valiant which completely integrated all of the different sightings and optics. The gun itself had a 2-axis gyro-stabilized mounting located underneath the breach and with the Centaur 1 FCS the gun could be directly slaved to either the commander’s gyro-stabilized day or thermal sights. Further, these balancing systems interfaced with the 3 primary sighting systems: the gunner’s telescopic laser sight, the commander’s gyro-stabilized panoramic laser sight, and the thermal imaging system. The ballistic computer took range data from the laser range-finders, manual values, and tracking data (for a moving target) and calculated a firing solution with supporting data from a tilt-sensor measuring the tilt-axis on the trunnion, with manually entered data such as ammunition type, barrel wear, and charge temperature. The Centaur system then superimposed a mark over the gunner’s sight graticule and tracked the target with the pressing by the gunner of the laser button. The gun was then ready to fire within 3 seconds of the tracking starting.

The elevation range for the 105 mm L7 gun was -10 to +20 degrees and it was capable of firing all commonly available 105 mm rounds. Storage was provided for up to 56 rounds of 105 mm, 44 rounds for the 120 mm Rheinmetall smoothbore, or 52 rounds for the L11A5. Rounds could be carried in the turret, in the basket as ready rack ammo and in a space alongside the driver as well.

Vickers Mk.4 Valiant Interior Interior showing the simplicity of the driver’s controls on the right and the stowage for 30 105 mm shells on the left. Note the single periscope for the driver indicating this is the early version. (Source: Pengelley)

Secondary armament included a single 7.62 mm machine Hughes chain gun mounted coaxially with the main gun and a second 7.62 mm machine gun (L37A2) in a remote-control mount next to the commander’s cupola, on the roof. In total, 3,000 rounds for these could be carried. Both of these weapons were interchangeable with a variety of commercially available 12.7 mm machine guns.

Advertising image shown by Vickers for the British Arms Export Exhibition of 1980. Note that at least two of the figures are shown in NBC suits and respirators. Source: Vickers

Firing trials at Lulworth took place at the end of 1982 against simulated targets using APDS at 1,500 m range and found to be excellent. By early 1983, the vehicle, refitted with the Universal Turret mount, was showing off the 120 mm L11A5 to potential Middle Eastern customers. Marketing literature from Vickers at the time sub-divided the configurations for potential buyers as Configuration 1 with the 105 mm L7A1, 60 rounds, of APDS or HESH, Configuration 2 with the 120 mm L11A5 with 44 rounds (different from the earlier plan for 52) of APDS or HESH, or Configuration 3 with the Rheinmetall 120 mm smoothbore with 44 rounds of APDS and HESH (MP).

The Vickers Universal Turret, as it would later be advertised for the Mk.7/2, fitted with the Rheinmetall 120 mm smoothbore gun. Note the storage for 15 rounds in the turret bustle. (Source: Lobitz)

Promotional shot of the Valiant taken at Ridsdale Ranges. Source: Ogorkiewicz

Sales

Other than the British Army there was other interest in the Valiant, specifically in the Middle East but also from some European nations including Spain who at the time were seeking a new tank. Vickers may have hoped for some success here as, after all, they had already sold a number of their Mk.3 tanks to Kuwait in the 1970s. In order to try and gain interest, the Valiant was packed up and shipped out to Doha, Qatar, a 3-month trip. This tour involved showing off the Valiant to Qatar, Jordan, Abu Dhabi (United Arab Emirates), and finally Egypt. The Valiant did its tour of prospective users offering these nations a tank objectively better in many ways than certainly the British Challenger. Sent with British Army crews, the Valiant, Challenger 1, and Stormer painted in desert colors performed a variety of trials whilst the team from Vickers traveled separately to talk about the technology. On one occasion, in Bahrain, there was a ‘mishap’ where the Vickers team got lost on the way to the firing trials and accidentally found itself driving past the targets on the firing range, something on which to focus the mind.

Despite these trials, there were no orders from this tour, and other than the sale of a single gold-plated Sterling SMG, was unsuccessful, although it had led to an invitation to participate in desert trials in the United Arab Emirates in July and August 1983.

In the desert outside Abu Dhabi, a Chieftain ARV provides support to the Vickers Valiant. Note the two-tone desert camouflage scheme. (Source: BAE)

Those trials in the UAE were to involve comparisons of the British Challenger 1, the French AMX-40, and the Vickers Valiant. Here, the lighter weight and automotive power of the Valiant was impressive leaving the other two contenders behind. During an off-road trial, however, the Valiant suffered a small disaster. A drain plug in the final drive had come out. This led to sand getting into the unit as well as a loss of lubricant and causing the unit to fail.

A new one had to be flown out from the UK delaying Valiant for two days but it was back operational to take part in firing trials where once more it outperformed the other two vehicles. It was not the only one of the three to suffer mechanical problems. The AMX-40 suffered a severe set of problems with the automotive system and was out of use for over a week. In fact, the only one without major problems was the Challenger 1. The UAE, however, bought the Leclerc instead.

The Fall of the Valiant

The Valiant had been a strong performer. Automotively powerful albeit it still a little underpowered but with a world-beating fire control system. The British had gone with the Challenger 1 MBT and there were no orders for the Valiant. The Valiant 2 was to improve on the Valiant with planned automotive improvements in the engine and suspension but whilst at Larkhill, the Valiant slipped off the low loader during transport and rolled into its roof. The optics were damaged but repairable, the hull was twisted and had to be scrapped. The Valiant was dead and all that could be salvaged was the significant investment in the turret. With no hull on which to make a Valiant 2 and with a large sum of money invested in a failed project, Vickers was in trouble. A review of automotive options for a new chassis were considered and would eventually lead to the attempt to use the Leopard 2 which created a whole new tank: the Vickers Mk.7/2.

An unfortunate accident which occurred during testing and evaluation when the Valiant fell off a low loader during transport. Landing on its roof, significant damage was done to the chassis. (Source: asrrse.co.uk)

Variants

Had the Valiant received orders, Vickers was planning a series of variants, specifically a bridge layer, an armored recovery vehicle (ARV) version and a self-propelled gun. Options also all available for the Vickers Mk.3.

The ARV was to be fitted with a 30-tonne direct-line pull capstan winch capable of up to 75-tonne of pulling by multi-reeving of the rope. A hydraulic crane was also available with an auxiliary 3-tonne winch.

The 13.4 metre long bridge laying version was to carry a class 60 bridge. The self-propelled gun variant was simply designed to take the universal 155 mm howitzer turret developed by Vickers Shipbuilding and Engineering. None of those three vehicles were ever built, however.

Conclusion

The Valiant, despite its good features, was not a success. It received no orders despite a lot of interest from the British and even being shortlisted by the Spanish in 1985, but Vickers would not give up. The turret was the biggest selling point, as a Universal Turret was able to offer a wide range of firepower and optical options. The turret would live on and was modified once more. It would go on to be tested on the Leopard 2 hull to create the Vickers Mk.7/2, having a maneuverability boost from its MTU engine. That vehicle would fail too, but the lessons learned would eventually lead to the turret contract for Brazil for their two EE-T1 Osório tanks.

The Vickers Valiant Main Battle Tank prototype failed to get any orders and was unfortunately lost in an accident. The vehicle is pictured with the 105 mm L7A3 gun. Illustration by Andrei ‘Octo10’ Kirushkin, funded by our Patreon campaign.

Vickers Mk.4 Valiant Specifications
Length	29.53 m long (with 105 mm gun) 10.62 m long (with 120 mm gun) 8.47 m (gun to the rear)
Width	3.3 m wide (with side skirts) 3.6 m with improved skirts
Height	3.24 m high (turret roof)
Weight	46.3 tonnes Combat laden (with Chobham) 41 tonnes Unladen (with Chobham) 30 tonnes (without Chobham)
Track length on ground	4.47 m
Ground Clearance	0.46 m
Trench Crossing	3 m
Fording (without preparation)	0.91 m
Vertical Obstacle	3 m
Main Armament	RO L7A3 105 mm rifle or L11A5 120 mm rifled main gun or Rheinmetall 120 mm smoothbore
Secondary Armament	coaxial 7.62 mm or 12.7 mm machine gun roof-mounted remote-control 7.62 mm or 12.7 mm machine gun
Crew	4 (driver, gunner, loader, commander)
Propulsion	Rolls Royce CV12TCA Condor diesel engine 1,000 hp at 2,300 rpm or normally rated for 1,200 hp. Possible to uprate to 1,500 hp. General Motors 12V71T diesel engine delivering 900 hp at 500 rpm. German MTU 872 1,200 hp diesel engine
Speed	51 to 61 km/h (road) depending on engine (Vickers state 70 km/h)
Suspension	Torsion bar
Proposed Production Armor	All aluminium alloy hull with Chobham across front 60 degrees. All steel turret with Chobham armor across front and sides.
Total production	1 prototype

Sources

Ground Defence International #69. November 1980
Ground Defence International #70. December 1980
Janes. (1985). Arms and Artillery. Janes Defence Group
Ogorkiewicz, R. (1983). Vickers Valiant. Armor Magazine March-April 1983
Lobitz, F. (2009). Kampfpanzer Leopard 2. Tankograd Publishing, Germany
Foss, C. & McKenzie, P. (1988). The Vickers Tanks. PSL.
BAE. (2012). The Tank Factory.
American Patent US4638713A, Thermal sleeve for gun barrels. Filed 25th November 1985, granted 27th January 1987
Pengelley, R. (1980). The Vickers Valiant Main Battle Tank. International Defense Review

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FV4201 Chieftain/90mm Gun Tank T95 Hybrid

Post author By Andrew Hills
Post date December 5, 2017
6 Comments on FV4201 Chieftain/90mm Gun Tank T95 Hybrid

United States of America/United Kingdom/Canada (1957-1959)
Main Battle Tank – None Built

ABC Countries

By the end of the 1950’s, tank development in both the UK and USA was becoming more streamlined with fewer outrageous ideas for atomic or super heavy monster tanks. The ‘Main Battle Tank’ concept had taken hold by 1957, inheriting the role of the medium tank. Heavy tanks were still seen, certainly in the US, as being the ones to take out the heaviest enemy armor but soon too that role was subsumed into the duties of the MBT.
The Soviets weren’t much for caring about such things and still had their own heavy tanks and well protected medium tanks which were causing consternation in the West. The Western powers lacked parity in both numbers and quality with the Soviets and both the US and UK had identified the need for a new medium tank for the 1960-1970 era. The United Kingdom, for instance, was still using the Centurion tank (a WW2 era design) and the USA, which was using the M48A2, was still developing the tank which would eventually become the M60.
In the short term, the UK would up-armor and up-gun their Centurions to meet the perceived threat of the Soviet T-55 tank until their own new tank, the FV4201, could enter production.
The FV4201 is better known as ‘The Chieftain’ and, despite being near the end of its development, many features still had not been settled on. The US equivalent program, the T95, was typical of US programs, an enormous entanglement of overlapping developments and was busily trying to encompass all of them. The project was still fairly new, however, with prototype hulls only authorised to be constructed in 1955. Thus, from 1957 to 1959, there were basically two tanks under development, the British Chieftain, which was nearing completion, and the American T95 which had only just started.
The United Kingdom, Canada, and the United States were already liaising closely in the new Cold War era on a variety of developments and tank design was not omitted from this. Work between the United States, the UK, and Canada, known as the ‘ABC’ countries (America, Britain, & Canada), had even achieved some degree of interchangeability and standardization for tank programs by 1957. Programs which had been fulfilled were standardization of the British 105mm gun, the British 120mm gun, an American version of the British 120mm gun, the American 105mm T254 and 120mm T123E6 guns, and three projects related to the FV4201 and T95.
These were:
-Mounting the FV4201 turret on the T95 chassis
-Fitting the US T208 90mm gun in the FV4201
-Mounting the US T95 turret on the FV4201 chassis
It was noted though that “in order to permit the FV 4201 turret to be mounted on the T95 hull, the U.K. consider modifying their turret ring with the T95 hull mounting surfaces”. It was agreed that “if the U.K. ring can be made interchangeable with the U.S. ring in respect to mounting surfaces on the hull, it will be possible to mount the complete turret providing major modifications are made to the turret basket”. The major modifications being that the British turret basket was too big for the T95, a smaller turret basket would be needed which would reduce significantly the amount of ammunition which could be carried. Even so, the expectation was that the T95 with a reworked 4201 turret and basket would carry at least 50 rounds of main gun ammunition. The panel reviewing the situation were adamant that all medium tanks must have ready rounds “stowed in the turret fighting compartment… in a favorable position for rapid loading of the main armament”.
That was not the end of the problems with the idea though. The turret bustle of the 4201 masked the air louvers on the T95 hull which “would undoubtedly affect the engine cooling”. One curious note records that one issue was that the driver’s periscope on the T95 hull interfered with the 4201’s gun mantlet. Exactly what this means is not clear as the FV4201 turret design was mantletless.

Guns

The British FV4201 was scheduled to enter production in 1962 with an expectation of prototypes available for trials by 1959. This new British tank meant to replace the Centurion was to mount a 120mm main gun using bagged charges. A lightened version this gun was also in development in the USA to weigh just 4156 lbs.(1885 kg). Since the initial specifications for the FV4201 were provided in the 1957 conference the design had changed slightly, improving the hull armor slope and the depression of the main gun (in a mantletless type turret) was improved from -7.5 degrees to -10 degrees.
The FV4201 turret would not be able to mount the T123E6 120mm American gun though as the weight would put the turret out of balance but it could mount the US 90mm instead. To do so would involve the use of an adaptor sleeve and the mounting surfaces of the gun but this was seen as having value for the tank in the short term.
On the other hand, the British 120mm bagged charge gun could be mounted in the T95E1 turret with only minor modifications made to the gun mount albeit at a weight increase of 1600lbs. (725.7kg). Of note here is that the T95E1 turret was the fifth turret in the American T95 program. When the T95 chassis was chosen to be common to both medium and heavy tank programs, five more chassis (for a total of 9) were ordered along with this turret. Four of those chassis went to the heavy gun tank program but as that program had no turrets ready three of the chassis were expediently fitted temporarily with existing turrets just for automotive trials. The remaining chassis got this new fifth turret and therefore was designated T95E1 to differentiate it from the others. The mention in the conference specifically for T95E1 can only, therefore, relate to this vehicle.

Medium tank guns

The 90mm T208 gun mentioned could fire the T320E60 APFSDS-T rounds at 5,200fps (1,585 mps) and defeat 5″ (127mm) of armor angled at 60 deg. at a range of 2000 yards (1828.8m). The other gun mentioned in the Tripartite Meeting on Tank Armament is the American 105mm T254 which is a lightened version of the British 105mm gun. The T254 was known to fit in the T95 turret, although “it is not planned now to install this gun in this type of turret since the installation is not ideal from the standpoint either of turret balance or turret configuration” but would be mounted on a T95 for test purposes (which would be known as T95E5). The advantage of the T254 gun was that if that gun became the standard US medium tank gun then it would be able to utilise the same ammunition as the up-gunned (105mm) British Centurion (assuming a suitable primer for the shell was selected). The Canadian contingent considered it “highly desirable that the gun and ammunition [for medium tanks] be standardized. To this end, the 90mm smooth bore can be placed in the FV4201 and the T95 turret modified to accommodate the 105mm X15 and possibly the UK 120mm bagged charge gun”.
The Canadians were anxious to see comparative firing trials between these two guns and to make an objective decision on their choice for a new medium gun tank although both were expected to exceed the requirement to defeat 120 mm of homogeneous armor plate at 60 deg. at 2000 yards which had been agreed as the standard at the Third Tripartite Conference.

Armor

Like the FV4201, the T95 was to use cast sections of armor for the nose with the sides and floor made from armor plate welded to the cast sections. This was a departure for the Americans who had already been using an all cast hull for the M48. The entire T95 turret was cast armor but the FV4201 turret was only cast in the front with the other sections made from plate armor welded on.
Overall, the T95 was expected to be a significant improvement over the M48A2’s which were already in service as “for example, the latter [M48A2] can be defeated from the direct front by the US 3000fps [914.4mps], 90-mm AP projectile on the upper hull front from 125 yards [114.3m] and on the turret front from within 1,550-yards [1,417.3m] range. The new medium gun tank, on the other hand, cannot be defeated from the front by this projectile”.
It was further theorized that the frontal armor was sufficient to defeat a theoretical Soviet 100mm AP shell traveling at 3,500 feet per second (1066.8mps) at 1,500 yards (1,371.6m) across a 60-degree arc. The armor was considered deficient, however, in terms of protection for the engine deck, sides, and rear, as well as having defective floor armor insufficient to protect from high-pressure mines. A final note on the protection for the T95 was the consideration of siliceous cored armor inside the frontal hull and turret castings although this still had not been done by this time and did not form part of the consideration for the interchangeability of the guns or turrets.

The Canadian Intervention

The Tripartite meetings of the ABC countries featured many Canadian needs. They did not class themselves as a tank producer nation, just a user, but they also had specific requirements they wanted from the tanks they were being expected to purchase. Being able to purchase either UK or US tanks effectively meant that the Canadians could be selective with what they wanted and expect that anyone who wanted to sell tanks to them would meet their demands.
For the new medium gun tank, they had agreed back in 1955 to the weight limit for this vehicle being set at 50 short (US) tons (45.36 tonnes). Both the T95 and FV4201 met this requirement, with the T95 being 20,000lbs (9,072 kg) under the weight limit.
The Canadians wanted standardization of guns, ammunition and gun mountings. They also demanded that any gun chosen had to meet the 120mm/60deg./2000 yard standard and be used in comparative firing trials. There is a small irony here that neither the FV4201 nor the T95 actually had that level of protection themselves. Further, the Canadians noted that, in comparing the designs of these tanks, the US had placed their emphasis on reducing the size of the vehicle and that while the T95 had less protection against kinetic energy ammunition than the FV4201, it did have a higher level of protection against chemical energy weapons (HEAT rounds).
In estimating the performance of the guns on offer, they determined that the UK 120mm bagged charge gun appeared to be more effective than the US 90mm smoothbore. In terms of sighting arrangements, the Canadians also preferred the British system for gun control as it was simpler, making use of a ranging machine gun compared to the US which “was still developing complex arrangements in preference to the ranging rifle system”.
In a nutshell, the Canadians wanted the best of both worlds, they wanted the hitting power of the British gun combined with the lighter, lower, more mobile US T95 to which they recorded that “the UK gun in the US tank would seem to be the logical answer. It may be technically possible to mount the 120mm bagged charge gun on the T95. With such a combination we should, for once, achieve a qualitative superiority over the Russians”.
The T95 with British gun combination favored by the Canadians was eventually effectively created by the US T95E6 mounting the 120mm T123E6 gun although the British 120mm X23E2 gun or lightened US version of it were still possible for mounting. In the meantime, while those experiments and considerations were going on, the UK had already submitted drawings to the Americans for a cost analysis for the re-engineering needed to fit the T208 and T208E9 guns in the FV4201. As it turned out, this project too came to nothing.
R.P. Hunnicutt (Abrams) records that the British 120mm gun was eventually mounted in a T96 turret in Study F of the T96 program (this being the heavy tank program) although the bagged charge was not popular with the US testers leading to the proposal to adopt a new breech and combustible case ammunition for it instead. The Americans were suitably impressed with the British 105 and 120mm guns though. So much so they made their own versions of them and “these two weapons and the original British guns were superior for tank use because of their lethality combined with lightweight, relatively short tubes, and short rounds requiring less loading space”. The only drawback of using the 120mm gun in the T95 turret was the necessity for a single loader to handle the two-piece ammunition” although a loader assist mechanism was considered to make this concern moot. Either way, the Americans elected to move on to a single piece round and modify the gun accordingly.
That modified gun was then fitted into a T95 turret in Study G (back to the medium tank program) producing a balanced gun capable of being stabilized for firing on the move.

T96 Study F turret with British 120mm bagged charge gun fitted on T95 hull. Note the use of a mantlet.Source: Abrams by Hunnicutt
T95 Study G fitted with the American version of the British 120mm gun Source: Abrams by Hunnicutt

Conclusion and one last hybrid

After the T95 program had been abandoned, the turret interchangeability concept didn’t go completely away. An initial assessment was even carried out on the XM60 as to whether it could take the British turret, the conclusion was that it was possible although it would certainly have been an odd-looking tank. The end outcome of all of the interchangeability studies is hard to gauge. The British stuck with their bagged charge gun, the American eventually chose their own gun for their own use and the Canadians were left without the tank they wanted. The option the Canadians had chosen suited their needs better than either the T95 or FV4201 could on their own: plenty of hitting power with a much more mobile vehicle. The T95 program was eventually terminated and the Canadians didn’t take Chieftains, preferring the mobility and firepower of the up-gunned Centurion instead.
The interchangeability of the guns was in itself a good idea, especially for replacement in wartime and the British turret and guns were well regarded. The interchangeability of the turrets was not easily rectified though, the Chieftain was nearly at the end of development and the British were unlikely to completely redesign the turret basket when there was no perceived market. The Canadians, after all, found the T95 turret acceptable in its own right, they just wanted the better gun. So, at the end of all this work, the overall outcome was that the interchange of T95 and FV4201 was indeed possible.
The FV4201 needed some work on the ring and basket, to take the T95 turret and the idea of mounting the T95 turret on the Chieftain was an altogether bigger task which no one was interested in trying. The report terminated discussion of the matter saying “it appears unlikely that the US T95 turret can be mounted on the UK FV4201 chassis without a major redesign of components which cannot be contemplated at this time”. As a result of the problems involved in modifying turret rings to match each other and overlapping demands for which gun was preferable, the whole affair was terminated with no prototypes completed.
The discussion does provide a real insight into just how hard it can be to design a tank to suit more than one role and customer and the idea of swapping turrets from the T95 and Chieftain tanks or even the XM60 as well as a variety of gun options remains popular if not in military circles then at least in those of modellers.

T95/FV4201 hybrid (T95 with FV4201 turret) specifications
Dimensions	Length – 426.1 inches (10.82 m) (est. based on T95E6) Width – 124 inches (3.15 m) (within the 124 inch limit imposed by the Berne International Loading Diagram) Height – >112 inches (2.84 m)
Total weight, battle ready	>32 US short tons est.
Crew	4
Propulsion	air cooled, 8 cylinder, 560 horsepower AOI-119505A with 4 speed hydraulic converter-type transmission providing at least 13.5 horsepower per ton
Suspension
Speed (road)	35 km/h est.
Range	>150 miles (241.4 km) at 17.5 mph (28.2 kph) with 230 US gallons (870.6 litres) fuel
Armament	various options
Armor	Sectional cast hull with welded plate and sectional cast turret with welded plate sides, roof and rear Hull front upper – 3.8″ @ 65 deg. (96.5mm) (to be equivalent to 4.4″ @ 60 deg. (111.8mm) which is an increase of 0.4″ (10.2mm) over the M48A2 which was 4″ at 60 deg. (101.6mm)) Hull front lower – 3.2″ to 5.5″ @ 50 deg. (81.28mm to 139.7mm) Hull sides – 1.5″ to 4″ (38.1mm to 101.6mm) Hull rear – 1″ at 0 to 20 deg. (25.4mm) Hull top – 0.8 to 1″ (20.3mm to 25.4mm) Hull floor – 0.5 to 0.7″ (12.7mm to 17.8mm) Turret – FV4201
Total production	zero
For information about abbreviations check the Lexical Index

T95E1 with British 120mm gun (the Canadian Option) specifications
Dimensions	Length – 426.1 inches (10.82 m) (est. based on T95E6) Width – 124 inches (3.15 m) (within the 124 inch limit imposed by the Berne International Loading Diagram) Height – 112 inches (2.84 m)
Total weight, battle ready	32 US short tons est.
Crew	4
Propulsion	air cooled, 8 cylinder, 560 horsepower AOI-119505A with 4 speed hydraulic converter-type transmission providing at least 13.5 horsepower per ton
Suspension
Speed (road)	35 km/h est.
Range	>150 miles (241.4 km) at 17.5 mph (28.2 kph) with 230 US gallons (870.6 litres) fuel
Armament	British 120mm bagged charge main gun with at least 50 rounds
Armor	Sectional cast hull with welded plate sides, floor and rear, and fully cast turret Hull front upper – 3.8″ @ 65 deg. (96.5mm) (to be equivalent to 4.4″ @ 60 deg. (111.8mm) which is an increase of 0.4″ (10.2mm) over the M48A2 which was 4″ at 60 deg. (101.6mm) Hull front lower – 3.2″ to 5.5″ @ 50 deg. (81.28mm to 139.7mm) Hull sides – 1.5″ to 4″ (38.1mm to 101.6mm) Hull rear – 1″ at 0 to 20 deg. (25.4mm) Hull top – 0.8 to 1″ (20.3mm to 25.4mm) Hull floor – 0.5 to 0.7″ (12.7mm to 17.8mm) Turret (T95E1) front – 7″ at 60 deg. (177.8mm)(compared to the M48A2 with just 3.7″ at 60 deg. (94mm)) Turret (T95E1) gun shield – 15″ (381mm) Turret (T95E1) sides – 3″ @ 45 deg. (76.2mm) Turret (T95E1) rear – 2″ (50.8mm)
Total production	zero
For information about abbreviations check the Lexical Index

Links, Resources & Further Reading

Report of the Tripartite Technical Conference on Tank Armament – October 1957
Abrams – Hunnicutt
Fourth Tripartite Conference on Armour – October 1957
Tank Factory – William Suttie

T95 hull with XM60 Turret and standard 90mm Gun.

The hull of T95 Pilot No. 2 with 90mm Gun T208.

FV4201 hull with T96 Study F turret and British 120mm bagged-charge gun, without fume extractor.

T95 hull with an impression of an Americanised FV4201 Turret with M48/M60 style commanders cupola and 120mm gun with fume extractor.

T95 Hull with the standard FV4201 Chieftain turret and 120mm gun.

All illustrations are by Tank Encyclopedia’s own David Bocquelet.

Straussler Main Battle Tank specifications

Vickers Mk.7/2

Specifications

Vickers Mk.4 Valiant Specifications

T95/FV4201 hybrid (T95 with FV4201 turret) specifications

T95E1 with British 120mm gun (the Canadian Option) specifications

Straussler Main Battle Tank

Vickers Mk.7/2

Vickers Mk.7

Vickers Mk.4 Valiant

FV4201 Chieftain/90mm Gun Tank T95 Hybrid

United Kingdom (1960) Main Battle Tank – None Built

Early Engineering Work

Designing the Ultimate Tank

Layout

Date

Armor

Crew

Armament

Engine, Steering, and Propulsion

Improved Mobility on Land and Water

Suspension

Conclusion

Straussler Main Battle Tank specifications

Sources

United Kingdom (1984-1986) Main Battle Tank – 1 Built

Layout

Unveiling

Optics

Tracks and Suspension

Automotive

Armor

Firepower

Markets

Termination

Conclusion

Vickers Mk.7/2

Sources

United Kingdom (1984-1986) Main Battle Tank – None Built

The background

Optics

Firepower

Layout

Armor

Tracks and Suspension

Automotive

The Rival and the Name

Conclusion

Specifications

Sources

United Kingdom (1977-1985) Main Battle Tank – 1 Built

The Chieftain tank replacement?

Layout

Unveiling

Optics

Tracks and Suspension

Automotive

Armor

Firepower

Sales

The Fall of the Valiant

Variants

Conclusion

Vickers Mk.4 Valiant Specifications

Sources

United States of America/United Kingdom/Canada (1957-1959) Main Battle Tank – None Built

ABC Countries

Guns

Medium tank guns

Armor

The Canadian Intervention

Conclusion and one last hybrid

T95/FV4201 hybrid (T95 with FV4201 turret) specifications

T95E1 with British 120mm gun (the Canadian Option) specifications

Links, Resources & Further Reading

United Kingdom (1960)
Main Battle Tank – None Built

United Kingdom (1984-1986)
Main Battle Tank – 1 Built

United Kingdom (1984-1986)
Main Battle Tank – None Built

United Kingdom (1977-1985)
Main Battle Tank – 1 Built

United States of America/United Kingdom/Canada (1957-1959)
Main Battle Tank – None Built