Categories
Coldwar American Prototypes

M109 Maxi-PIP Howitzer Improvement Program

USA (1979-1984)
Self-Propelled Gun (SPG) – 1 Prototype

During the mid-1970s, the US Military determined that there was a need to update, replace or overhaul their existing and aging fleet of self-propelled guns (SPG). The focus was on the replacement of the M109 SPG and several options were available. The US Army could select a foreign vehicle such as the French GCT, or the Italian/UK/German SP-70 project, or a new project could be started. The military, unsurprisingly, selected a US-based program and had to consider whether to replace the whole fleet with a common chassis fulfilling roles of command, resupply, and repair or instead, just modernize/upgrade the existing fleet.

Amongst the replacement vehicles considered, the proposal made by Food Machinery Corporation (FMC) under the name DSWS New Start (DSWS – Division Support Weapon System) was rejected by 1983. The emphasis instead of replacement was going to be upgrade and modernization. FMC had invested a considerable amount of time and financial resources into their design and would try to reuse this development in an M109 rework. This was to be the M109 Maxi-PIP (Product Improvement Program)

Artist’s impression of the FMC M109 Maxi-PIP project. Source: Janes

The Flaws

The existing US SPG fleet was a mix of vehicles, calibers, and ages. There was no simple common Ammunition Resupply Vehicle (ARV) either, and a common vehicle platform for both an artillery system and its resupply vehicles would have obvious advantages for parts, supplies, logistics, and training. The work on FMC’s own platform for all of this had been discontinued already though.

The rate of fire for existing in-service SPG’s was also too slow, of the order of just 4 rounds per minute manually loaded. The US Army wanted to improve on this and an automatic loader would achieve this with up to 12 rounds per minute being possible. Another problem was that the crews of existing SPGs were too large, which lead to logistical problems such as training and maintaining these soldiers in the field. An automatic loader and automatic subsystems would help reduce this human burden.

In particular, the existing engine of the M109 was considered underpowered for its role. An improved power-to-weight ratio of 20 horsepower per ton was set for the upgrade project along with improved reliability. The M109 was a product of the 1950s and simply did not reflect the realities of modern warfare. It was vulnerable to counter-battery fire from Soviet artillery as it took too long to stop, fire, and then move on. Modernized fire control systems, gun elevation motors, and ground mapping would allow the improved vehicle to fire, move, and fire again to reduce successful enemy retaliation. Finally, the old M109 just did not have the range needed to counter fire the Soviets, which was a huge tactical weakness. These requirements formed the basic needs of the Howitzer Improvement Program (HIP).

Howitzer Improvement Program

The 155 mm gun caliber would remain, but the barrel had to be between 38 calibers (5.89m) and 50 calibers (7.75m) long. It had to be able to fire all current and future 155 mm rounds and have a range of 25 to 30 km when using High Explosive Rocket Assisted (HERA) ammunition. Either a fully or semi-automatic loading system was needed to increase the rate of fire and reduce the number of crewmen. New electronics were also needed to enable a 1-minute fire-move-and-fire-again cycle, along with a facility to fire a 3 round burst in 10 seconds. Increased ammunition capacity of at least 50 shells was also demanded.

Artist’s impression of the FMC M109 Maxi-PIP project. Source: Janes
The mock-up vehicle on display. Source: Ed Francis
Rearview of the same mockup showing the resupply doors open. Source: Ed Francis

FMC M109 Modification Proposal

When the original FMC DSWS project was canceled, FMC had luckily also submitted a proposal to update the existing M109 fleet. It was as an alternative to their own proposal for a completely new vehicle with the 155 mm L/45 gun. The upgrade/update idea though was to combine the old M109’s with some of the elements from the completely new vehicle proposal.

This would include the new suite of electronics which would improve accuracy from the same 155 mm L/45 gun but the most obvious and important change would be the switch to an automatic loading system. Fed from two large drums in the back of the turret, the 155 mm shells would be replenished by means of two circular hatches at the bottom of each door. Both doors could also be opened to allow for complete inspection or repair of the drums. The autoloader would also decrease the crew for the vehicle by eliminating the need for one of the loaders.

This upgraded M109 would be marketed under the name M109 Maxi-PIP (Product Improvement Program) and had the advantage of retaining the turret (albeit modified) of the M109. A wooden mockup was shown to the military and received sufficient interest to have a single test chassis produced based on an M109. This prototype weighed in at just over 29 tonnes.

M109 Maxi-PIP weighed mockup. Source: US Army

The M109 Maxi-PIP was still under development in 1982 with an existing M109 chassis modified to simulate the new 29-ton (26.3 tonnes) vehicle weight. The engine fitted was a 500 hp Detroit-Diesel 8V71TA and was subjected to the NATO 400 hour engine test. Tests were still scheduled to take place with this engine into 1983. Various other types of engines were considered but 500hp in a 29-ton (26.3 tonnes) vehicle would only produce 17 hp/t which was not the required 20hp/t wanted, therefore this new vehicle was not able to provide the required mobility improvements.

Conclusion

The M109 PIP from FMC faded away and was completely canceled by 1984 with the decision being made at the time to simply modify the M109 fleet with new ammunition stowage and a longer range gun. Pacific Car and Foundry (PCF) had also made its own proposal to fulfill the requirements for the future artillery system under the name ‘Self Propelled Artillery Weapon’ (SPAW). The PCF proposal was also a fully automatically loaded gun system but was capable of firing unassisted shells to a range of 30km and to 40km with a rocket-assisted projectile. The SPAW would have had a crew between 2 and 4 and with an engine providing a power to weight ratio of between 20 to 25 hp/t and could move at up to 40km/h off-road. Neither project could meet the Army’s needs and, as a result of the failure to develop or accept a replacement, the existing M109’s soldiered on.

Artist’s impression of the ammunition stowage and loading system on the Maxi-PIP. Source: Richard Eshleman

As with many of these multi-year huge contracts in the US, this one is an enormous project of overlapping requirements. The HIP program did not end with FMC or PCF concepts though and was still going on into 1991. This was the date by which the vehicles for the program were meant to have been entering service yet development hadn’t even finished and only 8 prototype improved vehicles for the entire program had even been made by 1989.

The project was simply too large and phenomenally expensive. In 1989 alone, for example, the HIP program cost nearly US$28.5 million and nearly US$10.5 million the following year. It didn’t matter anyway for FMC. Their initial proposal had been rejected, as was their M109 improvement. The project was somewhat of a failure, no new vehicle was produced and a huge amount of financial resources was spent. The opportunity for a new and more capable platform producing a new family of vehicles was lost. The PIP had not managed to meet the needs for a future artillery system and the US finished out the 1980’s behind the Soviets in terms of self-propelled artillery, unable to select or develop a suitable M109 replacement.



Illustration of the M109 Maxi-PIP produced by Pavel Alexe, funded by our Patreon Campaign.

Specifications

Armament 155 L45 main gun, one cupola mounted .50 cal heavy machine gun
Ammunition 50 rounds in two 25 round drums with fully automatic feed capable of firing unassisted projectiles to 23km

Sources

GAO Report AD-A141 422 M109 to M109A5 Report, March 26th 1984
Janes Armour and Artillery 1984-5
US Army Tank Automotive Command Laboratory Posture Report FY 1982, US Army
Research Development and Evaluation Army Appropriation descriptive summaries, January 1990, US Army Congressional Report
Report ARLCD-CR-81053, Demonstration Prototype Automated Ammunition and Handling System for 155mm Self-Propelled Howitzer Test Bed, December 1981, US Army ARRADCOM


Categories
Coldwar American Prototypes

Cargo Carrier M548 with Surface-Launched Unit, Fuel Air Explosive (SLUFAE)

U.S.A. (Mid-1970s)
Mine Clearing Vehicle

Minefields are, quite rightly, well feared by troops and commanders alike. Hidden, silent killers, these weapons can lie dormant for years and cripple men and machines alike. With the Cold War stand-off between NATO and the Warsaw Pact in full flow, both sides planned to make extensive use of minefields to disrupt enemy movements and attacks. The side with the fastest and most efficient means of clearing a path through an enemy’s minefield would obviously have a significant advantage in a war.
Early research work with turning Fuel Air Explosive (FAE) technology into weapons was undertaken by the US Navy in the early 1960s at their China Lake Naval Weapons Center in California. By the mid-1970s, research had progressed sufficiently to weaponize FAE technology into two primary weapons systems: one ground-launched which was developed in conjunction with the US Army Missile Command (MICOM), the ‘Surface Launched Unit’ (SLU-FAE); and one delivered by air, the CBU-55/72. The design was completed by 1975, and prototype firings ready that year for testing the SLUFAE for its intended primary role, defeating enemy minefields. This evaluation was done in conjunction with the US Army Mobility Equipment Research and Development Center (MRDC) at Fort Belvoir, Virginia.

The ‘Surface-Launched Unit, Fuel Air Explosive’ or ‘SLUFAE’ mounted on the M548. This photo shows the arrangement of the tubes in the POD. Photo: US Army

The SLUFAE System

The SLUFAE system consisted of a single giant octagonal ‘pod’ containing 30 smooth walled 35cm diameter tubes, although the original artwork for the program had shown 36 tubes in a rectangular pod and then confusingly described it as a ‘30-tube’ system. These barrels were able to the fired individually or ripple fired at intervals variable from 1.0 seconds to 9.7 seconds in 1/10 second intervals. The whole system could throw all 30 rockets in sequence which was capable of breaching an 8m wide path 900m long. The minimum safe detonation distance was 100m so the carrier could park as close as 100m from the edge of the minefield and launch the rockets.

Uncamouflaged SLUFAE during test firing. The very large size of the rocket is apparent. Photo: US Army
The whole pod was to be mounted on a ground vehicle and the vehicle selected was the M548 Tracked Cargo Carrier vehicle, although it has also been described as being based on the M752 Lance Missile Carrier which was being decommissioned as a platform at the time.
Stowed horizontally on the back of the M548, the POD stuck up well above the vehicle line and could be elevated up to a maximum of 30 degrees when the POD was to be deployed.

SLUFAE rocket launched from the camouflaged POD on the M458. Use of such a system was liable to draw a lot of enemy attention. Photo: Zaloga via US Army

Rear of the SLUFAE showing the use of the POD mounted crane arm for reloading these large rockets. Photo: Yuri Pasholok

The rocket

The XM130 SLUFAE (also sometimes written as ‘SLU-FAE’, was a 2.55 m long, 345 mm diameter, 84.8 kg unguided rocket fitted with an XM750 Slowed Nose Probe (discriminating against the effects of foliage) and Mild Detonating Fuze. Propelled by a 5” (127 mm) ‘Zuni’ rocket motor inside the launching tube body, this would propel it from the vehicle-mounted tube out to a maximum range of 1000 m, although 700m was deemed to be the effective limit.

Preserved SLUFAE rocket (center, dark green) at the Hawthorne Ordnance Museum, Nevada. Photo: Courtesy of the Hawthorne Ordnance Museum
Once over the target, the rocket was retarded by a parachute in the tail shroud and the main charge, consisting of 45 kg of Propylene Oxide (PO) explosive liquid, was burst over the target forming a cloud 12’ x 54’ (3.7 m x 16.5 m) which was then ignited (150/1000 second delay) causing a huge explosion and overpressure on the target which would subsequently detonate any mines. An inert version for training use was designated XM131. Accuracy for this unguided system was poor though. with a dispersal of 2.6 m laterally and 6 m in range for every 300 m traveled, meaning a maximum deflection of 8.6 m laterally and 20 m in range leaving a chance that at the end of the lane of cleared mines that some mines may not have been covered by the overpressure.

Diagrammatic break down of the XM-130 SLUFAE rocket showing the large payload (8), burster charge (9) at the front and the Zuni rocket tube (3) behind. The retarding parachute is marked at (5). Photo: Dept. of Defense


The Cargo Carrier M548 fitted with the large Surface-Launched Unit, Fuel Air Explosive (SLUFAE) launcher fitted to the rear of the vehicle. Illustration by Andrei ‘Octo10’ Kirushkin, funded by our Patreon Campaign.

Testing

Testing of the SLUFAE on the M548 took place in 1975, with further tests throughout 1976 and 1977. Consideration was given to the effectiveness of ground-pressure detonation of mines, including tests of the FAE system (although not SLUFAE rockets) on frozen ground in Alaska, which provided concern over their effectiveness, particularly against frozen or partially frozen soils. By 1981, further studies were recommended into the performance degradation of this type of system in cold temperatures and against the frozen or thawing ground.

Montage showing demonstration of SLUFAE rocket against a target building at China Lake and alternative deployment of FAE device by helicopter. Photo: British Ordnance Collectors Network
The overpressure effects on vehicles and troops were devastating. Trucks were crushed by the overpressure and exposed troops would be killed or seriously injured. Light structures such as houses were seriously damaged, but the effect was very small against armored targets. The primary intended use had been seen in using overpressure against landmines causing them to detonate and under normal temperate conditions, it had worked. The use of FAE had even worked for underwater mines, making it suitable for use in clearing mines laid below the water line on a beach, but the carrier was unprotected and the whole system was huge.

Demonstrated effect of FAE explosives in 1975 showing a 2 ½ ton standard US Army truck completely crushed by the overpressure blast which also set it on fire and blew off major parts. Photo: US Army

Future Developments

The SLUFAE system was eventually not adopted for use. In the 1998 patent for an improved version of FAE mine clearance, a description of the SLUFAE rockets put the maximum range to just 700 m and that to ensure mines are destroyed a lot of overlap was required to destroy single impulse mines or ones buried in excess of 15cm deep. As a result, the clearance area from 30 rockets was just 8 m by 160 m, substantially less than the 700-1000 m lane originally intended. This is likely the key reason the system was not adopted. It just was not reliable enough. Systems such as ‘Giant Viper’ were more effective and provided a cleared lane through a minefield by virtue of the 183 m long hose filled with PE6/A1 High Explosive. That system was much simpler logistically as it was carried in a trailer and could be brought to a designated area by almost any vehicle rather than relying upon a dedicated and much bigger tracked carrier.
The SLUFAE was a good idea but was unsuitable for actual combat. The USMC, who was particularly interested in amphibious assault vehicles, looked at the Army’s SLUFAE for their own use in 1987. They concluded that “this system is not compatible with Marine Corps amphibious assault and tactical vehicles, does not provide a breaching capability starting at the high watermark, and does not meet the Marine Corps stated requirements”.
The development of SLUFAE had been quick in military terms, completing development and being officially accepted in December 1980 (FY 1981). It had been pursued, however without sufficient testing under different terrain conditions and the tactical disadvantages of this large, vulnerable and conspicuous machine were readily obvious. It was duly shelved and received no procurement orders.

Conclusion

By the 1990’s, FAE technology had continued with the addition of aluminum particles to increase the overpressure from the blast, but the SLUFAE rockets were gone. Nothing is known about the location of the SLUFAE launcher, but at least two rockets survive. One in a private collection and one in the collection of the Hawthorne Ordnance Museum in Nevada.

Minefield clearance with FAE from Patent US4967636A preparing the route for a tank. Photo: US Patent US4967636A
The original design had morphed to consider the use of a flexible hose containing FAE launched in a manner similar to that of the ‘Giant Viper’ system. Instead of exploding in the air, this version of the SLUFAE system would explode on the ground instead. The means of destruction was the same though – the creation of a pressure wave to detonate the mines. The system was never adopted though and production of the SLUFAE was limited to a single prototype.

Sources

Osprey Publishing, New Vanguard #252: M113 APC 1960-75, Steven Zaloga
Special Report 81-20, Mine/Countermine Problems during Winter Warfare, Virgil Lunardini, September 1981
NAWCWD Quick Facts, China Lake and Point Mugu, California, March 2008
Department of Defense Military Handbook – Fuzes, April 1994
William Stirrat, US Army Armament Research and Development Center Large Calibre Weapon Systems Laboratory, Minimum nonpropagation distance for the cloud detonator of the XM130 SLUFAE rocket, February 1984
Infantry Magazine Vol.66, US Army, March-April 1976
Jai Agrawek, High Energy Materials: Propellants, Explosives and Pyrotechnics.
James Dennis, MERDC Demonstrates Fuel Air Explosive Mine Neutralization Capabilities, US Army Research and Development Bulletin January-February 1975
US Patent US4967636A filed 23rd September 1988
Canadian Patent CA2197508, Land Mine Destroying and Disabling System, 13th August 1998 and 30th November 1999
Required Operational Capability for Amphibious Continuous Breach and Land Mine Countermeasure System. Department of the Navy, 1987
Remote Controlled Vehicle Mounted Minefield Detector System, US Army Mobility Equipment Research and Development Command. November 1982
US Army Mobility Equipment Research and Development Plan, March 1981
FY 1982 Department of Defense Program for Research Development and Acquisition

Categories
Coldwar American Prototypes

120mm Gun Tank T57

U.S.A. (1951)
Heavy Tank Prototype – 2 Turrets Built

The T57 started life in the early 1950s. At this time, the 120mm Gun Tank T43 (which would become the M103) was well on its way to becoming America’s next heavy tank, but even before it had entered serialization, ideas began to circulate about future upgrades.
One such idea was the possibility of mounting an auto-loading device in the tank’s turret, and further study into this idea proved that such a device would be ill-suited to the T43’s turret. As such, concentration turned to a new turret design, which would be mounted on pivoting trunnions. In other words, designers began to consider the addition of a new technology at the time, an Oscillating Turret. Testing at the Aberdeen Proving Grounds (APG) had already proved that smaller caliber guns worked in such turrets. There was no reason that a larger caliber gun, such as the powerful 120mm, wouldn’t work in such a turret. A development program was initiated on October 12th, 1951, with the project receiving the designation of 120mm Gun Tank T57.

One of the earliest concepts of the T57. Photo: Presidio Press

Development

On 12th October 1951, a development program began to design a 120mm armed heavy tank with an Oscillating turret and automatic loader. Two pilot models were authorized, and the tank was designated as the 120mm Gun Tank T57. The turrets, each with 2.1 meter (85 inch) rings, were to be tested on the hull of the T43. Two hulls of which were earmarked for this purpose.
The initial design for the autoloader was for a cylindrical type mounted directly behind the breach of the gun in the turret bustle. However, it was predicted that the measurements of such a device would take up a space of 76 cm – 1 meter (30 – 42 inches) but this depended on whether the cylinder would hold 11, 9 or 6 rounds. Army Field Forces (AFF) rejected this design, stating that such equipment would end up with the turret bustle being overly large in overall dimensions, as well as in the overhang of the bustle.
To overcome this possible design flaw, a contract was drawn up with the Rheem Manufacturing Company to design and construct the two authorized pilot vehicles.

Another early concept of the T57

Turret

The Oscillating type of turret consists of two actuating parts, these were a collar that is attached to the turret ring, allowing horizontal traverse, and a pivoting upper part that holds the gun, loading mechanism, and crew. Both halves of the T57’s turret were cast in construction, utilizing cast homogeneous armor. Armor around the face was 127mm (5-inches) thick, angled at 60 degrees. The armor on the sides of the turret was slightly thicker at 137mm (5.3 inches) but was only 51 mm (2 inches) on the bustle.
The sides of the collar were bulbous to protect the trunnions that the upper half pivoted on, with the other half consisted of a long cylindrical ‘nose’ and a low profile flat bustle. The turret was mounted on the unmodified 2.1 meter (85 inch) turret ring of the T43 hull.

Cutaway views of the enternal systems and layout of the turret. Photo: Presidio Press
Though it looks as though there were two, there were actually three hatches in the roof of the T57. There was a small hatch on the left for the loader, and atop the commander’s cupola which featured five periscopes and a mount for a .50 Caliber (12.7mm) machine gun. These hatches were placed on top of the third hatch, which was a large square that took up most of the middle of the roof. This large hatch was powered and granted a larger escape route for the crew but also allowed internal turret equipment to be removed easily. In front of the loader’s hatch was a periscope, and there was another above the gunner’s position.
Behind the large hatch was the ejection port for spent cartridges. To the right of this was the armored housing for the ventilator housing. On each side of the turret were ‘frogs eyes’, the armored covers for the stereoscopic rangefinder used to aim the main gun.

Gun

The initial Rheem concept had the gun rigidly mounted without a recoil system in a cast, low silhouette Oscillating turret, with the gun protruding from a long, narrow nose. The gun featured a quick change barrel, which was which was similar to the 120mm Gun T123E1, the gun being trialed on the T43. However, for the T57, it was modified to accept single piece ammunition, unlike the T43 which used separately loading ammo. This new gun was attached to the turret via a conical and tubular adapter that surrounded the breech end of the gun. One end screwed directly into the breach, while the front half extended through the ‘nose’ and was secured in place by a large nut. The force created by the firing of the gun and the projectile traveling down the rifled barrel was resisted by rooting the adapter both the breech block and turret ring. As there was no inertia from recoil to automatically open the horizontally sliding breech block, a hydraulic cylinder triggered by an electric switch was introduced which would be engaged upon the firing of the gun.
This new variant of the T123 was designated the 120mm Gun T179. It was fitted with the same bore evacuator (also known as a fume extractor) and muzzle break as the ‘T123’. The gun’s rigid mount was designated the ‘T169’, making the official nomenclature ‘120mm Gun T179 in Mount T169’
In the oscillating turret, the gun could elevate to a maximum of 15 degrees, and depress 8 degrees. Projected rate of fire was 30 rounds per minute. The main gun had a limited ammunition supply due to the large size of the 1-piece rounds. The T43 hull had to be modified to allow storage, but even then, only 18 rounds could be carried.
It was proposed that two .30 Caliber (7.62mm) machine guns would be mounted coaxially. This was later reduced to a single machine gun placed on the right side of the gun.

Automatic Loader

The automatic loader used on the T57 consisted of a large 8-round cylinder located below the gun, and a ramming arm that actuated between positions relative to the breech and magazine. The loader was designed for 1-piece ammunition but an alternate design was prepared for use with 2-piece ammunition.
Operation: 1) The hydraulically operated ramming arm withdrew a round and aligned it with the breach. 2) The rammer then pushed the round into the breach, triggering it to close. 3) Gun is fired. 4) Effect of gun firing trips the electric switch that opens the breech. 5) Rammer picks up a fresh round, at the same time ejecting the spent cartridge through a trap door in the roof of the turret bustle.

A diagram of the loading process. Photo: Presidio Press
Ammunition types such as High-Explosive (HE), High-Explosive Anti-Tank (HEAT), Armor Piercing (AP), or Armor-Piercing Ballistic-Capped (APBC) could be selected via a control panel by either the Gunner or the Tank Commander (TC). The HEAT round could punch through a maximum of 330mm (13 inches) of Homogeneous Steel Armor.

Hull

The hull that was used for the project was the same as the 120mm Gun Tank T43, which would later be serialized as the M103, the US’ last heavy tank. Armor on the hull was unchanged. The cast “beak” was 100 to 130 mm (3.9-5.1 in) at the thickest.
An 810hp Continental AV1790 12-cylinder air-cooled gasoline engine propelled this chassis to a speed of around 21 mph (34 km/h). The tank’s weight was supported on seven road wheels attached to the torsion bar suspension. The drive sprocket was at the rear while the idler wheel was at the front. The idler wheel was of the compensating type, meaning it was attached to the closest roadwheel by an actuating arm. When the roadwheel reacts to terrain the idler is pushed out or pulled in, keeping constant track tension. The return of the track was supported by six rollers.

Line drawing of the complete T57, with OScilliating turret mounted on the T43/M103 hull. Photo: Presidio Press

Crew

The T57 had a crew of four men. The Driver’s position was standard for T43/M103 hulls. He was located centrally in the bow at the front of the hull. Arrangements inside the turret were standard for American tanks. The Loader was positioned at the left of the gun. The Gunner was on the right with the Commander behind him.

Fate

The T57 project eventually ground to a halt. Progress became slow due to delays in procuring some equipment from the US Government. This problem was due, in no small part, to changing opinions in tank design. Designers were moving towards lighter vehicles that retained powerful guns, instead of heavy (as in weight and class) tanks.
One of the two pilot turrets constructed by Rheem was trial fitted to a T43 hull. Work on the project, however, stopped before tests of the systems could take place. The United States Ordinance Committee officially canceled the project on January 17th, 1957. Both turrets were subsequently scrapped, and the T43 hulls were returned to a supply depot for future use.
The T57 did, however, live on in another tank project, but this time in the shape of a medium tank. This project was designated the 120mm Gun Tank T77. It was a project to mount the T57’s turret on the hull of the 90mm Gun Tank T48, the prototype of the M48 Patton III. Just one photo, a model, and blueprints exist.
The Rheem Company would also continue to design tank components for the United States Military. Other projects they worked on included the 90mm Gun Tank T69, and 105mm Gun Tank T54E1 projects. Both of which featured similar turrets and loading systems.

A small scale mock-up of the T57. Photo: Presidio Press

TE to the Rescue

In late-2017, a scale model of the T57 produced by Rheem appeared on the internet auction sight, eBay. This model had appeared a number of times on the website without being purchased. The model was made for Fort Benning Armored Force Command. It is made from solid aluminum and weighs nearly 22 pounds (10 kg), it is also 2 feet (70 cm) long.

The scale model of the T57 from when the item was put up for auction on eBay.
Rather than let the model fall into the hands of a private collector, and be hidden from view, the Tank Encyclopedia team decided to step in a secure its fate in partnership with the U.S. Army Armor & Cavalry Collection, Georgia, USA. A fundraiser was organized and launched by Andrew Hills of FWD Publishing – and one of our writers – on the website ‘GoFundMe’ in November 2018. The thinking behind this was that he (all of us) wanted to see the model get to its rightful home – a national collection where it could be enjoyed by future generations and help foster a greater understanding of the evolution of American armour.
By the end of 2018, we had raised the necessary $700 to purchase the model. Just as planned, it was sent to the Museum. It is now safe and sound, reserved for future generations to see.

The T57 model at the U.S. Army Armor & Cavalry Collection. Photo: AACC

An article by Mark Nash

Specifications

Dimensions (L-w-H) 37.4 (including gun) x 8.7 x 9.45 ft (11.32 x 2.6 x 2.88 m)
Total weight, battle ready 48.5 tons (96 000 lbs)
Crew 4 (Commander, Driver, Loader, Gunner)
Propulsion Continental AVDS-1790-5A V12, AC Twin-turbo gas. 810 hp.
Transmission General Motors CD-850-3, 2-Fw/1-Rv speed GB
Maximum speed 30 mph (48 km/h) on road
Suspensions Torsion bars
Armament Main: 120 Gun T179 Sec: 1 Browning M2HB 50. cal (12.7mm), 1 cal.30 (7.62 mm) Browning M1919A4
Production 2

Links & Resources

OCM (Ordnance Comittee Minutes) 34048
April 1954 Report from the Office of the Chief of Ordnance (PDF)
Presidio Press, Firepower: A History of the American Heavy Tank, R. P. Hunicutt


Rendition of the T57 heavy tank in a fictional livery based on common styles from the era. Illustration by Alexe Pavel, based on an illustration by David Bocquelet.

Categories
Coldwar American Prototypes

120mm Gun Tank T77

U.S.A. (1951)
Heavy Tank Prototype – 2 Turrets Built

In October 1951, a heavy tank project was underway to mount an oscillating turret with an automatically loading 120mm Gun on the hull of the 120mm Gun Tank T43. (The T43 would later be serialized as the 120mm Gun Tank M103, America’s last heavy tank.). This was the T57, and the Rheem Manufacturing Company were granted a contract to design and build two pilot turrets and autoloading systems.
During the T57’s development, it became clear that it was feasible to mount a lighter armored version of the T57 turret on the hull of the 90mm Gun Tank T48 (The T48 later became the 90mm Gun Tank M48 Patton III). This combination granted the possibility of creating a ‘heavy gun tank’ that was lighter than any previously designed.
In May 1953, a development project was started to create such a tank. It would be designated the 120mm Gun Tank T77, and another contract was signed with Rheem to create two pilot tanks.

Hull

The hull chosen for the project was that of the 90mm Gun Tank T48. The tank weighed about 50 tons, with armor of up to 110mm thick.
The tank was powered by a 650 hp Continental AVSI-1790-6 V12, air-cooled twin-turbo gasoline engine. This would propel the tank to a speed of 30 mph (48 km/h). The tank was supported on a torsion bar suspension, attached to six road wheels. The drive sprocket was at the rear, while the idler was at the front. The idler wheel was of the compensating type, meaning it was attached to the closest roadwheel by an actuating arm. When the roadwheel reacts to terrain the idler is pushed out or pulled in, keeping constant track tension. The return of the track was supported by six rollers.

A small scale mockup of the T77. Photo: Presidio Press

Turret

The Oscillating type of turret consists of two actuating parts, consisting of a collar that is attached to the turret ring, allowing horizontal traverse, and a pivoting upper part that holds the gun, loading mechanism and crew. Both halves of the T57’s turret were cast in construction, utilizing cast homogeneous steel armor. Armor around the face was 127mm (5 inches) thick, angled at 60 degrees. This increased to 137mm (5.3 inches) of the sides of the turret and dropped to 51 mm (2 inches) on the bustle.*
*The T77’s turret was supposedly designed to be lighter by having thinner armor, however, Hunnicutt’s data shows it to be the same as the T57’s turret. Whether this is erroneous or not is unknown.
The sides of the collar were made to be round and bulbous in shape to protect the trunnions that the upper half pivoted on. The other half consisted of a long cylindrical ‘nose’ and a low profile flat bustle.

Cutaway views of the internal systems and layout of the turret. Photo: Presidio Press
Though it looks like two, there were actually three hatches in the roof of the turret. There was a small hatch on the left for the loader, and atop the turret, a commander’s cupola which featured five periscopes and a mount for a .50 caliber (12.7mm) machine gun. These hatches were placed on top of the third hatch, which was a large square which took up most of the middle of the roof. This large hatch was powered and allowed a larger escape route for the crew, but also allowed internal turret equipment to be removed easily. In front of the loaders, hatch was a periscope, there was another above the gunner’s position.
Behind the large hatch was the ejection port for spent cartridges. To the right of this was the armored housing for the ventilator. On each side of the turret were ‘frogs eyes’, the armoured covers for the stereoscopic rangefinder used to aim the main gun.

Gun

The initial Rheem concept had the gun rigidly mounted without a recoil system in a cast, low silhouette oscillating turret. The gun protruded from a long, narrow nose. The gun featured a quick change barrel, was basically identical to the 120mm Gun T123E1, the gun being trialed on the T43. However, for this turret, it was modified to accept single piece ammunition, unlike the T43 which used separately loading ammo. This new gun was attached to the turret via a conical adapter that surrounded the breech end of the gun. One end screwed directly into the breech, while the front half extended through the ‘nose’ and was secured in place by a large nut. The force created by the firing of the gun and the projectile traveling down the rifled barrel was resisted by rooting the adapter both the breech block and turret ring. As there was no inertia from recoil to automatically open the horizontally sliding breech block, a hydraulic cylinder was introduced. Upon firing the main gun this hydraulic cylinder was triggered via an electric switch.
This new variant of the T123 was designated the 120mm Gun T179. It was fitted with the same bore evacuator (fume extractor) and muzzle brake as the T123. The gun’s rigid mount was designated the T169, making the official nomenclature ‘120mm Gun T179 in Mount T169’
It was proposed that two .30 caliber (7.62mm) machine guns would be mounted coaxially. This was later reduced to a single machine gun placed on the right side of the gun.
In the oscillating turret, the gun could elevate to a maximum of 15 degrees, and depress 8 degrees. Projected rate of fire was 30 rounds per minute. The main gun had a limited ammunition supply due to the size of the 1-piece rounds. The T48 hull had to be modified to allow storage, but even then, only 18 rounds could be carried.

Automatic Loader

The automatic loader shared by the T77 and T57 consisted of a large 8-round cylinder located below the gun, and a ramming arm that actuated between positions relative to the breech and magazine. The loader was designed for one-piece ammunition but an alternate design was prepared for use with two-piece ammunition.
Operation: 1) The hydraulically operated ramming arm withdrew a round and aligned it with the breech. 2) The rammer then pushed the round into the breech, triggering it to close. 3) Gun fires. 4) Effect of gun firing trips the electric switch that opens the breech. 5) Rammer picks up a fresh round, at the same time ejecting the spent cartridge through a trap door in the roof of the turret bustle.

A diagram of the loading process. Photo: Presidio Press
Ammunition types such as High-Explosive (HE), High-Explosive Anti-Tank (HEAT), Armor Piercing (AP), or Armor-Piercing Ballistic-Capped (APBC) could be selected via a control panel by either the gunner or the tank commander (TC). The round could punch through a maximum of 330mm (13 inches) of Rolled Homogeneous Steel Armor.

Crew

The T77 had a crew of four men. The driver’s position was standard for T48/M48 hulls. He was located centrally in the bow at the front of the hull. Arrangements inside the turret were standard for American tanks. The loader was positioned at the left of the gun. The gunner was on the right with the commander behind him.

Fate

The T77 would share the same fate as other Rheem designed tanks such as the T69, T57 and T54. Like the T57, the T77’s development was arduously slow, and in 1957, the project was finally canceled by the US Ordnance Department. Both turrets were scrapped in February 1958.

An article by Mark Nash

Specifications

Dimensions (L-w-H) 20’10” (without gun) x 11’9″ x 10’10” ft.in
(9.3m x 3.63m x 3.08m)
Total weight, battle ready Around 48.5 tons (96 000 lbs)
Crew 4 (Commander, Driver, Loader, Gunner)
Propulsion Continental AVDS-1790-5A V12, AC Twin-turbo gas. 810 hp.
Transmission General Motors CD-850-3, 2-Fw/1-Rv speed GB
Maximum speed 30 mph (48 km/h) on road
Suspensions Torsion bars
Armament Main: 120 Gun T179 Sec: 1 Browning M2HB 50. cal (12.7mm), 1 cal.30 (7.62 mm) Browning M1919A4
Production 2

Links & Resources

OCM (Ordnance Comittee Minutes) 36741
Presidio Press, Firepower: A History of the American Heavy Tank, R. P. Hunicutt


Illustration of the 120mm Gun Tank T77 by Tank Encyclopedia’s own David Bocquelet.

Categories
Coldwar American Prototypes

Chrysler K (1946)

U.S.A. (1946)
Heavy Tank Concept – None Built

The Chrysler K was an American heavy tank prototype designed in response to the increasing interest in heavy tanks at the end of the Second World War. The growth in interest was thanks, in no small part, to the discovery of German plans for super heavy tanks such as the Maus and E100. Most importantly, however, it was the appearance of the Soviet IS-3 at the Berlin victory parade in 1945 that really jump-started the process.
The appearance of the IS-3 sent a chill down the spine of all major allied powers. Each nation invested large amounts of time, energy, and resources in heavily armored tanks with powerful main armaments, not least the USA, whose only heavy tank was the M26 Pershing. This vehicle was considered to lack the required firepower and protection to face tanks such as the new IS-3.
One of these early designs was a submission from the Chrysler Motor Corporation. Called the ‘Chrysler K’, it would be armed with a 105 mm main gun, and armor up to 18 cm (7 inches) thick.

Soviet IS-3 Heavy Tanks at the Berlin Victory parade in 1945. This pike-nosed heavy tank was the catalyst for many western heavy tank designs. Photo: Wikimedia Commons

Background, the Stilwell Board

On 1st November 1945, the ‘Stilwell’ Board was convened, named after the man heading the meeting, General Joseph W. Stilwell. The official designation, however, was ‘War Department Equipment Review Board’. The findings of this board, submitted in a report on 19th January 1946, agreed, for the most part, with earlier recommendations that Light, Medium, and Heavy tanks should all be developed. However, experiments with Super Heavy tanks, such as the T28/T95, would be abandoned. Another omission from the report was the development of dedicated tank destroyers, following the Armored School’s (based at Fort Benning, Georgia) opinion that the best anti-tank weapon would be another tank. As such, a Heavy tank was favored in tank versus tank combat due to powerful guns and thick armor.

Chrysler’s Submission

The famous motor car company, Chrysler, based in Michigan, submitted their design for an unconventional Heavy tank to the Armored School in a presentation by a Mr. F. W. Slack at Fort Knox on 14th May 1946. It would be known as the ‘Chrysler K’. The origin of the ‘K’ may lie with Kaufman Thuma Keller, the president of the Chrysler Corporation from 1935 to 1950, and advocate of the creation of Detroit Arsenal (DA). It is quite possible that the tank was named after him, given his position at Chrysler, and his relationship with the military thanks to DA.

Kaufman Thuma Keller, President of the Chrysler Corporation 1935-1950. Quite possibly the man behind the ‘K’. Photo: mountjoyhistory.com

Design

Chrysler’s design would incorporate a number of features that were sophisticated for the period they were designed in. These included an electric motor, remote controlled secondary armaments, and a ‘Driver in Turret’ arrangement.

Armament

The 105 mm Tank Gun T5E1 was chosen as the main armament for Chrysler’s heavy tank. Designed in 1945, it was the popular choice for American Heavy tanks at the time and was also mounted on vehicles such as the Heavy Tank T29, and the Super Heavy Tank T28. The T5E1 had a medium velocity of 945 m/s (3,100 ft/s). A variety of ammunition (which was two-part, separately loading. eg, projectile loaded then charge) allowed it to be as good a bunker buster as a tank killer, with the gun proving capable of penetrating concrete as well as metal. Ammunition types included APBC-T (Armor-Piercing Ballistic-Capped – Tracer), HVAP-T (High-Velocity Armor-Piercing – Tracer), (Armor-Piercing Composite Rigid – Tracer) APCR-T and HE (High Explosive). The APBC-T shell could penetrate 135 mm (5.3 in) of armor at a 30-degree slope or 84 mm (3.3 in) of armor at a 60-degree slope, 914m (1,000yd).
At 7.53 m (24 ft 8 in), the barrel of the weapon was rather long. It was concluded that if the turret was mounted in the usual place, ie, centrally, the gun would become hazardous in convoy travel or whilst maneuvering. As such, the decision was made to place the turret at the back of the tank, off-setting the length of the gun. This design choice resulted in the vehicle having an overall length of 8.72 m (28 ft 7.5 in). This is just 7.62 cm (3 in) longer than the M26, despite the 105 mm gun being 16.5cm (6½ inches) longer than the 90 mm gun of the M26. The gun could elevate up to 25 degrees, and depress to 4-degrees.
Secondary armament was machine gun heavy, with three .50 Caliber (12.7mm) heavy machine guns and two .30 Caliber (7.62 mm) machine guns. One of the .50 Cal. machine guns was mounted coaxially with the main gun, the other two were placed in secondary turrets on the left and right rear corners of the hull. They had a limited horizontal traverse, but could be elevated upwards to defend against air attack (quite how practical this was is debatable). The two .30 Cal. machine guns were placed in blisters at the left and right top corners of the upper glacis. It is unknown whether they were ball mounted and had a degree of traverse, or whether they were completely fixed. All of these weapons were controlled and fired via a remote control system that was an improved and simplified version of the turret control system on the B-29 Superfortress bomber. If they were fixed, it is debatable as to whether these weapons would’ve been any use at all. Fixed, forward mounted machine guns like these were abandoned from designs long before the ‘K’. As an example, the original versions of the Medium Tank M3 and M4 Sherman had fixed forward facing MGs, but not the later ones. The layout of Machine guns on the hull is similar to an Army Ground Forces (AGF) design for a medium tank.

Turret

One problem with the T5E1 gun was that it had a long breech. Still, the turret had to accommodate this, 100 rounds of 105 mm ammunition, and the crew which consisted of a commander, gunner, loader, and the driver. As a result of this, the turret diameter had to be wider than anything previously designed for an American tank. The internal diameter was 2.9 meters (9 foot 10 inches), while the turret ring was 2.1 meters (86 inches), as opposed to 1.75 meters (69 inches), the largest of previous designs. It stated that 100 rounds of the separately loading 105mm ammunition were carried by the tank and that they were stored circumferentially around the turret. However, an investigation into this reveals that there simply isn’t enough room for all 100 rounds inside. Though it isn’t stated in any source material, it is reasonable to suggest that ammunition was stored under the turret, as there is enough unaccounted for space from the bottom of the hull to the floor of the turret. As stated this is speculation but it is not unreasonable as it was a very common practice.
The turret was hemispherical in shape, and cast in construction – this shape offered excellent ballistic protection. The turret face was 18 cm (7 inches) thick, while the rest of the casting was 7.62 cm (3 inches) thick. Ammunition was stored circumferentially at the rear of the turret. The face of the turret was reinforced with a mantlet consisting of a large, thick disc. The exact diameter and thickness of this mantlet plate are unknown.
An unusual feature of the Chrysler, for the time, was the fact that the driver was located in the turret with the rest of the crew. It wasn’t the first time that a tank could be driven from the turret, however, as a remote control box in the turret of the T23 allowed control from within should the driver be knocked out. It was believed that having all the crew in the turret provided better communication and cooperation. The turret still had the ability to rotate 360-degrees. The driver’s seat (and presumably controls) were geared so that they were always linear (always facing forward in relation to the hull) to the tanks hull, no matter where the turret was pointing. His position was surrounded by pericopes so no matter where he was in relation to the turret, he would always be able to see where he was going.
The exact crew positions in the turret are unknown, but looking at the position of hatches and pericopes we can make an educated assumption. It would appear the Driver sat at the front left of the turret with the Loader behind him. The gunner sat at the front right, with the Commander at his rear.


A small-scale mock-up of the ‘K’ tank. This is as far as the project got. Note that the rear machine gun turret is traversed out slightly. Photo: Presidio Press.

Propulsion

With the turret moved to the rear of the tank, the engine would now take up the space left at the front end. The power requirements for the vehicle were based on a US Ordnance Department idea calling for 20 hp per-ton for this projected 60-ton tank. The gasoline-fueled engine was an unspecified design by Chrysler and was powerful with a projected output of 1,200 hp.
The engine was placed in the front end of the hull was to was to be connected to two electric motors that formed the tank’s final drives at the front of the vehicle. This system is similar to that used on the Medium Tank T23 prototype. The electric drive system on the ‘K’ tank was designed by a Mr. Rodger.
The engine system was fed by 600-US gallon (2727 liter) fuel tanks. The exact number of tanks is unknown, but it is likely to be at least two, judging by other American heavy tanks of the time.

Suspension

The suspension was the usual torsion bar type. There were eight twin road-wheels per side, with the idler at the back and the drive sprocket at the front. The idler was the same type of wheel used for the road wheels. The return of the track was not supported by rollers. This is known as a flat track suspension and is common on Soviet tanks such as the T-54 and so on. The track was 76.2 cm (30 inches) wide.

Hull

The hull was rather square in its overall shape, with the frontal plate 18 cm (7 inches) thick and angled at 30-degrees. Such angling brought the effective thickness up to roughly 36 cm (14 inches). Armor on the tank’s sponsons was less impressive being just 7.62 cm (3 inches) thick. They were sloped inwards slightly at around 20-degrees, this would’ve made the effective thickness 8.1 cm (3.1 inches). A 25 mm (1 inch) thick armored floor protected the underside of the vehicle. The tank was 3.9 meters (12 foot 8 inches) wide. For rail travel, the sponsons and outer halves of the road-wheels could be removed.
The overall height of the ‘K’ tank, turret included, was 2.6 meters (8 foot 8 inches) tall. This was 7.62 cm (3 inches) shorter than the M26. Altogether, the tank was projected to weigh 60 tons.

A modern side-on schematic of the Chrysler ‘K’ heavy tank concept. Photo: Tank Archives Blogspot.

Fate

Funds for tank design gradually dwindled after the Second World War. As such, the Chrysler K tank never left the development stage, with only line drawings and a scale model produced. Unfortunately, the drawings and scale model are not thought to survive, and only a photo of the model remains. The project was abandoned, with attention turning to more conventional tank designs such as the Heavy Tank T43, which would eventually become America’s last heavy tank, the 120 mm Gun Tank M103.
Some of the design features of the ‘K’ tank were carried over into future tank projects. The ‘Driver in Turret’ concept was utilized on the M48 Patton based M50/53 self-propelled gun, and also the MBT-70 and subsequent prototypes. To the east, the Soviets also used this concept in their prototype medium tank, the Object 416.

The Other ‘K’

This heavy tank was not the only tank designed by Chrysler to bare the ‘K’ designation. Twenty-two years later, in 1968, Chrysler would put forward another design intended to be a possible upgrade of the 105mm Gun Tank M60. The design featured a brand new, comparatively smaller turret and a new main gun.
Two guns were tested on the tank. One of these was the 152 mm Gun Launcher XM150, a modified version of the gun used in the MBT-70 project. The gun could fire conventional Kinetic Energy (KE) rounds, or launch Anti-Tank Guided MIssiles (ATGMs). The other gun was the 120 mm Delta Gun. This was a Hyper-Velocity Gun that was smooth-bore and fired an Armor-Piercing Fin-Stabilised Discarding-Sabot (APFSDS) round. The gun also used combustible cartridge cases, meaning the entirety of the round would ignite upon firing, much liked the bagged charges used on the 120 mm gun of the British Chieftain.
Another modification that Chrysler designed for the M60 was for the suspension, specifically the torsion bars. A modification by Chrysler allowed the wheels to have an extra 45 percent travel when actuating on their suspension arms.
Despite notable merits to the Chrysler’s ‘K’ tank, the design was not accepted into service. Two mockup turrets were constructed and tested on M60 hulls, but at the time, all spare funds were being spent on equipment for the lingering Vietnam War. As such, all work on the vehicle was dropped.

Chrysler’s other ‘K’ tank from 1968. This time being a possible upgrade of the M60. This is the first version with the MBT-70s XM150 152mm Gun/Launcher. Photo: Presidio Press

An article by Mark Nash

Specifications

Dimensions (L-w-H) 8.72 x 3.9 x 2.6 Meters (28 ft 7.5 in x 12ft 8in x 8ft 8in)
Total weight, battle ready 60 tons
Armor Bow: 18cm (7in), angled at 30-degrees (36cm, 14in, effective)
Sides: 7.62cm (3in), angled 20-degrees (8.1cm, 3.1in, effective)
Turret Face: 18cm (7in)
Turret Sides/Top/Rear: 7.62cm (3in)
Crew 4 (Commander, Driver, Loaders, Gunner)
Propulsion 1,200 hp Chrysler Petrol/Electric engine
Suspensions Torsion bars
Armament Main: 105mm Gun T5E1 Sec: 2 x Browning M2HB 50. cal (12.7mm) MGs in remote turrets, 3 x cal.30 (7.62 mm) Browning MGs. 2 x in fixed mounts on the bow, 1 x coaxial.

Links & Resources

Presentation by Mr. F. W. Slack, 14th May 1946. Original document provided by The Richard Hunnicutt Collection in the at the National Armor and Cavalry Museum Archives. Thanks for this are also extended to the Museum’s Curator, Rob Cogan.
Presidio Press, Firepower: A History of the American Heavy Tank, R. P. Hunicutt
Presidio Press, Patton: A History of the American Main Battle Tank, Vol. 1, R. P. Hunicutt


Profile of the Chrysler ‘K’ Heavy Tank with a speculative livery of Olive Drab with basic US Markings. Both the color and markings were commonplace at the time. Length and height wise, the ‘K’ wouldn’t have been much larger than the United States then serving tank, the M26 Pershing. At the time, the M26 was considered a Heavy Tank.


A head-on view of the ‘K’ Heavy Tank. This view shows just how wide tank would’ve been. While the ‘K’ was only a maximum of 7.62 cm (3 in) taller and longer than the M26, it was much wider at 3.9 m (12ft 8in), approximately 40cm (16in) wider than the M26. Note also, the 76.2 cm (30 in) wide tracks, and how far the remote rear turrets extend from the hull sides.

Both of these Illustrations were modeled by Mr. C. Ryan and were funded by our Patreon Campaign.

Categories
Coldwar American Prototypes

120mm Gun Tank T110

U.S.A (1954)
Heavy Tank Concept – Wooden Mockup Built

Improving the Breed

Even while the T43 (M103) was still in development, the U.S.A. was not done with attempts at making better heavy tanks. Development was split into two schools of thought. One based its work on the T43, leading to the T57 and T58 auto loading tanks; and the other started from scratch.
In June 1954, the Detroit Arsenal held its third Question Mark Conference, the goal of which was brainstorming ideas for new heavy tanks. Suggested designs included the TS-2, TS-5, TS-6, and TS-31.
Conditions these proposals had to meet were that a prototype had to be constructed within two years (hence “TS”, for “Tracked vehicle Short Development”), and it had to be able to fit within the confines of the Berne International Clearance Diagram; a code of standardization for rail tunnels established at the international conference at Berne, Switzerland, in 1913. (There is no single Berne National Tunnel, as claimed by Hunnitcutt’s ‘Firepower’; this was merely a building code for rail tunnels)
The TS-2 and TS-5 were both armed with a 105 mm (4.13 in) T210 smoothbore gun; in a turret on the TS-2, and in a fixed casemate on the TS-5.
The TS-6 and TS-31 were armed with the 120 mm (4.72 in) T123E1 gun; again in a turret on the TS-6, and casemate on the TS-31.
Power for the tanks would have been supplied by either a 700 hp Continental AOI-1490-1 engine with an XT-500 transmission (TS-2 and TS-5), or an 810 hp Continental AVI-1790-8 with an XT-500 transmission (TS-6 and TS-31).
In the end, the TS-31 was chosen for further development; it had a gimbal gun mount, and was estimated to weigh 45 tons. Chrysler was assigned to the development of the TS-31, which was given the designation “120mm gun tank T110”; at the same time, the T43 was entering pre-production.
The TS-31/T110 had a driver in the hull, a gunner to the left of the gun, a commander and his machine gun cupola to the right of the gun, and two loaders. It was rear-engined and had six roadwheels on either side. Armor was to be as thick as 9 inches (228.6 mm) on the gun mantlet. Despite the TS-31 concept being chosen as the winner, it still was slightly too big to fit through the Berne Clearance Dimensions. Additional problems were found with the off-center commander’s cupola: the additional metal to support it added to the tank’s weight and increased its size. These flaws led to Chrysler redesigning the tank.

Losing Some Weight

The second draft was an improvement over the original TS-31. It was slightly smaller, becoming shorter and the front becoming flat. The driver was moved into the casemate, to the left of the gun, with the gunner being moved to the right of the gun. Behind the driver and gunner were two loaders and the commander behind them. The commander was placed directly in the middle of the tank, leaving him to sit almost directly atop the engine and with his feet worryingly close to the gun breech. Despite all this, it was still too big to fit through the Berne Clearance Dimensions. Size, in addition to the Detroit Arsenal’s disapproval of the driver’s position, led to a second redesign.
The third draft was sort of a reversion to the original; the driver was moved back to the hull outside of the casemate, and the gunner was moved back to the left of the gun. The commander’s turret was moved slightly forward, so he would no longer have to sit on the engine, but was now forced to sit in a very awkward and cramped position in order to avoid being crushed by the gun’s recoil every time it fired. The casemate reverted to being rounded at the front. The third draft was no smaller in size than the second.

Detroit Fires Back

The Detroit Arsenal replied to Chrysler’s two proposals with the fourth draft of the T110. The casemate was moved to the back, hanging over the rear of the tank. The transmission was moved to the rear as well, joining the engine. In its place up front was a massive fuel tank, nearly encompassing the driver. The power plant (which was now a Continental 700 hp AOI-1490) was pushed to the left to afford the commander a more comfortable (but still probably hot) position on the far rear right. The suspension was changed to a more conventional (for the Americans) type, with smaller road wheels; although the original draft is without them, return rollers would have been necessary.

Hammering out a Design

Chrysler rejected the Detroit Arsenal’s idea to put the casemate on the very back on the tank and kept it in the middle. The driver was moved back inside the casemate, to the right of the gun. You may know this vehicle as the T110E3 or E4, although these designations are completely fictional. Chrysler originally tried to simplify maintenance on this design by allowing the engine to be pulled out, on rails, via a hatch in the rear of the tank. This feature created rigidity issues and the engine was returned to a standard position, now turned lengthwise in the tank. This new engine placement again left the commander stuck between the engine and the gun breech. The gun mantlet, which had been relatively tiny before, was much bigger in this iteration; weighing 2 tons and being 9 inches (228.6 mm) thick. The tank was now short enough to fit through the Berne Tunnel, but it was still too wide.
This version of the T110 was the first to have serious work done on it. A wooden mockup was built and engineering diagrams were drawn up. Gun traverse was 15 degrees to each side, with 20 degrees of gun elevation and 10 degrees of gun depression. Armor was 5 inches (127 mm) at a 60 degree slope from vertical. Secondary weaponry comprised the commander’s .50 cal (12.7 mm) M2 Browning, as well as a .30 cal (7.62 mm) paired with the main gun.
Artist's interpretation of design five
Artist’s interpretation of design five
The original TS-31/T110
Small scale model of design five
At some point, Chrysler realized that there was no need to stick with a casemate design, as a turret could be accounted for within the weight requirements for the tank. In its sixth iteration, the T110 was completely changed, becoming a far more conventional tank. The driver was moved to the middle of the hull, under the gun barrel. The crew was reduced to four instead of five men by dropping a loader. To ease the life of the remaining loader, a gun rammer was fitted. The gunner was on the left of the turret, with the commander above and behind him, and the loader on the right. This, the last version of the T110, shared the 85 inch (2.16 m) turret ring with the M103. Engineering diagrams and a full-size mockup were made, but by this time the T43E2 had been built and showed promise. The success of the M103, as well as changing ideas in terms of tank design, were the doom of the T110, and the project was canceled.
Artist's interpretation of design six
Artist’s interpretation of design six
The original TS-31/T110
Small scale model of design six
Even the definitive version of the T110 failed its main goal, as it was still too big to fit through the Berne Clearance Dimensions.

The original TS-31/T110
The original TS-31/T110
Chrysler's first revised T110
Chrysler’s first revised T110
Chrysler's second revised T110
Chrysler’s second revised T110
The Detroit Arsenal's T110 counter-proposal
The Detroit Arsenal’s T110 counter-proposal
The fifth T110 design -Chrysler
The fifth T110 design -Chrysler

The fifth T110 design -Chrysler
The original TS-31/T110
Schematics of the fifth T110 design
The sixth T110 design -Chrysler
The sixth T110 design -Chrysler
The original TS-31/T110
Schematic of the sixth T110 design

T110, Draft Six specifications

Total weight, battle ready Probably around 50 tons
Crew 4 (driver, gunner, commander, loader)
Propulsion Continental 700hp AOI-1490
Suspension Torsion Bar
Armament 120 mm (4.72 in) T123E1 rifled cannon
Total production A few wooden mockups

Sources

Presidio Press, Firepower: A History of the American Heavy Tank, R.P. Hunnicutt.
(This is also the source for every image used in the article)
Originally published on November 13, 2016.


The fifth T110 design submitted by Chrysler. The 120 mm cannon is mounted in a fixed superstructure, with a machine gun armed commander’s cupola on the roof. Illustration by Jaroslaw “Jarja” Janas.

Categories
Coldwar American Prototypes

155mm Gun Tank T58

U.S.A. (1952)
Heavy Tank Prototype – 2 Turrets Built

In the early 1950s, the American military’s quest for a powerful new heavy tank was well underway. The T28, T29, T30, T32, and T34 projects had all ceased in favor of the 120mm Gun Tank T43, which eventually became America’s last heavy tank, the M103.
While still in development as the T43, however, there were parallel projects competing for the role of America’s next heavy tank. One of these projects was the 120mm Gun Tank T57. It used the same hull as the T43, but incorporated new technologies for the turret. The turret was of the oscillating kind, but it was also outfitted with an autoloading mechanism.
In the Army Development Guide of December 1950, both the T43 and T57 were expected to more than meet the requirements of the military and be a worthy adversary of Soviet armor such as the infamous IS-3. However, in the Tripartite Conference of Armor and Bridging of October in 1951, it was recommended that a 155mm gun armed tank be developed instead.

A mockup of the T58 Heavy Tank. Photo: Presidio Press

Development

A list of recommended characteristics for this new heavy tank was outlined in a paper on the 18th of January 1952. Such recommendations included a gun that exclusively fired HEAT (High-Explosive Anti-Tank) or HEP (High-Explosive, Plastic. Otherwise known as HESH – High-Explosive Squash Head) rounds. This paper also recommended the construction of two prototype turrets complete with autoloaders and 155mm guns for installation on T43E1 chassis. The resulting vehicle received the designation of 155mm Gun Tank T58.
On the 10th of April 1952, a contract was drawn up with United Shoe Machinery Corporation of Beverly, Massachusetts for the design, development and manufacture of the two pilot turrets.

Hull

The hull that was used for the project was the same as that of the 120mm Gun Tank T43, which would later be serialized as the M103, America’s last heavy tank. Armor on the hull was the same. The cast ‘beak’ was 3.9 – 5.1 in (100 to 130 mm) thick.
An 810hp Continental AV1790 12-cylinder air-cooled gasoline engine propelled this chassis to a speed of around 21 mph (34 km/h). The tank’s weight was supported on seven road wheels attached to torsion bar suspension. The drive sprocket was at the rear while the idler wheel was at the front. The idler wheel was of the compensating type, meaning it was attached to the closest roadwheel by an actuating arm. When the roadwheel reacts to terrain the idler is pushed out or pulled in, keeping constant track tension. The return of the track was supported by six rollers.

Turret

The T58’s turret was one of the largest oscillating turrets ever designed, at approximately ¾ the length of the hull. Changes had to be made to the T43/M103 hull to accommodate the new large turret. When initially tested on one of the hulls, the turret bustle would collide with the mufflers of the main engine and auxiliary generator located on the engine deck. To fix this issue, the mufflers were relocated 20-inches (51cm) to the rear. A new travel lock was added to the deck to accommodate the larger gun.
This turret had similarities to the T69 medium tank prototype, in that its roof had multiples ways of ingress and egress. The turret roof was constructed from two removable plates. The rear plate was bolted in place, while the front section, like the T69, was hinged and could be opened outward by use of a hydraulic piston. The large opening made it easier to exit the turret in an emergency. In the open position, this opened section also provided a shield for the crew while evacuating. These sections were designed to be easily removed to permit installation of the autoloader mechanism and other components.
A ventilator was placed at the rear-right of the turret atop the bustle to vent gases and smoke produced when the gun is fired.

Line drawing of a face-on view of the T58. Note the size of the turret. Photo: Presidio Press

Links, Resources & Further Reading

Presido Press, Firepower: A History of the American Heavy Tank, R. P. Hunnicutt
An official US Government report dated April 1954. READ HERE
On History of War


A cut-away view of the inside of the T58’s turret. Photo: Presidio Press

Armament

Originally, it was planned to utilize the 155mm Gun T80. This proved unnecessary as the chosen ammunition for the gun was of the chemical type and did not require the high-velocity granted by the T80. Designers instead opted for a lighter weight version of the lower velocity 155mm Gun T7, the gun developed for the Heavy Tank T30. Firing HEAT through this gun, the maximum armor that could be penetrated (angled at 0 degrees) was 16 inches (406mm).
This modified version of the T7 was originally designated as the 155mm Gun Howitzer T7E2. It was later changed, however, to ‘155mm Gun Howitzer T180’. There was no actual change to the gun, just a change in nomenclature. The T180 differed greatly from the original T7 though. The breech block was changed from a horizontal to a vertically sliding type. A bore evacuator (fume extractor) was added towards the end of the gun, and a T-shaped blast deflector installed on the muzzle. The gun tube wall was thickened and the chamber lengthened about an inch (~25mm) to accommodate the plastic closing plugs used on the cartridge cases of the two-part ammunition.
Unlike the T57 that had a rigidly mounted gun, the T58 was outfitted with a four-cylinder hydro spring recoil system in a mount designated the T170. There were 2 springs to each side of the breach. To save space and remove the need of extending the length of the turret, the recoil of the gun was limited at 12 to 14 inches.
Secondary armament consisted of a coaxial .30 Cal (7.62mm) Browning machine gun, and a .50 cal (12.7mm) Browning heavy machine gun mounted atop the commander’s cupola. The oscillating turret provided an elevation of 15 degrees, with a depression of 8 degrees. The original specifications included a second coaxial machine gun, but this was not included.
The main gun was aimed via periscopic sights. There was one lens on each side of the turret, known as ‘frog’s eyes’. These types of sights were used on many American tanks from the early 1950s onwards, including such tanks as the T69, M48 and M60.
The armor on both the collar and upper part the turret was extremely thick, but exact measurements are unfortunately unknown.

Autoloader

The 155mm gun was fed by an autoloading mechanism located in the turret bustle. It was not too dissimilar to the one used on the T69 medium tank prototype, consisting of a 6-round cylinder magazine with an incorporated rammer. On the T69, it actuated up and down during the loading sequence. On the T58, due to the size and sheer weight of a fully loaded magazine, the cylinder was fixed in place.

Two diagrams looking at the front and back of the auto-loading mechanism. Photo: Presidio Press
The loading sequence was thus: The loader used an internal, electrically powered hoist attached to the turret roof to remove one of the 95 pound (45kg) shells from the ready rack and insert it into the loading tray of the cylinder. The round was then slid into an empty cylinder chamber. The loader then selected the requested ammo type by manually rotating the cylinder with a hand crank. The separately-loading ammunition (projectile then charge) was rammed into the breach as one unit. After firing, the empty propellant cartridge was ejected back into the cylinder, where it was removed by the loader before the sequence began anew.

Crew

The crew consisted of a Commander, Gunner and Loader located in the turret and Driver in the front of the hull. The Gunner was located at the front right of the turret, the Commander sat behind him under a vision-cupola. The Loader was positioned on the left of the turret under his own hatch.

Fate

Work on two pilot turrets continued into 1956 despite numerous design changes during production and delays in obtaining and producing various parts required for assembly. By this time, however, trends had shifted, and a tank such as the T58 was no longer thought a necessary to the military.
The T58 project, along with the T57 and many other projects, was canceled on the 17th of January 1957. Following this outcome, both pilot turrets were scrapped. All that survives today are a few photos and government reports.

An article by Mark Nash

Specifications

Dimensions (L-w-H) 37.14 x 12.34 x 9.45 ft (11.32(oa) x 3.76 x 2.88 m)
Total weight, battle ready Around 62.5 tons (125 000 lbs)
Crew 4 (Commander, Driver, Loaders, Gunner)
Propulsion Continental AV-1790-2 V12, AC Twin-turbo diesel 810 hp.
Transmission General Motors CD-850-3, 2-Fw/1-Rv speed GB
Maximum speed 21 mph (34 km/h) on road
Suspensions Torsion bars
Armament Main: 155mm Gun Howitzer T180 Sec: 1 Browning M2HB 50. cal (12.7mm), 1 cal.30 (7.62 mm) Browning M1919A4
Production 2


Illustration of the 155mm Gun Tank T58 by Tank Encyclopedia’s own David Bocquelet.

Categories
Coldwar American Prototypes

76mm Gun Tank T92

USA (1952-58)
Light Tank – 2 Prototypes Built

In May of 1952, the hunt was already underway for a new light tank that would replace the M41 Walker Bulldog which had only entered service the previous year. Three companies were competing for a production contract. These were the Cadillac Motor Car Division (CMCD) of General Motors Corporation (GM), Detroit Arsenal (DA), and Aircraft Armaments Incorporated (AAI).
Cadillac and Detroit would compete individually with their own designs. These would both be designated as the T71. The T71 was rather traditional in its design when comparing it to AAI’s proposed tank, which was rather unique, to say the least. As such, the latter vehicle would receive the designation of T92.

The initial T92 prototype. Photo: Presidio Press

Development

After review, a contract was handed to the AAI to produce a full-scale mock-up. Their tank was considered an extremely innovative design which offered greatly improved performance over previous light tank models. This also meant that it included newly developed features including some which were so novel they had never been tested before, which is considered risky when building a new tank.
The Chief of the Army Field Forces and the Assistant Chief of Staff authorized development of the tank in late July 1953. The United States Ordnance Technical Committee also approved the design in March 1954, with clearance given to produce a pilot vehicle. On the 18th June 1954, AAI was given permission to build an additional pilot vehicle. Meetings on the 5th of November 1954 and 27th of January 1955 resulted in recommendations for numerous design changes.
Development continued into January 1956, at which point the competing T71 project was canceled. This was thanks, in no small part, to the rapid progression of the T92, and the troublesome development of the T71 which ran into funding issues.

Design

Hull

Welded steel armor and castings formed the hull of the T92, which was extremely flat and made up of oblique surfaces. The hull was wedge-like in its shape and extremely low profile. One of the more outlandish thoughts behind the shape was that it would help to deflect the blastwave of a Nuclear Blast should it have taken one head on.

A comparative image showing the size difference between the T92 and the M41 Walker Bulldog. Photo: Presidio Press
The armor thickness was almost identical to the M41, which was 31.7mm (1.2 inches) at its thickest, but it was considerably lighter at 18-tons than the 26-ton Walker Bulldog. This was due to a reduction of overall parts, with some constructed from Aluminum alloy. Such parts included the access doors of the power plant, generator, and battery compartments. The fenders were constructed from a blend of Aluminium and fiberglass reinforced plastics. It was designed to be as light as possible to allow it to be air-transported or deployed via-parachuted drop.
Access into the hull, as well as the various cupolas over the various crew positions, was through a rather large, square two-part armored door in the rear. Each door was fitted with a vision block. To the left of the doors was stowage for the pioneer tools (shovel, pick-ax, etc). To the right was stowage for two fuel “Jerry” cans. These were stored vertically with one on top of the other.

A view of the rear of the tank showing the two-part door and stowage positions. This is the updated vehicle with the added idler wheels. Photo: Presidio Press

Mobility

The T92’s power pack consisted of a 357 horsepower AOI-628-1 (AOI: Air-cooled, Opposed, Inline) engine that was located in the front right of the hull. It was connected to an Allison XT-300 transmission providing 6 forward and one reverse gear. The top speed on road was 35 mph (56 km/h). There were two air intakes; the large grill on the upper glacis and a ‘mushroom’ ventilator at the right front of the turret. The exhaust ran to the back of the vehicle under the right sponson, ejecting fumes through a grille at its rear. The whole power pack (engine & transmission) could be removed and installed as one piece. Fuel was stored in two 75-gallon (341 liters) bladder-type tanks for a total of 150 gallons (682 liters). These bladders were located at the rear of the hull.
The driver sat to the left of the engine, just in front of the turret ring and was protected by a steel firewall. The vehicle was operated by two small control handles that were used to steer and brake. He had a hatch above his head fitted with vision blocks. It swung open to the left on a pivot. There was also an escape hatch beneath his position.
Suspension on the T92 consisted of a Torsilastic system which is not commonly used on armored vehicles. In the case of the T92, this consisted of a cylinder attached to the hull sides. This intern, consisted of a hollow shaft and a coaxial tube, with rubber between the shaft and the tube. The rubber was sulfurized to make sure the shaft and the tube were firmly attached. The Torsilastic suspension type eliminated the friction between metal parts and thus did not need to be lubricated as often as standard suspension types. The rubber acted as an elastic element, as well as a shock absorber, meaning the vehicle could be quieter and more comfortable to drive. This suspension system was also used on some LVT models and the M50 Ontos. The external nature of the Torsilastic suspension saved a great deal of room inside the vehicle that would otherwise have to accommodate the long torsion bars of a traditional suspension. There were 4 road-wheels per-side, each with a corresponding suspension unit. The drive wheel was at the front, and did not have traditional external teeth. There were long posts around the wheel which slotted in guide holes in the track which would pull it around. In the initial design, there were no return rollers. As such, the track would’ve been quite slack over the return which could result in ‘track-slap’ damage or the loss of the track. The meetings of November 1954 and January 1955 brought this to light, and it was recommended that at least two return rollers be installed. One was installed behind the suspension unit of the second road wheel, the other was installed behind the suspension unit of the last road wheel/trailing idler.
The tracks were a band type which did not require pins to hold the links together. They were mostly rubber and reinforced with steel cable, and were rather thin at just 16-inches (40.64 cm) wide. The full length of the track was 390.25 inches (9.91 meters), composed of nine separate sections. Two spare sections were stowed on the gun cradle at the rear of the turret.

Photo: Presidio Press

Turret

The turret and arrangement of the T92’s armament was perhaps the most unique feature of the vehicle. It sat on an 89-inch ring and was cleft in its design, with a large hollow in the middle cut out for the 76mm Main Armament. On either side of the gun were two cupolas which could rotate independently of the turret and were armed with machine guns. The one to the right of the gun was the commander’s and the one on the left was for the gunner. These cupolas were based on commander’s cupolas found on the M48 and M60 tanks. In the initial design of these, it was intended for both of them to be armed with Browning M2 .50 Caliber (12.7mm) machine guns. However, in the meetings of November 1954 and January 1955, it was decided to replace the machine gun in the Gunner’s cupola with a Browning M1919 .30 Caliber (7.62mm). The cupolas retained the ability to mount either weapon.
As well as the vision blocks in these cupolas, both the gunner and the commander were equipped with periscopes that enabled them to look over the gun. The cupolas were manually traversable but could also be brought into line with the main armament with the use of hydraulic slewing motors. The traverse range was 194 degrees, 10 degrees inboard forward, and 4 degrees inboard aft. The machine guns could elevate manually through a range of +60 to -10 degrees. Beneath each cupola was a suspended seat for the respective crew member to sit on, under which were drums for the machine gun ammo.
Both the gunner and commander could traverse the turret, aim and fire the main armament. The power elevation and traverse controls, as well as the gunnery controls, were mirrored in the commander’s position. The commander could override the controls to lay the gunner on to a target or engage it himself.

Illustration of the First prototype by David Bocquelet
The early version of the T92 utilized a trailing idler wheel instead of the traditional raised version which was added to the vehicle at a later date. This side view shows off the Tank’s unique profile. Illustration by Tank Encyclopedia’s own David Bocquelet.

Armament

Main armament of the T92 consisted of the 76mm Gun T185E1. This gun was ballistically the same as the 76mm Gun M32 found on the M41 Walker Bulldog and was even fitted with the same T-shaped single-baffle muzzle-break and fume extractor. This gun could fire Armor-Piercing (AP), High-Velocity Armor-Piercing (HVAP) and High-Explosive (HE) rounds.

A top down view of T92 pilot number 2 after arrival at Aberdeen on 22 July 1957. Note the unique turret and armament arangment. Photo: Presidio Press
The major differences with the weapon was its quick-change barrel, and the fact it was mounted upside down. This was to accommodate a semi-automatic loading system. The loader, who was seated in the left rear of the vehicle, placed one of the tank’s sixty 76mm rounds (28 in the main rack, 24 in the dispenser rack, 7 in the ready rack, and 1 kept in in the loading system) onto a tray behind the breach. When it is properly seated on the tray, it is automatically locked into position. The loader then held down a button for the duration of the cycle which consisted of the round being brought into line with the breach (whatever the guns state of elevation) and rammed in. The gun also featured a fully-automatic ejection system. When fired, the gun’s recoil would push the spent cartridge out of the tank through a small void in the armored box surrounding the breach. This was seen as essential as without it, the small crew compartment of a light tank like the T92 would soon fill with large, empty 76mm cases and the resulting irritant fumes.
The gun was mounted in a cradle in the center of the turret. The breach end was protected in an armored box and extended back to the rear of the turret. When the gun was depressed, the breach end lifted out of the turret roof. When the gun was elevated the breach sank into the hull. The voids created between the gun and body of the turret were covered with a canvas screen. Maximum elevation was +20 Degrees, maximum depression was -10 degrees. A semi-circular cage which acted as a guardrail was installed at the rear of the turret to protect the breach. It was to this that spare track sections were stored. Mounted above and to the left of the main gun was a coaxial Browning .30 Cal (7.62mm) M1919/M37 machine gun.

Tests

T92 Pilot No. 1 arrived at the Aberdeen Proving Grounds (APG) for tests on the 2nd of November 1956. Due to a miscommunication with constructors, some parts were missing from the vehicle. Namely, the Commander and Gunner’s cupolas. Weights were added to the positions to simulate for the automotive tests before the cupolas arrived at Aberdeen and fitted. T92 Pilot No. 2 arrived at Aberdeen on the 22nd of July 1957. This vehicle was used to evaluate the crew and their respective compartments and positions. At the time, it was expected that the T92 would enter full-scale production by mid-1962.

The T92 (with original tracks) taking part in cross-country tests. Photo: Presidio Press
Testing at Aberdeen identified a number of areas where the tank needed to be improved. These were mostly with the suspension. The band type track proved to be prone to breakage and throwing. After just 202 hours of test time, the track was replaced with the thinner (14-inch/35.56 cm as opposed to 16-inch /40.64 cm) traditionally linked tracks of the Light Tank M24 Chaffee. There were no long-term plans to keep this track for the production model, and plans were made to design a stronger band-type track. The adoption of this track necessitated the modification of the sprocket wheel to the traditional type with external sprocket teeth.
Another attempt to stop the track being thrown was the addition of a compensating idler wheel. This was the most drastic of the changes. Such idler wheels were mounted on a lot of tanks of the era, such as the M48, M60 or M103. They are attached to the closest roadwheel by an actuating arm. When the roadwheel reacts to terrain the idler is pushed out or pulled in, keeping constant track tension. These were mounted on a frame that was welded to the vertical rear plate of the tank.

The revised T92 with the added compensating-idler and the tracks of the M24 Chaffee. Photo: Presidio Press

Fate

In 1957, funding was made available for two further Pilot vehicles, each one would have the suggested improvements incorporated. Delivery of these was expected by mid-1958. However, the order was canceled prior to completion.
In 1957, it was discovered that the Soviets were working on an amphibious capable light tank. This would later come to be identified as the PT-76. The T92 was assessed to see if it could be made into an amphibious vehicle. This was soon proved to be unfeasible. The effectiveness of the 76mm gun was also now called into question. In a time where the larger 90mm gun was beginning to struggle, the 76mm was now seen as obsolete. Following this, the T92 project was canceled in late 1958. Light Tank design work would then focus on the United State’s own amphibious light tank, ultimately culminating in the problematic M551 Sheridan.
One surviving T92 was preserved for a long time at the United States Army Ordnance Museum at the Aberdeen Proving Grounds in Maryland. The tank has since been removed from the site with the closure of the museum in late 2010. It was moved to Fort Lee in Virginia where it currently resides in storage.

An article by Mark Nash

Specifications

Total weight, battle ready 18 tons
Crew 4 (Commander, Driver, Loader, Gunner)
Propulsion 357 horsepower AOI-628-1
Top speed 35 mph (56 km/h)
Suspensions Torsilastic
Armament 76 mm (3 in) gun T185E1
.50 Cal (12.7mm) Browning M2
2X .30 Cal (7.62 mm) Browning M1919A4/M34
Armor Up to 31.7mm (1.2 inches) thick
Production 2 Prototypes

Links, Resources & Further Reading

Presidio Press, Sheridan: A History of the American Light Tank, Volume 2, R. P. Hunicutt
Osprey Publishing, New Vanguard #153: M551 Sheridan, US Airmobile Tanks 1941–2001
Profile Publications Ltd. AFV/Weapons #46: Light Tanks M22 Locust and M24 Chaffee, Colonel Robert J. Icks
US Archives

Categories
Coldwar American Prototypes Failed Tanks

90mm Gun Tank T42

Failed tank

U.S.A. (1948-54)
Medium Tank Prototype – 6 built

In the early 1950s, the United States Military began a design program to develop tanks that would replace those currently in service. The faithful M4 Sherman had begun to show its age and was in the process of being replaced by the M26 Pershing and the upgraded M46 Patton.
At their core, however, these tanks were still very much vehicles of World War II era and did not make use of newer technologies that had begun to appear. One of the tanks to spring from the design program was the Medium Tank T42. Other tanks to spring from this program included the Light Tank T41 and Heavy Tank T43. These would become the 76mm Gun Tank M41 Walker Bulldog and the 120mm Gun Tank M103 respectively.

The wooden mockup of the proposed T42. Photo: Presidio Press

Design and Development

At a meeting at Detroit Arsenal on the 28th of September 1948, specifications outlined by the United States military for a new Medium Tank were put forward. On the 2nd of December, the designation of Medium Tank T42 was secured.
The Military’s Specifications were thus:

  • A weight of approximately 36 tons
  • Better armor protection than the M46 but equivalent armament
  • Main armament stabilization in elevation and azimuth
  • An automatic loading system
  • A concentric recoil system (Hollow tube around the barrel. A space-saving alternative to traditional recoil cylinders)
  • Blister mounted  .30 Cal (7.62mm) machine gun on each side of the turret
  • Coaxial .50 Cal (12.7mm) and .30 Cal machine guns.

A number of these initial features were based on the Prototype Light Tank T37. This included the blister mounted machine guns. Other features included a similar chassis length with five road wheels, powerplant and transmission, mudguards/sand shields over the tracks, and a turret ring diameter of 69 inches. This was the same diameter that was introduced in 1941 with the M4.
Construction of a mock-up was approved in March 1949 and reviews of this model were held in October and December, with a number of suggestions put forward to improve the design. The similarities to the T37 began to disappear. Ground contact length was increased from 122 to 127 inches (3.09 to 3.22 meters), the turret ring was widened to 73 inches and finally, the turret mounted blister machines guns were deleted.

Hull

The hull of the T42 was a combination of two parts. The forward bow portion was a single homogeneous steel casting, while the rear was a welded assembly of steel armor plates. The two halves were welded together in the middle of the tank. The casting of the upper glacis plate was 4.0 inches (101.6 mm) thick, sloped at 60 degrees.
The T42 eliminated the archaic feature of a bow machine gun and accompanying crew member. As such, the driver was alone in the hull. Room left over by the absent crew member was taken up by a 36-round ammunition rack.

One of the first T42 Prototypes. Photo: US Archives

Mobility

The T42 did retain the engine and transmission of the T37. This consisted of the Continental AOS-895 gasoline engine (AOS: Air-cooled, Opposed, Supercharged) rated at 500 horsepower, and the General Motors CD-500 cross-drive transmission. This gave the tank a top speed of 41 mph (66 km/h). The driver operated the vehicle with the Manual Control joystick, often known as the ‘Wobble Stick’.
The tank was considered underpowered, however. Tests were mounted by placing the powerplant in the hull of an unused Medium Tank T40 chassis and running it against a late model M4A3. These tests took place at the Aberdeen Proving Ground on the 7th of November 1950. The T42 proved to be only marginally more mobile than the M4, reinforcing the opinion that the tank was underpowered.
The tank ran on a five road-wheels with the drive sprocket at the rear. There were three return rollers unevenly placed along the return of the track. The wheels were attached to torsion bar suspension.

Turret

The turret was a completely new design, but not too dissimilar to that of the T41 (M41 Walker Bulldog) in length and shape. It was completely cast in construction. The lengthy turret bustle was used to store the radio set and also housing for the ventilator fan. The turret was manned by 3 crew members; Commander, Gunner, and Loader.
The outside of the turret was dominated most noticeably by the armored housings of the stereoscopic rangefinder lenses. Also known as ‘Frog’s Eyes’, this type of gun system continued to see use after the T42 on vehicles such as the M48 Patton III and M103. Atop the turret, on the right, was the commander’s vision cupola with an AA mount for a .50 cal. machine gun. The loader’s hatch was to the right of this.

Armament

It was suggested by a British liaison officer that the Ordnance QF 20-Pounder was far superior to the 90mm Tank Gun M3A1 used on the M46 Patton. Despite its use on Britain’s own Centurion and, being a more powerful weapon, the 20-Pounder was deemed unsuitable for use on a Medium Tank by the US.
The US instead opted for a newly developed 90mm gun, the T119. This gun was a vast improvement over the M3A1. Firing it’s APDS (Armor-Piercing Discarding-Sabot) round, it could punch through 11.1 inches (282mm) of homogenous steel armor, angled at 30 degrees, at a distance of 1000 yards (914.4 meters).
The main armament was complimented by the coaxially mounted Browning M1919A4 .30 cal. (7.62mm) Machine Gun and Browning M2HB .50 cal. (12.7mm) Heavy Machine Gun.

Nomenclature Change

On the 7th of November 1950, the United States Ordnance Committee instigated a change in nomenclature for tanks in the US Military. It was decided that weight designations (Light, Medium, Heavy) were no longer suitable due to changes in the way tanks were developed and employed on the battlefield, and the varying calibers now available. The caliber of the gun replaced the weight designation. For example, the T42 changed its designation from ‘Medium Tank T42′ to ’90mm Gun Tank T42’.

The Korean Tank Panic

Six prototypes were constructed and finally delivered to the Aberdeen Proving Grounds for testing on 30th December 1950. However, by this time, the Korean War had been raging for a full six months. To put it mildly, this caused a bit of a panic among the hierarchy of the US Military, and a crash program was launched to find a suitable tank to field in the conflict. The death warrant for the T42 was signed when the US Army Field Forces (AFF) declared the tank unfit for production. This did not stop the Ordnance Department though, who continued to work on the tank in the hopes that it could yet become the US Army’s next Medium Tank. Prior to this, in November, work had begun on the T42’s replacement, designated as the 90mm Gun Tank M47. Characteristics of the vehicle were outlined in January 1951.
The immediate answer to the panic was found by returning to the current tank in service, the M46 Patton. It was found that most of the T42’s issues were with its hull and the turret was found to be perfectly serviceable. As such, a program began to mount the T42 turret on the hull of the M46.
The M46 was slightly modified to accept the new turret. This modification took the form of expanding the hulls turret ring to match the turrets at 73 inches. This combination was tested with the use of an M46 hull. This vehicle was designated the M46E1. Only one was produced for tests purposes.
To bring the M46 hull up to the requirements for the M47, the angle of the 4-inch (101.6mm) upper plate was increased to 60 Degrees from the vertical. The air filter in the upper hull front was also removed, giving a better contour to the armor profile. This configuration was accepted and serialized as the Medium Tank M47 Patton II. However, it arrived too late to serve in the Korean War. The tank was declared obsolete in 1957 in the US Military but went on to see service in the arsenal of other countries military’s. In the US, the M47 was replaced in service by the 90mm Gun Tank M48 Patton III.

An early production M47. Photo: Presidio Press


The 90mm Gun Tank T42.

The 90mm Gun Tank M47 Patton II, the combination of the T42’s turret and the hull of the M46 Patton.

The Medium Tank T69 with an Oscillating Turret mounted on the Hull of T42 Prototype vehicle no. 3.
All three illustrations are by Tank Encyclopedia’s own David Bocquelet

Further Developments

The Aberdeen trials began with automotive tests. In an effort to improve the T42’s mobility problems, the prototype vehicles sent to Aberdeen were fitted with the upgraded AOS-895-3 engine and CD-500-3 transmission. Thanks to the substitution of some steel parts with aluminum, this incarnation was 500 pounds (227 kg) lighter than its predecessor. The overall performance was improved, finally meeting the original specifications and surpassing the results of the previous test using the T40 hull. The Army Field Forces were still not impressed enough. Considering the T42 still much too underpowered, they continued to refuse its adoption. By this time, their attention had shifted to the M47 and T48 (later M48) development program.
The trials did not start well for the T42. Pilot vehicle number 1 was completely destroyed by a catastrophic fire caused by a loose pin in the final drive which tore a hole in the fuel tank. This resulted in fuel spraying over hot components of the engine. The tank was a fireball in seconds. Pilot vehicle number 2 arrived at Aberdeen in April 1951 to continue the now delayed automotive tests. This vehicle was later modified to allow the installation of a new transmission, the XT-500. This necessitated a modification the rear hull. This took the form of replacing the sloping rear hull plate with a vertical one. The XT was more efficient and had a lower production cost of the CD model, with just 60 percent of the overall part-count.

The T42 with CD Transmission on the left, and XT Transmission on the right. Note the changes to the rear of the tank. Photos: Presidio Press
Despite the deletion of the blister machine guns on the turret, developers were keen to employ extra machine guns somewhere on the vehicle to compensate for the lack of a bow mounted weapon. One solution was the mounting of machine guns on the mudguards just above the idler wheels. This took the form of an armored box. The box would contain one Browning M1919A4 machine gun, 680 rounds of .30 caliber (7.62mm) ammunition, a pneumatic charger, firing solenoid and a compressed air bottle. The system would be operated by controls in the driver’s position. The guns were fixed in traverse and elevation. Though not practical to aim, it was found that the weapons provided a good suppressing fire over an area. Further development was suggested, mostly to add a degree of traverse in the guns, but it went no further. The whole concept was later completely dropped.
During the spring of 1953, in an effort to keep the T42 project alive, a plan was formed to turn it into an option for a lighter more economical tank. Modifications planned were a steel elliptical hull and flat track suspension (track return supported by road wheels, as used on tanks such as the Soviet T-54). Had these plans materialized, the vehicle would have received the designation of 90mm Gun Tank T87, or Medium Tank T87. May 1953 marked the end of this project and the whole T42 program in general. The project was officially ended in Autumn 1954.

One of the later T42 Prototypes. Photo: Presidio Press

T69, the Only Variant

One of the original specifications for the T42 was not researched until almost a year after the tank was declared unfit for service. This specification was that an autoloader would be added when such a device was available. It was found that trying to add an autoloader in a conventional turret was impractical as the breach of the gun would have to return to a 0-degree elevation angle for it to line up after every shot. For this reason, it was decided that an oscillating turret would be the best option. Oscillating turrets are divided into two parts. A lower collar attached to the turret ring, and an upper portion with the gun fixed in place. The upper portion pivots on trunnions under hydraulic power providing the gun elevation and depression. With the gun fixed in place, the autoloader has a straight path to ram in the shells.
The new turret was mounted on the hull of T42 prototype number 3 which was modified with the XT-500 transmission. The tank received the designation of 90mm Gun Tank T69, also known as Medium Tank T69. The tank took part in a number of trials but, like the T42, it was not accepted for service. It was found that the vehicle bore no advantage over conventional designs.

The T69 at aberdeen proving grounds for evaluation. Photo: Presidio Press

Survivors

No whole T42 survives today. The only way the vehicle does survive is through the uses of its parts. A single hull survives as the T69, which currently resides in storage at National Armor and Cavalry Museum, Georgia, USA. The turret can, of course, be found all over the world where there is an M47 on display.

An article by Mark Nash

T42 Specifications

Dimensions (L-W-H) 26’9″ x 11’7″ x 9’4″ ft.in (8.1m x 3.5m x 2.8m)
Total weight, battle ready 38 tons
Crew 4 (commander, driver, loader, gunner)
Propulsion Continental AOS-895 gasoline engine, (air-cooled six-cylinder supercharged 8.2-liter engine), 500 horsepower
Transmission General Motors CD-500
Maximum speed 41 mph (66 km/h)
Suspensions Torsion bars suspensions, shock absorbers
Armament 90mm Tank Gun T119
Sec: 2 x Browning M2HB .50 Cal. (12.7 mm) Heavy Machine Guns
+ 1 Browning M1919 .30 Cal. (7.62 mm) Machine Gun
Armor 4 in (101.6 mm)
Total production 6
For information about abbreviations check the Lexical Index

Links, Resources & Further Reading

Presidio Press, Patton: A History of the American Main Battle Tank, Volume 1, R. P. Hunnicutt
US National Archives

Categories
Cold War British Prototypes Cold War Canadian prototypes Coldwar American Prototypes

FV4201 Chieftain/90mm Gun Tank T95 Hybrid

USA/UK/Canada (1957-59)
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.