M-V-Yoh - Tank Encyclopedia

United States of America (1953)
Medium Tank – Small Scale Model Built

The M-V-Yoh was one of the tanks created in order to incorporate the many innovative ideas from the H. L. Yoh Company. These vehicles came into being due to the Detroit Arsenal conference dubbed Operation Questionmark. This series of conferences attempted to encourage greater interaction and exchange of ideas between tank designers and the United States Army. Due to the structure of the conferences, which encouraged thinking outside the box, the Yoh tanks came into being.

Context

After the end of World War II, the Axis powers were defeated, marking the beginning of a new era. However, the relationship between the United States and the Soviet Union rapidly soured. The stark contrast in their ideologies created an atmosphere where conflict seemed imminent. Despite the swift development of nuclear weapons by both nations, the importance of maintaining a formidable ground force was not overlooked by either side.

To stay ahead in the arms race, the United States and the Soviet Union made substantial investments in new military equipment. Amidst this technological competition, the enduring significance of tanks was not forgotten. By 1951, the Soviet Union had already started production of the T-54 tanks, while the United States still relied on the stopgap M47 tanks.

The M47 tank. Notice how the hull is based on the older M46, while the gun is a rifled 90 mm which had less firepower than its Soviet counterpart.
Source: Wikipedia

The United States, however, was actively engaged in advancing its own tank capabilities. The development of the T48 tank was underway, and by summer 1951, the United States had already initiated the search for a successor to the future M48 Patton. Recognizing the potential extremities of future battlefields, American strategists sought innovative designs to counter challenges both old and new.

In pursuit of groundbreaking tank concepts, the United States launched Operation Questionmark. This initiative aimed to foster radical ideas that departed from conventional thinking. The unique designs that emerged from this operation were envisioned to address the unprecedented challenges anticipated on the battlefield. Through Operation Questionmark, the United States laid the groundwork for the evolution of tank technology, embracing creativity and innovation to prepare for the extremes of modern warfare.

Development

During the initial Operation Questionmark meeting, which compared the M48 to seven other tank proposals, proposals M1 to M3 all featured standard crew and internal arrangements, with the engine located in the rear and the crew housed in the mounted turret. They bore a striking resemblance to the M48, characterized by a rounded turret and a cupola with an integrated machine gun.

Proposals M4 and M5 both incorporated a rear-mounted turret, a driver positioned next to the engine, and a standard three-man turret crew. The primary distinction between M4 and M5 lay in their engines, the 717 hp Ax-1100 and the 500 hp AOS-895 respectively.

The last two proposals, M6 and M7, introduced the most radical ideas. Both featured oscillating turrets and included autoloaders as the main armament. All crew members were situated in the hull, and the engine was front-mounted. The key disparity between these designs was the caliber of their guns. The M6 was armed with the T140 105 mm, while the M7 featured the 90 mm T139. The turret was entirely remote-controlled by the crew in the turret basket.

The M6. Notice the two-man crew and the fully automated turret
Source: Abrams – A History of the American Main Battle Tank

Despite their efforts to create something substantially more suited for the future than the M48 Patton, all of these tanks fell short. Some exhibited minimal improvements, while others suffered from fundamental design flaws. The M4 and M5, for instance, had to limit the size of the driver’s vision port to facilitate engine maintenance, while the M6 and M7 encountered issues with the automatic loading system.

Although none of the proposals from the first Questionmark conferences were accepted, the United States recognized the benefit of providing engineers with minimal restrictions. Users had the opportunity to assess various new designs, and designers obtained practical requirements for their concepts.

To explore additional design concepts, another research and development program commenced in April 1952. Contracts were ultimately awarded to the Chrysler Corporation, Associated Engineers, and the H. L. Yoh Company.

H. L. Yoh Company was originally named Duncan Tool Design. This company had expertise in engineering and was involved in an assortment of projects. They had worked on electric transmission and contributed to creating the modern supermarket. However the company was also involved with the United States’ military, and by 1938, they also shifted their industries to defense production. Duncan Tool Design was renamed H. L. Yoh after Harold Yoh bought out other shareholders, and the company still remained working on a diverse batch of projects. Before getting the contract in 1952, the company had no prior experience with tanks, but its engineers still ended up designing the Yoh tanks.

Special Features

On June 1st 1953, H. L. Yoh Company unveiled seven unique medium tank designs and, with them, several new modules for these armored fighting vehicles.

The first of these was an improved mantlet referred to by H. L. Yoh Company as the Gun Shield. The Gun Shield allowed for better balancing of weight and a better sealing of the mantlet. All the weight of the gun was set on the aft of the trunnion, which, in turn, helped balance the gun. The Gun Shield was also separated into two distinct sections, with one exposed to the outside, while a second layer of armor formed an arc around the rotating trunnion. Due to the second layer of armor, the mantlet always protected the inside of the tank from any projectiles. This seal also made it much more convenient for defending against nuclear, biological, or chemical threats.

Notice the spaced armor in the Gun Shield which would reduce the penetration of chemical rounds.
Source: Abrams – A History of the American Main Battle Tank

The second add-on was something referred to as the Ammunition Grab. It was designed to assist the loader in lifting and relocating heavy rounds. This device was designed to go on the off-hand of a loader and was operated by squeezing the ratchet trigger. The free hand was used to guide the shell, and when the grabber was not in use, it could be compactly stowed on the turret’s roof. The grabber was operated with three key components: the release trigger, ratchet trigger, and the up and down control for the cable. The grabber made contact with the shell with three pieces of padding. However, due to the small surface area of the padding, there may have been problems with either the grip or an overuse of strength on the weak shell casing, causing it to be crushed.

Notice the curvature of the grabber, meaning it would not be interchangeable between different sized shells
Source: World of Tanks

The third module was an armored ready rack resembling modern ammunition blowout compartments. The device consisted of a rotating carousel contained in a metal cylinder. The carousel could be rotated, and the shell containers themselves could pivot for the loader to retrieve more easily. The entire metal cylinder had a chimney-like vent that redirected an ammunition fire. The metal armor itself was too thin to properly protect against penetrators. However, the metal shell was only supposed to protect the ammunition from spalling. This also implies that the thin armor could not contain the explosions that may have occurred if the ammunition was struck.

Notice the window which could compromise the containment of ammunition blowouts.
Source: World of Tanks

The fourth and fifth modules were both ideas for an auto-loader. To provide context, automatic loaders were not a new concept for the engineers of the 1950s. One of the first mass-produced auto-loading tanks was the AMX-13, which was developed in 1952. But, the auto-loading systems introduced by H. L. Yoh Company was very different from previous ones.

The first autoloader proposed was a bustle autoloader similar to modern cassette autoloaders. The ammunition was stored in small compartments located above a conveyor belt. Ammunition was dropped onto the conveyor belts, which then moved the ammunition to the middle of the rack, aligning it to the breech. A small arm then pushed the shell into the breach, loading the round. After the shell was fired and ejected, the arm reversed, discarded the casing, and was ready for loading the next round. There were several advantages to having such an autoloader. First, the tank now required less space inside the vehicle, freeing up more space for the remaining crew. This also made the loading automatic, giving the commander the ability to select rounds and bypass a wounded or deceased loader. On top of that, it freed up the loader for other roles, and could man the machine guns and assist other crew members.

The gun would have to go back to 0º of gun elevation to load new ammunition.
Source: World of Tanks

The second autoloader proposed was a drum/revolver-style one. Compared to the previous design, it allowed for a much higher rate of fire. The shell was rotated into place, where a plunger then pushed the ammunition into the breach. The shell was fired, and the recoil, plus pressurized gas, pushed the plunger back, putting the empty casing back in the revolver. Some of the benefits introduced by this autoloader included freeing up the loader and consistent loading times. The wall of the autoloader could also protect the ammunition from spalling. However, this autoloader added a lot of size to the gun, which could restrict the elevation and depression angles. The gun would also be heavier, which could lead to a harder time moving the gun. On top of that, recoil seemed to have been unaccounted for in the drawings.

The autoloader was estimated to contain 12 to 16 rounds.
Source: World of Tanks

The sixth idea was an auxiliary machine gun. This 7.62 mm Browning M1919 machine gun was integrated into the side of the turret by the loader’s side. The reason for this was due to the commander’s machine gun being asymmetrically located on the right, so the left side of the turret would not have received machine gun coverage. The machine gun had a 60º arc to either side, 15º of depression, and 20º of elevation. The gun shield was round and had the same thickness as the rest of the turret wall.

Notice the bulge in front of the machine gun, which would protect the barrel from oncoming fire.
Source: Abrams – A History of the American Main Battle Tank

The seventh idea was for horizontally mounted shock absorbers for the tank’s road wheels. However, mounting shock absorbers horizontally was not a new idea. What is more interesting is the name selected for this suspension idea. The official name was “shock absorbers for Christie suspension,” but this scheme was clearly not a Christie suspension. Christie suspensions had large vertical springs fitted to absorb shocks to the road wheels.

Notice how the shock absorbers fit in the space created by the boat shaped hull.
Source: Abrams – A History of the American Main Battle Tank

The last two modules proposed by H. L. Yoh Company were both emergency traction devices. The first was a “track within a track” idea. A thinner, narrower track was driven by the rear sprocket underneath the main tracks. There would also be a two-layer sprocket so both tracks would be powered. The emergency track was looped around the last half of the track wheels, which provided enough stability for the tank to move. The benefits of this system included providing existing tanks with a quick modification. The crew could remain in the safety of the vehicle while still having some mobility. However, this system overlooked the severe reality of anti-tank mines. Mines could mangle the track wheels, which could be jammed into the ground and get the emergency tracks stuck.

Notice how thin the emergency track is compared to the standard tracks.
Source: Abrams – A History of the American Main Battle Tank

The second emergency traction device presented consisted of a pair of spiked walkers. They were driven by an extended shaft from the sprockets. However, how this would be accomplished was not specified. This was very unconventional, so it provided unique benefits but also faced incredible challenges. The benefits included traction while the sprocket was damaged and extra traction on rough/slippery terrain. However, the size of the walkers, extra weight, structural strength of the legs all contributed to making this unlikely to work.

Notice how small the pads are, meaning they would be extremely ineffective on muddy or swampy terrain.
Source: World of Tanks

Design

One of the proposed tanks was the M-V-Yoh, a design characterized by its radical features, including a narrow oscillating turret and a similarly narrow hull. The entire tank boasted well-angled surfaces, providing exceptional ballistic protection. The driver and loader were situated in the hull, while the gunner and commander occupied the turret. The turret featured a turret ring with a diameter of 53 inches (1,346.2 mm). The estimated total weight of the vehicle was 40 tons (36.29 tonnes).

The oscillating turret was supported on trunnions with yoke mounts, allowing for easy disassembly at the yoke mount. This feature enabled the separation of the turret and hull, facilitating operations such as shipping. While the specific size of the M-V-Yoh was not specified, it would have been approximately 225.2 inches (5.72 m) in length, excluding the gun, 129.98 inches (1.84 m) tall, and 74.8 inches (1.9 m) wide without tracks. The tracks themselves measured 28.74 inches (0.73 m) in width each.

Wargaming’s render of the M-V-Yoh. Note the inaccuracy of the cupola and the external .50 cal (12 mm) machine gun.
Source: World of Tanks

Turret

The turret of the M-V-Yoh consisted of two distinct parts: the collar (lower piece) and the upper body. Despite its extremely narrow design, offering limited space for the gunner and commander, the designers managed to incorporate a rangefinder into the structure. The specific rangefinder model was unspecified but is presumed to be either an M12 or T46 stereoscopic rangefinder.

A stereoscopic rangefinder operated with dual eyepieces, allowing the operator to fuse two images into a unified picture. Each eyepiece contained a distinct reference mark. The operator adjusted the rangefinder until a specific mark overlayed the target, and then rotated the prisms until the marks converged in their view. The distance to the target corresponded to the rotation of the prisms. The range of the rangefinder was the distance that could be seen with the operator’s eye, and the accuracy very much depended on the operator’s ability to rotate the prisms precisely.

Additionally, the turret featured two cupolas positioned towards the rear. The commander’s cupola was equipped with an integrated .50 caliber (12.7 mm) machine gun. While not explicitly detailed in the blueprints, an accompanying illustration in the tank proposal depicted a radio placed behind the loader.

Notice the radio antenna behind the gunner’s cupola.
Source: Abrams – A History of the American Main Battle Tank

Crew

In the M-V-Yoh tank, the driver occupied the front of the hull, with ammunition racks on both sides. Positioned behind the ammunition rack on the driver’s right, and facing towards the rear of the vehicle, the loader had a second, wider ammunition rack behind them. The blueprints illustrated two unmarked devices slightly behind the turret ring. The smaller box mounted on the roof of the hull was likely the “ammunition grabber,” while the larger box could serve as storage for machine gun ammunition.

Drivers had the option to operate with their head above the hatch or buttoned up, using periscopes to navigate the tank. Additionally, the driver had access to two .30 caliber (7.62 mm) auxiliary machine guns positioned to their left and right. The loader’s role involved utilizing the ammunition grabber to hoist rounds onto a semi-automatic loader located in the turret. This automated system would then load the round into the breech, making it ready to be fired. The gunner was situated behind the breech on the left side of the turret, while the commander occupied the right side of the gunner. The turret was very slim and no ammunition was stored there. The only other piece of equipment stored in the turret would be the radio, which would be behind the gunner, allowing for easy access. One problem with this arrangement is the difficulty in reloading the two coaxial machine guns. Normally in tanks with a turret crew of three, the loader would reload the machine guns. But, in this case, the loader would be located in the hull making it difficult for the coaxial machine guns to be reloaded. The turret crew would be completely separated from the rest of the crew.

Notice the faint red boxes around the tank and how the frontal idler wheel is attached by an extended tube.
Photo: Wiki Warriors

Firepower

The M-V-Yoh was equipped with the rifled 105 mm T140 E3 gun and the tank could hold approximately 48 rounds. Other tanks that used this gun include the American T95 and various other paper designs. However, due to the lack of data and information about the M-V-Yoh vehicle, the exact elevation and depression angles are unclear but, because it had an oscillating turret, the tank would probably have had less than 20º of elevation and have around 8º to 13º of gun depression. The gun’s length, excluding the breech, was 292.6 inches (7.43 m) long, and the T182 shell was tested to have 3.5 inches (88.9 mm) of penetration against rolled homogeneous steel angled at 60° and at a distance of 2,000 yards (1,829 m). The muzzle velocity of the T182 round was around 3,500 feet per second (1,066.8 mps) and the muzzle energy was 6,657,000 feet pounds (9025.68 kilojoules).

The penetration statistics of the T140E3 gun. Notice how the gun weighed 4,895 pounds (2.22 tonnes)
Source: Abrams – A History of the American Main Battle Tank

The T140 E3 gun could fire 5 different types of rounds: the T182, T246, T247, T279, T298, T277, and T79.

The T182 was the main shell for the T140. It was an APBC (Armor-Piercing Ballistic Capped) round, and it weighed 35 pounds (15.88 kg) and was offered in four variants, the T182, T182E1, T184E2, and T184E3.

The tank also fired the T279 which weighed 13.6 pounds (6.17 kg) with a 7.5 pound (3.4 kg) tungsten core. The HVAPDS (High-Velocity Armor-Piercing Discarding Sabot) round flew at 5,100 ft/sec (1,554.48 m/sec) which was around 1.5 times the speed of the T184.

The T298 was a fin-stabilized HEAT (High-Explosive Anti-Tank) round which flew at 2,700 ft/sec (822.96 m/sec). The gun also fired T246 a 26.8 pound (12.16 kg) High Explosive, T247 which is a smoke round, and the T140 also fired all sorts of training rounds which most of them weighed 17.38 pounds (7.88 kg).

Shell type	Shell name	Shell weight	Shell velocity
HE (high explosive)	T246	26.8 lbs ( 12.16 kg)	2400 ft/sec (731.52 mps)
Smoke	T247	???	???
APBC (armor -piercing ballistic capped)	T182	35 lbs ( 15.87 kg)	3500 ft/sec (1066.8 mps)
HVAPDS (high-velocity armor-piercing)	T279	13.6 lbs ( 6.17 kg) 7.5 lb (3.4 kg) core	5100 ft/sec (1554.5 mps)
HEAT-FS (high-explosive anti-tank fin-stabilized)	T298	22.5 lbs ( 10.20 kg)	3700 ft/sec (1127.76 mps)
HEP (high-explosive plastic)	T297	???	2700 ft/sec (822.96 mps)

Note the difference of weight between the complete round and projectile.
Source: Patton – A History of the American Main Battle Tank

Other than the main gun, the tank was also equipped with two coaxial .30 caliber (7.62 mm) machine guns. Two more 0.30 caliber auxiliary machine guns located beside the driver and the cupola also had an integrated .50 caliber machine gun.

The miniature model of the M-V-Yoh.
Source: Abrams – A History of the American Main Battle Tank

The tank’s autoloader was completely different from the ones presented in the special modules. No data has been revealed about the autoloader and no other tanks have ever been reported of having equipped it.

Powerplant

The M-V-Yoh was powered by the Continental AOSI-1195-5, an air-cooled 8-cylinder diesel engine providing a total of 675 gross hp. This engine was not used in any designs other than the M-V-Yoh’s competition. Associated Engineers Inc. also used this engine in their tank proposal but the engine was instead boosted to allow it to output up to 710 gross hp.

The M-V-Yoh utilized the XT-500-1 transmission which was not used in any other vehicles, and the tank was propelled by a rear sprocket. While the exact speed of the vehicle was not specified, it was estimated to range between 35 to 45 mph (56.33 to 72.42 km/h).

Despite the robust engine, the small size of the hull raised concerns about fuel stowage, potentially impacting the tank’s range compared to other designs. To address this, an external fuel tank was apparent on the rear of the tank, strategically positioned to be shielded from incoming fire. This additional fuel storage aimed to enhance the tank’s operational range and address potential limitations associated with its compact hull size.

The tracks were similar to that of the M48 and had the stranded rubber padding, however the reserve track is likely to be fully rubber to reduce the thickness of the tracks over all.

Armor and Protection

Although not explicitly stated, the curved nature of the AFV suggests that it would have been made of cast steel. According to the blueprints, the frontal armor thickness at the sagittal view measures 7 inches (177.8 mm) angled at 30º. However, due to the boat-shaped hull of the tank, only the tip of the hull has this thickness.

The upper plate, on average, measured 4.66 inches (118.36 mm) and was angled at 60º, while the lower plate was 3.49 inches (88.6 mm) and angled at 50º. The turret ring was 10.72 inches (272.29 mm) thick, and the neck consisted of two layers, each measuring 2.33 inches (59.18 mm) of steel. The frontal face of the turret was 9.32 inches (236.73 mm) thick and angled at 70º, while the roof and belly armor were 1.86 inches (47.24 mm) thick.

The side profile of the M-V-Yoh. Due to only one of the blueprints containing armor thicknesses, the armor on the sides of the hull and turret is unknown.
Source: Abrams – A History of the American Main Battle Tank

Usage of the Proposed Special Modules

The M-V-Yoh was equipped with only three of the special modules that were proposed for it. One of the installed modules was the “track within a track,” also known as the “reserve track.” These tracks were only looped around the last three road wheels and were significantly narrower than their normal counterparts. At only 13.98 inches (0.36 m) wide, they provided only half the traction when compared to the same length standard tracks.

The second module was the ammunition grabber located in the hull, stored across from the loader. It could be used to assist in loading rounds into the automatic loader. The third module included two auxiliary machine guns located beside the driver. However, this arrangement differed from what was proposed before and would give the driver an unreasonable amount of tasks to perform. The tank was also equipped with the proposed horizontal shock absorbers to save some of the already cramped internal space.

A close-up of what both tracks may have looked like together according to Wargaming’s interpretation in World of Tanks
Source: World of Tanks

Fate of the Project

The M-V-Yoh and its accompanying modules were ultimately rejected, as the tank failed to provide sufficient benefits when compared to the M48, and some of the supposed advantages may have even turned out to be disadvantages. The inner tracks would have added more complexity to the tried and tested system of tracked vehicles. The frontal and rear road wheels would have had different sizes, making them non-interchangeable. Additionally, the fundamental problems of oscillating turrets posed difficulties in protecting the tank from nuclear attacks. There were also inherent issues with the tank not being able to be properly shielded from NBC (Nuclear, Biological,Chemical) weapons, leading to its ultimate rejection.

Conclusion

The creation of the M-V-Yoh was spurred by the looming threat of a Cold War turning hot. In response, the United States military actively sought innovative ideas that could give them an edge over the Soviets. The tank incorporated many remarkable concepts, which, even viewed through a modern lens, remain impressive. The proposed modules also endured into the modern day in various forms. From the armored ready rack to the autoloaders, contemporary equivalents are still in use. The M-V-Yoh was both radical and safe, offering a fresh perspective yet maintaining a sense of familiarity. These attributes resulted in a tank that was different yet feasible, but unfortunately, it fell short of meeting the military’s specific requirements at that time.

M-V-Yoh. Illustration done by Oussama Mohamed ‘Godzilla’, funded by our Patreon campaign.

M-V-Yoh tanks Specifications
Dimensions (l x h x w)	225.2 inches (5.72 )(excluding gun), 129.98 inches (1.84 m), and 74.8 inches (1.9 m) (without tracks (28.74 inches (0.73 m) wide))
Weight	40 tons (36.29 tonnes)
Propulsion	Eight cylinder, air cooled, diesel Continental AOSI-1195-5. 675 hp XT-500-1 transmission
Top speed	35 to 45 mph ( 56.33 to 72.42 km/h)
Armament	Rifled 105 mm T140 E3 gun 4x 0.3 cal MG 1x 0.50 cal MG
Status	Small scale model