Tiny Soviet Amphibian | Object 911B Amphibious Light Tank
The evolution of warfare and technologies in the years following the conclusion of the Second World War had a major impact on the way warfare would be conducted in the future. Amphibious vehicles to be used for river crossing were now highly appreciated. With the proliferation of nuclear armament, radiation protection became a major feature for new vehicles.
Finally, as time went on, there was more and more appreciation towards mounted infantry operating using an armored vehicle, as opposed to trucks. Eventually, this led to the Soviet Union creating infantry fighting vehicles prototypes , and then vehicles based on their chassis. The Object 911B was the light tank version of the Object 911, an infantry fighting vehicle designed by the Volgograd design bureau, most famous for their PT-76 around this point in time.
Welcome to this Tank Encyclopedia video on the Object 911B ! Feel free to leave a like and subscription, as well as checking out our website for the full written article this video is based on, and countless others. The idea of a combat vehicle that would combine amphibious capacities, a dismounted infantry complement, and an armament that could provide fire-support to these infantry dismounts and accompanying tanks was developed in the late 1950s Soviet Army. This would culminate for a call of offer made in 1960, for what would become the BMP, or infantry fighting vehicle. The requirements were sent to a large number of design bureaus, and, at that time, called for an 11-12 tonnes vehicle that would feature a crew of 2 and transport 8 to 10 infantry dismounts. One of the manufacturers which began work on a design was the Volgograd tractor plant (VgTZ), formerly the Stalingrad Tractor Plant (STZ).
Volgograd had extensive experience in amphibious vehicles design from the PT-76, which it had been producing since the early 1950s, and of which a number of derivative designs had already been designed. Volgograd’s proposals, by 1963, took the shape of two distincts prototypes, the Object 911 and the Object 914. The Object 914 took the clear basis of the PT-76 chassis. The Object 911, however, was more distinct.
Though there was still PT-76 inspiration and a number of common parts, such as the hydrojets and road wheels, the vehicle differed massively in other aspects. Likely the most noticeable were the four large, retractable aviation wheels which could give the Object 911 a wheeled drive, intended for use on roads during transfers to increase maximum speed and reduce fuel consumption. Object 911 also used an adjustable suspension which could be used to change the ground clearance of the vehicle. In the same timeframe as it worked on infantry fighting vehicle prototypes, Volgograd had also designed and produced three prototypes of the Object 906. This was a vastly modernized and improved design based on the PT-76.
It included a new, more powerful diesel engine, as well as an autoloaded 85 mm gun which significantly improved firepower in comparison to the PT-76’s 76 mm gun, particularly against armored targets and at range. By 1963, the Object 906 was at testing stage with three prototypes, and would eventually be rejected within the year. At the same time, work had concretized on the Object 911, and manufacturing of the prototype took place within this year. If the Object 911 was to be adopted, it had been made clear by the GBTU’s requirements that the vehicle’s chassis was to be used for a whole family of various derivatives. This could, for example, include a light amphibious tank, something Volgograd had extensive experience with. The other Volgograd prototype from the program, the Object 914, used a more conventional drivetrain which could perhaps be easier to modify into derivatives.
But, being very similar to the PT-76, there would be little reason to design a light tank version of the Object 914, seeing as the Object 914 could already be described as an infantry fighting version of a light tank. In comparison, the Object 911 could provide a more interesting base, particularly as the vehicle had an overall low profile enhanced by an adjustable height suspension. Volgograd had already worked on a very low-profile amphibious light tank in the form of a derivative of the Object 906.
This was the Object 906B, which was armed with a 125 mm tube missile launcher and featured two crewmembers in the turret. While work on the Object 906 and the Object 906B was discontinued during 1963, re-using components from them, notably the autoloader from the Object 906 and the general layout of the Object 906B, could prove valuable. As such, in 1963, the designing of a light tank version of the Object 911 would be carried out. The resulting vehicle would be named Object 911B. While using the chassis of the Object 911, it introduced a large variety of changes, not all directly linked to its function as a light tank.
While keeping the same 73 mm Grom armament, it took inspiration from the Object 906B’s layout and the Object 906’s autoloader. A prototype of the Object 911B would be manufactured and tested in 1964. Object 911B design The Object 911B was a particularly low vehicle. Its height would vary between 1,265 mm and 1,615 mm depending on the set height of the suspension. This was particularly small.
At its lowest, the height of a child, and even at its highest, the height of an average to small man. This would result in increased survivability, as the vehicle would be a hard target to hit at range, though at the same time creating proper crew conditions with such a low profile could be difficult. Length was 7.1 m, and width was 2.8 m. The weight of the Object 911B when loaded with crew, fuel, and ammunition would have been 12.5 tonnes.
Thanks to its fairly small dimensions and reduced weight, the Object 911B was air-transportable by the Antonov AN-12. The Object 911B used a peculiar hull and armor layout in order to increase the survivability of the vehicle and crew. This is typically not an easy task on a light amphibious tank, which has to use light armor protection and cannot afford to have large, thick metal plates in order not to compromise buoyancy and to retain a light weight. To the front of the vehicle was what is typically described as a “cargo compartment”. This section was quite long, and did not contain any vital parts necessary for the vehicle to function.
This storage space was reportedly capable of containing two men lying down. The cargo compartment’s possible use to transport personnel in emergencies is further supported by the presence of two access hatches on the roof sides. When empty, the large size but low weight brought by this compartment would likely also help with the Object 911B’s buoyancy.
The armor protection of this part of the vehicle can only be described as minimal. The front plate was only 10 mm thick, angled at 45° towards the back, while the roof was 6 mm thick and the floor a mere 4 mm. The sides likely had the same 10 mm thickness as the front, but without the considerable angling of the front plates Behind this cargo compartment would be the crew compartment. The two were separated by an armored bulkhead. Being 35 mm thick, though mostly vertical with no or minimal angling, this bulkhead was actually intended to be the main frontal armor of the vehicle’s hull.
An advantage of its position inside the vehicle was that it covered significantly less space, and as such, was much lighter than a similar armor layout applied to the front of the vehicle. When added to the 10 mm of the front armor and the considerable empty space of air separating it from the 35 mm bulkhead, this armor layout was actually quite considerable for a light infantry tank, and would typically protect the crew from heavy machine gun fire, and often even autocannons. The front armor of the turret, which would not benefit from the 10 mm of armor of the cargo compartment and spacing separating it from the bulkhead received 40 mm of armor angled backward at 48° frontally, and 40 mm angled backward at 30° on the sides, with the same thickness to the rear. The hull sides were also quite thickly armored, with 45 mm on the upper sides and 20mm on the lower sides. The roof and floor of the crew compartment were also thicker, at 10 mm each.
The crew compartment, within the vehicle’s turret, contained the two crewmembers, a driver to the right and a commander/gunner to the left. The crew compartment was then separated from the rear compartment by another 35 mm bulkhead. The vehicle’s powerplant and transmission were to the rear. This part of the vehicle had the same light armor layout found on the front cargo compartment. The floor was 4 mm thick, while the roof and rear were 6 mm, and the sides likely 10 mm.
The lower rear plate was angled at 48°, while angling on other plates was inexistant or minimal. This light armor protection was a necessity to keep weight down, but penetrating hits in this section of the vehicle would obviously be much more damaging than in the cargo compartment, easily leading to the vehicle’s engine being damaged or destroyed. The Object 911B used the same UTD-20 diesel engine as had been used on the Object 911. This engine had previously been set as part of requirements sent to different manufacturers to produce an infantry fighting vehicle prototype and all competitors to the Object 911 also featured it. It produced 300 hp at 2,600 rpm.
Without any fuel or oil, the engine weighed 665 kg, and had a consumption of 175 to 178 grams of fuel per hp and hour. A total of 500 liters of fuel were stowed within the Object 911B. An advantage of the UTD-20 was its limited size, which was a very favorable feature for mounting it in light armored fighting vehicles such as the Object 911B, allowing for the very low silhouette adopted by the vehicle. The Object 911B used a two-shaft, 5-speeds gearbox. It was reversible, meaning the vehicle could drive with the same maximum speed and gear ratios backwards.
The vehicle was also capable of neutral steering. In addition to this engine and transmission, the Object 911B also featured two hydrojets. These were found in the rear sides of the vehicle. They were taken straight from the PT-76.
A trim vane could also be deployed to prevent waves from washing over the vehicle. The suspension of the Object 911B was directly based on the one found on the Object 911, but incorporated a number of changes. A standout feature of the Object 911 had been its four retractable aviation wheels, which allowed for wheeled drive. The advantages of such a design were higher maximum speed and reduced fuel consumption when driving on roads, which would prove useful out of combat. However, it led to increased complexity in production, maintenance, crew training, and cross-country mobility.
As such, these retractable wheels were removed from the Object 911B’s design. The suspension of the vehicles was not exactly identical. The Object 911B was longer and had a longer track run, and as such used an additional road wheel, bringing the number to six per side. These were stamped steel hollow road wheels, the same type as used on PT-76, or at least a very similar type.
Their main advantage was that their hollow construction both saved weight and improved buoyancy. The suspension’s height could be adjusted and considerably lowered. The highest ground clearance the Object 911B could raise itself to was 450 mm, which was more than any other Volgograd amphibious tank design from the era, including the PT-76 and the Object 906.
When fully lowered, the ground clearance would be reduced to 100 mm. These changes in ground clearance would result in the Object 911B’s height varying from 1,625 mm to 1,265 mm. The higher ground clearance would be useful when the vehicle was driving over rough or irregular terrain, preventing risks of the lower hull being stuck on an obstacle, which would damage it or result in the vehicle losing track tension and getting bogged down and stuck. The lower ground clearance, on the other hand, would have the obvious advantage of significantly reducing the already tiny silhouette of the Object 911B. The vehicle’s drive sprocket was mounted to the rear, with a front idler. As on the Object 911, three return rollers, made of aluminum, were also present.
The tracks used on the Object 911B reportedly varied from the RMSH type used on the Object 911. Crew compartment and positions The crew compartment of the Object 911B was mostly in the vehicle’s turret. Both crewmembers were seated in this turret, with the driver to the right of the gun and the commander/gunner to the left. The turret was of a fairly wide but very low design, differing significantly from the standardised turret featured in the Object 911.The turret rotation speed seems to have been of 30 degrees/second.
The crew compartment appears to have been fairly low, at around 1.15m, and therefore quite cramped, however it had been made to be as resistant to radiations as possible. There was a radiation and chemical reconnaissance device in the vehicle, which would automatically shut the hatches if it detected an anomaly. The vehicle featured the common R-123 radio and R-124 intercom systems used on many Soviet vehicles of the time. The gunner on the Object 911B was located to the left of the gun.
Right on top of his head, was a fairly large rectangular hatch he could enter or exit from. Vision devices at the gunner’s disposal included a large periscope to the front and three prismatic periscopes to the side. The gun was automatically loaded, but could also be loaded manually, a task he would handle if the autoloader was no longer working. The driver had by far the most peculiar position on Object 911B.
His seat, as well as the controls, were placed in a sort of ‘bathtub’. This ‘bathtub’ itself rotated within the turret. It would systematically remain aligned with the front of the tank. This was meant to allow the driver to always look straight in the position he was driving towards, but on vehicles with similar devices, such as the MBT-70, this is known to have made drivers disorientated and sick, and this may have been an issue here as well.
Advantages included much better visibility for the driver, as well as, in most vehicles, resulting in less chances of crew casualties from anti-tank mines (mines would usually explode under the first road wheel, which the driver would be further away from thanks to his placement in the turret - the presence of the armored bulkhead would also grant protection against fragments). In the matter of crew survivability, the driver being in the turret could also usually escape the vehicle faster, and there would be no risk of the opening of his hatch being compromised by the gun barrel at an unfortunate time. When reversing, this crew position was even more peculiar. A mechanism was built within the transmission gear mechanism to allow the vehicle to be driven in reverse.
When wanting to reverse, the driver would be able to disconnect the clutch and pedals of his position, which t would then rotate 180°, and the controls would then be reconnected to the gearbox. In this fashion, when reversing, the driver would face towards the rear and could look straight towards where he was driving, making this essentially quite similar to driving towards the front. When it came to vision, the driver had three prismatic periscopes as well as a night vision device to enable safer and easier night driving.
Armament The main armament of the turret was a 73 mm 2A28 Grom low-pressure smoothbore gun. This was a fairly short gun, with a 2,117 mm tube and 2,180 mm total length. The design was overall made to be very simple and light.
For example, it lacked any bore evacuator, and the gun fumes were instead to be evacuated from the turret, which featured a ventilator for this purpose. The gun overall weighed only 115 kg and had an average barrel life of 1,250 rounds. Gun elevation angles in the Object 911B extended from +30° to -3°, which was limited even by Soviet standards. There was only a single shell type available to the 2A28 Grom in the 1960s, the PG-15V. The projectile was fin-stabilized and featured a rocket engine towards the rear, with propellant present towards the middle of the grenade. This allowed it to reach a higher speed than would typically be expected from a gun as short as the Grom, with a maximum velocity of 655 m/s.
The projectile’s armor penetration was officially rated at 300 mm at all ranges. In practice, this was slightly higher, with an average of 326 mm and a maximum of 346 mm. The shell was not without issues, however.
The downside of HEAT projectiles and a very short barrel were an overall low accuracy and high dispersion. The Grom’s PG-15V projectiles were notably very vulnerable to wind. The nominal maximum range of the Grom was of 800 m, but even at this range, only a 34% hit rate was achieved against a T-55 during trials. Additionally, for a significant amount of time no high-explosive shells existed for the Grom, and as such it had to use the same HEAT projectiles against infantry, where they were not completely useless but quite limited. While the Object 911B also had a 40 rounds ammunition stowage, its autoloader only held 27 at a time. The commander/gunner could feed more rounds into it once some were expended, or in the unlikely scenario all rounds within the autoloader were expended and no new shells had been placed into it, he could manually reload the gun as well.
The autoloader mechanism was a horizontal electrically-driven conveyor belt. It would ensure a rate of fire of 9 rounds per minute. The 2A28 Grom was supplemented by a 7.62 mm PKT coaxial machine gun. Mounted to the right of the gun, it would effectively be the only reliable means of dealing with infantry in the open.
A total of 2,000 7.62 mm rounds were stowed within the Object 911B. Unlike the Object 911, the Object 911B did not feature a Malyutka anti-tank guided missile. Performances The Object 911B prototype was completed and trialed in 1964. The vehicle was able to reach a maximum speed of 72.5 km/h on road..
On water, the vehicle could reach a similar maximum speed of 10 km/h. Maximum range on road was 500 km. The vehicle’s armor protection was tested against two different threats. The first was against 76.2 mm projectiles fired at ranges of 2,000 m with a muzzle velocity
of 665 m/s. This was likely kinetic projectiles fired from the PT-76’s D-56T (this velocity matches with the BR-350B and BR-354 APBC-HE shells, the latter which was more common by this point in time). The frontal crew compartment armored bulkhead and turret armor were both found to resist penetration at this range.
These were satisfactory performances. While the D-56T was not a very powerful gun and the projectiles were fired at a long range, a light amphibious tank is not a vehicle which is expected to resist armor-piercing weapons at pretty much any range, and indeed many vehicles fulfilling a similar role, such as the PT-76 or M551 Sheridan, would still be fairly easily penetrated even at this range. More representative of the armament a light tank with good armor protection for the type may be expected to resist, the Object 911’s crew compartment was also tested against the 14.5 mm KPV. The weapon failed to penetrate both the front bulkhead and the hull sides. If resistant to this weapon, the Object 911B would also resist an US M2HB Browning .50cal, and under favourable conditions perhaps even some 20 mm autocannons.
Conclusion Ultimately, the Soviet Army did not adopt the Object 911B, and work on the vehicle was discontinued after the trials ended in 1964. A number of reasons can be found behind this rejection. The most important likely was that the related Object 911 was rejected in favour of Object 764, which would become the very famous BMP-1. The Object 911B had faults of its own: The Object 911B was only armed with the same 73 mm 2A28 Grom as the BMP-1 and a coaxial machine gun, but did not feature the Malyutka ATGM which was crucial in improving the vehicle’s capacities against armour at medium and longer ranges. In short, while very interesting in several aspects, the Object 911B did not fulfill any niche where a vehicle of its kind was necessary, and as such it is not surprising it was not adopted by the Soviet Army. Unlike the Object 911, the Object 911B does not appear to be preserved at the Kubinka Tank Museum, or at least not in its visitable parts, as no modern photos of the vehicle have emerged.
It may have been scrapped, or still be preserved outside of public view. This concludes Tank Encyclopedia’s video on the Object 911B. We hope you liked it ! Don’t forget to check our website and our Patreon, and until next time, keep us in your sights !
2022-04-08 00:44
