SU-45

Soviet Union (1935)
Self-Propelled Gun – 1 Prototype Built

Prior to the Second World War, the Soviets were experimenting and developing a series of projects intended to improve the performance of already existing armored vehicles. One of these projects was an attempt to resolve the issues with the weak armament of Soviet amphibious tanks. This would lead to the creation of the experimental SU-45. While one prototype would be built, its poor performance would eventually lead to the cancelation of this project.

The SU-37 project

The Soviet Scientific and Technical Department Agency of Automobiles and Tanks (which was part of the Ministry of Defense of Red Army) issued a request to the director of plant №37 to begin designing and building a new self-propelled vehicle based on the T-37A amphibious light tank. The timeline was quite short. The order was given on 22nd March and the first prototype was to be completed by 11th April the same year. In reality, this task could not be achieved effectively in such a short period of time.

The T-37A was an amphibious light tank developed during the early 1930s in the Soviet Union. It was lightly protected and armed with only a single machine gun. The crew consisted of the driver and the commander/machine gunner. The T-37A was primarily intended to perform reconnaissance operations. Over 2,000 vehicles would be built, with most being lost during Operation Barbarossa in 1941.

When the tactical and technical requirements arrived, they included an option to use either an unchanged T-37A chassis or to build a completely new chassis with some elements taken from this vehicle. Other requirements included a maximum weight of the vehicle of 3 tonnes. The armament would include one 45 mm gun with a traverse of 30° (in both directions) and elevation of -8° to +25° and a DP machine gun. The ammunition load for the gun was to be 50 rounds, with an additional 1,000 for the machine gun. The overall armor protection had to be at least 5 mm thick (except the roof, which would be open-top) including an armored shield for the gun.

The new vehicle, which would receive the SU-37 (Samokhodnaya ustanovka – self-propelled) designation, was to have the same amphibious properties as the T-37A. It should have supplemented the weak firepower of the T-37A formations with its stronger armament. In addition, it was to fulfill a mobile anti-tank role on a regimental level.

The improved SU-45 replacement project 

Despite the short-term development goal, the actual design work on the new self-propelled vehicle dragged on. Almost from the start, a number of problems arose. One issue was the weight of the new vehicle was much larger than expected. This prevented it from being able to cross water obstacles. Another even greater problem was that many components for the T-37A were no longer being produced. A team of engineers under the leadership of I. Arharov was tasked with resolving the problems with the SU-37 and trying to find a better solution.

In November 1935, a mock-up version of the new modified self-propelled vehicle was presented to the Agency of Automobiles and Tanks of the Ministry of Defense. The basis for this new vehicle was the T-38 amphibious light tank. The T-38 was an improved version of the T-37A. It had a slightly modified suspension, overall simpler construction, better buoyancy properties, and the turret position was changed to the left side of the hull. The armament, crew configuration, and armor were the same. Over 1,200 of his vehicles would be built from 1936 to 1939.

This vehicle incorporated the chassis, transmission, and engine from the T-38. The main gun was still the same 45 mm anti-tank gun. The driver/gunner was initially positioned on the right side. The commission requested that the driver’s position be changed to the left side and that he no longer have to operate the gun. The first prototype was to be built by the start of 1936.

Name 

In the documents of the Agency of Automobiles and Tanks of the Ministry of Defense, the project received the “SU-45” designation. It is somewhat confusing that the Soviet Military Authorities decided to name the previous prototype based on the chassis on which it was based (SU-37 from T-37A) and the second prototype by the main gun caliber. This designation practice would continue on, many later developed self-propelled vehicles receiving names based on their gun caliber.

Author D. Nešić, (Naoružanje Drugog Svetsko Rata-SSSR) notes that the designation for this vehicle was T-45. This should not be confused with a Soviet attempt to improve the T-60 tank during the Second World War. If this is a mistake or misunderstanding on behalf of the author is difficult to know.

Specifications

Note that, due to the generally obscure history of this vehicle, sources greatly disagree about nearly all of the SU-45 components.

Chassis

For the construction of the SU-45, a modified chassis of a T-38 light amphibious tank was used. The front part of the chassis housed the crew and the main gun. To the rear, the engine and the transmission were placed.

Engine and transmission 

The SU-45 was powered by a four-cylinder liquid cooling 40-45 hp GAZ-A engine. The maximum speed of the SU-45 with this engine, on a good road, was 45 km/h. The off-road speed and operational range are unknown. The GAZ-A engine was started by using a MAF-4001 electrical starter. The position of the transmission was changed to the rear.

Suspension

With the increased number of crewmen, added ammunition, and other changes, the weight of the vehicle reached 4.5 tonnes (or 4.3 tonnes, depending on the source). The T-38 running gear had to be redesigned. This included adding an additional roadwheel (on both sides), making it five in total (from the original four on the T-38). While the added wheel was suspended individually, the remaining four were placed in pairs on a bogie suspension unit. All five wheels were rubber-tired. The idler and drive sprocket on the SU-45, in comparison to the T-38, had switched positions. The driver sprocket was now at the rear, while the idler was at the front. The two return rollers remained unchanged.

Superstructure

Not much is detailed in the sources about the superstructure’s design. The SU-45 was actually an open-topped vehicle. To shield the crew from the weather and elements, a canvas cover could be placed on top of the vehicle. Its overall construction, based on the few existing photographs, appears to have been simple in design. The SU-45’s side armor plates were flat, while the front plate was at an angle. The front, where the crew compartment was located, was slightly raised in comparison to the rear engine compartment. This was meant to provide the crew with protection but also to reduce the vehicle’s overall weight.

On the right front plate, a large square-shaped driver’s visor was placed. In its center, a smaller vision port was located. On the opposite side of it, a ball mount for the machine gun was located. Close to it, a pyramid-shaped cover can be seen. Its purpose is not clear, but it is likely to have been a protective cover for the gun’s sights.

Armament

The 45 mm M1932 anti-tank gun was chosen as the main armament of this vehicle. It was the standard Soviet infantry anti-tank gun prior to and during the first years of the war. While it would be replaced with larger caliber weapons, due to the large production numbers, it remained in use during the war. The 45 mm M1932’s armor penetration at 500 m (at 0 degrees) was 38 mm. The rate of fire was some 12 rounds per minute.

The main gun on the SU-45 was positioned in the front center of the vehicle. It was protected by a round shield placed in front of the gun. The elevation of the gun was -3° to +10°, while the traverse was 10° in both directions. The ammunition load consisted of (depending on the sources) between 50 to 100 rounds. The latter number seems to be unlikely, given the small size of the vehicle. The secondary armament consisted of one 7.62 mm DT machine gun. It was placed in a ball mount and positioned to the left side of the vehicle. It was operated by the vehicle’s commander. The ammunition load for this machine gun was around 1,100 rounds. The machine gun was also provided with a pivoting mount to be used as an anti-aircraft weapon.

The Crew

Depending on the source, this vehicle is listed to have either two or three crew members. In case it had three crew members, these included a commander/gunner, loader, and the driver. Despite initial plans to change the position of the driver to the left, on the prototype, he was seated on the right side. The remaining crew members were positioned opposite the driver. The commander was overburdened, as he had to operate the gun and the machine gun and command the vehicle, greatly reducing his effectiveness.

Armor protection 

The SU-45 was lightly protected, with armor plate thicknesses ranging from 6 mm on the sides to 9 mm on the front. These armor plates were connected using screws and rivets. This armor thickness was sufficient, at best, against small-caliber bullets.

Ultimate fate

Despite the plans to complete the first prototype by January 1st, 1936, due to many delays, it was only completed in the spring of that year. Once ready, a series of trails with the SU-45 were carried out. During these, a number of flaws in the design were noted. The T-38 chassis was overloaded and often led to mechanical breakdowns. The engine was underpowered, with an ineffective cooling system which often led to overheating. The transmission was also problematic and unreliable.

Seeing the results of these trials, the Agency of Automobiles and Tanks of the Ministry of Defense insisted that all these flaws and problems be resolved. The experiment would be carried on to the experimental T-38M chassis, but ultimately lead nowhere, and the whole SU-45 project was scrapped.

Conclusion

The SU-45 was intended as a lightweight self-propelled vehicle which was to provide additional support fire for the amphibious light tanks in cooperation with other units. The SU-45 design ultimately proved to be a failure. Having too great weight prevented it from being used as an amphibious vehicle. The engine had overheating problems. While it had much-improved firepower in comparison to the vehicle it was based on, it retained weak armor protection. This vehicle would never enter production and the Soviet units had to rely on their obsolete T-37 and T-38 vehicles. During the Second World War, these also proved to be unsatisfactory designs in many regards.

 

SU-45 specifications
Dimensions (L-w-h)	4.2 x 2.36 x 1.62 m
Weight	4.3 to 4.5  tonnes
Crew	3 (Commander/Gunner, Loader, and Drive)
Propulsion	40-45 HP GAZ-A engine
Speed (road)	45 km/h
Primary Armament	45 mm M1932
Secondary Armament	7.62 mm DT machine gun
Armor	6 to 9 mm
Total production	1

 

Source

• L. Ness (2012) World War II tanks,  Harper Collins Publisher
• D. Nešić, (2008), Naoružanje Drugog Svetsko Rata-SSSR, Beograd
• Svirin M. N. (2008) Самоходки Сталина. История советской САУ 1919-1945, Эксмо
• A.G. Solyankin (2002) Отечественные бронированные машины. XX век Том 1, Цейхгауз
• http://aviarmor.net/tww2/tanks/ussr/su-45.htm