Competitor from Gorkiy
In September of 1941, the Artillery Committee of the Main Artillery Directorate (GAU Artkom) initiated work on installation of more powerful armament into the T-60 tank. Management of design groups from Molotov GAZ and factory #92 "Novoye Sormovo" (called "OAO Nizhniy Novgorod Machinebuilding Factory today), one of the leading tank and artillery cannon factories at the time, was called to a meeting to discuss this issue. These two factories were built in the same city, about 10 km between gates. If the development was a success, this would significantly simplify cooperation.
When replacements of the TNSh are discussed, it is often mentioned that the gun was picky and jammed often. Of course, there were such cases, but they were often connected with improper use of the system. Some complaints were the result of factories taking certain liberties in producing ammunition. There was even a decree issued by the GKO (#627, September 4th, 1941) prohibiting factories from making changes to the gun or its ammunition without the approval of the People's Commissar of Armament. Another important factor is that the program to improve the T-60's armament began in September of 1941, and complaints about the TNSh started arriving only in October. Before that, the complaints were not about the gun.
Diagram of a 45 mm gun in the T-60 turret, designed by the factory #92 design bureau.
After studying captured tanks, it was decided that the T-60 would be re-armed to use the mod. 1938 45 mm tank gun. According to the requirements, the stock turret had to be retained. Initially, the GAZ and factory #92 design bureaus worked together on the project, but there were disagreements. As a result, each factory would provide their own variant of the re-armed turret. Model prototypes were due in December. In the case of the GAZ modernization, the process ended with the creation of the T-70. This article will discuss the fate of the factory #92 project.
The design bureau's engineers, under direction from V.G. Grabin, decided to use the existing layout of the turret as much as possible. The sight was placed in the middle of the gun mantlet, with the DT machinegun to the left and the 45 mm gun to the right. The commander's seat was displaced to the rear of the turret, between the cannon and the machinegun, just like in the T-60. The trigger button for the gun was on the turret traverse flywheel handle, and the trigger for the machinegun was on the elevation mechanism flywheel handle.When the project was presented, factory #92 already had blueprints for the 45 mm gun mount. After a tank was received, it would be possible to begin producing it in metal.
T-60 with the ZiS-19 gun
Meanwhile, factory #92 had other ideas about arming the T-60. The factory began development of the 37 mm ZiS-19 tank gun in August 1941 on its own initiative. The gun had the same ballistics as the 37 mm automatic AA gun mod. 1939 (61-K or ZiK-37), and use the same ammunition. The new tank gun consisted of only 153 parts (to compare, the 45 mm gun consisted of 436 parts). The mass of the 37 mm gun was 235 kg with the mantlet, compared to the 403.3 kg of the 45 mm 20-K.
37 mm ZiS-19 tank gun.
It's not surprising that, along with installation of the 45 mm gun, the design bureau promoted the idea of installing its own gun into the T-60 turret. Towards the end of 1941, this was seen as the more promising variant. The designers had their reasons, and it's hard to argue with them.
The 45 mm gun mod. 1938 was much heavier than the TNSh. Installing it made the turret unbalanced. As a result, it was difficult to turn the turret at high gun elevations. A 30 kg counterweight was proposed on the brass catcher, but the massive weight made the already not excessively roomy T-60 turret even more cramped. Operating the turret traverse mechanism became more difficult.
The same gun in three quarters view.
After a review of modernization projects, factory #92 was tasked with the production of a ZiS-19 prototype by January 15th, 1942, and a completed tank with the gun was expected for trials on February 1st. Working blueprints were developed between December 20th and January 13th. The prototype was built between January 12th and January 19th. On January 14th, blueprints of the ZiS-19, a list of parts, and main characteristics were sent to GAZ. On January 27th, a turret with the gun arrived at factory #92 (the gun was installed on January 19th).
ZiS-19 in the stock T-60 turret, February 1942.
The installation of the ZiS-19 in the T-60 turret was done with minimal changes, according to the requirements. Compared to the 45 mm rearmament project, the changes were negligible: only the seat was shifted to the left, like on the GAZ project. The gun system and cradle were installed in a modified gun mount. Thanks to the compact recoil mechanism on top of the gun, the ZiS-19 did not take up much space compared to the TNSh. The stock TMFP sight was retained, as well as the machinegun mount. A new welded gun mantlet was attached to the mount with bolts.
ZiS-19 gun at maximum elevation.
As it often happens, the deadlines were missed. Gunnery trials began on February 21st and ended on February 24th, 1942. In total, 181 shots were fired from various elevation angles. The recoil length was 140-170 mm. Trials showed that the robustness of the system, recoil mechanism, breech, and semiautomatic mechanism was satisfactory. The effort required to operate the traverse and elevation mechanisms was within acceptable norms. At the same time, there were complaints about the comfort of using the system. Due to the limited size of the turret, the gunner could not straighten out or stand up. The seat was deemed uncomfortable, and a saddle-like seat that flipped back was suggested.
The gun mantlet was similar to the one installed in the T-60.
According to Artkom instructions written on February 27th, 1942, two tanks should be sent to the Gorohovets proving grounds by March 9th: the T-60 with a 37 mm gun from factory #92 and a T-60 with a 45 mm gun from GAZ. In reality, events developed differently. Since there were many complaints about the commander's station, the design bureau made a significant amount of changes to the design, which took time. As a result, the new tank only arrived at the Gorohovets proving grounds on March 27th. By that time, it underwent significant changes.
The second variant of ZiS-19 installation in the T-60 tank. As you can see, the turret differs from the stock one significantly.
The resulting design had little in common with the original turret. The only part that was unchanged was the bottom part. The hatch was moved from the roof to the rear, and replaced with an observation device from the T-70. The turret gained a new wedge shape. The gun mantlet became cast, similar to the T-70's gun mantlet. The layout of the armament was also similar to that of the T-70: the sight was shifted to the left and the DT machinegun was installed in its place. These changes increased the volume of the turret, but using the stock T-60 turret was no longer possible. As for GAZ, their tank arrived only on April 18th, and it was not a T-60 armed with a 45 mm gun, but a T-70.
The new turret was not particularly roomy.
Trials of the ZiS-19 in the new turret began on April 19th. Results showed that due to the higher muzzle velocity, the lifespan of the ZiS-19 was shorter than the 45 mm gun. Penetration, rate of fire, and precision were similar, but the ZiS-19's HE shell was far inferior. Since one of the main tasks of light and small tanks was fighting infantry, this characteristic was very important.
Nevertheless, the 37 mm gun performed well, and if all its established defects could be resolved then it could be used on the T-70. The simplicity of the ZiS-19 at almost half the weight of its competitor was commended. There was a big problem, however: by the time trials were complete (July 19th), the T-60 was out of date. In early June, a GKO decree was issued ordering the removal of the T-60 from production at factories ##37, 38, and 264. The gun was also too late for the T-70; by then work was underway to create a 45 mm tank gun with a lengthened barrel, better known as the VT-42. That design seemed much more promising.
Thanks to work of several Russian historians, an impression was created that the T-45 was a competitor of the T-70. In reality, this is not true at all. The history of the tank begins in the spring of 1942 as the "T-60 that didn't want to go".
On March 9th, 1942, GKO decree #1417 "On organization of T-70 tank production at factories #37 and #38" was issued. According to this document, the production of the T-60 tank that was achieved with such difficulty at factory #37 was over, and the T-70 would be produced instead. The factory was not prepared for this turn of events. Factory management spent a whole month trying to convince the NKPT that factory #37 was incapable of producing the T-70. Finally, on April 12th, 1942, GKO decree #1581 "On production of T-60 tanks at factory #37" was issued, according to which production of the tank was retained until August 1942.
Experimental T-45 light tank, June 1942.
Meanwhile, the factory encountered another problem: the engines. Over the first quarter of 1942, GAZ shorted them 664 units. As a result, the assembly plant of factory #37 stood idle for 8 days in April. Meanwhile, 230 hulls (100% of quota) were produced, and the lack of engines was blocking production. The possibility of using the ZiS-5 engine which was considered during the design of the 060 hull back in July of 1941 came in handy.
Factory #37's design bureau got to work on installing the ZiS-5/ZiS-16 engine into the tank. The core of the group was composed of designers who worked at the 22nd department (experimental tank related developments) of factory #37 before its evacuation to Sverdlovsk. In spring of 1942, N.A. Popov came to head the design bureau, who was the senior designer on the T-40 project. He replaced G.S. Surenyan, who headed the 22nd department before the evacuation, as well as the design bureau after.
The tank engine was taken from a ZiS-16 bus, which traveled 35,000 km by that point without refurbishment. The tank version of the ZiS-16 engine was indexed ZiS-60. Compared to the ZiS-16, the new engine had a different exhaust collector, flywheel housing, and the crankshaft cone with an attachment for the ventilation fan. The ignition mechanism from the T-60 and a reinforced radiator were used. In addition to the new engine, the tank was equipped with a new gearbox that had different gear ratios. The exhaust system was also changed.
The design of the T-45 differed little from the T-60.
The tank with the new engine began trials on May 19th. The tank was artificially loaded to 6800 kg, which was equal to the mass of the tank that the factory design bureau was working on. The result of the trials, which lasted until June 9th, showed that the maximum speed of the T-60 with the ZiS-16 was 40.5 kph, 1 kph higher than expected. The engine was not as loaded as the GAZ-202, was not as loud, and there was no difficulty in servicing it. The main problem was the cooling system, which was deemed inadequate (to be fair, the T-60 with the GAZ-202 engine also had cooling issues). Overall, the idea of installing the ZiS-5 and ZiS-16 in the T-60 was deemed successful. In order to full test out the design, five tanks with new engines were ordered.
At the same time, factory #37's design bureau was working on a deeper modernization of the small tank. The issue was first raised at a meeting of the People's Commissariat of Tank Production on May 14th. The proposal was made by factory #37 and passed on through Military Engineer 1st Class Afonin and consisted of installing a 45 mm gun in the T-60 and increasing its armour to 35 mm. By the time the topic was discussed, the vehicle in question, indexed T-45, was almost ready.
The military was opposed to the idea. The development was considered irrational, since a more powerful gun and thicker armour would increase the load on the engine and transmission. The project was given the green light thanks to the chief engineer of the T-50 tank, S.A. Ginzburg, who was serving as the deputy chief of the technical department of the People's Commissariat of Tank Production at the time. Since April of 1942, Ginzburg was pushing the idea of building a light assault gun on the T-60 chassis at factory #37, and he had common interests with the factory's management. Ginzburg was present at the meeting where the proposal was made, and definitely had an influence on the decision. The minutes contain the following note: "Test this tank over 200 km. Send the results to GABTU. Don't make any more of these tanks for now."
As in the modernization of factory #92, the 45 mm gun was shifted to the right in order to make the turret less cramped.
It's easy to explain the T-45: factory #37 didn't want to built the T-70. In order to built it, 1140 new parts would have to be mastered, and 545 new stamps made. 825 new devices and 2300 new instruments were needed. In comparison, the T-45 needed only 224 new parts, 104 stamps, 175 devices, and 255 instruments, plus 132 parts, 85 stamps, 149 devices, and 433 instruments from the T-70. Production of the T-70 also meant that twice as many engines would have to be used, and Gorkiy was already having trouble with supplies. In this situation, an attempt to create a simpler tnak with more powerful armour and armament and equipped with a locally sourced engine seemed very logical.
The main external difference of the T-45 from its predecessor was the turret with a bustle, which carried a 45 mm mod. 1938 tank gun and a coaxial DT machinegun. A simplified version of the T-60 turret traverse mechanism was used to turn it. The sides of the turret were 35 mm thick, which was equivalent to the T-70. The armour of the hull was left at the level of the T-60, with the exception of the upper front plate, which was thickened from 15 mm to 25 mm. If necessary, the thickness could be increased to 35-45 mm, making it equivalent to the T-70. The hull was mostly the same as the T-60. The main difference was in the driver's hatch, which now turned sideways.
Curious fact: even though the Sverdlovsk T-60s had welded hulls, the T-45s used rivets.
Since the factory only had one ZiS-16 engine, the T-45 used the weaker but much more common ZiS-5 (the engine was taken from a truck that already traveled 12,000 km). The top speed dropped to 37.2 kph. In case of successful trials, the factory could begin producing T-45 tanks with ZiS-5 engines, and switch to the ZiS-16 once production at the Miass factory began. Aside from the new engine, the T-45 used the gearbox and final drives from the T-70. Since the mass increased to 7 tons, reinforced torsion bars were also installed.
The first stage of trials began on May 20th, and opened with gunnery trials. A rate of fire of 7-8 RPM from standstill and 3 RPM on the move was reached. Servicing the gun was easier than on the T-60, the turret became roomier. However, the heavier turret resulted in deformation of the turret platform roof. Despite this defect, all 25 shots hit the target. The production vehicle would have its TMFP sight replaced with the TOP sight from the 45 mm gun.
Even though the T-45 turret was built on the base of the T-60 turret, the results were noticeably different.
Mobility trials were carried out from June 6th to June 13th. In total, the tank traveled 1505 km, of those 189 km over asphalt, 805 over stone, 410 km over gravel, and 110 km over dirt roads. The trials led to complaints about the ventilation fan mount, which broke twice. The engine also often worked at high RPM, which could lead to premature breakdowns. There were also some instances of track links breaking, which is less of an indication of poor design and more of a result of low quality shipments from factory #183. There was also a tendency for road wheel tires to layer. Despite a series of complaints, the trials were deemed a success, especially considering that the tank was driving with a foreign engine, and a used one at that.
The reports on trials of the T-60 with the ZiS-16 engine and the T-45 were sent to GABTU towards the end of June. By that time, both this tank and the T-60 with the ZiS-19 gun looked hopelessly obsolete. Nevertheless, the tank got to fight. According to correspondence, the single T-45 was sent to the Western Front in late September of 1942.