Saturday, 4 July 2020

Dead End on Wheels

The 1930s were a time of experiments in the field of armoured vehicles. Some of these experiments were successful, some not so much. Some tanks passed trials and were even accepted into service, but failed to enter mass production. For instance, the convertible drive T-29 tank was supposed to replace the T-28. It was accepted into service, but not mass produced for a variety of reasons. The T-46 was its comrade in sorrow. This tank was supposed to become the most numerous in the Red Army, but only four were built. That was the end, the idea of replacing the T-26 failed.

Replacement for the T-26

The T-26 tank was accepted into service with the Red Army on February 13th, 1931. Production was organized at the Bolshevik factory, where it replaced the MS-1 (T-18) that same year. Building a licensed copy of the Vickers Mk.E was largely a forced measure. The T-18 quickly became unsatisfactory in the army's eyes, particularly due to its mobility. Attempts to modernize it were unsuccessful. As a result, a decision was made to rely on foreign experience. On the other hand, the USSR was far from the only nation to use this tank. Many tank building nations did not hesitate to outright copy this design. Soviet military leaders picked correctly. It was the T-26, not the BT, that became the workhorse of the Red Army. This tank didn't impress anyone with its high speed, but it was 1.5 times cheaper, significantly more reliable, was a much more stable platform for the 45 mm gun, and had room for modernization to spare.

There were drawbacks. The Vickers Mk.E engine had a tendency to overheat and the tank required very careful driving on soft soil. The instructions specified precisely how to drive cross-country without throwing off the tracks.

Draft of the T-46 prototype, November 1933.

The Experimental Design Machinebuilding Department (OKMO) at the Bolshevik factory performed a lot of work on modernizing the T-26. A single turreted version of the tank was put into production in 1933. The design was superior to the Vickers Mk.E Type B, which was never produced in the USSR. The T-26 also received the 71-TK radio in the turret bustle that year. The Soviet tank was radically reworked. It surpassed its predecessor in many ways, especially armament and observation. Nevertheless, the question of replacing the T-26 was already raised in the summer of 1933. This was not a total replacement, but a "convertible drive tank based on the T-26". The OKMO received this order on August 17th, 1933. By this time, OKMO was extracted into its own organization: factory #185. N.V. Barykov became its director. This tank was initially called T-26A. Its mass was estimated at 10 tons, and it would have a 200-250 hp engine. The top speed was set at 50 kph on tracks and 70 kph on wheels with a range of 300 km. The tank would be armed with a 45 mm cannon and a "super high rate of fire" machine gun. Like the T-26, this tank had a crew of three.

Even though the tank was based on the T-26, next to nothing was left of it at the design stage.

100,000 rubles were allocated to developing the T-26A, and a prototype was expected by the end of 1933. However, by October it was clear that this deadline was very optimistic. The tank also changed its name to T-46 around this time. In addition to the difficult task, factory #185 was overloaded with work. After the start of Moscow's GKB that worked on the MS-1 set in 1931-32, Leningrad became the center for tank development. One of the ideologues of the T-26, S.A. Ginzburg, moved there from Moscow. He had a row with the head of Moscow's GKB S.P. Shukalov, who considered it best to develop a dometic tank rather than working on a foreign one. Factory #185 became a think tank. The T-28 and T-35 were developed here, the T-26 was radically improved by its designers, and a number of other tanks were designed. The downside was a large number of projects which affected the delivery dates.

The T-46 had a larger turret than the T-26 since it had a 76 mm gun as an armament option.

The lead engineer of this new project was M.V. Simskiy, M.P. Zigel also made a large contribution. The project was directed by the Deputy Chief Designer O.M. Ivanov and Chief Designer S.A. Ginzburg. The draft of the T-46 was ready by November 30th, 1933. The tank was different from what was initially required. Nearly nothing remained from the T-26 even at the early stages, only the shape of the turret and hull remotely reminded of its predecessor. Calculations showed that it would weigh about 11 tons, having reached the dimensions of the BT-5. Factory #185 proposed a tank that could theoretically replace both the T-26 and the BT-5, although realistically the T-46 was only planned as a replacement of the T-26.

The air cooled 300 hp MT-5 engine was used, alsod developed at factory #185. The top speed on tracks was going to be 50 kph, and 75 kph on wheels, even more than the BT-5 developed. The running gear changed completely due to the convertible drive. The tank received a coil spring suspension, the springs were moved inside the hull. The road wheels were similar to those used on the BT tanks, but they had a different design. The T-46 had two wheels per side powered by a system of propeller shafts, rather than just one with gears. The front two wheels on each side were used to steer the tank. The armament was also unusual. The main option was a 45 mm gun, but then it turned out that the 76 mm KT-28 or PS-3 could be used. The KS-2 flamethrower was installed on the right side of the turret. A coaxial DT machine gun was used. The T-46 had a larger turret than the T-26 to accommodate all this.

The design was not simple, which ended up being the death of the tank.

On paper this was a very interesting tank with no analogues in the world. On the other hand, the project first had to be approved. A meeting was held at factory #185 on December 6th, 1933. Ginzburg, Simskiy, and engineer K.K. Sirken, a representative of the UMM dealing with experimental work and an experienced tank designer, were present. A list of 30 improvements that had to be made to the project was composed. The very complex gearbox was reviewed separately. The road wheels also triggered a torrent of correspondence. The 280 mm wide track was considered too narrow to allow the wheels to function properly. There were also issues with the experimental MT-5 engine. A letter from Chief of the 2nd Department of the 3rd Directorate of the UMM Pavlovskiy arrived on July 23rd, 1934, where he outlined 115 changes (initially 119). All of this did little to speed up work. The subcontractors also delayed assembly by systematically dragging their heels on producing components and assemblies for the tank.

T-46 with aerodynamic covers tested in a wind tunnel in the fall of 1934.

The tank changed with the requested improvements.Initially, the T-46 had a turret with a protruding roof, like the T-35. The Izhora factory proposed a flat replacement in September of 1934, which would make production simpler. Another interesting addition was an aerodynamic cover for the tank, which was tested in a wind tunnel. The goal here was to create a tank that could accelerate to 100 kph. The test was performed at the Zhukovskiy military aviation academy. Work did not progress past these trials, but the idea itself looked interesting.

A difficult future

Time did not stand still while factory #185 debugged their design. According to a decree issued in 1934, a prototype was due in November. The second tank would be built in the first quarter of 1935, and a pilot batch of 5-10 tanks was expected in the 4th quarter. Mass production of the T-46 would begin at factory #174 in 1936. However, the delays at subcontractors shifted the timeline. As of October 31st, 1934, factory #185 estimated that the deadlines slipped by about 4 months (chiefly due to the engine parts). 

The first type of track, 280 mm wide, did not turn out well. The ground pressure was too high and it was incompatible with the drive sprocket crown.

The result of all this was that even assembly of the first prototype was late by half a year. The tank was delivered in May of 1935 instead of November 1934. Like the T-29, a part of the work of organizing relationships with subcontractors fell to M.I. Koshkin. Koshkin's name is often associated with another tank, the T-46-5, but that is a mistake. Work on this tank began only after he moved to factory #183. As for the experimental prototype, it changed even more by this point. An AA machine gun mount developed for the T-26 and BT-5 was installed on the roof. Another machine gun was installed in the turret bustle, increasing the total number of machine guns to 3. The tank gained a lot of weight. Its combat mass grew to 15 tons. In part, the extra 4 tons were caused by thicker armour, which was now equivalent to the T-26. The number of wheels used to steer was reduced to one per side.

T-46 prototype, September 1935.

The T-46 trials program was approved on April 26th, 1935. In total, the tank would travel for 2000 km on wheels and tracks. In practice, by August 27th, 1935 the tank travelled for only 6 km on tracks and 150 km on wheels. Trials on tracks were going poorly. Even though the Red Triangle rubber factory warned that the 280 mm tracks were too narrow, the tank went into trials with these tracks. The pitch of the track did not match the drive sprocket, which led to the tracks jamming up and slipping off. The tracks had poor traction with the ground. Factory #185 tried to resolve the situation by adjusting the crown, but that was not enough. Deputy Chief of the 7th Department of the ABTU Brigadier-Engineer V. Sviridonov suggested that T-28 track should be used. This proposal was accepted. The mass of the tank grew by another 426 kg, but the majority of the issues were resolved. The ground pressured dropped significantly, which was important for off-road mobility. The production vehicles would have lighter tracks. The tank reached a speed of 52 kph on wheels in third gear. The gearbox jumped out of 4th gear, so it was not used.

The same tank on tracks.

A large list of corrections was composed as a result of factory trials. These were required both for the prototype and the pre-production tanks. The corrections had an effect. In trials that continued until October 4th the tank covered a much greater distance. The total distance travelled was 1020 km, 374 on wheels (369 on a road and 6 km on a dirt road) and 646 on tracks (574 on a road, 40 km on a dirt road, and 22 km off-road). The speed increased along with the reliability. The tank reached a speed of 82 kph on wheels, accelerating to 73 kph in 40 seconds. Few cars at the time could show such performance. The top speed on tracks was 56.3 kph with 51.5 kph attained within 35 seconds. The average speed on a highway was 40-50 kph on wheels and 35-45 kph on tracks.

The T-46 was the first tank in the world to use a cannon and a flamethrower.

The situation with driving on wheels off a highway was worse. In theory, the average speed was 30-35 kph, but only if the terrain was solid. If the tank moved onto soft soil then movement became impossible. The wheels began to slip and the tank quickly dug in with its drive wheels. The tank also slipped into a ditch once when driving on a dirt road. To be fair, the BT-7 could also not drive on wheels in these conditions, but the ground pressure of the T-46 was a lot lower. The BT-IS with three powered wheels per side fared a lot better in this situation.

Like other Soviet tanks in the mid-1930s, the T-46 received a rear machine gun.

The T-46 performed much better on tracks. The tank could climb a 20 degree slope on wet muddy terrain even though it slipped in initial trials with the first type of tracks. The idea of using T-28 tracks turned out to be very good. A short 34 degree slope could also be conquered, and the tank drove confidently at a 20 degree tilt. The T-46 crossed a 0.8 m tall wall in factory trials, but reared up and hit its front on the ground hard. The tank was not damaged, but the driver his his head on the dashboard.

The T-46 initially had two mufflers. They were removed in the fall of 1935.

The trials were deemed to be a success. The tank showed itself well off-road and demonstrated respectable mobility. The range on wheels was 350-400 km, and 175-200 on tracks. There were, however, questions about a number of components. There were some complaints about the gearbox, the suspension, transmission, and controls. In addition to reliability, the issue of ease of service was very important. However, there is one very important fact that must be noted. The BT and T-29 had issues with damage to road wheel tires, the T-46 had no such issues. They did not develop in the future either.

The T-46 showed good off-road mobility on tracks.

The successful factory trials served as a ticket to the next stage of testing. On October 8th, 1935, Deputy People's Commissar of Defense M.N. Tukhachevskiy signed order #0195 on conducting military trials of the T-29 and T-46 tanks. The T-46 had travelled for 1034 km by that point. Military trials took place from October 19th to the 29th. This time the tank was only driven on tracks. Due to a broken engine piston the tank could not be tested on wheels. Experience from factory trials was used for conclusions instead. The trials took place near Leningrad.

Trials in the forest.

The T-46 travelled for another 270 km during military trials. The top speed on a rain soaked gravel highway was 58 kph. The tank reached this speed on T-28 tracks, which would later be replaced with lighter ones. The average speed was also very high: 49 kph. The tank drove for 31 km until the crank arm of the rear left road wheel broke due to a production defect.

One of the more problematic elements of the tank: the gearbox.

The next stage of the trials took place on dirt roads and off-road. In both cases, the driving conditions were very difficult. The tank could drive on a pothole-riddled dirt road covered in 10-15 cm of wet snow at an average speed of 17 kph, a respectable result considering the road quality. Swampy off-road terrain also covered in 10-15 cm of snow were crossed at 14 kph. The commission was satisfied in both cases. According to them, this performance was evidence of good speeds in combat.

Tank driving in snowy terrain, late October 1935.

The tank could conquer a long 22 degree slope and a 7 meter 30 degree slope. The maximum tilt at which it could drive was 30 degrees. The tank conquered a 2.5 m wide trench and a 1 m tall wall. The tank also crossed a 2.5 m deep crater 8 m in diameter. The range was also measured: the tank could drive for 200-225 km on a highway and 90-110 km on snow covered dirt roads and off-road. There were few defects this time, all of them linked to production quality.

The tank performed admirably at military trials.

Study of the crew conditions was performed separately. The driver's station was criticized. It was hard to climb in and out and the steering wheel got in the way. The windshield was also inconvenient. The process of getting in and out was deemed tiring. The steering wheel also hit the driver's hands while driving. Most of the complaints were made around driving on wheels. The fighting compartment received a better evaluation. It was easy to climb in and the ammunition racks were designed well. However, there were complaints here too: the seats could not be adjusted vertically, the radio station was not located comfortably, the flamethrower and the trigger mechanism for the main gun were not placed well either. As with factory trials, it was hard to access components for maintenance. A proposal to make the suspension softer was also made.

Engine damage during trials.

Despite a number of issues and a complex design, the commission deemed the trials a success. The new tank was faster and more maneuverable than the T-26, the armament was more powerful and easier to operate. The advantages outweighed the drawbacks discovered during trials. The commission did not balk at the price, either. A single T-46 cost 200,000 rubles compared to the T-26 which cost 80,000. This was evidence enough to accept the tank into service. This was not the end of trials. By July 7th, 1937, the tank had travelled 1228 km on tracks and 1706 on wheels.

False start

Officially, the T-46 was accepted into service on February 29th, 1936. In reality, preparations for mass production began earlier. As mentioned above, the tank was supposed to go into production in 1936, but delays moved that date back. The tank transformed during trials of the first prototype. It initially had a muffler, this was later removed. A proposal followed to raise the front of the hull. This requirement could not be fully carried out, but the production pilot received special "skis" on the front to help it negotiate obstacles off-road. There were many such changes introduced into the pilot blueprints.

Pilot T-46-1, 1937.

The tank's index changed in September of 1935. The vehicle retained the name T-46 for some time, but it was largely called T-46-1 from then on. The armament also changed. The tank received a KS-45 flamethrower in early February of 1936. A smoke generator was added to the rear. There was a proposal to install nighttime shooting spotlights (similar to those used on production T-26 and BT tanks). Another planned change was a gyroscopically stabilized sight. A remote controlled variant called TT-46 was also worked on. There was also a chemical tank called KhT-46 developed. It had a T-26 turret with a DK 12.7 mm machine gun instead of a cannon.

Skids were added to the front of the tank to improve off-road mobility.

Factory #174 was supposed to produce this tank. However, the idea of producing it at STZ was also raised in the spring of 1936. Production of the T-26 tank was fruitlessly being organized there for some time. Before all this, at least one pilot tank had to be built, and things were not going well in that respect. According to Sviridov's report all of the necessary changes were not yet made to T-46-1 blueprints by mid-June of 1936. As a result, the tank was not ready in the summer of fall of 1936. This triggered a torrent of furious letters from ABTU chief Khalepskiy. Officially, the pilot tank was delivered in November of 1936, in reality work bled into December and eventually it was fully finished in March of 1937. Meanwhile, the Izhora factory was at work on hulls and turrets for production tanks. Bad news came from the factory in December of 1936. Penetrations were found in the sample armour after firing trials.

The tank has a number of differences from the prototype, especially the road wheels.

One might get the impression that the ABTU didn't have enough problems. A decision was made in early July of 1936 to improve the strength of the armour. This meant that the T-46 would get a turret platform with sloped sides and a conical turret. The deadline for this work was October 1st, 1936. The Izhora factory was involved, they would have to deliver the experimental hull and turret by November 15th and the whole tank was due on February 1st, 1937. This project received the index T-46-3 in the fall of 1936. The hull and turret would be built from cemented armour, but in October the Izhora factory decided to make them homogeneous. The excess amount of work led to the T-46-3 being delayed until 1937. Issues continued to accumulate at a breakneck pace. Barykov estimated that 32 groups of components would need to be changed for the T-46-3. This was essentially a whole new tank. The mass grew to 17 tons.

A smoke generator was added to the rear.

The T-46 found itself in a situation that cannot be described as anything but critical by early 1937. Trials of the pilot began at factory #174 on December 3rd. Three runs were made, each of which was met with more and more defects. Two more production tanks were finished in December, both of which also had defects. The factory built four production tanks, none of which were suitable for service. All four were undergoing repairs as of April of 1937. Factory #185 appointed P.I. Naumov to be the chief engineer on the T-46-1 project, he was also responsible for the T-46-3. Factory #174 signed a contract for a whole series of vehicles on January 28th. These included 25 ordinary T-46-1 tanks (due in February-June of 1937), 23 T-46-5 (October-December 1937), 2 KhT-46, 25 T-46-1 with radios (October-December 1937), 12 T-46-3, 10 remote controlled T-26-3, and 3 KhT-46 with conical turrets.

Hull of the T-46-3, summer of 1937. This tank delayed the production of the T-46 even further.

Thunder struck in the summer of 1937. Committee of Defense decree #94ss "On types of tanks in the Red Army and tanks to be produced in 1938" was signed on August 15th. It removed the T-46 from production and tasked the STZ design bureau to develop a replacement. This began the work on two more failed T-26 replacements: the STZ-25 and STZ-35. Punishments for the T-46 were handed out even earlier. Factory #174 directo Dufur was removed from his post not just for the T-46, but for failure to meet T-26 production timelines. The director took a hit on behalf of factory #185, as it was their vehicles that were supposed to replace the T-26 at factory #174 (SU-5 and AT-5 SPGs). Instead of 400-500 T-26 tanks factory #174 delivered just 17 vehicles. Factory #185 suffered as well, even though they received 54,700 rubles for bonuses and Ginzburg got an Order of Lenin to boot. Koshkin got lucky when he was moved to factory #183 (although he didn't get a bonus for the T-46 either). Zigel was executed on May 6th, 1937. Simskiy suffered the same fate, even though he served as the technical director of factory #48 at the time. Ginzburg was also arrested, but he was lucky. He was freed some time after and resumed his technical work. Other engineers and designers also suffered.

Hull and turret of a T-46 tank used as a pillbox, 1941.

One T-46-1 tank ended up at the NIBT proving grounds. It is not know what happened to it after. Nevertheless, the T-46 took part in fighting, just not in their initial form. The hulls and turrets that were produced were dug in as fortifications before the war. These were just hulls and turrets with no armament. This is how one T-46 survived to this day. The first complete specimen can be seen at the Victory Museum, a second hull without a turret is on display at Patriot Park. As for the replacement for the T-26, it eventually materialized in the form of the T-50 tank in 1941. This tank also had a sad fate: it was accepted into service, but production didn't have time to start properly due to the war.


  1. Another very interesting article which adds a lot to current knowledge. However I have two questions that may be of interest;
    You mention the T-28 track being used, were the road wheels also T-29 or BT items? They seem very similar even up to the T-34.
    In the pillbox photo there is an additional circular hatch behind the two originals. Have you any idea when they were added?
    Thanks for the great work you're doing to spread information into the English-speaking world.

    1. The T-46 had different wheels from the T-29 and BT. The T-34 got brand new wheels too.

      I don't know about the hatch.

    2. Thanks for the reply. Bit of a surprise TBH but just shows that you can never assume anything.