Sunday 31 August 2014

Churchill Impressions, Part II

Here, you saw some Soviet experiences with the Churchill tank. Of course, that was not the only encounter of Soviet engineers with such a vehicle, and more evaluations were made. This specific one is for a Churchill III.

"Evaluation of reliability of the MkIV and its mobility data
  1. The English heavy tank MkIV has insufficient reliability of some components and is a vehicle with an unfinished design, not ready for production. 
  2. The MkIV tank crosses slopes poorly, as it loses its tracks at a 20 degree angle. This angle is too small. It is still possible for the tracks to slip off at angles less than 20 degrees.
  3. The fuel expenditure is reasonable on all road types.
Design evaluation
  1. The hull is abnormally long compared to its width and height. The front of the hull is located low, between two high-rising tracks, covered by large mudflaps. This reduces visibility for the driver and hull gunner. Observation periscopes installed near the driver and gunner to little to improve visibility. When the gun is facing forward, the barrel does not clear the mudflaps. This leads to the mudflaps breaking off when hit by the shockwave from a shot.
  2. The observation devices installed in the turret provide satisfactory vision. Identical devices have been found in the model 1939 Polish Vickers tank.
  3. The tank engine is very modern, of the car and tractor type. The engine uses a minimal amount of deficit metals and is suitable for mass production. However, the engine of the MkIV is an unfinished design, and its reliability is doubtful. The toughness of cylinder block heads is also in doubt, as they are relatively short compared to their width (the engine has valves on the side). If the toughness is insufficient, the head will warp, causing it to punch though the layer between the head and cylinder block. If not noticed in time, this will cause cylinders to break down prematurely. When using the MkIV tank, water levels in the engine must be observed carefully. If water levels start dropping, the cause must be found immediately.
  4. In the tank's transmission, the turning mechanism, placed in one assembly with the mechanical gearbox, deserves attention. The turning mechanism lets the tank turn in place, lets it turn easily, and retain good maneuverability for a heavy tank on the move.
  5. The hydraulic servos reduce the efforts required to operate the tank.
  6. The suspension is insufficiently robust for a 40-ton tank. As trials showed, welding seams rupture, and inner road wheels fly off the bogeys, followed by outer road wheels along with the axles, the bogey balancers start rubbing on the track, and quickly break. The flanges of the road wheels are placed immediately next to the track links, which causes friction, and wears down both the track and wheel. The wheels heat up during motion, and friction with the track increases. The track pins have insufficient robustness, and break.
  1. The English heavy tank MkIV "Churchill" has sufficient armament, protection, and maneuverability to be capable of fighting German tanks effectively.
  2. Currently, the MkIV is an unfinished and unpolished design. When used in the army, the MkIV will require frequent repairs and replacement of parts and components.
  3. Several elements of the tank (turning mechanism in the same assembly as the gearbox, etc) are original, and can be recommended for use in domestic vehicles."

Saturday 30 August 2014

Churchill Supplies

"To the Deputy Commissar of External Trade, comrade Krutikov

In Spring of this year, it was decided that England will supply the USSR with Mk-4 "Churchill" heavy tanks. As of November 9th, 1942, we have received 84 Churchill tanks.

According to a report of the former member of the Military Mission of the USSR in England, Engineer-Colonel comrade Kovalev, the English were told in February-March of 1942 that our Government agreed to receive 50 Churchill tanks in lieu of Matilda tanks. The English were informed that subsequent orders for Churchill tanks will depend on the performance of these tanks in combat.

The English themselves have supplied 25 tanks for trials. Despite the fact that these tanks have entered mass production, they have not had much experience in battle, and testing on our fronts was desired.

As a result of short term use in our units, several serious defects that decrease the tanks' combat ability have been discovered.

Therefore, I ask that you inquire about the approved number of Churchill tanks at our Military Mission in London and communicate the necessity of immediate correction of these defects.

The English have been told of these defects, and an Englishman, Captain Cox, was demonstrated them personally.

From our side, I am in agreement with the previous decision to order small amounts of Churchill tanks and deem it wise to withhold subsequent deliveries until the correction of defects can be confirmed. I attach a list of discovered defects.

Reply with your decision,
GABTU BTU Chief, Engineer-Colonel Afonin"

CAMD RF 38-11355-938

The list of defects is included in this article.

Thursday 28 August 2014

Chrysler Visit and Sherman Inspection

"Report on the visit to the Chrysler factory in Detroit

From September 3rd to September 5th, Lieutenant-Colonel Demyanenko, Engineer Sorvin, and Engineer Prishipenko visited the Chrysler tank factory. The goal of the visit were:

  1. Familiarization with the design of the Chrysler gasoline tank engine and collection of data on its performance, especially in winter.
  2. Familiarization with the Chrysler tank factory for evaluation of its production capacity.
  3. Personal driving of the M4A4 medium tanks on a proving grounds to obtain necessary data for comparison with M3 and M4A2 medium tanks.
We left Washington on September 2nd, at night, and arrived in Detroit on the morning of September 3rd. We were accompanied by Lieutenant Gerber from the War Department, an aide-de-camp of General Christmass, the chief of tank design and production at the War Department. General Christmass is the chief tank designer in the USA.

When we arrived in Detroit, we were presented to the a Colonel, the chief of the Detroit division of the War Department. The Colonel was very interested in our opinion of American tanks. In particular, he wanted to know about our opinion of the M4A4 tank with a Chrysler engine. This tank has been finalized, and production increases with every month. He also told us that production of M4A2 tanks with General Motors diesel engines and Canadian Valentine VII tanks, which also only use the General Motors diesel, will be complicated in the future. This is caused by a shortage of diesel engines, which are in demand by the American Navy for speedboats. The amount requested by the Maritime Department is very high, and will only increase. 

Note: these engines are built by America's only diesel factory owned by the General Motors company near Detroit. In July of this year, Engineer Sorvin visited this factory. By talking to employees and observation, he was able to establish that the factory produces about 5000 double and single tank diesels (model 6046-Series 71 and model 6004) per month with three shifts working around the clock.. The factory was being expanded to increase production. New mechanical and assembly plants were being built.

The discussion with the Colonel indicated that the above reasons will result in a reduction, or even complete cancellation, of the M4A2 medium tank. At the same time, he highlighted the advantages of the Chrysler engines, built based on automotive engines that the factory has built millions of. He mentioned that there will be no problems with supplies, and like car engines, they will be familiar and easy to service for any driver.

Chrysler's deputy chief engineer of engine production joined us during the trip to the engine factory, located close to Detroit. He stayed with us for the duration of the visit. At the factory, we met with the engine production chief, Mr. O'Malley. With him, and a group of managing engineers, we took a tour of the factory. 

Note: before we left the factory, Mr. O'Malley gave us some documents regarding the quality of parts finish at the factory. These documents are included with the report.

In many offices an laboratories, a cooler is present, capable of generating temperatures of -30 degrees Celsius. During our visit, experiments to examine the starting of a Chrysler tank engine were being carried out in one of these coolers. Additionally, two engines were being tested for wear, actual power, oil and fuel expenditure, etc. During our visit, one of these engines has been working for 400 hours, another for 300 hours. The engines were artificially loaded with Froude hydraulic brakes and an electric balancer machine.

Data gathered during these trials is not yet available, but will be available in the near future.

The next day, we went to the Chrysler Tank Arsenal factory. At the factory, we were accompanied by factory director, Mr. Richay, and the chief engineer of the factory.

The Chrysler tank factory was building M4A4 medium tanks. This factory is famous not only in America, but throughout the whole world. A lot has been written about the construction of this factory in American media, especially in 1940.

In 1941, for the opening date of the factory, the July issue of the Army Ordnance magazine had photographs of the factory, and data on the production capacity and amount of workers. The entire factory, excluding the power plant and warehouses, takes up an area of 1400 by 900 feet. Up to 70% of the ceilings and walls are made of glass. 

Until recently, aside from engines and armament, the factory built everything. Currently, due to increased demand, some components are produced at other Chrysler factories (suspensions, front hulls with gearboxes, final drives). According to the factory director, the September production plan is 600 tanks, and in December, the factory should produce 1000 tanks. 

The tank assembly area takes up the left third of the factory building, lengthwise (see map). The area has 5 assembly lines, which allow for work on 500 tanks simultaneously. 

We attempted to calculate the production capacity of the factory:
  1. The amount of turret base production machinery was counted.
  2. The amount of turret ring teeth cutting machines was counted.
    Based on our estimates, this is the bottleneck in the production.
    Note: turrets arrive at the factory already cast, in need of mechanical finishing.
  3. By asking the factory direction (a real enthusiast of his craft), an chief engineer, we learned the time it takes to finish the bottom of the turret and the turret ring teeth. 
12 carousel machines are used for cutting down the bottom of the turret. It takes 7 hours to process one turret base, so in a day, about 4 turrets can be made. The factory director told us that to increase production to 1000 tanks, three more such machines are needed. We witnessed foundations for these machines being built. The need for more equipment is explained by the fact that an amount of machines is always undergoing preventative maintenance, but the production must always continue. 5 large tooth-cutting machines are used for cutting teeth for the turret ring. It takes 3 hours to process a turret ring. In one day, 40 turret rings can be made.

As such, the production of 1000 tanks per month is possible even now. Finished tanks are fuelled and oiled right at the end of the factory, and drive straight to the proving grounds for testing. The proving grounds are positioned close to the factory building, and consist of a 2-3 km long looped road. The road has varied terrain (concrete, dirt road, sand, elevations and descents). Quality assurance takes 50 miles. After driving for 50 miles, tanks with defects are sent to a refurbishment section for defect correction, after which they are subjected to another 10 miles of track trials. If there are no defects, the tanks are shipped by rail to a tank depot, where radios are installed. Here, instruments and ammunition are loaded into the tank. From here, finished tanks go to army units or to export. 

Due to increasing production, every department is working on installing additional equipment.

Proving grounds and tank driving

After breakfast, we drove to the proving grounds, 12-15 miles from the tank factory. The proving grounds used to be a Cadillac car proving grounds. Next to the good road for testing cars, there is a 2-3 km long tank track, which consists of a dirt road with grades. There is a section of the track that crosses a stream 0.5-0.75 meters deep, but with a hard bottom. The exit from the stream is on a 40 degree grade, which continues for 25-30 meters. There are no muddy, destroyed sections of the road. There are no swamps or trenches. There are no vertical obstacles. When we noted that the proving grounds were insufficient, the factory representatives told us that the tanks were tested at the Aberdeen Proving Grounds (Maryland), where there are allegedly all sorts of obstacles. 

Note: Engineer Sorvin went to the Aberdeen grounds in early August to observe trials of an M4A2 medium tank, and concluded that their proving grounds have nearly identical obstacles as this these proving grounds. 

When we arrived at the proving grounds, we started with a loop around the track in a 2.5 ton Dodge truck (a company owned by Chrysler). All three axles of the truck are powered. The vehicle passed the entire tank route well, including the stream and a small section of bushes, covered in deep gouges.

After breakfast, we personally drove tanks through this route.

There were two tanks there, an M3 medium tank with a Wright engine and an M4A4 medium tank produced by the Chrysler factory with their tank engine. Engineer Sorvin and Lieutenant-Colonel Demyanenko drove these tanks. The impressions are as follows:
  1. The M4A4 is undoubtedly superior to the M3, and has superior mobility and acceleration.
  2. The 40 degree grade coming out of the stream can be traversed by the M4A4 tank in second gear, while the M3 tank can only traverse it in first gear.
  3. The M4A4 tank has a more comfortable driver's compartment than the M3.
  4. Both tanks are definitely worse compared to our T-34, and possibly even the KV.
  1. The Chrysler tank factory is the one of the newest and largest tank factories not only in the US, but in the world. All factory equipment (machines, devices, cutting and measuring tools, valves, and internal transportation) is new, mostly produced in 1939-1942.
  2. The factory is currently capable of releasing 1000 tanks monthly. This capacity is guaranteed by the company engine plant, which produces 35 tank engines daily.
  3. The factory produces the M4A4 medium tank with a gasoline engine. This tank is used by the American army and is mass produced at all American tank factories capable of producing medium tanks.
    Note: the M4 medium tank is available in four modifications:
    1. M4A1 with a Wright air-cooled gasoline engine.
    2. M4A2 with two General Motors water-cooled diesel engines.
    3. M4A3 with a special 6-cylinder Ford water-cooled gasoline engine.
    4. M4A4 with a 30-cylinder Chrysler water-cooled engine. 
  4. The M4A4 tank is identical to the M4A2 (as well as other M4 modifications) in hull design, suspension, armament, observation devices, and communications devices.
    The M4A2 is well known in the Soviet Union from previously sent documents, and all of its drawbacks are repeated on the M4A4 (high ground pressure, height, insufficient amount of vision devices, difficulty in installation and removal of components, difficulty in service, etc)
    The tank's mobility (speed, maneuverability), ability to cross obstacles, and hp/ton is nearly identical to the M4A2 tank with the General Motors engine.
    The M4A4 is superior to the M3, both in the engine, which works on much lower octane gas (65-70) and is water-cooled, and the mobility.
  5. Overall, thanks to a lack of experienced tank designers, the Chrysler factory is building tanks whose design and combat performance does not measure up to the potential of such a first-class tank building giant.
Engineer Sorvin.
September 7th, 1942

CAMD RF 38-11355-760

An M4A4 tank was sent to the Soviet Union anyway, where trials showed that it was not good enough to order instead of the M4A2.

Wednesday 27 August 2014

World of Tanks: Today in History: Tsar Tank

Many armoured vehicles were developed in the early 20th century that are amusing in hindsight. One should not forget that this was an era of trial and error, and if not for these wondrous vehicles, perhaps we would never have seen "classic" tanks.

The source of Nikolai Lebedenko's inspiration, according to his own admission, was the araba carriage, which had large wheels that could easily traverse bumps and pits. As a result, the engineer came up with a vehicle that had two massive front wheels (about 9 meters in diameter) and a small rear guiding wheel. An immobile casemate was installed at about the height of a two-story house, which could hold a machinegun or a cannon. Two machinegun sponsons were placed by the sides of the casemate, and a turret was planned for the bottom. According to calculations, the speed of this vehicle would be 17 kph.

Lebedenko's design, surprisingly, received approval from many military directorates. During an audience on February 8th, 1915, a model of the tank running around the carpet thrilled Emperor Nikolai II, who personally ordered for 210,000 rubles to be awarded to Lebedenko to finance the project.

Components for the vehicle were produced at a factory in Khamovniki. From spring to the end of summer of 1915, assembly took place at Orudyevo station, near Dmitrov. When the vehicle was completed, its gigantic size earned it the name "Tsar Tank".

Mobility trials began on August 27th, 1915. The tank moved, crushing trees with its massive front wheels. However, since its mass was not evenly distributed, and difference between wheels was so huge, the tank almost immediately sank into the ground. Even two 240 hp Maybach engines could not pull it out. This was immediately recorded as a strike against Lebedenko. The second strike makes one wonder why it was not noticed while the tank was still on paper: the front wheels of the tank. The fragile spokes did not even need a direct shell hit, a close explosion was enough. If a wheel was destroyed, the tank would fall like a house of cards.

Lebedenko's tank could be considered a complete failure, if not for the fact that young engineers A. Mikulin and B. Stechkin gathered valuable experience by working on this project. Later, these men became well known specialists in the field of engines.

Attempts to pull the vehicle free did not succeed, and the Tsar Tank remained in the forest near Orudyevo. In 1923, the vehicle was disassembled for scrap.

Original article available here.

Tuesday 26 August 2014

M-17 203 mm SPG

"Conclusions on the factory #172 203 mm self propelled gun M-17

The project proposed by factory #172 consists of a 203 mm gun on the chassis of the mass production SU-152 SPG. The M-17 differs from the SU-152 in the following ways:
  1. Increased caliber (203 mm vs 152)
  2. Increased shell weight (100 kg vs 43.5 kg)
  3. Caseless ammunition
The main components: immobile armour, frame, mobile armour, are all from the SU-152. The gun mount and recoil brake are all effectively the same as on the 152 mm gun, with the exception of an additional casing to prevent separation of seams and the countercoil buffer being replaced with the simplified type.

The gun barrel used is from the experimental 203 mm M-40 gun with the full charge.

Observation devices, controls, fuel system, communication systems, electric components, heating and ventilation systems are identical to the SU-152. In order to reduce recoil, the barrel is equipped with a muzzle brake.

In order to allow for gun depression of -3 degrees, the roof is sloped up by 3 degrees.

16 shells are places in special magazines in the left bay of the fighting compartment. When the magazine is opened, the shell rolls onto the magazine tray under its own weight, from where the loader pushes it into the rammer tray.

The tactical-technical characteristics of the M-17 compared to the SU-152 are shown in the following table:

Characteristic M-17 SU-152
Combat weight, tons 45.8 44.85
Hp/ton 13.1 13.2
Ground pressure, kg/cm^2 0.81 0.8
Armour, mm
Front 60 75
Side 45 60
Rear 45 60
Roof 20 20
Armament 203 mm gun 152 mm gun
Muzzle velocity, m/s 460 650
Propellant mass, kg 8.2 6.8
Shell mass, kg 100 43.5
Gun elevation, degrees 20 20
Gun depression, degrees -3 -3
Ammunition capacity 16 20
Rate of fire per 80 seconds 1 2
Barrel length with muzzle brake, calibers 22.6 46.3
Recoil length, mm 875 850

Upon examination of the project, the following was established:
  1. It is very possible to produce a 203 mm SPG on the SU-152 chassis using factory resources.
  2. High parts commonality with the SU-152 will allow for a rapid production of a prototype with minimal production costs.
  3. In order to reduce weight, reduction of armour thickness is allowed.
  4. The amount of ammunition on board is reduced by 4 shells (16 instead of 20 on the SU-152), which is insignificant, as the power of a 203 mm shell greatly surpasses the power of the 152 mm shell.
  5. A rate of fire of one round every 80 seconds is acceptable for this caliber.
  6. The placement of ammunition in the fighting compartment, convenience of loading, and ramming mechanism are satisfactory, but require testing with a physical prototype.
  7. The mass of 45.8 tons is the limit for this suspension, and the prototype mass should not surpass this limit.
Conclusions and recommendations:
  1. The 203 mm gun on the M-17 greatly surpasses the 152 mm gun in power.
  2. It is reasonable to produce a 203 mm SPG alongside the SU-152 for destruction of highly reinforced enemy fortifications.
  3. The mass of the M-17 SPG should not surpass the mass of the SU-152.
  4. In order to bring the 203 mm gun to self propelled mounts, I consider it reasonable to build a prototype of the factory #172 project with corrections by GBTU USA and provide it for GAU and GBTU trials for a final decision.
Chief of the Self Propelled Artillery Directorate of the GBTU, Engineer-Colonel Alymov
Chief of the 3rd Department of the GBTU USA, Engineer-Lieutenant-Colonel Kovalev
June 24th, 1943"

Monday 25 August 2014

World of Tanks History Section: Kursk Fiasco: Breaking the Wehrmacht's Back

On August 23rd, 1943, Soviet forces captured Kharkov. This day counts as the official end date of the Battle of Kursk. The Wehrmact lost, with great losses in manpower and "metal". Hitler's loud exclamations turned out to be nothing but hot air.

What did the Germans' loss at Kursk mean? Having lost the battle, the Germans lost strategic initiative on the Eastern Front. In the future, they were limited to limited offensives and counteroffensives, for instance von Manstein's counterattack in November of 1943 at Fastovo. Strategic operations such as Fall Blau were unthinkable.

"[Operation Citadel] was our last attempt at regaining initiative in the East. When it did not succeed, which equalled a failure, initiative was completely ceded to the Soviets. Operation Citadel was the decisive turning point on the Eastern Front." - E. Manstein, "Lost Victories"

During preparations for Citadel, many German commanders warned that it will result in a waste of reserves that were so painstakingly gathered in the first half of 1943 after the Stalingrad catastrophe. In their opinion, due to the "aerial offensive" of the Allies (raids on strategic objects in Germany by the American 8th Air Army), a possible landing in Italy, and evidence of upcoming offensives on various sections of the Eastern Front, the German army should retain a defensive strategy.

Germany turned out most sensitive to losses of vehicles. By June 23rd, after nearly three weeks of fighting, Soviet forces reached initial positions from which Germany began its offensive. Many damaged German vehicles remained on territory retaken by the Red Army.

"As a result of the failed Citadel offensive, we suffered a decisive defeat. Armoured forces, reinforced with such difficulty, were ineffective for a long time due to significant losses." - G. Guderian, Memories of a Soldier

The drain on German reserves led to Germany being unable to effectively resist further Red Army offensives. On July 12th, 1943, the Orel Offensive Operation began. On August 5th, Orel was liberated. On August 3rd, the Belgorod-Kharkov Strategic Offensive Operation began. Kharkov was taken on August 23rd. Further offensives in 1943 on the south and central sections of the front led to liberation of a significant part of the Ukraine.

The political significance of the Battle of Kursk was also one of the greatest in the war. The failure of Citadel made it clear that the fall of Germany is only a matter of time. A few months after Kursk, Soviet and Allied leaders discussed the composition of the post-war world at the Tehran Conference, most notably Roosevelt's proposal to split Germany into five states. Additionally, the issue of the declaration of war against Japan by the Soviet Union after the defeat of Germany was discussed.

Article author: Andrei Ulanov.

Andrei Ulanov is an historian and an author of books and articles on the Great Patriotic War. His most prominent works are "Order in Tank Forces" and "First T-34s" (co-authored with Dmitriy Shein). Currently, he is working on books on AT measures of Soviet infantry and combat use of T-34 tanks in 1942.

  • Sh.P. Sanskoyev, B.L. Tsybulevskiy, Tehran-Yalta-Potsdam. Sbornik Dokumentov, 2nd ed. Moscow, 1970
  • V.N. Zamulin, Kurskiy Izlom, Reshayushaya Bitva Otechestvennoy Voyny, Moscow, Eksmo, 2007
  • F.V.Mellentin, Tankoviye Srazheniya 1939-1945, Boyevoye Primeneniya Tankov vo Vtoroy Mirovoy Voyne, Moscow, IL, 1957
  • E. Manstein, Lost Victories, Moscow, Terra Fantastica, 1999
  • G. Guderian, Memories of a Soldier, Smolensk, Rusich, 1999

Sunday 24 August 2014

State of Affairs, 1932

"Conclusions of the RKKA staff based on materials provided by the Directorate of Mechanization and Motorization on the development of armoured forces

May 10th, 1932

1. T-27 tankette

Given that the Red Army possesses the T-26, the T-27 is unsatisfactory as a reconnaissance vehicle for motorized infantry for the following reasons: low maximum and average speed, limited off-road capability, insufficient horizontal traverse, poor visibility, low range, lack of backup driving controls. It is necessary to produce a new amphibious tankette that is capable of performing reconnaissance for motorized infantry. For infantry, the T-27 is not very useful due to its limited off-road capability and difficulty in shooting on the move.

I think it is necessary to rapidly perform trials of an amphibious tankette with the aim of producing the improved variant instead of the T-27. Preliminary trials of the tankette show a top speed of 30-31 kph on a highway, good maneuverability and satisfactory buoyancy. Drawbacks include an overly rigid suspension, engine overheating, low fuel capacity (6 hours of driving), low speed on land and on water, poor off-road performance (drives over trenches with difficulty, hits the propeller on highways. The amphibious tankette requires the following characteristics:
  1. A speed of 50-60 kph on a highway, no less than 35-45 off-road, 15 kph on water with perpendicular current.
  2. Capable of crossing trenches 1.6-1.8 meters wide.
  3. Fuel capacity to run the engine at maximum RPM for 8 hours.
  4. Capable of traversing a 35-40 degree grade that is three times as long as the tankette.
  5. 360 degree traverse with one regular or high caliber machinegun.
  6. Gyroscopic compass and speedometer.
  7. Armour should protect the crew and mechanisms from SMK and AU armour piercing bullets from 50 meters.
  8. Crew of two.
  9. Ammunition capacity: 3000 rounds for the machinegun.
  10. Water cooled engine.
2. T-26 light tank

Trials of a 45 mm gun with a coaxial machinegun in the T-26 turret show that the semi-automatic mechanism is unreliable, the turret is cramped (420 and 430 mm for the gunner and loader, which reflects poorly on the rate and precision of fire, the turret does not turn fast enough, leading to poor agility of fire. The foot trigger is poorly positioned, the optical sight is unreliable, the ventilation is inadequate, which reflects on the combat ability of the crew. After trials of this mount are done, two others must be tested immediately.
  1. In order to increase the rate of fire and precision, push the gun forward, tilt the front of the turret, and remove the rear turret bustle, designed to balance the turret. 
  2. Make a wider turret with a tilted forward section and lack of turret bustle.
If the tank commander is to the right of the gun (acting as the loader), give him a second periscope, otherwise he cannot control the tank as he cannot see.

Rapidly finish the trials of the 45 mm gun, and produce only tanks with a single turret, carrying a 45 mm gun capable of rotating 360 degrees with 110 rounds of ammunition and 3000 bullets. Install a gyroscopic compass and speedometer. Work on the following issues:
  1. Extend fuel capacity to 10 hours at maximum engine RPM.
  2. Investigate the issue of buoyancy (or underwater driving) with a tank on the T-26 chassis.
  3. Investigate the possibility of a convertible drive.
  4. Investigate the possibility of making the tank air-tight.
  5. Increase the speed to 50 kph on tracks and 100 kph on wheels.
  6. Increase the reliability of mechanisms, reaching 1000 km before medium repairs are needed.
3. TMM-1 and TMM-2

Due to the variety of theaters of war and special climate conditions where winter lasts 3-5 months, it is more reasonable to develop air cooled engines and have automotive factories produce them instead of making the vehicle rely on availability of water in the summer and antifreeze in the winter. TMM-1 and TMM-2 vehicles based on imported water-cooled engines are of no value. It is reasonable to develop domestic engines for armoured vehicles.

4. Fast BT tank

Factory trials of the original and domestically produced BT tank show that the tank can drive on asphalt and dirt roads on wheels. The original was not trialled on tracks, as the left idler was broken. Our tank was not trialled on tracks over a large distance, and it is impossible to make conclusions of its tactical value. 

Given current tactical-technical qualities, the BT cannot be considered a fully functional battle machine, capable of driving on wheels on wet dirt and dirty roads. RKKA UMM should, without stopping production, design a BT tank with four drive wheels, later increasing that number to six. The track removal and installation process should be mechanized, as taking 30-45 minutes to install tracks and 15-30 minutes to remove them is excessively high. 

RKKA HQ insists on rapid modernization of the BT and construction of a prototype amphibious tank.

5. T-28 medium tank

We currently produce no medium tanks. The construction and trials of a prototype should be accelerated in order to begin production in August-September.

6. Heavy tank

I consider it necessary to have a heavy tank designed for penetration of enemy defenses, fortresses, and fighting enemy heavy tanks. The tank should have the following technical-tactical characteristics:
  1. Speed: 40-50 kph
  2. Range: 300-400 km
  3. Air cooled engine
  4. Maximum grade: 45 degrees
  5. Ability to cross trenches 7 m wide
  6. Capable of moving on railroads (foreign and domestic) on its own power
  7. Can cross water hazards either by driving underwater or swimming
  8. Capable of knocking over two trees at once, with a diameter of 0.5 meters each
  9. Armour should guarantee protection from a 3-inch shell fired at 800 m/s at 50 meters.
  10. Armament:
    1. 1 152 mm gun with 360 degree traverse
    2. 2 semi-automatic 76 mm guns with 280 degree traverse
    3. 12-14 machineguns
    4. 2 37 mm AA autocannons and 2 AA machienguns (out of the 14)
  11. Ammunition:
    1. 152 mm shells: 60
    2. 76 mm shells: 200
    3. 37 mm shells: 1000
    4. 2000 rounds of ammunition per machinegun
  12. A radio
  13. The tank should have a gyroscopic compass, speedometer, and observation devices.
  14. The tank should be impenetrable to gases.
  15. The combat weight should be less than 150 tons.
  16. Blueprints of the tank should be delivered to the RKKA HQ no later than August of this year. Work with the aim to have a prototype by the start of 1933.
Conclusions on tanks
  1. Tanks are a powerful offensive force, and their development should follow corresponding types: first light and medium, then heavies and tankettes. Meanwhile, the plan for 1932 has equal amounts of tankettes as tanks: 3000 T-26, 2000 BT, 5000 T-27. I deem it necessary to make a push for light tanks for next year.
  2. Currently, there is no complete data on the tactical-operative value of vehicles in the RKKA. I consider it necessary to investigate the issue of testing the BT, T-26, T-27, D-13, and D-8 in combat conditions (three vehicles of each type) in order to determine the following:
    1. Daily range of vehicles on highways, dirt roads, and mixed terrain in various conditions.
    2. Average speed over 100, 200, 300, 400, and 500 km on highways, dirt roads, and mixed terrain, with various obstacles (water, swamps, sand, elevation, etc)
    3. Average range of night marches on various roads.
    4. Exhaustion of crews of tanks and armoured cars after day and night marches.
    5. The capability of each vehicles to cross various obstacles: trenches, elevation, fording, driving over sand, swamps, stumps, etc.
    6. Accuracy of shooting from 100 to 2000 meters.
    7. Reliability of vehicles, increase reliability to 5000-8000 kilometers
  3. Perform trials no later than May of this year. Perform additional trials in fall-winter conditions. The RKKA considers performing these trials for all combat and auxiliary vehicles, both domestic and foreign bought.
7. Tractor

The tractor will work in motorized infantry units, and must have the same tactical-technical characteristics as a T-26. The tractor should be based on the T-26 chassis, and not only be useful for transporting infantry, but also evacuating the wounded, delivering ammunition and fuel, and as a command vehicle for motorized and tank units. It can also be used as a mobile workshop for battlefield repairs and a radio tank.

8. Engineering vehicles

An experimental prototype has been built with a 76 mm mountain gun on a T-26 chassis. As the tank does not have a rotating turret, I would suggest withholding production. It is necessary to develop a T-26 tank with a semi-automatic 76 mm gun in a rotating turret. It is also unreasonable to produce SPGs using Moreland trucks, as they are imported and have poorer off-road performance than Ford AA trucks.

9. Sapper tank

No complaints about the sapper tank. Aside from a sapper tank, we need a mine carrier tank. The mine carrier tank should have the same characteristics as a light tank, and should carry 1200-1500 AT mines, and two machineguns. The mine carrier is meant to lay mines in three rows in an interleaving pattern 1.5 meters away from one another during tank battles, when being chased by enemy tanks, when retreating and creating minefields for defense, on flanks, etc.

RKKA HQ Chief, Egorov"

Saturday 23 August 2014

T-70 Gun Choice

In the process of improving the combat performance of the T-60, the issue of re-armament came up. The two choices were the existing 45 mm tank gun and a newcomer, the more compact 37 mm ZiS-19. However, the 37 mm gun was at a severe disadvantage.

"To the chief of the artillery department of the GABTU BTU, Military Engineer 1st grade, comrade Nenarokov

In response to your letter #705118s from March 22nd, 1942, I reply that the NKV technical council lacks data on the factory #92 37 mm gun. Data has been requested.

Preliminarily, it can be said that that the 37 mm factory #92 gun uses a 0.7 kg shell with the muzzle velocity of 850 m/s. The existing 45 mm gun has a 1.41 kg shell, and the muzzle velocity of 760 m/s. We are also modernizing the 45 mm model 1937 gun to increase the muzzle velocity to 920 m/s. The modernization can be transferred over to the 45 mm tank gun.

Comparing the penetrations of the systems, we get the following table of theoretical armour thicknesses that can be penetrated at ranges of 200, 400, and 600 meters at an angle of 30 degrees from normal. The armour is non-cemented.

Muzzle velocity
37 mm
45 mm
45 mm modernized

From the point of view of production, most parts of the 45 mm tank gun are interchangeable with the 45 mm anti-tank gun, currently in mass production at two factories. It would be relatively easy to satisfy the requirement for such a gun. A 37 mm gun would have to be manufactured anew at one of the factories.

Currently, there is no free manufacturing power at any factory, and resolving this issue will be difficult. 

Considering the aforementioned, I consider it correct to select the 45 mm tank gun for use in the T-70 tank.  I will be able to provide additional reasoning when I receive the data from factory #92.

Chair of the NKV technical council, Professor, Doctor of Technical Sciences, E. Satel"

Friday 22 August 2014

World of Tanks History Section: BDR G1B

In July of 1930, French military command decided to motorize five infantry divisions. The goal was very ambitious: these motorized units were supposed to cover 200 km in a day. Not a single existing French tank was capable of this feat. It was decided that a new vehicles must be created.

The new tank began development in 1935-1936, and was meant to reinforce infantry divisions. It was supposed to have 40-60 mm of armour, a 47 mm gun, and weigh no more than 20 tons. This was the mass that bridges and army pontoons could hold. A heavier tank would also be unsuitable for transport with trailers and railroad cars of the time.

Seven companies submitted a bid for tender. Among the competitors was Baudet-Donon-Roussel (BDR), specializing in building truck trailers. Their first prototype put the commander directly in the path of ejecting shells. With every shot, he risked injury.

No company managed to fulfil the weight requirement of the tender. Given the armour and armament required, it was impossible.

In 1938, the new tank received the designation G1. The army increased the maximum weight to 35 tons. Additionally, a 75 mm howitzer officially became the vehicle's main weapon.

The BDR company was so caught up in the secrecy of the project that even the wooden mockup was stored in a secret remote location. Because of this, the engineers could not demonstrate the mockup in time, as they did not have time to dismantle the wall behind which it was hidden.

The BDR G1B had a series of novel solutions: gun stabilizer, optical rangefinder, partial automation of the loading process. Compared to other French tanks, it could have been a qualitative leap forward, like the T-34 was for the Soviets.

The BDR G1B did not enter production for many reasons. Its mass was over 47 tons, it was too tall, Baudet-Donon-Roussel lacked the necessary production resources. None of the seven companies involved managed to complete their project.

Original article available here.

Thursday 21 August 2014

D-5 and S-31 Trials


As a result of aforementioned trials, the following conclusions can be made.

  1. Ballistics. The ballistics of the 85 mm tank gun is nearly identical to that of the 85 mm AA gun model 1939, which makes it easy to use existing ammunition, artillery tables, and exploring the issue of armour penetration. If desired, the ballistics may be improved by mounting a muzzle brake, which will introduce the ability to improve penetration and lighten the load on the recoil system at the cost of abandoning shell compatibility with the 85 mm AA gun. Composing new artillery tables will not be difficult.
    Trials used shells from the 85 mm AA gun model 1939.
    Decrease in ballistics during the trials was negligible (near 1%) and can be traced to the condition of the barrel and chamber size changes (2-4 mm), which is typical for this kind of weapon.
  2. Precision. The precision of the 85 mm tank guns is very satisfactory at medium and close distances, nearly identical for both systems. However, the D-5T-85 system was more stable, due to the superior design of the recoil mechanism (positioned above), lesser vibrations, and less deviation when shooting.
  3. Range. The range is acceptable given the maximum elevation of the D-5T-85 on both tanks and S-31 on the IS: 12-13 km. For the S-31 gun on the KV-1S with a regular turret ring, this range is reduced to 7 km due to a limited elevation.
  4. Firing on the move trials shows that using these guns on the move is effective. At 10-15 kph, the guns hit the target 50% of the time and can be increased to up to 75%.
  5. The armour penetration of the guns is the same as the stock 85 mm AA gun: at point blank, the gun penetrates 98 mm of armour at 30 degrees, at 600-1000 meters, it penetrates 88-83 mm with regular AP-HE. Improved penetration may be achieved with the use of a muzzle brake, as stated above, or by using a subcaliber shell.
  6. Rate of fire. When firing a 16.2 kg shell from new caliber guns, the rate of fire is 10-12 RPM. Without adjusting aim, and with other favourable conditions, the rate of fire increases to 15 RPM. In old KV-1S turrets, this rate of fire cannot be reached due to more cramped working conditions, and is reduced to 5-6 RPM.
    The D-5T-85 system achieves a superior rate of fire due to its shorter recoil and smaller dimensions, which create more favourable working conditions for the crew.
  7. Robustness. The robustness is satisfactory, and use of stock 85 mm AA gun shells is acceptable.
    After previous trials, both guns have been improved, but the D-5T-85 gun has received more noticeable improvements. The recoil mechanism used to be weak, now it works acceptably and matches calculations. Recoil length is stable, there have been no failures to return.
    The S-31 system has demonstrated failures to return. Performance data differs from calculations, and the same breakdown that was seen earlier has occurred, where the bolts holding the mount cover broke off.
    The following defects occurred with both systems: 
    1. Insufficiently reliable breech. Misfires, accidental closures, shell rim biting, failure to extract.
    2. Unsatisfactory function of the trigger mechanism.
    3. Sharp, uneven return with a knock at the end.
  8. As mentioned above, the ease of use and service is greater in new IS turrets with the D-5T-85 gun as opposed to old KV-1S turrets due to the larger size of the turret and turret ring and smaller dimensions of the gun with a smaller recoil length.
    However, even in the IS turret, a series of defects need to be resolved, such as revising the ammunition rack, shields, and aiming, sight, and firing mechanisms. 
  9. TsAKB moved from 0-75 steel for the barrel to 0-70 steel. Parts quality needs to be considered carefully, considering unfortunate experiences with insufficient reliability of the S-31 barrel and breech. 
  10. The preparation of the vehicles and service during trials by factory #100 has done well. The S-31 system was prepared less thoroughly.

Based on trials held on August 22nd through 24th, 1943, of the 85 mm tank guns in the IS and KV-1S tanks, the Gorohovets proving grounds makes the following conclusions:
  1. The 85 mm tank guns are identical in their design, purpose, and characteristics compared to SPG guns tested on August 2-4, 1943 (GANIOP report #02913, August 6th, 1943). The guns have been improved and completed trials with fewer faults.
  2. The D-5T-85 is a superior design, which has the following advantages over the S-31:
    1. Lack of dead balancing weights in the turret.
    2. Smaller dimensions.
    3. Smaller (and acceptable) range of deviations.
    4. Greater robustness and reliability.
    5. Easier maintenance and assembly.
Because of this, the D-5T-85 gun designed by factory #9 can be recommended for use in heavy and medium tanks in the Red Army.

It is necessary to accelerate work on resolving the defects listed in this report."

Wednesday 20 August 2014

World of Tanks: Today in History: T-35 Assembly

On August 20th, 1932, assembly of the experimental five-turreted T-35-1 tank finished.

In 1931, a German engineer named Eduard Grotte worked in the USSR. Under his guidance, the design bureau of the Leningrad Bolshevik factory created a two-turreted TG-1 tank. Due to several reasons, the TG-1 didn't make it into production. Experience gained when building the TG-1 was applied to creating a heavy breakthrough tank, designated T-35. The first prototype was completed on August 20th, 1932.

The tank impressed the Red Army UMM, but trials revealed many weaknesses in the design. Work to remove them finished in April of 1933, resulting in T-35-2 and T-35A tanks. The T-35A entered production, and was later called simply T-35.

There is an opinion that the T-35 was inspired by the English A1E1 heavy tank. This opinion is not confirmed by archive documents. There is no evidence that the Soviet Union purchased any documentation regarding the tank. It is most likely that Soviet engineers came up with the idea of a five turreted tank independently.

The T-35 was very powerful for its time. It had no equal in firepower, as it was armed with three guns (one 76 mm and two 45 mm) and six machineguns. For a period of time, the enormous tank became a symbol of Soviet military might. Its crews were picked from the most experience tankers and it was serviced by the best mechanics.

When evaluating the tank objectively, one must admit that it had many weaknesses. Its mass meant that it had trouble with soft terrain. The driver had to apply a lot of force to drive the tank. The transmission and engine broke down frequently. If damaged in battle, the tank would be difficult to evacuate. The repairs were also very complicated, especially in the field.

The Spanish Civil War showed that the time of tanks with thin armour has passed, due to the abundance of anti-tank guns. Attempts to add appliqué armour to the tank failed. It was necessary to build tanks with anti-cannon protection from scratch, like the KV that replaced the T-35.

From 1933 to the start of the Great Patriotic War, T-35 tanks did not see combat. They were occasionally used in training exercises, but mostly the T-35 only participated in parades, inspiring respect for Soviet weapons with its fearsome look.

By June 22nd, 1941, the Red Army had 48 T-35 tanks in service in the Kiev Special Military District. All were lost at the beginning of the war, and only 7 in combat. 35 tanks broke down and were abandoned by their crews. 6 vehicles were undergoing repairs at the start of the war. These tanks last saw combat during the Battle for Moscow.

The Soviet medal "For Courage" depicts a stylized image of the T-35 heavy tank.

Original article available here.

T-34 Bug Report

Since tank engineers aren't going to be riding their creations into battle (well, not usually), they are going to miss small things that are obvious to tankers, especially when this is a new factory that is producing the tanks. Here's one such instance.

"List of suggestions for the T-34 tank composed at the technical conference of the 85th Independent Tank Brigade
  1. Engine compartment
    1. Pay attention to the processing and installation of hoses in the oil system. All new vehicles have leaks that lead to loss of pressure.
    2. Tanks that come from Gorkiy factory do not have steam redirection valves installed in the cooling system. This means that water cannot be drained.
    3. The fuel system distribution valve nut is too small. It is necessary to increase the size of the nut to make it match the supplied wrench.
    4. Gorkiy factory tanks have low quality steam pipes. Over 220 km, 18 have burst.
    5. Gorkiy factory tanks have low quality block head liners. Of the 32 tanks in the brigade, 5 have been punctured.
    6. The assembly quality of tanks coming from the Gorkiy factory is low. Fuses are not fully inserted, engine anchor bolts can be turned with a regular wrench, etc.
    7. The air exhaust valve is too low, this does not let the driver observe the appearance of fuel in it, and leads to fuel leaking into the fighting compartment. Raise the valve 60-80 cm.
  2. Suspension:
    1. The idler teeth are too small, after several readjustments it holds tracks poorly. Make the teeth bigger.
    2. Tanks that came from the Gorkiy factory do not have spikes for driving on ice. These are necessary.
    3. Strikes at the idler crankshaft can bend it. Strengthen the crankshaft.
    4. Tagil factory vehicles have very soft suspension springs, and the tanks shake, this impedes fire.
  3. Fighting compartment:
    1. Tanks don't have an AA machinegun mount. It is necessary to have a mount like the English Matilda tank, using the spare DT machinegun in an AA role.
    2. The hatch springs are weak, reinforce them.
    3. It is necessary to include a key to set the timers on shrapnel shells.
    4. Install a throat microphone in the tank instead of a regular microphone, this will free up the commander's hands and will let him have more clear communication within the tank (without interference from a working engine).
    5. The lower trigger mechanism is inconvenient as it can hit the driver when turning the turret.
    6. The battery wires come in contact with the oil pipes in motion, the insulation rubs off, and the wires spark.
    7.  The commander needs a rangefinder to correct fire. 
  4. Transmission compartment:
    1. TPU wires pass by the friction clutch levers and get in the way in fighting conditions. Move the wires so that they do not get in the way of the driver's arms.
    2. Gorkiy factory tanks have their final drive calibration locked with two bolts. This is inconvenient, as it is hard to get to the bottom one. Alter the design such that there is only one bolt, like on the Stalingrad factory tanks.
  5. Driving compartment:
    1. The tanks used to have periscopes on the side of the driver's compartment to observe terrain. These periscopes are no longer installed, and the driver cannot look to the sides. It is necessary to keep using the periscopes.
    2. During road marches, the driver's hatch is open. In order to protect him from rain, snow, and dust, it is necessary to have a removable plastic shield like on the T-70.
    3. Redesign the antenna, make it extendable like on the KV tank. The shockwave and debris from bombs can knock it off.
    4. Tanks are poorly equipped with instruments, missing pliers, oil cans, wrenches, and some tools are of poor quality. For instance, the track tightening wrench is weak and bends.
Technical Department Chief, Lieutenant-Colonel Vasilyev"

Monday 18 August 2014

Upgunning the T-60

"To the chief of the GABTU Armour Directorate, Brigade Engineer Korobkov

Report on the issue of rearming the T-60 with a 45 mm model 1938 gun

The 20 mm ShVAK gun installed on the T-60 showed itself lacking in combat conditions (it is hard to manufacture, hard to study, demanding on the battlefield, lacks interchangeable parts, etc). The Molotov GAZ factory is developing a project to install a 45 mm tank gun and a DT machinegun into a T-60 turret, while maintaining the 900 mm turret ring and turret size.

The gun position is as follows (see diagram #1).

The 45 mm tank gun is shifted to the right. Next to it is the DT machinegun, and left of that is the TMFP sight. The gun is loaded by one person, and it is only possible to fire from either the gun or the machinegun. 

The shells and machinegun disks are stored on the walls and the floor. The ammunition capacity is not yet determined. The turning mechanism is to the right, the elevation mechanism is to the left. The triggers are buttons, both for the gun and machinegun. 

Second project: Factory #92

Retaining the size and turret ring of the current turret, the T-60 is armed with a 45 mm gun, DT machinegun, and TMFP sight. The placement in the turret is as follows (see diagram #2):

The 45 mm gun is shifted to the right of the center, and the DT machinegun is shifted to the left. The gun is serviced by one person (tank commander). His seat is positioned in the rear of the turret, between the gun and machinegun. The trigger for the gun is placed on the handle of the turning mechanism, and the trigger for the machinegun on the handle of the elevation mechanism. 

Factory #92 has blueprints for the mount, and has begun assembly on December 20th, when they received a T-60 tank. 

Molotov factory (comrade Astrov) does not have blueprints, but they have a prototype, although it is imperfect and unfinished.

Drawbacks of both projects:
  1. The turret with a 45 mm gun is unbalanced, as a result of which, turning is difficult.
  2. Servicing the gun alone (loading, observation of the battlefield, aiming, etc) reduces the rate of fire of the gun. The gunner must lose sight of the target after he fires to load, and then re-acquire the target every time.
  3. In order to access the turning mechanism while sitting, the gunner must put his hand under the gun, which is uncomfortable.
  4. The brass catcher needs a 30 kg weight to balance the 45 mm gun.
  5. The recoil resistance (R=3500 kg) acts on the turret ring gears and strikes the turning mechanism, since the gun is off center.
  6. The fighting compartment is cramped and uncomfortable.
Advantages of the projects:
  1. The tank's firepower is increased. The penetration and range are increased. The tanks are easier to supply with ammunition.
  2. The 45 mm gun is already in use in the Red Army. It is reliable and easy to produce.
Having weighed the advantages and drawbacks of both projects, a final conclusion is only possible after trials. Propose to GAZ and factory #92 that they should have the prototypes produced in metal by January 15th, 1942, and perform trials on January 25th, 1942, so that the drawbacks can be evaluated. 

Personally, I consider the GAZ modification superior. I think it is necessary to order a new turret (cast) with a turret ring that is 25-30 mm wider for trials on January 25th. The automotive factory already has a project for a cast turret (see diagram #3).

Until the issue of the 45 mm gun is resolved, the turret will contain a DT and a ShVAK or a DShK. As the 45 mm gun is large for the current T-60 turret, aim for the new 37 mm gun designed by factory #92. Experimental prototypes of the gun will be ready for January 15th, 1942.

Data on the 37 mm gun: 
  • Mass: 170 kg
  • Ammunition: 37 mm AA gun shell
  • q: 0.72 kg
  • λ: 170 mm
  • Maximum pressure: 2800 kg/cm^2
  • Length: 2315 mm
  • Energy: 30,724 ton-meters
  • R=513 kg
  • Recoil brake: hydraulic
  • Return mechanism: sprint, in one cylinder
  • Penetration at 0 degrees (according to the Jacob de Marre formula):
    • 100 meters: 54.65 mm
    • 500 meters: 45.8 mm
    • 1000 meters: 35.8 mm
It is reasonable to ask factory #92 to accelerate the production of this gun and test it on the T-60 by February 1st, 1942.

Military Engineer 1st class, N. Ogurtsov
December 30th, 1941"

Sunday 17 August 2014

HEAT Tester

Since HEAT does not depend on the velocity of the shell, testing it is easy, all you have to do is hold a shell up against an armour plate, and detonate the charge. No need for large proving grounds or anything costly like that!

Except, there is one problem. Shells fired from rifled barrels without stabilization had different results when tested in this manner, whereas fin-stabilized shells had the same results. In order to test rotating shells, this device was invented.

"The device for testing rotating shells is made from a Г-shaped piece of metal. One end of the device is attached to the ground in proximity to the plate. The other houses a 50-105 Watt electric motor, which provides a rotation of 10,000 RPM when connected to a 30 V power supply, and 20,000 RPM when connected to a 40 V power supply. The axis is positioned vertically. 

The shell was rotated with a thin steel string, one end of which was connected to the motor, the other to the detonator. The motor was powered by a 220 V power supply through a transformer. The rotation of the shell was measured with a tachometer. When the shell reached the necessary rotation speed, it was detonated with a PM-1 device, where one terminal was connected to the shell casing with a metal loop, and the other was connected to the spinning wire."

Saturday 16 August 2014

World of Tanks History Section: Hunting King Tigers

In the summer of 1944, the Red Army was advancing on all fronts. The Germans defended with equal desperation and skill, occasionally revealing nasty surprises for our forces. Since they have long-lost strategic initiative, they had to rely on wonder weapons. In Poland, during August battles for the Sandomierz foothold, this role was played by new PzKpfw VI Ausf B Tiger II tanks, nicknamed "King Tiger" by Soviet soldiers.

Armoured Ram

The Germans understood that Sandomierz opened the road deep into Poland, and losing it was catastrophic. The plan was to strike between two Soviet armies. The offensive would be joined by the 501st heavy tank battalion (45 King Tigers).

The 53rd Guards Tank Brigade lay in the path of the Germans, commanded by Colonel Vasiliy Arkhipov. He was an experienced officer, having fought enemy tanks back in the Winter War. He was well capable of competently organizing defenses, including tank ambushes.

The King Tiger suffered from technical problems. Before the August 11th offensive, only 12 of the 45 501st's King Tigers remained operational. The rest broke down.

Initially, the enemy achieved significant gains. By August 12th, King Tigers overran infantry defenses and reached the villages of Szydłów and Ogledow, next to Staszow. This is where their luck ran out.

Black Sunday

On August 13th, at 7:00, under the cover of fog, 11 Tiger II tanks and two APCs with infantry formed up for an attack on a nameless height east of Ogledow. On the eastern slopes, an ambush with two Soviet tanks awaited them. One was a T-34-85 commanded by Guards Lieutenant Alexander Oskin. At 300 meters, he opened fire. Three tanks were destroyed, the rest turned back.

That day, on another section of the front, two IS-2 tanks from the 71st Independent Heavy Tank Regiment, attached to Arkhipov's brigade, faced King Tigers. Before dawn, a platoon of IS-2 tanks commanded by Senior Lieutenant Klimenkov set up next to Ogledow. When our infantry went into an attack, they spotted a King Tiger in some bushes in the south of the village, and informed our tankers. Klimenkov moved out to a prepared position and set a house on fire with two shots. The Tiger began retreating.

Klimenkov's next shot shattered his track. The crew bailed out and ran. Soviet infantry took over the tank, turned the turret towards the Germans, and opened fire. Meanwhile, Klimenkov destroyed another tank on the right flank. The attack on Ogledow failed.

Seven more King Tigers tasted defeat that day. At 14:00, they attacked our positions at Ogledow from height 271.2. Senior Lieutenant Udalov let them approach to 700-800 meters, and opened fire with his IS-2. One tank burned, another was damaged. When the German tanks passed the ambush and continued on, Udalov went around through a forest road, cut off their advance, and destroyed another tank. The enemy retreated, but soon repeated his attempt. This time, the Germans hit Senior Lieutenant Belyakov's ambush, who opened fire at 1000 meters, and destroyed a tank on his third shot. The rest turned back. Our tankers, combined with artillery, deflected 7 tank attacks that day.

On the night from August 13th to August 14th, Arkhipov's 53rd brigade captured four King Tigers. According to Soviet reports, the Germans lost 31 tanks at Szydłów and Ogledow. Reports mentioned the poor mobility of the new Tigers, which were frequently bogged down in the sand, and large size, which made aiming easier.

Trophy trials

The appearance and capture of new tanks did not go unnoticed. The King Tigers underwent extensive trials. How did Soviet specialists find the trophies?

The King Tiger, weighing 68 tons, had high fuel consumption due to its worn out engine, 971 L for 100 km, instead of 700, as specified in the manual. 860 L that could fit in the tank was enough to travel 90 km on dirt roads.

In comparison, a Panther can travel 120 km with 750 L of fuel, and the 44-ton Soviet IS-2 could travel 135 km on its 520 L tanks, spending 400 liters on 100 km.

The IS-2 was also superior in speed: 17 average kph on dirt roads, compared to the King Tiger's 13.4 kph.

While driving to the proving grounds, the tank showed its poor reliability. Final drives broke twice, on the 1st and 113th kilometer. The drive wheel broke on the 86th and 103rd kilometer, the second time taking out the torsion bar of a road wheel with it.

The planetary mechanism gave the King Tiger a good turning rate, but two track links and 12 track pins broke during turning. The pins shattered into several pieces. Additionally, the turning mechanism was expensive and complicated.

The convenient positioning of aiming mechanisms, a backup electric trigger mechanism, hydraulic foot-operated turret turning mechanism, and monocular ball-mounted sight with variable field of view gave the King Tiger good precision and a rate of fire of 5-6 RPM.

The crew positions were well designed and comfortable, aside from the commander's seat. The report mentions that it is too low, and its height cannot be adjusted, making it so the commander had to lift himself up to observe through the cupola. The cupola's vertical field of view was also insufficient.

Despite the thick armour (150 mm UFP at 50 degrees and 190 mm turret front at 10 degrees), the armour was of low quality, worse than first Tigers and Panthers. Due to the poor armour, welding seams were unreliable. Even if the armour was not penetrated, it formed see-through cracks. After 3-4 hits from 500-600 meters with 100-122 mm shells, an armour plate would be completely destroyed.

The side armour was significantly less protected than the front plates, and therefore more vulnerable. The tank's protection was insufficient for its excessive size and weight.

The most effective way to fire on a King Tiger was a volley from a battery (3-4 guns) of high caliber guns at a range of 500-1000 meters.

The conclusion is that the King Tiger could be, like its predecessor, a dangerous opponent in a defensive line prepared ahead of time. For instance, the 17-19 tanks of the 501st battalion claim 250 Soviet tanks and 142 guns destroyed in the winter of 1943-1944.

In order for this to happen, the King Tiger must already be at the spearhead of the offensive, and not trying to catch up with the increasing strength of Soviet attacks, frequently unaware of where they are happening. The unreliable suspension, poor mobility, and very vulnerable sides were frequently fatal for King Tigers, as it happened at Sandomierz.

Author: Evgeniy Belash

Evgeniy Belash is a historian, an author of books and articles on the First and Second World Wars. His best known work is "Myths of the First World War". Currently, he is working on the manuscript of a book on the application of tanks in the 1920s and 1930s.

  1. NIBT report on brief Tiger B trials.
  2. NIBT report on ballistic testing of the front hull and turret of the Tiger B.
  3. Report of the combat actions of the 53rd Guards Tank Brigade from April 19th to September 1st, 1944.
  4. Report of the combat actions of the 71st Independent Heavy Tank Regiment from July 14th to August 31st, 1944.
  5. A. Isayev, Operatsiya Bagration, Moscow, Yauza, Eksmo, 2014, p. 71
  6. P. Schitkin, Konigstiger: neudachniy debut, Korolevskiye Tigry na Sandomirzkom Platsdarme, "Mir Oruzhiya", 2005 #8, p. 14-25
Original article available here

Friday 15 August 2014

T26 Variants

The development process of the Heavy Tank, M26 "General Pershing" resulted in a number of modifications that received their own designations.


Aside from the ten T26E1 pilot vehicles, a T26 with an electric transmission was also built, and shipped to Fort Knox for trials. As of April 10th, 1945, it travelled 1200 miles, with 224 hours and 38 minutes of operation time. The electric transmission is described to have "stood up very well", not requiring excessive maintenance.


In October of 1944, a wooden mock-up of the T26E1 with a 105 mm howitzer is completed. In January of 1945, the project is formally approved, at which point the vehicle is renamed T26E2.


A 90 mm gun with improved ballistic performance, designated T15, was ordered, with 100 units recommended for procurement on December 21st, 1944. The gun was originally designed for one-piece ammunition, but it was uncomfortably long. A variant of the gun with two-piece ammunition was also developed, designated T15E2. A pilot vehicle was sent to Aberdeen for a test firing, and shipped overseas afterwards. Tanks carrying the T15E2 were designated T26E4 on March 1st, 1945, and 1000 such vehicles were authorized in lieu of M26 tanks. Characteristics of the vehicle were expected to remain the same, except for an increased in mass of 3500 pounds. Drawings for the production model and a second pilot vehicle were nearly complete on April 10th, 1945, with the first such vehicle scheduled for completion on May 15th, 1945.

A replacement of the T15E2 90 mm gun was ordered by Major General G.M. Barnes to obtain a more desirable balance condition and use one-piece ammunition. The gun was mounted further forward in the turret to free up space in the fighting compartment, requiring the use of an equilibrator system to correct the 80,000 pound imbalance. Approximately 40 of the new rounds would fit into a T26E4 tank with a redesigned ammo rack. A pilot vehicle was scheduled for completion on October 1st, 1945. 


The success of the M4A3E2 "Jumbo" Sherman led to research into an equivalent modification of the T26 tank. This modification had the effective armour of 8 inches in the front, as well as a new equilibrator, to offset the heavier gun mantlet. The vehicle's weight was estimated to be 97,000, but the tracks were widened with 5 inch wide connectors, making the vehicle's ground pressure 11.5 psi. The width of the tank with these tracks was 143 inches, 124 inches for railroad transport. The recommendation to perform this modification of the T26E3 and name it T26E5 was submitted on January 18th, 1945, and approved on February 8th. On March 29th, 1945, it was recommended that the thickness of the front armour be increased further, and 27 of these tanks be produced. The new T26E5 would have:

  • A 6 inch thick UFP positioned at 46.5 degrees
  • A 4 inch thick LFP positioned at 54 degrees
  • An 11 inch thick unsloped gun mantlet
  • Increased equilibrator capacity
  • Increased thickness of the front turret ring splash guard
  • Decreased width of the rear portion of the hull escape hatch doors to eliminate a turret weak spot
The weight of the vehicle increased to 107,000 pounds, and ground pressure grew to 12.1 psi. The vehicle was thought to be capable of speeds that could seriously damage the two front bogies on rough terrain, and modifications to the shock absorbers, torsion bars, and wheel bearings were designed, just in case. However, these changes did not make it to the production line, as it was decided to perform them on an individual basis. 

These changes made the tank unwieldy. The only bridge capable of carrying it would be the M4 Floating Bridge, at a current speed of less than 5 miles per hour. The bridge, only 148 inches wide, could not safely accommodate a T26E5 when extended track connectors were uses. A T26E5 was built and delivered to the Aberdeen Proving Grounds in July of 1945. 

Planned modifications 

In 1946, the design was scheduled to be upgraded to use a new 105 mm gun (not a howitzer), with a new transmission, a 750 hp Ford 12-cylinder engine, and a longer chassis. It is planned that the production of this new tank will be possible without significant changes to the T26 production process.

A 155 mm gun was also planned, capable of penetrating a 6 inch armour plate at 2000 yards, but also capable of firing a 95-lb HE shell, as well as a gun "of greater power and velocity than the 105-mm. gun... [with] muzzle velocity of about 3,500 feet per second normal and 4,800 feet per second with the tungsten carbide projectile". The T26 has been sufficiently future-proofed, according to the author. "These development programs will provide the American Army again in 1945 with the most powerful and best tank on the battlefield, and should the war continue, will provide our troops with a still more powerful tank in 1946."

Thursday 14 August 2014

History of the Pershing: T20 to M26

I've posted about American T20 series tanks before, but not in significant detail. This article will go into much more detail about the T20 tank and its descendants that ultimately resulted in the M26 Pershing tank. Since the supplier of these documents did not wish for them to be reproduced fully, this article series will only contain photographs from the scanned documents.

While the Ordnance Department was working on Sherman tanks armed with a 76 mm gun and a 105 mm howitzer, another project was underway to produce an entirely new medium tank. The new tank would have the same engine, transmission, and suspension as the Sherman, but a lower silhouette and a turret mounting a 76 mm gun. The next step in the project would be an upgrade to a 90 mm gun and use an improved electric transmission. In parallel, a heavier design that also mounted the 90 mm gun was being developed. This project, approved on May 25th, 1942, resulted in the T20, T23, T25, and T26 tanks.

The Army did not appreciate the results of the program. On September 13th, 1943, the Chief of Ordnance recommended that 500 T23 tanks be produced, 500 T25 tanks, 500 T26 tanks, and 500 T71 GMCs (an M10 tank destroyer with a 90 mm gun). The Commanding General of the Army Service Forces declined this recommendation on October 4th. A T23 with a 90 mm gun was built and shown to various high ranking officers, but the army was "not in favour of the 90-mm gun" as there was never a specific request for this gun, nor did it fit into the 30-ton weight limit. 250 T23 tanks armed with 76 mm guns, as well as 40 T25s and 10 T26es were approved on June 3rd, 1943. Development of these tanks progressed well enough for 500 additional units of each type to be requested in September, but the Director of the Requirements Division advised that "the proposal to build these additional quantities was not favourably considered at this time". However, when the Ordnance Department repeated the request in December of 1943, they were given permission to produce 250 additional T26 tanks (260 in total).

The electric transmission was deemed too heavy during the design process, and replaced with a Torqmatic in the two heavier designs, resulting in the T25E1 and T26E1 tanks.

The first T26E1 was completed by Fisher Tank Division, and arrived at Aberdeen on March 6th, 1944. A demonstration was held on March 30th, with the Secretary of War, Chief of Staff, and other high ranking military members present. The demonstration was impressive enough that "this new tank, which is superior to all known tanks" was approved for large scale production. At this point, the tank is described as having "...three speed Torqmatic transmission to increase the mobility of the vehicle and decrease driver fatigue, and a torsion bar suspension and 24-in. center-guide track to increase maneuverability and dependability in the field. The tracks were driven by the rear sprocket. Power was supplied by a 500-hp Ford GAF engine. Thicker armour was used for added protection, thicknesses of up to 4 1/2 in. on the turret front being used. One of the outstanding features of the vehicle was the use of the 90-mm Gun M3, which fired a 24-pound projectile capable of piercing a 4-in. armor plate at 2,000 yards."

Another demonstration was held in April of 1944, showing the T25E1 and T26E1 to the Secretary of War, Undersecretary of War, and Generals Marshall, McNair, McNarney, Porter, Weldron, Clay, Maxwell, Somervell, and Styer.

The tanks continued trials at Aberdeen until May 21st, 1944, racking up 1593 miles on the first pilot vehicle and 569 on the second. The overall design of the vehicle was considered sound, and the transmission, suspension, and gun were satisfactory. However, there were problems with cooling the engine and differential, oil leaks, repeated failure of the connection between the engine and flywheel, and the ammunition rack was deemed unsatisfactory. The vehicle was also found to be very wide. It was only possible to use the 60-ton Bailey bridge (among many others, the photograph of crossing a Bailey bridge is missing from the document) if the curb was removed, or protected with timber. Aberdeen gave the recommendation to put the tank into production, provided that the aforementioned defects were corrected.

T26E1 crossing the Trestle Bridge. A scribble across the medium classification indicates that this photo was archived not long before the classification changed.

Efforts to correct the defects were made from May 22nd to September 10th, by which point the first vehicle accumulated 4025 miles and the second 1805 miles. A new Ford V-8 engine operated satisfactorily for 1500 miles. Among many modifications made to the vehicle was a mount for a crane capable of carrying the tank's power train.

 On June 29th, 1944, the designation of the vehicle changed again, this time from "Medium Tank, T26E1" to "Heavy Tank, T26E1". The tank is described as "It has a weight of 43 tons, a maximum of 4" of armor giving 6.9" basis for frontal plates, and 24" tracks. Except for weight, thickness, and track width, it resembles the medium tank, T25E1".

2750 T26E1 heavy tanks were ordered, and 3188 T26E1 tanks armed with a 105 mm howitzer (later designated T26E2), despite the fighting compartment of the latter not having been designed yet. At this point, 122 T23 tanks have been made (including a prototype made in November of 1943), with the remaining 128 tanks due by October of 1944, 40 T25E1 tanks have already been manufactured, and 6053 T26 tanks are required for 1944 and 1945. 10 T26E1 tanks with 90 mm guns have been produced up to this point, with 105 more to come before the end of the year. The remainder of required T26E1 tanks armed with 90 mm guns and all T26E1 tanks armed with 105 mm howitzers will be produced in 1945.

Development of a tungsten carbide HVAP shell for the 90 mm gun began in July 1944, with the objective of penetrating a 6 inch plate at a 30 degree angle at 2000 yards.

The development of a T25E1 and T26E1 armed with a 75 and a 76 mm gun was ordered by the Commanding General, Army Ground Forces, on July 15th, 1944, but the Ordnance Department requested a low priority for this development, citing that "the 75-mm gun is now furnished in quantity in the Light Tank M24, the medium tanks of the M4 series, and the Assault Tank M4A3E2. The 76-mm gun is now being produced in quantity on the medium tanks of the M4 series."

The 10 finished T26E1s weren't sitting around gathering dust. As of November 10th, 1944, they went through approximately 20000 miles of testing, resulting in more changes to the design, such as a 23 inch track. Research continued into improving the cooling, braking, and ballistic performance of the vehicle.

In December of 1944, the tank was considered "far superior to any tank of equal speed or weight" by the Ordnance Committee. At this point, the improved tank was renamed T26E3, to avoid confusion with the ten pilot vehicles. Twenty tanks were shipped to Europe on February 7th, 1945, on the "Heavy Tank Mission", accompanied by Major General G.M. Barnes of the Ordnance Department. Ten tanks entered action on February 23rd, 1945, with the Third Armoured Division. A few days later, the other ten went into battle with the Ninth Armoured. 

The Heavy Tank, T26E3, nicknamed "General Pershing", was standardized as the Heavy Tank, M26 on March 29th, 1945.

Cross-section diagram of Heavy Tank M26 showing interior arrangement.