O-I
O-I
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[Client Values; Actual values in
950,000  Cost |
| 1060212 HP Hit Points |
| 150.36/150.539.8/155 t Weight Limit |
- Commander
- Gunner
- Driver
- Radio Operator
- Radio Operator
- Loader
| 11001200 hp Engine Power |
| 29.4/10 km/h Speed Limit |
| 1618 deg/s Traverse |
| 7.3230.15 hp/t Power/Wt Ratio |
| NoNo Pivot |
| // mm Hull Armor |
| 150/150/105150/150/105 mm Turret Armor |
AP//HE
AP/HEAT/HE Shells |
0/3600/190
540/4800/660 Shell Cost |
| 300/300/360700/700/890 HP Damage |
| 175/201/53121/150/75 mm Penetration |
|
5 r/m ▲
2.31 r/m Standard Gun ▲ Rate of Fire Standard Gun |
|
1500 ▲
Standard Gun
▼
Standard Gun
▲
1617 Standard Gun ▲
Standard Gun
▼
Standard Gun
▲ Damage Per Minute Standard Gun |
|
0.43 m ▲
0.58 m With 50% Crew: 0.533 m ▲ Accuracy With 50% Crew: 0.718 m |
| 3.2 s 3.7 s Aim time |
| 1818 deg/s Turret Traverse |
| 360° Gun Arc |
| -10°/+20°-10°/+20° Elevation Arc |
| 10060 rounds Ammo Capacity |
| 2020 % Chance of Fire |
| 370 m 370 m View Range |
| 300 m 425 m Signal Range |
VI
950000
The O-I is a Japanese tier 6 heavy tank.
Development of the superheavy tank was started after the Battles of Khalkhyn Gol in 1939. The vehicle was designed as a maneuverable fire unit that was unprecedented in scale—its hull alone weighed 100 tons. Only one prototype was built, without a turret and made of construction steel. Trials were discontinued due to the unreliable engine; at the end of 1944, the prototype was scrapped. The 15 cm howitzer was to be mounted on the tank after its assembly.
Also known as Derp Demon. The O-I is basically a KV-2 on steroids. Not only does it carry the most powerful gun of its tier, the O-I also sports some of the toughest protection in tier 6; it easily can hold itself against tier 7 tanks with its thick armor & raw firepower. It had two gun choices; a powerful 10cm AP gun with high penetration and a trademark 15cm "derp gun" with insane alpha damage. The O-I has the similar distinctive look like it's brother "O-I exp" and offers a unique, fun play style with it's Insane armor & raw firepower.
However, like every Japanese heavy tank after tier 4, it is huge and massive (even larger than most of tier 10s) as well as quite slow, and will usually become the primary target of SPGs, gold rounds and flankers.
As of update 1.9, the O-I is no longer researched from the O-I Exp. it is instead researched from the Chi-Nu.
The O-I leads to the O-Ni.
Modules / Available Equipment and Consumables
Modules
Guns
| Tier | Gun | Penetration (mm) |
Damage (HP) |
Rate of fire (rounds/minute) |
Dispersion (m/100m) |
Aiming time (s) |
Weight (kg) |
Price (  )
| |
|---|---|---|---|---|---|---|---|---|---|
| VII | 10 cm Cannon Type 92 | 175/201/53 | 300/300/360 | 5 | 0.43 | 3.2 | 1792 | 68500 | |
| VII | 15 cm Howitzer Type 96 | 121/150/75 | 700/700/890 | 2.31 | 0.58 | 3.7 | 1432 | 71200 |
Engines
| Tier | Engine | Engine Power (hp) |
Chance of Fire on Impact (%) |
Weight (kg) |
Price ( )
| |
|---|---|---|---|---|---|---|
| VII | 2x Kawasaki Type 98 V-12 (550) | 1100 | 20 | 1020 | 51000 | |
| VIII | 2x Kawasaki Type 98 V-12 (600) | 1200 | 20 | 1020 | 77500 |
Suspensions
| Tier | Suspension | Load Limit (т) |
Traverse Speed (gr/sec) |
Rmin | Weight (kg) |
Price ( )
| |
|---|---|---|---|---|---|---|---|
| V | O-I | 150.5 | 16 | B/2 | 25000 | 10000 | |
| VI | O-I Kai | 155 | 18 | B/2 | 25000 | 19800 |
Radios
| Tier | Radio | Signal Range (m) |
Weight (kg) |
Price ( )
| |
|---|---|---|---|---|---|
| II | Type 94 Mk. 4 Otsu | 300 | 40 | 0 | |
| IV | Type 94 Mk. 4 Hei | 350 | 90 | 2350 | |
| VI | Type 96 Mk. 4 Bo | 425 | 50 | 14000 |
Compatible Equipment
Compatible Consumables
Player Opinion
Pros and Cons
Pros:
- Choice of two guns: 10cm gun and 15cm gun, both of which have ridiculously high ammunition stock.
- High Hp (1060) + insane 150mm front armor with next to no true weakspots gives even some tier VII's problems, and able to take tremendous punishment before going down.
- Excellent view range, especially for a heavy.
- Has tall turret, very easy to shoot over cover & allied tanks.
- 15cm is capable of two-shotting most tanks in its tier, like the KV-2, even with AP. It is also slightly more accurate.
- Insane mass + high hp engine makes it good at shoving dead tanks for additional cover and highly resistant to rams.
- Because of Large Mass, tank is able to mount Superheavy spall liner, increasing already excellent survivability even more.
- Moderately easy stock grind since the 10cm gun deals a large amount of damage and has great penetration. And doesn't need tracks to mount modules and lacks additional turret to research.
- Shares most of its modules with other later Japanese super-heavies. You can grind and research the radio and engine for the next tank.
- Fear factor: powerful, high damaging gun + thick armor all around makes it a scary tank to face.
Cons:
- Huge size and weak side armor leaves O-I very vulnerable to flanking, artillery and gold rounds. Though rear armor is thicker than sides, and the rear mini turret is strong as the front ones. Difficult to hide and sports hideous camo ratings.
- Both guns, especially the howitzer, are inaccurate, have long aim time and poor gun handling.
- While surprisingly accurate at long range, ironically the howitzer has an infuriating tendency to miss at point blank range, often with fatal results.
- Horrifyingly poor mobility, bad ground resistance, slow acceleration and bad top speed (25 km/h) makes for a really slow tank.
- Terrible camouflage ratings, can be easily spotted.
- Absolutely terrible DPM on both guns; 15cm has even longer reload than KV-2 and 10cm has absolutely terrible DPM (300 worse than O-I Experimental despite being higher tier!)
- Inner side armor is only 30mm thick and possible to hit and overmatch from hole above tracks.
- Will still have to rely on HE in most cases against some tier 7s.
Performance
In terms of firepower, the O-I has it in spades. Stock, the tank comes with an excellent 10cm gun capable of going through any tank you might have to face while dealing respectable damage with decent accuracy, but a rather long aim time. There is a second gun for the O-I and it is a 15cm devastating alpha howitzer, similar to that mounted on the KV-2, with a slightly slower rate of fire, lower accuracy and a horrid aim time. However, this gun can be a lot of fun to play, especially when striking lightly armored foes which is common at tier 6.
Game play with the 10cm gun allows you to engage targets at a longer range and good penetration. It also allows you to play a more supportive role by sniping when you are bottom tier. With this gun, it allows an O-I to laugh at opposing heavy tank's armor, while you effortlessly bounce incoming fire. With the 10cm gun, it also allows you to more reliably handle opposing O-Is. However, 10cm is more ineffective against higher tier heavies as well as loses its feared ability to one-shot tanks. Be wary that while the gun reloads faster than howitzer, it still has very low DPM and poor accuracy which means that O-I wont deal damage very quickly.
With the 15cm derp cannon, your play style will have to change radically to make up for the shortcomings of the gun's long aim time and poor accuracy. This means that getting up close and personal in any brawl will allow you to negate your gun's main problems and ensure every shell hits. Having knowledge of what might appear in front of your tank is crucial as well, to make sure the correct shell is loaded. The AP shell in the 15cm gun is better than that in the KV-2, with improved penetration. 121mm may not seem like much, but at tier 6, it is sufficient to go through many tanks frontally. In exchange for the better AP shells, the HE shells do not penetrate as much armor, as compared to the ones on the KV-2. However, thin-skinned targets will be wrecked easily by it. When you are bottom tier, the large caliber HE shell will allow you to do damage in all situations, as long as the shell hits your target.
In conclusion, the O-I is ridiculously powerful for a tier 6 vehicle. It has a flexible choice of guns for different play styles. The O-I has also seen increased use in tier 6 strongholds due to it's armor and derp gun. It should be noted that the gun depression is a lie - it is only -10 degrees in the very front in between the two turrets, and is between 4 degrees and 6 degrees everywhere else.
Early Research
- The Type 96 Mk. 4 Bo radio carries over from the Chi-Nu and should be installed immediately.
- Research either the 15 cm Howitzer Type 96 or the 2x Kawasaki Type 98 V-12 (600) engine.
- Research whichever module you didn't choose previously.
- Finally, research the O-I Kai suspension.
Suggested Equipment
Gallery
Historical Info
History and development
After 1939, the Imperial Japanese Army quickly came to realize that previous forms of mechanized warfare were proved inefficient after their defeat at Khalkhin Gol.
Development of the super-heavy project was spearheaded by Colonel Hideo Iwakuro, the head of the Ministry of War of Japan (陸軍省 Rikugun-shō). Iwakuro opposed Japan’s advances towards the Soviet Union in 1939, and with the Japanese defeat, he decided to initiate a project to construct a heavily armored tank capable of withstanding large-calibre field cannons. Iwakuro assigned Colonel Murata of the 4th Technical Research Group to design and construct the super heavy tank in 1939. Colonel Murata noted Iwakuro’s words as described;
「満州の大平原で移動トーチカとして使えるような巨大戦車を作ってほしい。極秘でだ。」
“I want a huge tank built which can be used as a mobile pillbox in the wide open plains of Manchuria. Top secret.”
「今の戦車の寸法を2倍に延ばして作れ。」
“Make the dimensions twice that of today’s tanks.”
The 4th Technical Research Group began designing the super-heavy vehicle throughout 1940, attempting to meet Colonel Iwakuro’s vague instructions on the ultimate goal of the project. By March 1941, the research group had finished initial tank design and was ready to begin construction. The following month, a group of pre-selected engineers were chosen to partake in the building of the super-heavy tank. One recorded engineer was Shigeo Otaka, who stated they were sent to the 4th Technical Research Group’s previous headquarters in Tokyo. There, they were guided through a barracks containing multiple small fitting rooms, where they were to conduct meetings and reports on the progress of construction of the super-heavy vehicle. Towards the end of the barracks facility was a fully-enclosed room devoid of windows, with soundproofed walls to prevent external personnel from overhearing discussions related to the project. Each officer present possessed a portion of the project’s blueprint, which, when assembled, projected the full design of the tank, labelled "Mi-To". The name originated from a collection of the Mitsubishi industry and the city, Tokyo; given to the vehicle to uphold secrecy of the tank’s project.
Colonels Murata and Iwakuro
The chosen engineers voiced their concerns regarding the Mi-To’s design noting that previously, the largest-sized Japanese tank had been the prototype Type95 Heavy in 1934. Issues that had been noted with heavy tank experiments in the years preceding the Mi-To showing Japan’s generally unsuccessful testing on multi-turreted vehicles exceeding the weight of standard armored vehicles. However, with the threat of a second Russo-Japanese conflict becoming more apparent, the project continued despite the engineer’s doubts on the size and mobility of the vehicle.
Four engineers who survived to record the dealing had with the project
On April 14th 1941, the engineers began the construction of the Mi-To under secretive means. This entailed privately-made mechanical parts and equipment being shipped to the construction zone. Colonel Murata’s original concept was to complete the super-heavy tank three months after the initiation of Mi-To’s construction. This, ultimately, did not come into fruition; as technical issues on the project began to arise. Due to the limitation on material consumption by the government, the amount of parts that could be secretly shipped-in began to dwindle. By the first month of construction, essential construction resources had been depleted and the issues with the vehicle’s cooling system further caused delays. The construction of the Mi-To was postponed until January 1942, a delay of nine months.
After the Mi-To’s construction was resumed, the hull was completed on February 8th 1942. The tank had reached near-completion and was being prepared for mobility testing. Mitsubishi built the four turrets for the tank in May of the same year. Initial assembly of the tank’s armament took place soon after the turret’s superstructures were completed. However; the project once again did not have the necessary resources needed for the few remaining parts required for the final assessment. Due to this, the primary turret was removed as it lacked a 35-millimetre-thick roof plate, which had not yet arrived. Thus, the project was put on standby, until further development could continue. The total weight of the vehicle at the time was 96 tons, due to the lack of remaining structural plates and absent 75mm bolted-on armor.
O-I documents previewed by FineMolds
The date on which the construction of the tank resumed is unknown, although active testing of the tank was scheduled for late 1943. The tank was unveiled to the Imperial Japanese Army’s highest command in 1943, and received a name change to O-I. This followed Japanese naming convention (O translating to Heavy, I for First, making it "First Heavy") that was standard. In his place was Lieutenant Colonel Nakano, Murata's assistant and colleague. Tomio Hara, head of the Sagamia Army Arsenal, was also present. Following the demonstration, senior officials within the IJA requested that field trials begin in August of the same year. The tank was disassembled at 2:00 AM one night in June of 1943 and sent to the Sagami Army Arsenal in Sagamihara, 51 kilometres from Tokyo. The vehicle arrived at the depot in June, and was reassembled and tested on the 1st of August.
On the day of the trials, the O-I performed satisfactorily until the second hour of the tests. While manoeuvring on off-road terrain, the tank sank into the ground by up to a meter; attempts at traversing the hull to extricate the vehicle proved fruitless, resulting in further sinking due to the vehicle’s suspension coils compressing. The tank was eventually towed out, and further testing was continued on concrete. However, the earlier damage to the suspension resulted in vehicle’s movement damaging the concrete, which in turn, further damaged the suspension bogies to the point that further testing could not continue. The trials were postponed, and later cancelled the following day.
Nevertheless, the trials conducted at the testing field were considered to be a success, and the vehicle was deemed ready for use in spite of its flaws. The engineers began disassembly of the tank on the 3rd of August due to resources being limited and the inability to maintain the tank in the field. Disassembly of the tank was completed on August 8th. Two days later, the engineers noted in a log that they were to inspect the parts and conduct research to fix the issues the O-I would face.
The fate of the O-I after its field-trials which took place on the 1st of August is unclear. Russian reports claim the Japanese were in possession of a wooden O-I mock-up mounting a Daimler-Benz DB 601A engine in 1945, however other sources point to the scrapping of the remaining parts of the same year. The remains of the O-I reside at the Wakajishi Shrine, with a track link of the prototype still present.
Remaining track link of the prototype O-I tank
Design
The O-I was conceived out of the necessity to produce an armored vehicle capable of withstanding modern weaponry being able to return fire with similar firepower. The O-I was designed to act as a mobile pillbox, supporting infantry and mechanized groups along the border of the Soviet Union. The tank had a length of 10.1 meters, width of 4.8 meters, and a height of 3.6 meters. The dimensions of the vehicle closely matched those of the Panzer VIII Maus. The tank was envisioned to have a standard thickness of 150 millimeters front and rear, in order to protect against common anti-tank weapons of the time, yet it was constructed with armor 75 millimeters thick. However, an additional armor plate could be bolted on to bring the total thickness of the armor to 150 millimeters. The use of additional armor allowed for ease of construction and transportation, while also providing the tank with additional defense. Side armor on the hull superstructure was 70 millimeters thick. The additional armor plates were 35 millimeters thick, but armor surrounding the suspension was only 35 millimeters thick. This made the tank’s theoretical armor on the side 75 millimeters. There were eight wheel-supporting beams located on both sides of the suspension area which added an additional 40 millimeters of armor to specific locations on the side of the O-I. 40 ladder pieces were placed around the tank to provide crew with the ability to climb onto of the vehicle with ease.
The two 47mm cannons used in the two frontal turrets were also modified to fit the armor layout of the tank. The weapon’s barrels were reinforced with steel to secure them to the tank, due to the standard gun not adequately fitting into the turret.
The tank was both designed and built with two inner armor plates to divide the interior into three sections; walls with two doors each and an ultimate thickness of 20mm. This allowed the crew and modules to remain relatively safe while the structure was kept safe with supporting stands. These supports allowed the interior armor plates to stay stable and also prevented collapse. Inside the O-I were two Kawasaki V-12 engines, both located in the rear, parallel lengthwise, to give room for the rear turret operator and transmission. The transmission copied that of the Type97 Chi-Ha’s, but used larger parts and gears making the total weight heavier. The vehicle had a coil spring system, with eight 2 wheeled boggies, totalling 16 individual wheels.
General
- Name: O-I
- Factory: Private - Mitsubishi
- Units Produced: 1
- Type: Super Heavy Tank
- Year Built: February 8th 1942
- Length: 10.1 m
- Width: 4.8 m
- Hull Width: 4833 mm
- Height Full: 3.6 m
- Turret height: 1065 mm
- Track width: 800 mm
- Track Pitch: 300 mm
- Track Thickness: 58 mm Half, 108 mm Full
- Total Weight: 150t (96t prototype)
Engine=
- Name: Type98 V12 Kawasaki
- Power: 550hp (1100hp total with second engine)
- Weight: 1020kg
- Gears: 6
- Lubricant type: Oil
- Maximum speed: 40kmh onroad (96 ton prototype), 29.4 kmh (design) onroad
Hull
- Hull height 2530 mm
- Hull Width: 4833 mm
- Upper Front Plate: 150mm @ 56,29°
- Lower Front Plate: 150mm @ 45°
- Lowest Front Plate: 70mm @ 70,5°
- Side plate: 35mm @ 0° + Bolted 35mm @ 0°
- Superstructure side plate: 75mm @ 0°
- Upper Rear Plate: 150mm @ 18°
- Lower Rear Plate: 150mm @ 33,01°
- Lowest Rear Plate: 30mm @ 75,99°
- Top plate: 50mm @ 0°
- Bottom plate thickness: 30mm @ 0°
Primary Turret=
- Turret height: 1065 mm
- Turret side faces: 150mm @ 90°
- Turret top: 50mm @ 0°
Armament
- Model: Type96 15cm Howtizer
- Weight: 4,140 kg
- Elevation: -5 ° to + 20 °
- Amount of ammunition: 100+
- Type of ammunition: Type95 APHE, Type92 Spifire HE, 4th Year HEAT
Ammunition Types
- Name: Type95 APHE
- Shell weight: 36000g
- Muzzle Velocity: 540m/s
- Penetration: 125mm @ 230m, 120mm @ 510m, 112mm @ 755m, 102mm @ 1000m
- Explosives: 6150g
- Name: Type92 Spifire HE
- Shell weight: 36000g
- Muzzle Velocity: 540m/s
- Explosives: 6150g
- Name: 4th Year HEAT
- Shell weight: 21040g
- Muzzle Velocity: 650m/s
- Explosives: 6150g
Secondary Armament
- Model: Type1 47mm Experimental
- Weight: 600(+/-) kg
- Elevation: -10 ° to + 20 °
- Amount of ammunition: 100+
- Type of ammunition: Type1 APHE, Tungsten Alloy Toku Kou Prototype
- Name: Type1 APHE
- Shell weight: 36000g
- Muzzle Velocity: 810m/s
- Penetration: 65mm @ 200m, 65mm @ 500m, 50mm @ 1000m, 45mm @ 1500m
- Explosives: 250g
- Name: Tungsten Alloy Toku Kou Prototype
- Shell weight: 36000g
- Muzzle Velocity: 810m/s
- Penetration: 85mm @ 0m, 79mm @ 200m, 70mm @ 500m, 56mm @ 1000m, 45mm @ 1500m
- Explosives: 250g
Historical Gallery
Historical Accuracy Errata
The 150 ton O-I was never supposed to mount the 10cm gun.
- The hull rear armor was decreased for balancing reason
Sources and External Links
| Light Tanks | IRenault Otsu • IIType 95 Ha-Go • IIType 97 Te-Ke • IIIType 97 Chi-Ha • IIIType 98 Ke-Ni • IVType 5 Ke-Ho |
| Medium Tanks | IIChi-Ni • IIType 89 I-Go/Chi-Ro • IVType 1 Chi-He • VType 3 Chi-Nu • VType 3 Chi-Nu Kai • VIType 4 Chi-To • VIIType 5 Chi-Ri • VIIISTA-1 • VIIISTA-2 • IXType 61 • XSTB-1 |
| Heavy Tanks | IIIType 91 Heavy • IVType 95 Heavy • VO-I Experimental • VIHeavy Tank No. VI • VIO-I • VIIO-Ni • VIIIO-Ho • IXType 4 Heavy • XType 5 Heavy |
| Tank Destroyers | |
| Self-Propelled Artillery |
