STA-4 and STA-1B discussion

[JapanWeeb89]

like the title says this is a discussion to hopefully get enough information among the users to make a suggestion or make a good recopilation of information about the STA-4 and the STA-1B

STA-4

the STA-4 is generally regarded as just a type 61 with a mg on a cupola like the M48 so I have these 2 magazines from 1979 and 1980 about the Type 61

In both of them there are some facts mentioned about STA-4 and sadly I can’t confirm if this information is true so that’s why I’m making a post in the forums about it, if you guys need me to post more photos I will upload them ASAP, hopefully we can make a spec profile about the vehicle, to start with there’s an interesting chart which compares the peformance of 3 vehicles:

In all sources about Type 61 the engine is stated to produce 570 hp, as you can see this chart claims that STA-4 had a slightly better engine capable of producing 590 hp, not a ton of difference but is still 20 hp more, in the other magazine there is an image which says:

So now there are 2 mentions of the upgraded performance of STA-4 compared to STA-3, now I coudn’t seem to find the specific mention about what was changed on the magazine but this is mainly because I don’t speak Japanese(I wish I did though) so there is a language barrier, another interesting fact is that the magazine claims that both STA-3 and STA-4 were equipped with a semi-automatic reloading system which of course they weren’t put into production with Type 61

So this pretty much means that STA-4 will perhaps work as an upgraded Type 61 in game by having the reloading system of STA-3 and a slightly better performance, but I want to read what you guys think about it because all of this info is found on 2 magazines of the same company, does anybody have more information about STA-4? is this info accurate or is wrong? I will appreciate reading you guys responses to this.

STA-1B

In the magazines there’s also a mention of a prototype variation that I haven’t seen being talked about anywhere, this is the STA-1B:

does anybody knows anything about this vehicle? the magazine has some paragraphs that talk about the vehicle having a better engine capable of producing 600 hp but apparently was lost due to the vehicle catching fire.

is an odd vehicle and I’ve never heard about it until I read it.
Thank you for your attention, sorry for the long post I don’t know how to shrink the images, hopefully this can be a nice discussion about this 2 vehicles

[Константинович7]

Perhaps any information regarding the autoloading system?

[MAUSWAFFE]

@JapanWeeb89

does anybody knows anything about this vehicle?

I think I’ve read before that the updated engine and transmission intended for the STA-3 and STA-4 tanks was first tested with the STA-1 and STA-2 tanks.
The STA-2 would receive the new transmission, while the STA-1 would receive the new engine. Both would be redesignated as STA-1B and STA-2B respectively.

Images of STA-2B were already known, besides the transmission it also added a new mantlet and mounted the rangefinder. Though it’s only images of it being used as museum display.

Spoiler

STA-1B catching fire during testing would explain why there way no images before. You might actually have made the first picture of it available to the internet!

[MAUSWAFFE]

Japanese Wikipedia has some more info on these vehicles, stating:

"In the development, two prototypes, STA-1 and STA-2, were produced. The main difference was the vehicle height. STA-1 was longer in length, and had four upper road wheels on one side and seven road wheels on the other side, in order to achieve a low profile (2.2 meters high). It was made of ordinary steel plate and completed in December 1956. STA-2 was 2.5 meters high, shorter in length than STA-1, and had three upper road wheels on one side and six road wheels on the other side. It was equipped with an air-cooled diesel engine, torsion bar suspension, torque converter, powered steering, etc., and was made of protective steel plate and completed in February 1957 (Showa 32). The left front left side of the turret of STA-1 and STA-2 had a hole for a stereo range finder, but the range finder was not installed and the hole was filled with a patch. An elliptical cylinder-shaped range finder was installed on the right front right side of the turret. The main guns of the STA-1 and STA-2 were equipped with smoke extractors and single-baffle muzzle brakes, similar to the M3A1 90mm tank gun. The engine was still under development, so a Mitsubishi DL10T V12 liquid-cooled diesel engine (500hp/2,000rpm) was installed, which was a modified version of an existing civilian marine engine. In July of the same year, the engine of the STA-1 was replaced and it was designated the STA-1B. The steering transmission of the STA-2 was replaced and it was designated the STA-2B. The initial plan was to achieve the required performance with just these two prototypes, and to proceed with additional prototypes in preparation for mass production, but the first two prototypes did not meet the required performance.

The low height of the STA-1 was evaluated, but the engine room interfered with the turret when it rotated, so the overall length was increased to avoid this, and the gap between the tracks became narrower relative to the ground contact length. This would increase resistance during turns and have a negative effect on maneuverability, so the STA-1 proposal was not adopted, and the STA-2’s 2.5-meter height was adopted, as it was necessary to further downsize the engine and transmission for practical use. In addition, tests of a new engine were conducted on the STA-1, and it was found that the auto-clutch had a large power loss, so it was changed to a mechanical two-stage clutch.

(Initially, the prototypes STA-1 and STA-2 were equipped with a two-stage torque converter made by SRM of Sweden, but there were problems with power loss and agility, and the performance did not meet the requirements.) In the late 1950s, domestic technology at the time lacked the know-how to develop a torque converter for tanks that could match the diesel engine output of over 500 horsepower, so the transmission and steering device of the STA-2 were later changed to the “Chito type” based on the wartime Type 4 medium tank (the prototypes STA-3 and STA-4 had a mechanical high/low switching two-stage clutch transmission and a Cletrak type steering device).

As a result of technical and practical tests carried out over a period of about one year from the end of 1956, it was decided to make a second prototype, which was based on the design of the STA-2 but with the turret shifted backwards to create more space for the pilot, and the STA-3 was completed in January 1960, and the STA-4 in November 1959. They were delivered to the Defense Agency in April 1960. The muzzle brake was changed to a T-shape, the engine power was increased, the number of portable machine gun bullets was increased, and the excess weight up to the weight limit was diverted to defensive armor, etc.

Original Text

"開発ではまずSTA-1、STA-2という2種類の試作車が製作された。大きな違いは車高で、STA-1は低姿勢（高さ2.2メートル）を追求したため、全長は長く、上部転輪は片側4個、転輪は片側7個。材質は普通鋼板で製作され、1956年12月に完成した。STA-2は高さ2.5メートルで、STA-1より全長が短くなり、上部転輪は片側3個、転輪は片側6個。空冷ディーゼルエンジン、トーションバーサスペンション、トルクコンバータ、動力付き操縦装置などを搭載、防御鋼板で製作され、1957年（昭和32年）2月に完成した。STA-1とSTA-2の砲塔前方左側には、ステレオ式測遠機のための穴が設けられていたが、測遠機が装備されておらず、穴はパッチで塞がれていた。砲塔前方右側には、楕円柱型の測遠機が装備されていた。STA-1とSTA-2の主砲は、「M3A1 90mm戦車砲」と同様に、排煙器とシングルバッフル式の砲口制退器を備えていた。エンジンはまだ開発中だったため、既存の民生用船舶エンジンを流用して改造した三菱DL10T V12液冷ディーゼルエンジン（500hp/2,000rpm）が搭載されていた。同年7月、STA-1のエンジンを換装し、STA-1Bと呼称。STA-2は操向変速機を換装し、STA-2Bと呼称した。当初の予定ではこの2輌の試作車だけで要求性能を達成、量産準備のための増加試作に入る予定であったが、第1次試作の2輌は要求性能に達しなかった。

STA-1の低車高は評価されたものの、砲塔の旋回時に機関室が干渉し、これを避けるため全長が長くなり、履帯の接地長に対して相対的に輪間が狭くなってしまった。これでは旋回時などに抵抗が増し、運動性に悪影響を与えるため、実用化にはエンジンとトランスミッションの更なる小型化が必要であるとしてSTA-1の案は採用されず、STA-2の車高2.5メートルの配置が採られた。また、STA-1にて新型エンジンのテストが行われ、オートクラッチのパワーロスが大きいことが判明、機械式2段クラッチに変更された。

（当初、試作車STA-1、STA-2ではスウェーデンのSRM社製2段型トルクコンバーターを導入し搭載したもののパワーロスと敏捷性に問題があり、要求を満たす性能ではなかった）1950年代後半当時の国産技術では、500馬力超のディーゼルエンジン出力に見合う戦車用トルクコンバーターの開発ノウハウは不足しており、後にSTA-2ではトランスミッションと操向装置は、戦時中の四式中戦車を参考にした「チト式」に変更されている（試作車STA-3、STA-4では、トランスミッションは機械式ハイ・ロー切換2段クラッチ、操向装置はクレトラック式となった）。

1956年（昭和31年）末から約1年かけて行われた技術試験と実用試験の結果、第2次試作が決定され、STA-2の設計を基に、砲塔を後方にずらして操縦席に余裕を作ることとなり、STA-3が1960年（昭和35年）1月、STA-4が1959年（昭和34年）11月に完成し、1960年（昭和35年）4月に防衛庁に引き渡された。砲口制退器をT字型に変更、エンジン出力の増強、携行機関銃弾の増加、制限重量までの余裕を防御装甲に振り向ける、などが行われた。"

61式戦車 - Wikipedia