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Posts posted by Monochromelody

  1. The Al Khalid derived from Norinco Type 90IIM MBT. It was in the early 90s, when India started to test their Arjun MBT. Pakistanis looked for a MBT design that could be produced by herself. 

    Norinco provided their own Type 90IIM prototype, this is an MBT design which comprised many Western components, such as engine and transmission. 

    There were 4 prototypes for Al-Khalid development, namely P1, P2, P3 and P4. 
    P1 has a Chinese tank diesel engine with ZF LSG3000 transmission. 
    P2 has a British Perkins CV12 Condor diesel engine with French SESM ESM500 transmission. 
    P3 has a Ukrainian KMDB 6TD-2 2-cycle boxer engine with its own twin planetary gearbox. 
    P4 has a German MB871 engine with ZF LSG3000 transmission, similar to South Korean K1 MBT. 

    Norinco and Pakistanis planned to adopt one of the Western powerpack at first, but due to CoCom (Coordinating Committee for Export to Communist Countries) restrictions, China is under embargo, which means China would not import weapons form Western countries. Obviously P3 powerplant would be the only choice. All those descriptions on the internet about ESM500 in Al-Khalid is fatally wrong. 


    The Al-Khalid pre-production batch and production version all equipped with Ukrainian KMDB 6TD-2 powerpack.

    It is an extremely compact design, the engine laid transversely in engine room, twin planetary gearboxes connect to both left and right end. The 6TD-2 has two crankshafts: the front one drives the mechanical supercharger, while the rear one drives the gearboxes. The cooling system covering the whole engine room, the engine itself has no mechanical connection to the cooling system, and the cooling system doesn't need mechanical drive. The cooling system based on a unique principle: exhaust gas driven ejector. The exhaust gas from the engine is injected through the outlet ducting, produce a low pressure in the outlet side, that will suck in cold air from the inlet side. This principle is also used in the T-64, T-80UD and T-84, but as far as I know, Swedish Ikv 91 is the only western tank that have similar cooling principle. 


    As a result, the total length of powerpack is significantly shortened, much more shorter than the European powerpack mentioned above. This leads to a spare storage room between the fighting compartment and the engine compartment. This storage is for extra ammunition and fuel, when turret points 3 or 9 o'clock, the top cover of the storage could be opened from outside, containing 10 rounds for main gun, with projectiles on the outsides, semi-combustible charges on the inside.

    The data table from HIT also describe the ammunition capacity as 39+10, means that 22 ready rounds in the T-72 type carousel autoloader, 17 backup rounds scatter around the fighting compartment, and extra 10 rounds could be carried in the storage room. 


    The driver of Al-Khalid control the vehicle via steering wheel and an automatic gear control box. The steering wheel and gear control box send electrical signals to the computer, then computer control the hydraulic servo actuator to perform engage and disengage of brakes and clutches, making steering and gear changes, as well as adjusting the speed and torque of the engine.


    Mechanically the gearboxes are nearly the same as T-64s and T-72s, but have different side reducer unit. The KMDB side reducer unit is designed as a secondary gearbox, acting like a forward-reverse selector. When both reducers were put into reverse, the vehicle can reverse using the normal forward ranges. From 1st gear to 4th gear, all could be used as high speed reverse, and that's why KMDB said this is a 7F4R gearbox system. And if only one reducer was put into reverse, the track will be driving in opposites direction, causing the vehicle turns within its tracks, a.k.a. pivot steer or center steer. T-84 also applied this driving and steering system.  

    The advantages of Al-Khalid's powerpack is the versatility: all 3 types of MBT in the Pakistanis arsenal, T-80UD, T-84, Al-Khalid, share the same engine and gearbox. 

  2. Disappeared for a long period, Mai_Waffentrager reappeared four months ago. 

    This time, he took out another photoshoped artifact. 


    He claimed that the Japanese prototype 105GSR (105 mm Gun Soft Recoil) used an autoloader similar to Swedish UDES 19 project. Then he showed this pic and said it came from a Japanese patent file. 

    Well, things turn out that it cames from Bofors AG's own patent, with all markings and numbers wiped out. 


    original file→https://patents.google.com/patent/GB1565069A/en?q=top+mounted+gun&assignee=bofors&oq=top+mounted+gun+bofors

    He has not changed since his Type 90 armor scam busted. Guys, stay sharp and be cautious. 


  3. Jagdpanzer 38(t) Hetzer, is a famous late-war Jagdpanzer. 

    On the very early version of Hetzer, it did got a muzzle brake, but such device was removed on later models. 


    After war, Switzerland bought some Hetzer from Czechslovakia, named as G-13. Muzzle brake became standardise on G-13. 


    But, have you ever seen a Hetzer with a muzzle brake like this? (below)


    Some source like Tanks-Encyclopedia describe this as "early production Hetzer with muzzle brake" but I really can't tell which German KwK or PaK have such British style muzzle brake, like those on Cromwell tanks. 

    There are two possible reason for this strange version: 

    1. A very early Hetzer lost its muzzle brake and the crew found a British vehicle wreckage, ie. Cromwell or Churchill or even AEC armour car, took the muzzle brake as an ad-hoc replacement. 

    2. A very early Hetzer lost its main gun and the crew found a British QF 75 mm gun, and fit it into the gun cradle. The QF 75 mm gun uses exactly the same ammunition as the M3 75 mm gun. 

    Further pics: 



    Is there any evidence in Patton museum about this vehicle? 

  4. On 10/25/2018 at 12:19 AM, Collimatrix said:


    IS-4 could neutral steer.



    Nicholas Noran a.k.a. "Chieftain" mentioned about this in his program "Chieftain's hatch", but it was a mistake. 

    The ИС-4s use a ЗК-steering mechanism, named after its designer.


    Г. И. Зайчик(1905-1977)


    М. К. Кристи(1890-1965)

    According to the ИС-4 heavy tank operator's manual(Руководство по эксплоатации тяжёлого танка ИС-4), published by Soviet Red Army in 1949, the tank could pivot on one track when in neutral position. 

    Pivot on spot is different from pivot on one track. 


    R=B/2 is pivot on spot, R=B is pivot on one track. 

    Some historical document films also shows ИС-4 pivot on one track. 

  5. The US CD-850 is another instance for triple differential steering system. On the British Merritt-Brown, when the vehicle goes forward, the sun wheel and ring gear of the planetary always counter rotate. On CD-850, when the vehicle goes forward, the sun wheel and ring gear rotate toward the same direction. The neutral steering of CD-850 is similar to the Merritt-Brown system. 

  6. Another approach to neutral steering is the triple differential steering system. 

    Henry Edward Merritt, an engineer and gearbox designer, is famous for his unique invention, Merritt triple differential transmission. The first British mass production tank with triple differential transmission is the Churchill tank. 


    The Churchill tanks have a Merritt-Brown H4 gearbox, 4 stands for four gears forward, H stands for horizontal, because the two rows of gears in the gearbox are horizontally located. 

    A great advantage of Merritt's design is compactness. The transmission incorporate the range gears and steering mechanism into a single box, thus reduce the longitude size. The H4 transmission can provide four gears forward, one gear reverse, and a neutral position for neutral steer.

    The basic design itself is simple, but how to explain it could be a little bit difficult. Three differentials are arranged like this: 


    The left and right differentials are used for combining the driving power flow and steering power flow, and the steering differential is used for creating different speed of the steering gears. The bevel pinion gears are not easy to produce, so the design transformed into cylindrical gears. 


    ↑The Z5 gearbox on Cromwell cruiser tank

    When driving forward, the sun wheel and ring gear of planetary F1 and F2 always counter rotate. The carrier of F1 and F2 rotate on an average speed of the ring gear(forward) and the sun wheel(reverse), and because the ring gear rotates faster, the carrier rotates on the same direction with the ring gear, so the vehicle goes forward. 

    When steering brake J1 actuated, the sun wheel of F1 is stopped, now the carrier of F1 accelerate. The steering differential C then drives the sun wheel of F2 back rotate even faster(double time), so the carrier of F2 decelerate.

    When in a Cromwell/Centurion/Chieftain/Scorpion, the driver pulls right steering lever, which actuated the left steering brake, makes the track on left side go faster, the track on right side go slower, and the vehicle turns right. 



    Another important design feature of the H4/Z5 gearbox is the reverse gear. When reverse gear is selected, the main shaft(E) of the gearbox is locked and stopped. The main shaft is connected to the F1/F2 ring gear, so the ring gear is brought to a stop. F1/F2 sun wheel going reverse, driving the planetary carrier reverse. This design has advantages and disadvanteges. The advantage is that the gearbox doesn't need to insert a idler wheel between range gears to change the driving direction, thus ease the operation of gear changing. The disadvantage is that the reverse gear is very slow, due to the large reduction ratio. The reverse gear ratio of Z5 gearbox is approximately 22.894, makes the tank's reverse speed very slow. 


    When the vehicle is stopped on a solid plain terrain, and neutral position is selected, the planetary carrier stay still.  The sun wheels go reverse, bring the ring gear and main shaft rotates forward. Pull left steering lever, right sun wheel is stopped and forward-rotating ring gear bring the planetary carrier slowly forward, so the right track goes forward. The left sun wheel reverse double-time and faster than forward-rotating ring gear, bring the planetary carrier slowly reverse, thus the vehicle pivot in place. 

  7. 13 hours ago, Collimatrix said:

    Interesting that these tracked AFVs have double or triple differential steering systems, but none of the Russian MBTs do.

    T-14 Armata uses double differential steering systems and is able to neutral steer. 

    Some Russian prototype MBTs can also perform neutral steer, like T-80UM-1 Bars and T-80UM-2 Black Eagle. 

    The first Russian tank with neutral steering is Object 770 experimental heavy tank.

  8. 2 hours ago, heretic88 said:

    A lesser known fact is that certain soviet AFVs can also neutral steer, for example the MTLB and all its derivatives, and everything based on the GM-123 chassis, like SP Artillery or certain elements of the 2K11 Krug SAM system.

    Here a beautifully restored 2S3M, at 1:55


    Yes, Soviet tanks started to have dual-flow transmission after WWII, like Объект 770 heavy tank, Объект 906 amphibious tank and so on. 

    The МТ-ЛБ transmission is similar to АТ-Л artillery tractor's transmission, which is also dual-flow transmission. 

  9. The neutral steer, or pivot steer, means the tank drive one track forward while the other track backward, to perform a turn-on-spot. 

    The very first tank with neutral steer, believe it or not, is the German A7V in WWI. 


    Here is the transmission of A7V. 


    The transmission incorporate two independent gearbox, each connected to a 100-hp engine. The gearbox use clash gears to select speed, and bevel gear to select forward or reverse. It's easy to perform a neutral steer. 


    Those tanks with electric transmission(St.Chamond, Porsche Tiger, etc.) can easily perform neutral steer, for their twin driving electric motors can rotate in opposite direction. And tanks with twin driving hydraulic motors(Panzer IV mit Hydrostatischem Antrieb) can neutral steer in a similar manner. 


    As mentioned above, the simplest way to neutral steer is to have seperated gearboxes or sub-transmissions driving both tracks. US airborne tank M551 Sherridan and Ukraine T-84 Oplot are modern approach of this manner. Althought they neutral steer with tracks driving in different speed, thus they cannot pivot steer precisely on the central spot. 




    The neutral steer capability is more common on dual-flow transmission. 

    A dual-flow transmission, or “双流传动” in Chinese, means the power flow from engine into the transmission splitted into driving power flow and steering power flow, then they join together with mesh gears or planetaries. Control these power flows allows the driver to change speed and steer left or right. 


    The dual-flow principle itself came up even earlier than the tank. The 1899 Vedovelli Priestley electric taxi equipped with double differential steering system, is capable of neutral steering. 


    And the first tank with dual-flow transmission is the Schneider-Renault SRB, then evolved into the Char B1 heavy tank. 



    The Char B1 tank's dual-flow principle is quite simple. The power splitted into two: the driving power flow into gearbox and drive the main differential; the steering power flow into the appareil Naëder, a hydrostatic pump-motor assembly, can rotate on different speed and direction. 


    Char B1 can use appareil Naëder to control its hull howitzer precisly, this principle inspired the Swedish Strv 103 tank. And the US M1 Abrams tanks use a HSU(Hydrostatic Steering Unit) based on the same principle of appareil Naëder. 


    (To be continued)

  10. On 9/8/2018 at 10:09 PM, Alzoc said:

    SGA made 299 plans of the AMX factory available online.

    Ranging from 1936 to 1959 with a few documents on the M4A4 but also the Pz IV (suspension) and the Panther.



    Sad to find out there is little information about AMX M-4's ZF transmission. ZF's official website mentioned that they converted a Entwicklung-Series tank transmission to meet French 1000-hp AMX M-4 tank design. This ZF-type transmission was widely used among early post war French heavy tank programs. 

  11. 204812qjzvatev6v7tsvs7.jpg

    From a Japanese magazine PANZER screenshot, it says: 

    This is a Type 61 tank with a sort of ad-hoc spaced armour, using for target practice in exercise. 

    The armour plates surrounding the turret and side skirts make it looks like a WW2 German Panzer IV. 

    The crew tried to pull out a practice round stucking in the side skirt, this round was fired from a recoilless rifle. 

    According to the vegetation of the exercise range, the vehicle was painted in a 4-colour camouflage. 

  12. On 7/24/2018 at 5:08 AM, Serge said:

    During the late 70’s, an attempt was made to use the AMX-10P as a light recce tank, the AMX-10C :


    A wheeled chassis was preferred as the successor of the EBRC. This is the AMX-10RC.


    An APC/IFV version was available : the AMX-10RTT wich never found any customers. 

    Could you please tell some detail about the development of AMX 10 series AFV?

    Thank you.

  13. On 7/22/2018 at 10:54 AM, Scolopax said:

    That's basically it.  This example is just it before it got the further add-on armor and official designation.


    You can tell it is not a 1A5 model because the coincidence rangefinders are still there, but interestingly, the thermal sight is present as well.  I assume that it was needed for the new gun and that the old sights were just not removed.

    According to Rolf Hilmes' KPz Leopard 1 1956-2003, p.43, 

    In year 1983, the Bundeswehr send two Leopard 1 tanks for 120 mm cannon conversion: one Leopard 1 A5 with cast turret, one Leopard 1 A3 with welded turret. 


    And in Tankograd No.5014, p.30, 

    The conversion of normal Leopard 1 A5 also included the preparation for installation of a 120mm smoothbore cannon, though never realised in production models. 



    According to the gear train schematic, AMX 10RC have a triple-differential steering mechanism. This is more common on British after-war period armoured vehicle but quite rare on a French AFV. It differs from a Merritt-Brown gearbox, for the ring gear and sun gear of the steering planetary both driven in the same direction. 

    Designed in the 1970s, the transmission of AMX 10RC shares some similarity with the TN15 gearbox of Alvis Scorpion light tank(FV101). Both of them combine the forward-reverse selector with the input bevel gears. 

    The gear shifting part use a set of constant mesh gears with synchronizer and planet gears to have different gear reduction ratio. In total it can provide 4 forward ranges, as well as 4 reverse ranges, having the same gear ratios. 


    When the range set to 'neutral' position, a pivot steer would be made. A pair of hydraulic-actuated disc brake is used for steering, controlled by a pair of steering levers. 

  15. 37 minutes ago, Collimatrix said:

    Triple differential systems have a single steering radius per gear ratio of the transmission.  Chieftains, for instance, have six forward gears, which means that they have six turning radii when moving forward.  If the tank is in high gear it will turn a very wide radius.  If it is in low gear it will turn a much tighter radius.  If it is in neutral it will spin one track forward and one track backwards.

    Yes, Chieftain tank has a single steering radius for every gear, while Leopard 1 would have two steering radius for every gear, 4×2=8. And Ariete tank have 4×3=12 steering radius in total. 


    The British prefer triple differential system for it's easier to produce and maintain, and a braking drum could probably be cheaper than a multidisc clutch. 

  16. 2 hours ago, Collimatrix said:

    Double differential and triple differential steering systems aren't that different.

    As far as I know, double-differential system split and transfer steering power flow by engaging different clutch(direction clutch, sometimes radius clutch), or brake certain steering planetary gear, or simply by a hydraulic pump-motor unit. 

    Triple-differential system split steering power flow by braking either side steering planetary gear(usually sun gear), transfer steering power flow to the other side via a differential. 


    It's much easier for a double-differential system to achieve different steering radius. For example, 

    Single radius: Somua steering system(Somua S35), 5SD-200D(AMX 30B), CD-500(M41 Walker Bulldog), MT75(Japan Type 74)

    Double radius: Maybach Argus(Tiger I), ZF 4HP250(Leopard 1)

    Triple radius: ZF LSG3000(K1 MBT, C1 Ariete, EE-T1 Osório)

    Step-less steering: Naëder system(Char B1), FBTV-2B(Strv 103), SLM system(Panzer 68), HSWL 123(KJPz 4-5), HSWL 194(Marder IFV), HSWL 354(Leopard 2), S6-80(SK105), X1100(M1), TN54(Challenger 1)

    All these are double-differential system. 


    Triple-differential system usually have single radius, like CD-850 series(M46 to M60), TN12(Chieftain)

  17. As we know, AMX 10 RC is a very special wheeled AFV for it's skid steering system. 

    It can perform neutral steer, a.k.a. pivot steer or steer in place. 



    The transmission case is similar to some tank transmission. 



    The driver uses steering levers instead of a steerig wheel, and it's almost identical with those on AMX 10P tracked AFV. 


    ↑wheeled AMX 10 RC

    ↓tracked AMX 10 P



    It even had a variant running on tracks: 



    As for steering principle, there are different descriptions. 


    Some info says AMX 10 RC use a triple-differential system, like some British tanks and AFVs. A similar skid-steering wheeled vehicle, TV1000 "Rhino" also use steering levers instead of steering wheel, and it have triple-differential system. 




    When I looked for historical information, I found that French invented the first double-differential steering system for wheeled vehicle since 1898. And French tanks used double differential system since 1920s:


    Renault NC: "Cletrac" type double differential, or controlled differential. First tank using Cletrac system. Single radius. 

    Char B1: "Naëder" type double differential, steering control via steering wheel connected to appareil Naëder(Naëder device). First production tank with hydrostatic steering mechanism. Step-less steering. Pivot steer. 

    Somua S35: "Somua" type double differential, steering control via steering wheel connected to mechanical steering clutch. Single radius. Pivot steer. 


    ARL 44: "ZF" type double differential, steering control via steering wheel. According to the document Notice du Char de transition, it can perform double radius steering and pivot steer. 

    Char Lorraine 40t: "ZF" type double differential. Detail unknown. Double radius. Pivot steer. 

    Char AMX 50: "ZF" type double differential. Detail unknown. Double radius. Pivot steer. 

    AMX 13: "Cletrac" type double differential, or controlled differential. A more compact design, steering mechanism integrated with gearbox. Single radius. 


    AMX 30: "Cletrac" type (1961 prototype or before), single radius; 

                    "Somua" type variant (early version AMX 30B, 5SD-200D), single radius, pivot steer; 

                     hydrostatic double-differential (AMX 30B2 upgrade, ENC-200), step-less steering, pivot steer. 


    There's no clear evidence that French could gave up their experience on double-differential mechanism and turned to British triple-differential. 


    I tried to look for AMX 10RC operator's handbook, but only gunnery handbook found on the internet. 


    Any further detail information about AMX 10RC transmission would be appreciated. 



    Some of you may have seen this pic recently on WT forum, in some thread arguing the protection of JGSDF Type 90: 

    Discussion on WT forum





    To be straight, the Chinese annotation in the table said it is just a GUESSING.


    This annotation could be totally nonsense but unfortunately a barrier between languages prevent you guys see throught it. 



    In fact, again, this document itself is about JGSDF Type 10 MBT, not Type 90.


    Same trick, different people, huh?



    JGSDF specification handbook of Type 10 MBT



    page 59, Appendix B, performance (regulations) and data



    Let's talk about these regulations and how they were made and encrypted. 



    You may know that Japanese have Hirakana and Katakana, like Latin have letters and capital letters. 



    As you can see, some of the most crucial numbers and descriptions are covered by a Hirakana or Katakana or Romaji(Latin letters).



    These numbers and descriptions were collected and listed in some append book, called Bessatsu(別冊). 



    When you look up to the append book, just like viewing the answer sheet of an exam paper. But when numbers and descriptions were censored, you'll never know what it said. 



    For example, the frontal protection: 


    “耐弾性 - 正面 - 正面要部は、【あ】に射距離【え】m相当存速において、貫徹されない。”



    耐弹性 - 正面 - 正面重要部位可抵御【あ】以相当于射击距离【え】米存速的射击,不会贯穿。

    It read like this: 

    Protection - Frontal - Frontal crucial part should withstand 【あ】 firing at a distance of 【え】meter speed reduce equivalent, and not penetrate. 



    【あ】stands for certain type of ammunition, probably APFSDS, but don't know whether it is production shot or experimental.



    【え】stands for certain firing distance, could be 1000 , 1500 or 2000 (meters), but on such a long distance, shot could be effect by wind and gravity, thus cannot aim on the protection area of target vehicle precisely.



    The usual solution is to fire from a much closer range, from 200 to 550 meters, while reducing the propellant charge so that the end speed of AP shot could match the speed drop on certain distance. This is an equivalant method. 



    Some people argue that Type 90 MBT can withstand AP shot (JM33) firing from another Type 90 MBT, on a distance about 250 meters. The source of this statement came from an unknown video clip, which they have never seen. Firing on closer range is for better aim, and they could have use reduced charge to simulate a much longer range, but we cannot prove. 



  19. Share some less-known information about cold war period tracked vehicle transmission




    Mithubishi transmission MT75 for STB, later known as Type 74.

    The basic layout of MT75 is similar to the CD-500 transmission on M41 light tank, used by JGSDF in a short period after war.

    But the Japanese tank designers prefer mechanical gearbox rather than hydramatic gearbox, they use a electro-mechanic high-low range instead of a torque converter. The high-low range part is described as "1次変速"(range first stage).

    The steering mechanism is a single-radius, double differential type, operated by engaging steering clutch, also resemble the CD-500. 







    Allison X-700 transmission, a 800-hp class transmission to replace XTG-411 on T95 medium tank in 1960s. 

    Trials were successful but finally never adopted. The Army decided to develop a 1500-hp class transmission for XM803. 

    X-700 then evolved into X-1100 transmission. The X-200 and X-300 were basically smaller variants of X-700. 

    X-1100 users: M1 and its variants; Korean K9 "Thunder"; Turkish T-155 "Firtina"

    X-300 users: Warrior IFV; CV90 series

    X-200 users: M113 upgrade (A2 standard)






    Allison XHM-1500-B2, a hydrostatic-mechanical transmission developed in early 1970s. A competitor against X-1100 but less successful. 

    Different parts were shown in different color. 

    Orange: power input and forward-reverse shifting mechanism;

    Blue: hydrostatic-mechanical speed range (mechanical planetary gears were not shown in cutaway);

    Red: hydrostatic differential steering system; 

    Green: output shaft and planetary gears. 



    Hope you enjoy these pics. 

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