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Apr 8, 2013

American Prototype Light Tanks Post-WWII Part 3: The T71, T92, and the M551

Author: Priory_of_Sion

To finish off my other two articles about Postwar American Prototype Lights I will discuss the T71, T92, and the XM551.

The T71 and the T92 originated from the US Ordnance Committee in 1952, by 1953 they had chosen 3 designs. They were the T71 by Detroit Arsenal, the T71 by Cadillac, and the T92 by AAI.

Detroit's T71 was an 18 ton vehicle with an oscillating turret and an 76 mm autoloader(same ballistically to the M41's 76 mm gun). With ~340 hp it would be fairly quick. The frontal armor was a pike design similar to the IS-3.

Cadillac's T71 was a conventional style tank without an autoloader. It used the same gun as the Bulldog. It was to weigh a little less than 18 tons and would have the same engine as the other T71. Both T71s lost out to the T92 due to rapid progress in the T92's development. 

In WoT the hull is from the Cadillac T71 while the turret is from Detroit. If I recall correctly, The_Chieftain has alerted Minsk of their folly. In a future patch expect the T71 turret to be reunited with its hull.

The T92 is a very unique design which emphasized smallness. Weighing a little over 18 tons and armed with the same 76 mm gun the T92 was very close to being put into production which was planned in 1962. The 375 hp engine of the T92 would allow it to be very mobile. The 76 mm gun was located in a cleft turret which allowed for -10 degrees of comfy depression. The T92 was equipped with a semiautomatic loader. This would fire 1 round at a time and did not have any sort of drum. Each round would be put into the semiautomatic loader one at a time. After the round is fire the shell is automatically ejected. Protection is effectively the same as the M41 but lighter weight materials such as aluminum were used to protect parts of the T92.

This is the semiautomatic loader.
T92 size compared to the M41.
Some people say that UFOs are actually flying T92s from another dimension.

The first T92 arrived at Aberdeen in 1956, the second arrived the next year. Both proved capable machines but there were problems found, in all 50 changes were to take place and ranged from problems with the tracks to problems with the shell case ejector. In 1957, before the 2nd pilot T92 arrived at Aberdeen, Congress found out about Soviet PT-76 and its amphibious capabilities. The T92 was unable be modified to become amphibious due to the design of the vehicle. In 1958 the T92 was cancelled.

The XM551 was to be born out of the ashes of these 1950s prototypes. In 1959 requirements for an Armored Reconnaissance/Airborne Assault Vehicle(AR/AAV) were set, is was to be amphibious, air mobile, to have greater firepower than the M41, and to be quick. AAI and Cadillac presented thier designs. AAI's  12.5 ton AR/AAV featured a 3 man crew with a 152 mm gun-launcher. The armor was very weak and was to go upwards to 65 km/h.

Cadillac's design was heavier and featured 4 crew members which improved the fighting performance of the 152 mm armed vehicle. Armor protection was improved over the AAI vehicle, but was to be aluminum. In June, 1960 the Cadillac AR/AAV was accepted for further development as the XM551. Armament was decided in 1961 to be the 152 gun-launcher which won over the M32 76 mm gun, the M41 90 mm gun, and  105 mm gun(an M68 was mounted eventually in the 1980s actually just so you know). A 285 hp engine was mounted in the XM551 giving it some speed. Testing began at Aberdeen in 1962. These tests proved the XM551 was full of issues. FOUR more "generations" of pilot XM551s were tested until most of the chinks were worked out. You would think that if this thing needed so much modifications that it might not be worth it. By 1965 production of the M551 Sheridan commenced. In combat however the M551 was a failure.

Here is an excerpt for the book The World's Worst Weapons on the M551. 
"The resulting vehicle(M551) was all but useless for anything except distracting enemy fire from more useful assets." 

By 1970 the Americans started development to replace the Sheridan, the US never did adopt another light tank though. Many projects, some conventional some outright weird, we drawn up and some where extremely close to production. Today the US relies on the Abrams, Bradley, and a plethora of other vehicles to fill the void.

Now in WoT the Detriot Arsenal T71 is already in game and is expected to have the hull changed. The Cadillac T71 would be a great addition to the game being a good tier 7 light material. AFAIK the T92 is on track to become the tier 8 light tank after the M41. I personally would advice WG to reconsider the T92's position. It doesn't offer any great advantage over the M41 in anything, the T92 would be a let down at tier 8. If I was a developer the T92 would be a tier 7, maybe a crossover vehicle between the M41 and T71(DA). The XM551 is tricky. The 152 mm gun-launcher would be limited to only HE and HEAT rounds and guided missiles is a no-go. The armor of the XM551 is extremely weak and is liable to catch on fire every time it is shot.The Sheridan also is less comfortable(only -8 depression compared to the -10 on most other American Lights). Due to these reasons the XM551 should be excluded from WoT IMO.

Sheridan: A History of the American Light Tank vol. 2 by R. P. Hunnicutt
The World's Worst Weapons by Martin Dougherty 


  1. Am I imagining things or does the Detroit T71 hull have a rear final drive? That'd be an useful change to help avoid engine hits - given the thickness or rather lack thereof involved it's not like the IS-3ish armour sloping would be of much practical consequence...

    Looks a mite taller than the Cadillac hull tho'. :(

    So how exactly did that T92 semiauto loader work or rather what made it special? I'm fairly certain automatic ejection of spent casings has been de rigeur since the Soixante-Quinze of 1897, so that's nothing to write home about...

    1. The Final drives are in the front, where ever you see the drive sprocket that's where a the final drive for any track is.

  2. The Detroit Arsenal T71 did have a rear engine/transmission. Unfortunately the ammo storage is moved up the the front sides.

    The pike frontal armor won't make the T71 hull any more resilient but should provide a lucky bounce once every 30 odd games.

    For the semiauto loader--Imagine a drum autoloader with a 1 round capacity.

    The automatic case ejector propelled empty shells out of the breech to outside the back of the turret automatically. I am fairly certain it was one of the first vehicles to do that.

    1. The French "revolvers" prolly have primacy on that - the AMX-13 mass production *started* around the time these things were being drawn up after all.

      Anyways, am I interpreting this correctly if I think the T92 system first disposed of the spent casing and then automatically loaded the shell held in the "ready tray" frame behind the breech? If so that sounds like a rather useful setup, though whoever was in charge of feeding it with fresh shells probably would've had to watch his fingers in a more intense engagement...

      Random observation: and there's that same MG miniturret cupola again. Looks pretty much identical to the ones in the other LT project drawings too. Must've been some kind of listed requirement at the time I guess. What's with the "pipe" on top of the things though? Ventilation, periscope?

  3. The French AMX-13 doesn't seem to have an automatic ejector, I might be wrong.

    You seem to understand the semiauto loader now.

    Weird thing is the cupola only made it onto two production vehicles:the M48 and the M60.

    No post-M551 or post-M60 design had a cupola similar to the one seen in most 1950 designs. I don't really know the story behind the rise and fall of the cupola though.

    Periscope, that little pipe should be a periscope.

    1. Take a look at any of the French "oscillators"; there's always some kind of hatch or whatever at the back of the turret bustle, in line with the gun.
      Plus they're explicitly described to have such an ejector system in eg. ;)

      Giving the commander an independent MG cupola seems like an useful enough idea, but I'm guessing it was found to not be worth the trouble and expense? Plus I understand the big "second turret" of the Pattons was found to be disturbingly vulnerable to enemy fire - these are rather smaller though.

    2. There is a reason I am not a French Tank Expert, I know that site however and it is right 100% of the time. The T92 was the first Murican tank to have that system though.

      I'll ask The_Chieftain if he knows the reasoning behind the cupolas.

    3. Random aside: do you know what's that circular thing at the back of the T92's turret? Looks like a freakin' Medieval castle tower with crenellations and all... :P

      Is it just a particularly odd-looking way to carry some spare track?

  4. Were the T71 or T92 airmobile - ie could they be dropped in with paratroopers similarly to the Tetrarch or Locust?

    1. The T71 and the T92 were not designed with that in mind. They both also weighed a little too much for the planes back then if I understand correctly.

      One of the reasons the M551 was developed was to supply paratroopers with a tank.

  5. Protip - try to look this up.

    They did put L7 on XM551 successfully.

    That would be a tier 10 light material.

    1. I mentioned that(I called the L7 the M68 since that is what the US called their L7). That happened in the 1980s btw on the regular M551 chassis. The M551 could be a tier X light but I would say the costs out way the benefits of the M551 in WoT. Tier X lights and the M551 are not planned by WG anyway.

    2. I am pretty sure that WG confirmed that tier 10 lights are possible in far future.

    3. WG has confirmed up to tier 8.
      ARAIK they've only ever said "we'll see" to any higher than that.

  6. Better idea on the crossover is have the Cadillac T71 crossover between the Detroit Arsenal T71 and M41.
    T92 would work as a tier 8 prem light tank with limited mm. Something along the lines of the Type 62.

    1. Not sure about the T92 being a tier 8 premium, tier 7 maybe.

    2. If it has the same gun as the T71 and AMX 13-sized it might be too much for premium tier 7.

  7. Sory, can I use these photos to create page about T71 in wikipedia


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