Tank Turret Rotation in WWII

a rollin foxholeLet’s adumbrate about tanks again. Fascinating things, although we always took Willie and Joe’s words to heart: a movin’ foxhole attracks th’ eye. (Alas, the only version of that classic we could find does not embiggen). Anyway, our interest has been more, shall we say, historical curiosity than professional.

To put it another way, we’re all about studying them, but we’re just as glad we spent our career under the sky and stars rather than under some inches of cold-rolled.

The nature of tank war is the nature of all war, in general, with some specialized details particularly adapted to the idea of fighting a mobile machine, and units of these mobile machines.

In armored warfare as in any other, the ability to fire the first shot is the guarantor of life. The ways you can get the first shot include:

  1. Seeing the enemy first. This has some impact on tank equipment as well as tactics. Some tanks are ill-equipped for observation in a 360º plane, making them very vulnerable for an off-axis attack. Of course, the crews train to fight the tank they have, and will develop methods to minimize this weakness.

    M26_Fireball

    T26 Pershing named “Fireball”. The 88mm mantlet penetration killed the tank and two of the five crew. Germany, 1945. They probably did not see the Tiger 100m ahead that hit them, but they were backlit by a fire. The Tiger also hit their muzzle brake with another shot.

  2. Concealment and firing from ambush. As many an infantry school instructor has crowed to students at once excited and aghast: “Ambush is murder and murder is fun!” This rewards a tank that can fire from concealment, without making a lot of noise that alerts the enemy’s dismounted scouts, without a lot of movement to betray the position. In addition, there are great advantages in the defense to be able to fire from a hull-down position. (And to a small turret, which complicates the enemy’s target solution).
  3. Outranging the enemy through superior accuracy or terminal ballistics. The components of accuracy are optic, gunner, gun, and integration. While it’s obviously important to hit the enemy first, it’s also important not to hit the enemy at a range beyond that where you can kill him. Otherwise, you’ve exposed yourself and blown your first-shot advantage for nothing.
  4. Getting on target faster. Here optics — including a good field of view for the gunner — and superior speed and control of main gun aim are the objective. If your turret slews very fast, that’s good, but not if the fast slew can’t produce fine control.
  5. Having more tanks, so that the enemy was servicing another target when your first shot kills him. This is a production and reliability play, but also rewards commanders for ingenuity in bringing their forces to bear in greater numbers at a decisive point.

The next best way to win the fight was having the first effective shot because your tank was harder to hit (or, harder to kill). This is clearly a less desirable position to be in than the one where you drop your tungsten calling card into the enemy’s brisket when he still was unaware you were there.

By World War II (and still today, apart from some unusual vehicles in both cases) the design of a tank was stabilized as a rear-engine vehicle with a rotating armored turret carrying primary and (most) secondary armament. The gun was placed on target in elevation by the gunner raising or lowering the barrel, and in azimuth by the gunner (with direction and sometimes assistance from the commander) slewing the turret.

Caught in the open: fate of many a tank and crew.

Caught in the open: fate of many a tank and crew.

In a textbook illustration of the principle of convergent evolution, WWII tanks of all nations were more alike than they were different. But different nations’ main battle tanks rotated their turrets differently — and some were effective despite a much slower rotation than their peers, which seems illogical.

  • British and Russian tanks rotated electrically. If you ever owned a ’60s British car, you have to have some sympathy for the grimy crews and mechanics struggling to keep the ancestor of Lucas electrics humming. British tanks used spade grips for the controls to rotate the turret. The British had a mode switch which let the gunner control traverse on a “coarse” or “fine” setting. The T-34 used electric for coarse and manual for fine traverse. The T-34/76 used separate wheels for electric and manual, attached to the same traversing gear. In the T-34/85, though, the same handle was used as a lever for electrical control and a crank for manual — ingenious! Rather than explain a T-34’s system, which used the same controls for manual and electric traverse, we’ll let the Military Veterans Museum show you in this 1-minute video:

  • Germans used a hydraulic system, driven by power take-off from the main engine. This was a mechanically simple and reliable system, but it had a key deficiency, as we’ll see. The Germans used foot pedals to slew the turret — left pedal went left, right pedal, obviously, right. The gun was then laid with final precision using a manual handwheel.
  • American tanks used a hydraulic system, but drove it electrically. Instead of a PTO from the main powerplant, like a tractor, the hydraulic system was energized by a pump driven by an electrical motor. Also, only the Americans applied stabilization gyroscopes to tank main armament, beginning with the M4 Sherman (on the early Sherman, in elevation only). This gave the tank a rudimentary shoot-on-the-move capability, and perhaps more usefully in tank fighting, reduced the amount of displacement needed to get on target after moving. When hydraulic system production threatened to constrain tank production, some American tanks were fitted with an electrical system also. The electrical substitute system was designed to have similar performance. American tanks used hand controls to slew the turret, and a foot pedal to fire the armament.
  • Most Japanese tanks had manual traverse only. Indeed, some light tanks and tankettes simply had a machine gun turret where the gunner moved the turret by leaning on the machine gun! While Japanese artillery and naval guns often featured bicycle pedals for traverse, the larger tanks had crank wheels to traverse the turret for coarse position. For fine position, the gun itself usually had a few degrees of traverse, and separate hand wheels. While Japanese naval optics led the world, their tank and AT optics lagged, as did most other aspects of tank development. Late in the war, electric traverse was incorporated in the Chi-Ha and Chi-Nu tanks; early Chi-Has, the bulk of those encountered by the Allies, were manually operated.
  • Some early and light tanks of many nations had manual rotation, and almost all power-rotating turrets had manual as a back-up. For example, the Panther had not only the gunner’s fine-tuning handwheel, required because of the lack of precision in the hydraulic system, but also a hand-lever for the gunner and a separate wheel for the loader. Having backups like this was important, because reliability of the systems on WWII tanks was not all that great. Engines, which were often modified or derived from aviation engines, lasted a few hundred hours before an overhaul was required, and hydraulic or electric motors were scarcely more durable. The tanks used at the peak of the war in Europe were war babies, designed once combat was underway and designed and manufactured with all due haste. They hadn’t had a long debugging cycle. Wartime memoirs are full of tales of operating with one or more systems degraded.

While in theory any system can be engineered to give you any rate of rotation, the German approach of shaft-driven hydraulics had a weakness: the turret could only power-traverse if the main engine was running. For the fuel-critical Germans, this was always a problem. This approach also meant that the speed of rotation depended on engine speed. You only got full-speed rotation at full throttle; at anything less, it was degraded.

How fast could turrets rotate?

The vaunted Panther tank had, in its first iteration (Panther Ausführung D), one of the slowest-turning turrets in the war, taking a full minute to traverse 360º. The gearing on the turret was changed in the Ausf. A, the next version, and all subsequent Panthers, giving the tank a competitive 15-second full-circle. But that didn’t last; a November, 1943 decision to govern the engine to a lower max RPM reduced slew rate to 18 seconds on Panthers from that point forward — if the crews didn’t learn about and adjust the governors. This was done to try to increase engine reliability: more Panthers were being lost to breakdowns than to Allied gunfire.

What’s interesting is that even though the early Panther turret was quite slow, it was still fast enough to track all but the fastest-moving tanks. All greater speed than a circle-a-minute buys, then, is ability to change targets, or get on a sighted target, faster.

The American system spun a Sherman turret 360º in fifteen seconds, too. The system in the M36 tank destroyer had the same performance, also. (Not surprising as the automotive  gear in the tank destroyers was lifted from the Shermans).

The undisputed slewing champ of WWII tanks was the Russian T-34, which could bring its turret all the way around in 12 seconds.

We couldn’t find any credible information on the slew or traverse rate of Japanese tanks.

The final lesson in all of this brings us back to convergent evolution: despite the different approaches taken by the major tank producers of the era, their performance was roughly similar (excluding the lagging Japanese, who deemphasized tank development and production because of their limited production capacity, and overwhelming naval requirements).

Sources

Directorate of the Armored Forces of the Red Army. T-34 Tank Service Manual. Translator unknown. Retrieved from: http://www.allworldwars.com/T-34%20Tank%20Service%20Manual.html

Green & Green, Panther: Germany’s Quest for Combat Dominance. pp. 107-120.

Military Intelligence Division. Japanese Tank and Anti-Tank Warfare. Washington: War Department,  1 Aug 1945. Retrieved from: http://usacac.army.mil/cac2/cgsc/carl/wwiispec/number34.pdf (bear in mind that as a wartime intelligence document, this is not fully-processed history!)

Zaloga, Steven J. Japanese Tanks 1939-45. Oxford, England: Osprey, 2011.

Zaloga, Steven J. M4 Sherman vs. Type 97 Chi-Ha. Oxford, England: Osprey, 2012.

18 thoughts on “Tank Turret Rotation in WWII

  1. Martin S

    Tanking appeals to me, as a slightly fat, lazy and somewhat infirm person. Going to war sitting down, what’s not to like.

    Then the reality of tanking sets in. It is a very physical profession, with much heavy labour to get the beasts running and keeping them running.
    Then there’s the practical bit, things like taking a shit while on the move, or worse buttoned up. Crapping in empty ammo cans, as one guy stated on a forum, does not make it sound quite as romantic as the dashing cavalry of times gone by. Then again, many contemporary accounts of those times don’t leave much of the romanticized image either.

    And as stated above, outside a tank you can dig in and hide, a tank just leaves you a target with dubious protection at best.

    I’ll keep my tanking to sims like Steel Beasts Pro PE, thank you very much.

    If the Russians come, I’ll be digging a foxhole in the garden. Practical on so many levels, including the added bonus of being easily extendible as a grave.

  2. Expat

    “. If you ever owned a ’60s British car, you have to have some sympathy for the grimy crews and mechanics struggling to keep the ancestor of Lucas electrics humming”
    Back when I owned 60’s XKE’s. Beautiful cars that went like stink. All were equipped with Lucas electrics. Jag owners used to say that the reason Brits liked warm beer was because Lucas made their refrigerators.

    1. Hognose Post author

      One of my one-time team sergeants, Hal Cash, was legendary for his Lotus Elan which burned to the metal bits on the highway one day, with Hal standing beside it, fit to be tied.

      There were a lot of Corvettes in the unit after that.

  3. Brad

    Rear engined tanks

    It occurs to me a primary reason for rear engined tanks, was because the earliest tank designs relied on vision slits in the armor for the crew to see outside while buttoned up. A need obviously obsolete when periscopes replaced vision slits.

    With the evolution of tanks to ever larger and heavier cannons for primary armament, a front engined tank with a rear mounted turret takes less space and is better balanced. The aborted Nazi Maus is an interesting early example of a front engined, rear turreted heavy tank.

    1. Hognose Post author

      The Israeli Merkava is a strange tank indeed (containing as it does a micro-APC compartment for dismounts) but it has a front engine. As I understand it, the priority in Merkava design was protection of the crew.

      1. Bill K

        One hopes that more than the Israelis prioritize crew protection. Or what have we Americans been prioritizing all these years in tank design? Bucket seats and a smooth ride?

        1. Hognose Post author

          We’ve tried to build balanced tanks: mobility, protection, firepower. Russia has prioritized mobility and firepower. They build a powerful tank that’s low narrow and lightweight so it can go places a US or UK tank can’t go.

          1. Brad

            No question the M1 is a great tank. But the wars America has fought in the Middle East demonstrated the greatest flaw of the M1, the huge operational logistics tail needed to support a tank with a 1,500 hp gas-turbine engine and 500 gallons fuel capacity during offensive operations. Though the US military seems more fixated on the other M1 flaw, the strategic logistic burden of transporting 60 ton tanks across an ocean.

          2. Hognose Post author

            Brad, I’d just like to add that the wars also show that the M1 (and the slightly newer Challenger) is no longer where the state of the art has to be. In the 1992 Desert Storm war nothing killed an M1 except friendly fire from another M1. In Iraq, they began to fall both to very large IEDs (made from aerial bombs… not much you can do about 500-2000 lb bombs, about 2/3 of that being HE, going off under your seat) and to Iranian-sourced EFPs which were based, rather annoyingly, on published USAF research.

            The Israelis and the Russians saw some of these problems before we did and have also struggled to solve them.

      2. Brad

        Front engined and not

        I suspect most post-war tanks were rear engined because they were evolutions or even just minor modifications of earlier rear-engined designs. Most front engined post-war armored vehicles tended towards light vehicles. A favorite of mine is the T-92 light tank which almost replaced the M41 76mm armed tank.

        But the Merkava isn’t the first main combat tank with the engine in front. I think that honor belongs to my favorite medium tank, the Swedish Stridsvagn 103 aka the ‘S’ tank. Lots of fascinating design choices went into the Stridsvagn 103, which I believe is about as good as a tank massing less than 43,000 kg can get.

        Of course the Swedes replaced the ‘S’ tank with the Leopard 2, and I can hardly blame them for that. A heavy tank with special armor is perfect for the defensive strategy of Sweden. I imagine the end of the cold war gave a lot of countries the chance to buy first line tanks at bargain prices. With such large stockpiles of first rate tanks in the world, it will probably be a very long time before any newer and interesting tank sees service.

        1. Hognose Post author

          Lots of cunning engineering in Sweden, going back to the days die-hard Saab fanboys mixed their oil in the gas to run the 2-stroke motors. Some of the last Saabs were badge-engineered Subarus.

  4. Brad

    More tank posts please!

    Recently I became somewhat obsessed with learning all I can about tank technology and history. So I share your fascination and I enjoy reading your posts about tanks very much.

    1. Expat

      Brad,
      Get yourself over to the UK and check out their tank museum. If you take the wife, leave her shopping in London. You’ll both have a great time.

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