The Chieftain's Survival Guide: Stabilization Systems
Gun stabilization systems first came into common usage in the interwar period on warships. They generally use the principle of ‘rigidity in space,' and the fact that spinning objects tend to resist movement.
As the mount in which the gyroscope was positioned moved up or down due to the motions of the ship, the system would recognize the pressure of the gyroscope resisting this movement, and as a result apply the signal to the gun elevation and traverse drives to attempt to keep the guns stable and pointed at the target. The reason this came into effect for warships over tanks first is twofold. Firstly, there is a lot more room on a ship for mechanisms, and secondly, a battleship’s movement due to the sea is substantially slower than that of a tank moving cross-country.
Eventually, however, the systems were miniaturized to such an extent that they could be placed into tanks. Early stabilization systems were mounted in American M3 tanks, both the light tank’s 37mm and the medium tank’s 75mm. They eventually became standard on many subsequent tanks, though M26 and M103 were exceptions. These early stabilization systems were, of course, limited. They applied solely to elevation, and, frankly, couldn’t usually keep up with the movements of the tank itself. However, they did at least tend to keep the target within the field of vision of the gunner and allow for a faster lay onto the target.
Centurion was the first production tank to have two-axis stabilization, in both elevation and traverse. Again, however, it wasn’t truly enough to allow the tank to have a proper fire-on-the-move capability, but at least over lightly rolling ground against near targets, it was good enough.
A change in the concept of gun stabilization came with the idea that the sights and the gun need not be linked. In today’s tanks, the sight is fully stabilized, the gun just tries to keep up. It is much easier for the motors to stabilize the 5”x6” mirror in a sight head than it is to stabilize a 2-ton cannon. In a normally functioning modern tank, the gunner controls the sight, not the gun. When the gunner fires the main gun, he is actually closing part of a firing circuit. There can be a small delay between the pulling of the trigger and the actual detonating of the propellant while the fire control system waits for the gun to catch up with the sight. When the sight and gun are in total alignment, the rest of the firing circuit is closed, and the round is fired. In the event of a stabilization system malfunction, the gunner reverts to controlling the gun, with the sight trying to keep up. This is why you’ll hear a description of the difference of ‘normal mode’ and ‘emergency mode’ in an Abrams tank as “In normal mode, the gun is slaved to the sights, in emergency mode, the sights are slaved to the gun.”
Of course, that’s not the end of the story. There is still a further limitation of the ride of the tank. Though the sight and gun may be somewhat stabilized even over the roughest ground, you still have the problem that there is nothing stabilizing the gunner’s seat. As the tank is being thrown around by the bumps, so is the gunner. As he’s holding onto the gunner’s handles, the effect then is that (even if he can keep his eye to the sight), a lot of unintended inputs will be placed into the fire control system. There have been moves to try to minimize this effect.
Obviously a smoother suspension system is a good first step, but the latest British tank, Challenger 2, has a gunner’s control handle which is fixed in position, and the gun is moved with a thumb switch akin to a joystick’s hat. As a result, the gunner can hold on to something solid as he’s being thrown around, and should be able to keep the gun on target more accurately. As a result, though claims of accuracy at 30mph on a par with stationary fire for modern tanks may be correct on the test range on roads and trails, such claims must be treated as somewhat suspect when dealing with such speeds on rough terrain.
The most recent form of gyroscopes are not really gyros at all, as they have no moving parts. Laser Ring Gyros work on the basis of a laser beam bounced off a number of mirrors, and as the mounting moves, the light projected is bounced in different angles which is registered by the system and interpreted as motion.
Vertical stabilizers in World of Tanks which can be mounted on a number of vehicles are best considered as equivalents to the stabilisers as found in American WWII vehicles. You will be disappointed with the results if you’re attempting to fire at any distance when driving at full tilt, but the speed it takes for the aiming circle to shrink to full accuracy will be increased, thus allowing you to get the first accurate shot off compared to an opponent not so equipped.