The gyro helps establish center-of-mass equilibrium for the BattleMech in a variety of environments. In normal or high gravity, at least one full set of accelerometers is used. Since accelerometers experience little acceleration in low-G environments, gyros should also possess a traditional gyroscope for direction sense, as piloting in zero-G is not inherently more difficult than in normal or high gravity (see Notes). Neither accelerometers nor rudimentary gyroscopes require extensive space or mass within the BattleMech.
However, gyroscopic orientation-sensing and accelerometer feedback is insufficient to maintain control of the 'Mech. Accelerometers and gyroscopes can not distinguish between intentional and hazardous changes in acceleration or direction, for instance the jerk felt when accelerating from standing to running or the sudden change of mass due to a lost limb, respectively. To distinguish between intent and peril, the MechWarrior's own equilibrium is monitored by a Neurohelmet connected to the gyro's computer. If both the MechWarrior's equilibrium and the balance-sensing mechanisms of the BattleMech agree, the gyro attempts to stabilize the machine.
The BattleMech gyro is able to assist with correcting falls through interactions with massive, rotating wheels, likened to "reaction wheels". Multiple wheels spin continuously within the active 'Mech, with 1 or more stabilizing each axis, x, y, or z. In the event both the gyro and the pilot's neurohelmet interface detect an imbalance, the gyro will attempt to correct the imbalance by gripping one or more wheels, feeding off their immense angular momentum by pulling or pushing against their spin. The resulting torque is often sufficient to stabilize the 'Mech.
However, utilizing angular momentum in this fashion is inherently fraught. In order to counteract undesired gyroscopic effects and allow the 'Mech to operate normally, the constant motion of the gyro's "reaction wheels" requires the gyro is constructed in one of two ways. Gyros can be housed in a freely moving concentric spheres. The sphere(s) itself is immobilized only in moments of imbalance. Alternatively, each axis can be stabilized by multiple wheels spinning in opposite directions. If the net angular momentum about each axis equals 0, the 'Mech will be able to move properly.
While the wheels within the gyro have been likened to Reaction wheels, this analogy is false. Traditional reaction wheels are set in motion in order to fix an orientation on an axis by conservation of angular momentum. In contrast, torquing against the gyro's "reaction wheels" rectifies the 'Mech's imbalance by adding angular acceleration.
Standard gyros were developed for IndustrialMechs and have changed little since the Mackie was introduced. All standard gyros take up ~1/3 of the center torso's space. A one-ton gyro taking one-third of the center torso is sufficient to correct imbalances in a BattleMech massing up to 100 tons and moving up to ~22 kph. However, higher-velocity maneuvers often require more torque, because MechWarriors or pilots will often add to the imbalance with their own maneuvers. The same 100-ton BattleMech would require an equally bulky four-ton gyro to oppose an imbalance at a velocity of ~65 kph (see Notes). Maximum momentum of a 'Mech also determines engine output, so gyros are frequently proportional to the engine-rating.
Gyros utilizing newer construction materials and/or design philosophies became available in the late 3060s. These differ in mass, bulk, and armor of the components, but are equally effective at re-establishing equilibrium. Compact gyros are condensed, requiring more mass to achieve the same moment of inertia due to their smaller size. Heavy-duty gyros provide redundancy and provide more protection. Extra-light gyros trade mass for bulk in their "reaction wheels". The improved materials of an XL gyro are much lighter and can manage stresses better than standard gyros, allowing them to increase their moments of inertia and angular velocity in order to provide equal torque.
- While low-Gravity environments can alter ballistic trajectories, there is no mention of low-G or zero-G impairing 'Mech operation in Total Warfare, Tactical Operations, or Strategic Operations.
- Gyro corrections torque against a 'Mech's momentum. Some BattleMechs with Myomer Accelerator Signal Circuitry, Triple-Strength Myomer, and Superchargers can reach much greater momentum, and therefore should require more massive gyros. However, this is not mentioned in the rules.
- Total Warfare, pp. 59-61, "Piloting/Driving Skill Rolls"
- Tactical Operations, pp. 23-24, "Piloting Skill Rolls"
- Strategic Operations, pp. 119-120, "Zero-G Ground Unit Combat"
- TechManual, pp. 34-35, "Gyroscope"
- TechManual, pp. 219-220, "Gyros"
- TechManual, pp. 48-50, "Install Engines And Control Systems"
- TechManual, p. 232, "Myomer Accelerator Signal Circuitry (MASC)"
- TechManual, p. 240, "Triple-Strength Myomer"
- Tactical Operations, p. 345