Sentinel STN-4D

         The Sentinel is a medium BattleMech, though its 40-ton mass puts it at the low end of its weight class. Designed to provide battalion-level BattleMech support for infantry and light-armor units, the ‘Mech has good maneuverability, long-range hitting power, and an advanced communications system. Equipped with the powerful VidCom-17 and Targa-7 long-range targeting and tracking system, the Sentinel is ideal for patrols or as a mobile observation post. The ‘Mech also carries a StarLink/Benicia Model AS829G communications system. Capable of simultaneous operation on multiple frequencies, this system not only allows the Sentinel to closely monitor and command units operating under it, but also keeps the ‘Mech in close contact with rear-area artillery units so that it can easily call for fire when needed.
         Defiance Industries first produced the Sentinel in 2651 for House Steiner’s private army. The ‘Mech appeared one year after the Star League Council passed an amendment allowing the Council Lords to double their personal household forces. Originally intended for infantry support, the ‘Mech soon took on the role of guarding military installations and the Steiner family’s major landholdings. By the early 28th century, the SLDF and the private armies of Houses Davion and Marik had also begun to deploy Sentinels.
         After the fall of the Star League, the Sentinel appeared most often in the vanguard of the Steiner and Marik armies. In this position, the Sentinels took disproportionate losses. Currently only a handful of Sentinels remain, more heirlooms than weapons of war.

         The Sentinel’s 40-ton frame is powered by an 11.5-ton Pitban 240 fusion engine, giving the ‘Mech a walking speed of 65.4 kph and a top running speed of 97.1 kph. Shortly after the ‘Mech’s original deployment, concern arose over the choice of the Pitban 240 because of rumors about shielding problems with the Pitban 240s being produced by Defiance Industries. After a number of Sentinels were pulled from the field because of chronic overheating, an investigation found that the heat circulation system rather than the engine shielding was at fault. The faulty components were replaced in all subsequent versions, which includes most of the remaining Sentinels.
         Well-equipped for combat, the Sentinel carries a Defiance autocannon, a Defiance-2 SRM launcher, and a Defiance B-1A small laser. The original design included a Kawabata autocannon, which had twice the Defiance autocannon’s cyclic rate of fire, but which also turned out to have serious problems. When fired at its maximum rate, the weapon vibrated violently, jarring the internal circuitry in the BattleMech’s weapon arm. This often caused the pilot to lose control of the arm, effectively rendering the autocannon useless and cutting the Sentinel’s combat capabilities almost in half. Repairs, though relatively simple, kept the ‘Mech out of combat for half an hour or more. Modifications to the mount and circuitry reduced the problems somewhat, but by 3014 the Sentinel’s manufacturers decided to reequip the ‘Mech with the easier-to-maintain Defiance autocannon. Trouble also cropped up with the original design’s Defiance A-1 small laser, which was prone to problems after extended field operations. The designers therefore substituted the more rugged B-1A laser in 2678.
         The Defiance B-1A small laser is mounted in the right torso, just below the Streak-2 SRM launcher, an arrangement that has caused problems of its own. The addition of the B-1A small laser displaced the SRM ammo feeding system by half a meter. Though not a problem under normal circumstances, this shift made the missile-feeding mechanisms prone to jamming whenever the ‘Mech fires its SRMs while performing an abrupt maneuver. When this occurs, the pilot has one more shot, but must correct the problem before he can fire again. The standard procedure for clearing such a jam is to open up the ammo-feeding access panels and manually readjust the missile rounds. As this is impossible to do in combat, many pilots tap hard against their machine’s chest area with the ‘Mech’s free right hand to clear up the problem.