The Dragon Tank is a robotic attack machine that the Chancellor set loose on Crono and Lucca in 1000 A.D. in Chrono Trigger. It's the "boss" enemy the player must defeat after escaping the Guardia Castle prison.
The Dragon Tank is made up of three parts, the Head, the Body and the Wheel (also known as the Grinder). The Tank Head heals the rest of its body and replenishes Hit Points.
The Dragon Tank even has instructions. For more information on that document, see Dragon Tank Owner's Manual.