It usually consists of a percussive system and a rotative system. The first steam-powered ships used variants of the rotative beam engine. The limiting factor for this widening was mechanical, especially shaft deflection at high rotative speeds. Boulton & Watt developed the reciprocating engine into the rotative type. The main pumping plant consists of four Woolf compound, rotative, beam pumping engines. Since April 1, Mexico holds the rotative presidency of the UNSC. Water-returning engines were superseded by the rotative beam engine, that could power rotating machinery directly. They were all rotative beam engines, with a flywheel and rotating output shaft.