<P> Over time manufacturers of automatic washers have gone to great lengths to reduce cost . For instance, expensive gearboxes are no longer required, since motor speed can be controlled electronically . </P> <P> Even on some expensive washers, the outer drum of front loading machines is often made of plastic . This makes changing the main bearings difficult, as the plastic drum usually cannot be separated into two halves to enable the inner drum to be removed to gain access to the bearing . </P> <P> Some machines now use a direct drive motor, a low aspect ratio device, where the stator assembly is attached to the rear of the outer drum, whilst the co-axial rotor is mounted on the shaft of the inner drum . Direct drive eliminates the need for a pulley, belt and belt tensioner . </P> <P> In the early 1990s, upmarket machines incorporated microcontrollers for the timing process . These proved reliable and cost - effective, so many cheaper machines now also incorporate microcontrollers rather than electromechanical timers . </P>

When was the first automatic washing machine invented