Spin speeds and how they got there
A little history and technology might help explain the "spin evolution." The Bendix machines had a spin speed of approximately 310 rpm. These machines had a split-phase or capacitor-start motor which ran at a constant 1725 rpm, and was direct coupled to a 2-speed constant-mesh transmission which drove a pulley. This was belted to a much larger pulley on the tub. During wash/rinse, the pulley was driven through the "1st gear," or highest gear reduction. During spin, a solenoid pulled a clutch lever which connected the pulley to the higher gear ratio. (Commercial Dexter machines used a similar transmission but with 2 solenoids, giving it 3 speeds; wash/rinse, slow extract of about 200 rpm, and high extract of about 350 rpm-still desperately slow). Early Westinghouse fl machines also used a transmission, but belt-driven by the motor. Top loaders mostly had a spin speed of 450-650 rpm. During the early and middle periods of electric washers, the Easy twin-tub had the fastest spin speed, I believe about 1725 rpm, but the tubs were of very small diameter. Likewise, in later years the Hoover twin-tubs and its knock-offs (Sanyo, etc.) used a split-phase motor to do the washing and a series-wound "universal" motor (like the one in your mixer, power drill, vacuum cleaner, etc.) to operate the spin tub and drain pump. These motors are capable of almost unlimited no-load speeds, and rotated the tubs at speeds of at least 1800 rpm. By the 1960's, Westinghouse had come out with a f.l. machine driven entirely by belts from the constant-speed motor; by shifting variable pulley halves together to produce a larger diameter motor pulley, they were able to get a tub spin speed of about 650 rpm. Some European machines, however, were using series-wound motors to operate their front loaders, which was made much easier with the advent of microprocessor motor speed controls. These enable the series motor, which normally has widely varying speed characteristics, to mimic the constant-speed induction motor for washing/rinsing, while maintaining the ability to run at extremely high speeds for extracting (my old White Westinghouse, which had a spin speed of 680 rpm, ran its motor at about 16,000 rpm to achieve this). Nowadays, most fl's use a 3-phase induction motor operated through a variable-frequency inverter; much quieter, and the motor can be used as a brake. I.e. a 8-pole induction motor run on standard 60-Hz current will run at about 850 rpm (550 on 50-Hz across the pond). If the Hz is increased to several thousand Hz, the speed will correspondingly increase. This is how, for instance, my Duet HT spins at 1250 rpm; with its large-diameter tub, it extracts really well at that speed. Some machines, like the LG, use a direct-drive brushless dc motor; essentially a flywheel with magnets in it surrounding a circular arrangement of electromagnets which are energized in sequence by a microprocessor. This type of motor is also used in the new generation of top-loaders like the Oasis. Standard top-loaders are still limited by their transmissions to about 650 rpm; the Oasis and similar machines can run at 1000 or more, and these motors also allow customized agitation patterns, as the agitator plate is also run by this motor. In other words, mechanical complexity has greatly decreased and been replaced by electronic complexity. Given the benefits such as much better extraction, it seems to be a pretty good trade-off!
