Maytag Neptune

The Neptune

When Maytag introduced the Neptune washing machine in 1997, it was a major engineering coup. It was a front loader machine, but Maytag had designed it to eliminate some of the shortcomings of earlier front loading washing machine designs. The drum was tipped up 15 degrees to make loading and unloading easier, and also helped to ease the cantilever load on the rear tub bearing. They positioned the door at the highest point of the machine, and sloped the front top of the machine and door to keep people from bumping into a corner with their shoulders during loading/unloading. The door was made 17 inches wide, offering a large opening area. The tub was suspended by pneumatic struts which helped to absorb imbalance forces. To further reduce imbalances, a fluid damper was incorporated, and sensors were included to detect any unbalanced condition - accelerometers to detect imbalances so that the speed could be adjusted as compensation, and displacement sensors which could stop the machine if the drum assembly actually moved too far. It uses no agitator - the laundry is cleaned by tumbling in the water in the bottom of the drum.

The original motor assembly, a switched-reluctance design, was supplied by Emerson, and was the first high-volume application of this type of motor. This type of motor has windings in the stator, but no windings or magnets in the rotor. A simple and relatively cheap design, this motor gives good speed and torque, and provides a soft start. Unfortunately, this type of motor requires more complexity in the electronics, and needs some type of position feedback system to properly commutate the phases. It is this author's opinion that the tachometer utilized by Emerson on this unit wasn't robust enough to survive consistently, and when it failed or worked loose, it may have caused some spectacular failures in the motor control board.

Even the seemingly simple drum pulley required engineering. At 14 inches in diameter, it has to take some 50 in/lbs of torque. It has to retain it's shape while pressed onto the shaft, with the tension of the belt, through heat of railcars and warehouses. It couldn't loosen or warp. A glass-reinforced, heat-stabilized black nylon Celanese resin was selected to provide a compressive strength of roughly 22,000 psi, well beyond most glass/resin materials. The combination of high strength and an inherently low friction coefficient gives long life to the belt and pulley components.

Various system actuations were performed by a device known as a wax motor, supplied by Eltek of Italy, which is a linear actuator that heats a wax-like module when power is applied, and then expands and extends a plunger. Once the power is removed, the wax cools, and a spring retracts the plunger. Simple and elegant, with a low moving parts count, these devices would last forever, in theory. In practice, however, a different story unfolds. While these were used to position the bleach and fabric softener dispensers, and to lock the washer's door, the door latch wax motor seemed to be problematic - it basically shorted out, and caused a massive surge current through the main machine control board, eradicating the driver triac and a bias resistor in the process. Upon cooling, the wax motor would seem to be OK again, as the short would dissipear, and the unit would function again... for a while.

Another section of the machine worth mentioning is the drum seal. This flexible boot was designed by Medibeg, a Belgian manufacturer of medical and appliance rubber seals and parts, along with Maytag, specifically for the Neptune. While Medibeg, even with their extensive experience designing similar seal systems, didn't initially believe that something of this size and compliance could be done, their designers and Maytag designers worked together and produced a workable boot for the Neptune. Time eventually revealed that there was a drainage/moisture problem with this boot, which allowed mold and mildew to grow within the fold of the drum boot. Maytag contrived a retrofit for the Neptune which included a new boot design with a drain at the bottom, a new inner door panel with a drain tube for collected moisture, and a new main control board which provided cycle enhancements to help reduce mold and mildew formation. At one time, this was offered free to consumers as a goodwill effort when they contacted Maytag about this problem.

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