"Why is there a DC motor in a 60hz AC world? That mskes no sense at all and only seems to increase the complexity and decrase the reliablity of the machine in that it would need a DC power supply and all its sensitive rectifiers diodes and capacitors... "
David,
The reason the engineers likely chose a DC motor on the earlier models is for reasons of speed, and directional control. A DC motor is easily controllable whereas a standard 60hz AC motor is much less so.
So now to discuss reliability. Assuming we do need speed and directional control we could achieve it via electrical or mechanical means. I can say that doing it electrically is very likely to be more reliable in the long run and cheaper and far more versatile then using a mechanical transmission system. Its very likely more efficient also. The electronics have since evolved and now they are using polyphase AC motors along with a variable frequency solid state inverter drive. This gives even greater control with higher motor torque and no brushes to wear out. Electronics nay-sayers will complain of yet more complexity though, but solid state electronics are amazingly reliable if designed correctly.
Looking at this problem in a similar but totally different light. The machine shop I manage just bought a new CNC lathe. It has NO mechanical transmission at all. Just a 25 horsepower motor and a belt to the spindle. The motor is driven by an huge variable frequency solid state inverter that allows it to run the spindle in either direction from a few hundred to a few thousand RPM with infinite control. It has full control of torque and braking also. All things a mechanical transmission can't do and in the long run we get better reliability and versatility, and I'd bet its cheaper and more efficient to boot!
The dynamics of modern appliance design are driven by a lot of factors. Consumers crave more features, even if they aren't useful, and demand lower costs. This puts the manufacturers in a tough position. Add in the (necessary) goal of reducing energy and water consumption and we all get what we get. It would be wonderful if a manufacturer would build a 20 year machine chock full of features that was class leading in water/energy consumption, but alas sales would be pitiful and the company would go bankrupt. American consumers don't buy for quality and reliability on the whole, and its a damn shame!