Upright Washing Machine - Why no shaking during final spin cycle?

[sir_manning]

Hello all

As anyone with a front-loading washing machine knows, watching them in action can be great entertainment. Well, I was bored tonight and did just that. During the final spin cycle, the drum spins really, really fast (not too sure how many rpm) to wring most of the water out of the clothes. Magically, the wet clothes seemed to plaster themselves evenly around the drum so that axis of rotation was in line with the center of mass. If this hadn't been so, the drum would have caused some serious vibrations when it got up to speed.

So my question is, what is the process that causes the clothes to distribute evenly around the drum?

 

[MATLABdude]

I don't know a definitive answer, but could it just be that the sheer amount of water wrung out of the clothes means that small differences in distribution don't throw the axis off so much as when they're soaking wet?

 

[sir_manning]

Yeah that may be... but even dry clothes have a pretty good weight to them.

I guess this questions isn't limited to front-loading washing machines as upright ones have a fast final spin-down cycle as well. Come to think of it, clothes become evenly distributed around the upright washing machine drums as well.

After thinking about this a little more, perhaps it isn't so amazing. As long as the clothes can separate themselves with relative ease, the force they experience due to the acceleration of the drum going up to speed would probably be enough to separate any large clumps.

 

[mgb_phys]

Front loading machines spin at upto 1600RPM. If you get something like a duvet cover, with clothes trapped inside, or sleeping bag at one side they will shake violently.
They switch spin directions as they pump the water out to try and distribute the load evenly and have safety trips that shut them down if the forces get too high.

I once worked on a project to develop an active suspension to try and make them quieter but we didn't get anywhere - the 20kg lump of concrete in the base still works best.