Washing Machines -RPM or RIP?

Is the humble washing machine sitting in your kitchen a potential Claymore waiting to explode?

Your average washing machine has a drum approx 40cm in diameter. This enables you to load about 6 kg of clothes in one go. During a spin cycle this drum spins on average from 1,000 to 1,600 RPM.

The reason for these high speeds are to expel water from the clothes during the spin cycle. As the clothes are spun around the centrifugal force pushes the water out of the holes in the drum. The faster the spin and the more the holes in the drum the dryer the clothes become over the time of the spin cycle.

Now as your load is 6kg of DRY clothes, when wet they can easily be twice as heavy. So just as the spin cycle starts there is about 12 kg of weight in the drum. What happens when this 12kg weight is spun at 1,600 RPM?

The centrifugal forces increases the G force, gravitational force, acted upon the load. On Earth we experience a steady 1 G, or one gravity. If you weigh 80kg at 1 G you would weigh 160kg at 2 G, 240kg at 3 G etc. If you go on a rollercoaster you can experience up to about 3 G. Fighter pilots can experience up to 9 G, then they pass out because the blood weighs too much for the heart to pump it to the brain.

Now back to our washing machine. The 1,600 RPM spin speed in a drum with a 40 cm diameter produces an amazing 572 G. Visit this web site if you want to find the forces being generated inside your washing machine.

So at the point your washing machine enters it’s spin cycle your smalls are subjected to 572 G, therefore 12 kg of wet washing at 572 G = 6,864 kg, or almost 7 metric tonnes! This is slightly more than the curb weight of 2 Hummers.
A Hummer yesterday.

I’m unsure how much kinetic energy there is in this situation but it has to be significant. If there was a catastrophic failure in the drum and this energy was released the damage, as you can imagine, would be significant. From now on I shall vacate the kitchen during the spin cycle, I dont want to be there if the drum ruptures, I guess it would at least be a clean death.


Leave a Reply

Your email address will not be published. Required fields are marked *