Spin drier 2

[GregLocock]

Despite enormous amounts of off centre weight in unpredictable locations, a spin dryer does not shake itself to pieces. The drum is allowed to oscillate as it sees fit and by some advanced gobbledygook in dynamics the centre of mass of the drum and contents tends to align with the axis of the bearing, hence minimising forcing of the rest of the machine.

Many thousands of years ago when I was at university I was told of the advanced gobbledygook, but can find no reference to it online. Any ideas?

Cheers

Greg Locock


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[drawoh]

GregLocock.

When I bought my front-loading washing machine, the installers told me to not mount the thing on casters. I am very glad I followed their advice.

I have a lot of practical experience with optical scanners with reciprocating, rotating mirrors. I have worked out the scanning forces and the resulting bending of the mirrors. I have often wondered why the optical devices do not walk around the office and off the workbenches onto the floor.

Answer: If your off-centre load or my reciprocating mirror is attached to something heavy enough, it won't move under vibration.

--
JHG

 

[Tmoose]

"the centre of mass of the drum and contents tends to align with the axis of the bearing, hence minimising forcing of the rest of the machine."

I think the bearings are mounted in VERY soft isotropic mounts. Critical speed <<< operating rpm. Like 3X. So the CG self centers, the "shaft" centerline describes a circular orbit of diameter ≈ CG offset X 2.
The VSI mounts are SO SOFT and have large travel thus the transmitted forces are quite low.


Vibration Isolation theory. Low transmissibility.

https://www.lord.com/products-and-s...dustrial/isolators/vibration-isolation-theory

Not shown in the LORD link is the LARGE motion of the equipment on "this side" of the isolation mounts.

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTM1hApDlvQQsBqb48hcx9D6gJM8F6C-gH1oQ&usqp=CAU

 

[GregLocock]

Turns out there are pages and pages on 'self balancing rotors'. Tmoose - yes, I had guessed it was operating way above first resonance. But normally I'd have expected the out of balance to get worse, not better as the thing accelerated, ie it would flop over and stay flopped over. I'm gently wondering about spinning tops, and the tennis racquet theorem. Anyway, the urgent necessity of this has gone. Thanks all.

Cheers

Greg Locock


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