One for the mechanical engineers - washing machine vibration dampening

Tim Watts wrote in news: snipped-for-privacy@squidward.sv.dionic.net:

Firstly are you really sure that you have the feet perfectly adjusted? Can you adjust one whilst it is vibrating?

Yep - they are adjusted :)

an old tyre

I'm happy buying pre cut squares - I cut up a tyre once. It was bloody hard work! So you think a hardish rubber is the one to go for at those sorts of frequencies?

You're sticking 90kg on it. Tyres are free. You'll only know for sure by trying it or getting some rubber data & calculating. Ideally you want over 2mm deflection at rest.

NT

As hinted in the Sorbothane description there are a number of variables, principly the mass of the vibrating object and the frequency. Any damping/isolation mountings need to be matched to both. Think I'd wander off to the Sorbothane site and see what information and/or products they have available.

Thank you - I shall have a looksee. It's a rather interesting mini project...

JOOI how do you move a 90kg WM with rubber feet into position on rubber sheets in a quite a tight niche? (I have enough trouble sliding our Bosch under the worktop using thin sheets of laminate. I think I'd have to get a hulk in if we ever bought a Miele.)

You don't!

You rock the machine whilst popping said pads underneath. Luckily once the plinths are off, both back feet are accessible (just) from the sides.

has a rather nifty little app. It seems that making 100mm square plates in pairs (sandwich) with 4 x 25mm squares or 10mm thick (or discs more ideally) pads of 40 Durometer sorbothane has an isolation factor of 33% at 10Hz with 12lb load (50lbs per foot, divided over 4 sorbothane sub pads).

Glues with superglue apparently.

I think that is well worth a go - not least because it's cheap and easy and the whole pad will be just 20mm thick allowing for 2 layers of steel.

I am wondering how well it would work with just 1 layer of steel and the sorbothane bearing onto the chip...

Okay, probably a daft idea. How's about one of those plastic kneeling mats cut up and shoved under the legs?

We still need the steel plates - spreading the load a bit on the chip seems like a good idea.

Personally, all floating chip floors should be banned. Had no end of trouble when I lived in Sutton - tried to lay laminate - floor had sunk at all the doorways due to the jablite being pounded. Had to use quite a bit of card to pack it level.

Insulated floors can be done right (usually with spacers between the chip and the concrete base, or mini rafters with insulation between. Floating something as insubstantial as chip on jablite (not even celotex which is a bit more rigid) is a s**te idea.

Best way IMO for flats would be 3" screed on celotex and build underfloor heating in while your at it... But that would cost a few pounds more.

OK, thanks. But for the record I don't call that "quite tight in a niche". Now c.15mm clearance either side (not by my design) I do call tight - and quite a few other, Anglo Saxon words when I need to shift the bugger.

I think you should be thinking of some sort of harmonic damper. ;-). Steel plate on top connected by some short flexible legs.

It should work, in theory...

Tim

The first test that should be done is to make sure where the fault is, run the machine empty, if it vibrates it is probably the machines fault if not it is usually the load.

There's 2mm either side :) But quite a lot above.

The access is only from under the neighbouring units after removing the plinth.

No fault in the machine, it runs whisper quiet empty and even at 1600 it's fine. There seem to be resonances somewhere in the 800-1200rpm region.

I shall take my phone around and record it - might be able to find an FFT app and analyse the sound, assuming my phone can pick up that low.

Ah, - I see now, thanks.

For that sort of application I have some pieces of hard rubber, about 20cm or so square, that are used under the rails on the very nearby West Coast Main Line - they'd been thrown down the bank by the railcrackdroids. I reckon if they'' withstand a goods train... At a guess, the specific loading is less for a washing machine than for a train. Might be available at a railway line near you ;-)