One for the mechanical engineers - washing machine vibration dampening

[Chris J Dixon]

I'm afraid this is beyond my technical experience, but reminds me of a situation at work.

It had become standard practice on the equipment we were making, for railway rolling stock, to mount the rack of electronic equipment on bonded rubber mounts. Whilst in its original implementation it may have worked well to isolate it from high frequency diesel engine vibration, no attempt was ever made to do any calculations, and the design carried over to EMUs.

Eventually a vibration type test was called for, and a resonance was discovered. In due course, it was found that the rubber mounts were actually making matters worse, and the test was passed without them. Since everything was built by then, a solid metal mount was made, with which it went into service.

Chris

[Tim Watts]

With Sorbothane's windows program (their "sagulator" of the vibration world) I'm actually finding it quite interesting.

Isolated it to 10Hz is a dominate bad frequency (1200RPM) and there's another lower down, perhaps around 7-8Hz.

These are difficult as normally the solution is pure bulk (25mm+ of rubber). But the idea of putting 4-5 separate mini pads of sorbothane between 2 4" steel plates is looking massively more effective than a single continuous sheet of the same material.

In fact more, but smaller seems to make the numbers get better.

I have no idea how this works in reality, but will be finding out soon, once I've found the optimum grade of sorbothane and played with the thickness (5mm, 10mm, 15mm)

Fascinating - you'd think rubber was always better, but...

[Tim Watts]

I'd noticed they'd started using those as I watched the work commence at London Bridge and the Bermondsey dive-under.

I still have my pandrol clip paperweight that I painted in blue hammerite 20 years ago :)

[PeterC]

Near the rubber pads was a 10" piece of line*. The shape is very good as a versatile anvil, so I brought it home. Only about 300 yards, but there was frost on it and I was already using one hand, so it was bloody cold and I had to stop about every 4 fence posts to put the line on the post and change hands.

*No officer - the clack-clack isn't my fault.

[Tim Watts]

I had a bit of rail once - it is heavy isn't it!

[PeterC]

A few years ago, near Northampton station, there was a big pile of old lines. I saw a machine that was picking up a line and just shearing it in to lengths that would go on a lorry - kevlar gloves not needed!

[Tim Watts]

Shearing stone cold rail. OMG. That must be some machine!

[Chris J Dixon]

Indeed it is.

The different sizes are identified by their weight per metre, and in the UK are likely to be in the range 40 kg/m to 60 kg/m.

Chris

[RayL12]

Before I go on to read other posts; can you not adjust the machines own damping?

[Tim Watts]

I don't think so. Never heard of every being able to do that.

[tabbypurr]

I've done that long ago when the shocks were worn out. I did momentarily wonder whether to suggest adding containers of sand to the tub/weight/etc, but rubber pads are much easier.

NT