[gsferrari]

Quote:

Originally Posted by HiGHFLYiN9 Have you seen those Houdini Maglev's GS? I thought that was an interesting idea.

Who is Houdini and what are the Maglevs??

 

[ooheadsoo]

I don't know what the maglev is but it sounds like this: http://www.gr-research.com/levitator.htm

I don't know what kind of isolation it has in the horizontal plane but you could always couple it with the roller bearing method.

 

[gsferrari]

Levitation is not going to help...it may absorb the really tiny high frequency vibrations if the mass on the upper plate is sufficient BUT large vibrations will still transmit over to the upper plate. Converting from mechanical to magnetic force still tranfers energy...which is reconverted to mechanical motion at the other end.

The only way to deal with vibrations is by converting them into a lossy form of energy like heat...and losing this energy into the environment as fast as possible...ideally over several stages so that the final stage is nearly vibration free...

I am going all weird here...sorry

 

[ooheadsoo]

How would the pulley deal with that?

 

[sr20dem0n]

How about suspending the platform from a set of very weak springs?

You'd probably want them in tension (hanging). With a high enough mass, the platform's inertia would be too much for the weak springs to move, they'd just stretch and compress as the base moves with the floor/wall and the platform would stay stationary. Maybe attach the springs to the platform through some rubber "buffers" to eliminate any high frequency transmission. You'd need to pick the springrates based on the weight of everything you'll have on the platform, so it couldn't be universal, but it seems pretty easy. Hell you could probably even use several slinkies (use more or less to change the effective spring rate), just cut them so they aren't so long.

 

[gsferrari]

Quote:

Originally Posted by ooheadsoo How would the pulley deal with that?

damping...the levitation thingy doesnt have any damping other than the mass of the upper plate. It could still work...sure thing - nice idea too (similar to the BULLET train?)

As for suspending with springs -might be a bad idea...prone to stretching and oscillation. Actually your idea is good - a steel wire is basically a spring with high spring constant.

 

[ooheadsoo]

In that case, there's sorbothane. http://www.sorbothane.com/ There's a calculator there that lets you calculate fs and stuff like that. Sorbothane is easily available from carr-mcmaster. Pandafeet also makes some custom cut ones. Gary from panda has a simple whitepaper there on his site: http://www.pandathumbaudio.com/vibration.htm

I use it under my bookshelves and the calculator pretty much works. My speakers are decoupled from my desk from about 150-180hz down iirc.

 

[sr20dem0n]

Quote:

Originally Posted by gsferrari damping...the levitation thingy doesnt have any damping other than the mass of the upper plate. It could still work...sure thing - nice idea too (similar to the BULLET train?)

But if the assembly were to move up, say if it was sitting on the floor which was vibrating, unless the cable could stretch there would be no damping, the base, pulleys, masses, and platform would all move up and down at the same rate. Since the masses and platform are balanced, if the pulley moves up neither the mass nor the platform will move more or less than the other, the force on each will be equal and since obviously the masses are equal, the acceleration of each will be equal.

That's for the first assembly, with the second one there are the springs which change things. If the masses weighed more than the platform and the springs were in compression it obviously wouldn't work, if the base moved up the masses would stay stationary (or at least more stationary than the platform) and they would pull down on the cables which would pull up on the platform. So now you have the base/pulleys moving up and the platform is also moving up relative to the base, it would actually amplify any oscillation. If the platform weighed more than the masses and the springs were in tension it could work, but that just goes back to my suggestion earlier, you're simply playing with the degree at which the springs are in tension. With my suggestion they would be supporting the entire weight of the platform, with this one they would only be supporting part of it.


Quote:

Originally Posted by gsferrari As for suspending with springs - bad idea...prine to stretching and oscillation. Actually your idea is good - a steel wire is basically a spring with high spring constant.

Well, it would just depend on what springs you use, there are some (I don't know any details) that won't lose their shape, such as those used in automotive suspensions. They're constantly compressed several inches, yet even after years of this you can pull them off and they go back to their original length. A slinky probably wouldn't go back to its original shape though, I was just brainstorming...

The oscillation I could see, but that's why I suggested very weak springs. With a high mass and low spring rate the resonant frequency would be so low that it would be of no concern. Any oscillations in the base would be transmitted to the platform, but they would be at maybe a tenth of a hertz or slower, I doubt that would have any effect on anything, but I could be wrong.



I love discussions like this....I've been out of the physics/mechanics realm for a couple of years. Took a few classes in physics, statics and dynamics a couple of years ago and have been doing math and electrical since, this is a nice break

 

[gsferrari]

Quote:

Originally Posted by sr20dem0n I love discussions like this....I've been out of the physics/mechanics realm for a couple of years. Took a few classes in physics, statics and dynamics a couple of years ago and have been doing math and electrical since, this is a nice break

Me too brotha! Some people here HATE me for this but I just love discussing stuff like this...

Keep those ideas coming. Post a drawing or two of a suitable isolation platform. I am off to do some reading and revision of moment analysis

 

[viator122]

gsferrari, are you considering looks at all? should this be living room-friendly?

 

[gsferrari]

Quote:

Originally Posted by viator122 gsferrari, are you considering looks at all? should this be living room-friendly?

What! With pulleys and chains and cufflinks!!

Nope - looks are secondary - it is the design and geometry that is important...the darned thing has to work. Imagine the benefits! Besides - the drawings are pure exaggeration...everyting will be much more closely packed...wires will not be so long..pulleys will be small...

 

[HiGHFLYiN9]

Eat your heart out GS

 

[gsferrari]

Quote:

Originally Posted by HiGHFLYiN9 Eat your heart out GS

NICE!!! Pulleys at the edges of the platform to reduce friction....pulleys on top of the "pins" and 4 sided suspension.

Sounds super

Looks even better

 

[HiGHFLYiN9]

Now to make the prototype... anyone have four lava lamps they aren't using?

 

[rickcr42]

Quote:

As for suspending with springs -might be a bad idea...prone to stretching and oscillation.

best isolation system I have ever heard and seen used some HEAVY ASS steel coil springs loaded with cement pavers top and bottom for mass.That baby could handle a small earthquake and the turnatable would play without skipping.the guy had one for the CDP,one for the Vinyl and one each for his monoblocks.

Butt ugly but very effective in practise

i know a guy who was crazy enough to build a turntable platform like the one at the Decware site.Weighs about 700 pounds (no moving that sucker !) and again will withstand a small earthquake but cost him somewhere around $50 to make !

My favorite DIY componant isolation rack style is a simple 2x2 inch framed oak structure spiked to the floor and with corian (or real marble) shelves that drop down onto spikes "up" or just the shelf dropped in "naked".
Then each componant on the rack gets its own isolation platform and mass or nothing depending on need.
can be stained and lacquered any shade so it is very wife freindly.Build is easy,cost is painless and it can be colored to fit any decor.More like furniture than "out there".

usually the simple fix is the best fix in my opinion and the more complicated a thing the more things that can go screwy

as always,just my opinion and means nothing