PSN-L Email List Message

Subject: Re: possible vertical using magnets?
From: "meredith lamb" paleoartifact@.........
Date: Fri, 9 Nov 2007 13:13:50 -0700


Randall,

Yes, its fatally flawed.....the mass will always go down in that setup....it
has no
where else to go (sorry).  I'd think; putting the spring in back of the
pivot, with the
spring attachment above the pivot (upright metal fixture holder on the boom
itself)
would make it more workable (per your drawing).

My hard drive and crossed rod pivot vertical experiment is somewhat
similar.  There the
spring is in back of the pivot, but does go down at a slant.  I can't go
past the
vertical point of the pivot, without it going "bonk" down.  I can get up to
about
1/4" away from the pivot for ~ a 2.5s period that "seems" fairly time
stable.  Going
closer can extend the period (once it hit 11s); but, alas, it was just too
unstable
over time.

Meredith Lamb

On Nov 9, 2007 12:40 PM, Randall Peters  wrote:

> Kay,
>    We know how you feel, but here's one more  'drinnk from the firehose'.
>  We're 'on a roll', looks like.
> Meredith, like yourself, I saw the need to somehow communicate pictures;
> so I've placed one on my webpage at:
> http://physics.mercer.edu/hpage/psn/vertical-using-magnets.gif
>
> Anybody know instinctively if it's fatally flawed?  I know Chris you don't
> like 'knife edges'.  Maybe they're not as bad with load reduction by the
> pulling shown here.  What about your thoughts, Charles, since I like your
> idea?
>
> And Keith, we're not opposed at all to what you've mentioned.  I wrote a
> paper on the pendulum that moves in a way you'd like.  Check out the pages
> that result if you type 'rattle in Seattle' into Google.  I wouldn't be
> surprised if my
> 1988 paper "Chaotic motion from support constraints of a nondriven rigid
> spherical pendulum", Phys. Rev. A 38, 5352
> prompted the commercial development that resulted in the 'oak and brass'
> pendulum that writes in sand and which recorded that Seattle earthquake.
>
> Randall
>
>
Randall,
 
Yes, its fatally flawed.....the mass will always go down in that setup....it has no
where else to go (sorry).  I'd think; putting the spring in back of the pivot, with the
spring attachment above the pivot (upright metal fixture holder on the boom itself)
would make it more workable (per your drawing). 
 
My hard drive and crossed rod pivot vertical experiment is somewhat similar.  There the
spring is in back of the pivot, but does go down at a slant.  I can't go past the
vertical point of the pivot, without it going "bonk" down.  I can get up to about
1/4" away from the pivot for ~ a 2.5s period that "seems" fairly time stable.  Going
closer can extend the period (once it hit 11s); but, alas, it was just too unstable
over time.
 
Meredith Lamb

On Nov 9, 2007 12:40 PM, Randall Peters <PETERS_RD@..........> wrote:
Kay,
   We know how you feel, but here's one more  'drinnk from the firehose'.  We're 'on a roll', looks like.
Meredith, like yourself, I saw the need to somehow communicate pictures; so I've placed one on my webpage at:
http://physics.mercer.edu/hpage/psn/vertical-using-magnets.gif

Anybody know instinctively if it's fatally flawed?  I know Chris you don't like 'knife edges'.  Maybe they're not as bad with load reduction by the pulling shown here.  What about your thoughts, Charles, since I like your idea?

And Keith, we're not opposed at all to what you've mentioned.  I wrote a paper on the pendulum that moves in a way you'd like.  Check out the pages that result if you type 'rattle in Seattle' into Google.  I wouldn't be surprised if my
1988 paper "Chaotic motion from support constraints of a nondriven rigid spherical pendulum", Phys. Rev. A 38, 5352
prompted the commercial development that resulted in the 'oak and brass' pendulum that writes in sand and which recorded that Seattle earthquake.

Randall



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