Re: [Phys-l] techshop opportunity

[brian whatcott <betwys1@sbcglobal.net>]

On 1/3/2011 3:36 PM, Stefan Jeglinski wrote:
> > A long period pendulum clock, w/electromagnetic escapement.
> > Here's a short period one:
> > http://www.bmumford.com/clocks/em2/index.html
> Interesting. I used to collect clocks, and still have 7 French
> mantles, 2 American mantles, and 2 German grandfathers. All 80-180y
> old. Think I'm more fascinated with well-built mechanical clocks than
> accurate electronic-driven clocks, Mumford's notwithstanding.
>
> I think of more interest to me would be the manufacture of an
> interesting/unusual/non-tiny pendulum *structure* that exhibits
> unusual (to the lay person anyway) properties, eg, very long period,
> or a mix of chaotic/nonchaotic behavior (inspired by the
> magnet-driven executive desktop toy, or in a different vein, [1]). I
> do have a large high spacious entryway that does nothing but convect
> heated air up to warm the 2nd-floor ceiling :-)
>
> [1] http://arxiv.org/abs/0902.1829
>
>
> Stefan Jeglinski
1)
It was quite a while ago. I read a piece probably in Sci American, about 
a person who made a particular kind of kinetic garden sculpture - I 
fancy that an example  sat or sits on the campus of the Mercedes 
headquarters....

Essentially it consists of three posts: a short fixed base pole five or 
six feet tall, and a second pole pivoted to it at about 1/4 of the 2nd 
poles length, and at its end,  a third pole was pivoted, also 
counterbalanced for its 3/4 extension.   The balance was achieved by 
lead weights.
A curious effect was obtained by setting the two pivot rods at 45 
degrees to the horizontal
so that the two plain bearing tubes set in the posts were also set at 45 
degrees to their long axes.

For the long posts, I used aluminum rain gutter tubes which I seem to 
recall were about 12 feet long each.    the plain bearing tubes were 
provided with flanges to rivet them to the gutters, and the lead weights 
were bolted through. Provided the bearings provded a smooth, low 
friction joint, a modest breeze would set the thing into a curious, 
quasi chaotic motion which was attractive to watch.

2) I found the Cornell drive for the short (3m) foucault pendulum 
described in the Arxiv paper you mentioned above was a splendid piece of 
work, for anybody with any background at all in the elliptical ills of 
the short Foucault. Push mode seemed well described, well analyzed, and 
well depicted. Thanks

Brian W