DOUBLE DODGY Subject: Pendulum Physics: Is there any notable Multi-Pendulum ?

[RJSV]

Hi there:
   I'm wondering if there are 'special' types of pendulum assembly, using the term assembly because there would be MULTIPLE little pendulums, having both strong and weak mechanical links or interacting parts?

   I'm thinking along the lines of chaotic behavior, partially. But just interesting motions, initially watching. For example, having a slight periodic swing, for several times, but then a surprisingly LARGE swing,
and going back to the more-normal appearing small swings.
   In other words: A basic physics / mechanics system having several modes or periods of oscillation.
(That's what Engineers do, very deep into signal theory and frequency domain math).

   My table-top 'sculpture' has one little 'rocking' piece, up high, mounted (actually loosely resting on) another bigger piece (stiff wire), where the whole 'thingy' rocks at much slower, longer period.
Believe it or not, there is a lot of math, CHAOS theory there, I admit to being ignorant to much of the dynamic.
...but it's fun to watch, wind makes it rock in interesting ways, here at my California OUTDOOR DESK.

[RJSV]

Here is a picture, using a Champaign Ice bucket as base, having heavy wire thing balanced, but the upper stretch of wire has 'another' oscillating member: that's the clear tube, set on the wire up top.
The lower weights keep the whole assembly balanced upright.
   I had noticed the upper tube will rock fast, while the lower weights and the whole wire assembly seems to switch between one mode, for a while, then the other for a while. By mode I mean the location or center of the rocking motion keeps shifting between the two
while appearing to be 'chaotic'.

[Gregg]

It looks like a fun concept and inexpensive hobby.
You might get some inspiration from the art works of Alexander Calder who more or less invented the concept of mobile art.  His life story is pretty amazing; his wikipedia page is a good read https://en.wikipedia.org/wiki/Alexander_Calder

[TimFox]

Coupled non-linear oscillators are an intriguing phenomenon, and the study thereof predated modern chaos theory.

[Haenk]

https://www.google.com/search?q=kinetic+sculpture

Brings up hours of joy, both in reading and watching.

[PlainName]

For example, having a slight periodic swing, for several times, but then a surprisingly LARGE swing

Not a pendulum, but this might fit the bill:



edit: soz, dunno how to show the Youtube image, but finally figured it out.

[RJSV]

Thanks, folks.
Enclosed picture shows level view, the 'MAIN' pendulum is the whole stiff-wire frame, including a plastic weight, down attached to the eyelet loops for keeping the thing balanced upright. The wire is off of an older bucket (handle).  I don't like to toss out things of use, scavenged for free.  (Friend laughed, when I claimed it's 'Sanford and Son junkyard', from 1977 TV comedy show).

   So, up top, the clear piece will rock four times, then the 'main' big pendulum thingy does a discrete shift, maybe 1 CM and then the smaller clear piece does another four rocking (cycles), this time around the center of motion that just changed. Then back, but the big main assembly does not oscillate smoothly, rather it does one, jerky shift, them stops, accommodating the four little rocking oscillations, of the smaller cyl up top.
   The whole 'machine' stays together, in tight wind, there on my outside desk. I get more daylight out here, but local squirrels, I suspect, often 'visit' at night, scattering my desk-top sculpture to the dirt.

   We also get 'napping' deer visitors and extra special is the 'visits' from POSSUM usually after 3 (am !).
Lucky to have such variety in a big city type urban region... (East Oakland / Hayward, CA.)
-- Rick B.

[RJSV]

Thanks, dunkemhigh, the home-made double pendulum shown, has very similar timing, as that weightless wing nut, spinning smooth, but going through periodic 'overturns', between two different stable postures.
   Also, when thinking about friction, not much more than some contact - rolling type friction, of wire frame in the ice bucket edge.  The bucket upper edges, themselves, are also subject to the ice bucket 'flextures', where the width itself can oscillate (slightly) as the plastic is fairly thin. Maybe or maybe not any significance.
   Also question, of this plastic base being, itself, able to rock a little, when set down (on irregular surfaces), such as setting on a pencil.
  I don't imagine any strongly asserted friction factors.