Date: Tue, 24 May 2011 10:26:41

Author: Jerry DiMarco

Subject: Re: Phase locking metronomes


This may be observable in person but on the video it is
questionable. There are only 11 seconds on the video where the metronomes
are in sync and the camera is not moving (56 - 67 sec). A probe tip was
pressed against my monitor screen for reference during that time period,
and I could not detect a definite glitch in movement of the cans or
board. The motion of the camera certainly adds to the apparent motion of
the apparatus, and I thought I saw glitches initially, but they occurred
while the camera was in motion. I know there has been further
experimentation to verify this phenomenon, I'm just saying it isn't
apparent in the video...


At 5/23/2011 07:38 PM, you wrote:
>Interesting - notice that when they are synchronized - the supporting cans
>have a noticeable 'glitch' every four beats.
>Any explanation for this effect? Or is it just my overactive imagination??
>It's definitely noticeable and an interesting observation. Will have to
>try and set the metronomes for a different frequency and see what
>happens. For example, if the frequency is divisible by three, will there
>be a noticeable kick every third beat? -- Wolfgang
>Yes, and it was interesting how the jiggle didn't occur at every tick.
>I've wondered about this also. When we filmed this Daniel and I used the
>same cans that we use for the "Reactionary Roadbed" demo (radio controlled
>car moves one way while road moves the other), so my guess is that it has
>something to do with deformations in the cans?
>There are several parameters to vary. See, for example, our in-depth
>description found here:
>For starters I just tried tweaking the frequency and was able to make the
>"kick" every fourth beat go away completely, or morph into what appears to
>be a beating phenomenon. Further experimentation is in order -- Wolfgang
>I wasn't watching for that. But I could hear the clicks of the metronomes
>go between nearly perfect and then slightly out of phase.
>Excellent demo and video, by the way.
>Nope... that's a different effect than the can motion. It takes place
>over a few dozen cycles.


Jerry DiMarco
Manager of Lecture Demonstrations and Instructional Labs
Montana State Univ., Physics Dept.
Bozeman, MT

Our Motto: "A demo a day helps learning to stay"

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