Jack Forster[Elite User]
4381
Actually AFAIK the 'vaccum chamber test' has . . .
Mar 04, 2005,04:04 AM
. . .not been done on the Journe watch.
With respect to classic linear resonance where a 'passive' oscillator is driven by some external force at one of its natural frequencies, I don't think (pardon the nitpicking but this thread is all about picking nits, right? ) that the frequencies are different with the powered and unpowered oscillator; if this were so resonance definitionally would not be occuring. Um, actually, the unpowered oscillator CAN'T have a frequency, because it's unpowered; it can ONLY oscillate if it's driven by the 'powered' oscillator (to borrow your language) in which case it's impossible for it to have a 'slightly different frequency.' In the case of two powered oscillators, if the frequency is different, resonance is impossible; what's actually happening (as far as I can see) is that two resonators which are basically at the same frequency (errors in rate due to friction, mechanical tolerances, etc. etc. aside) gradually begin to beat 'in step.' So it's not that the frequency is different, it's that they're out of synchrony with each other.
Incidentally, regarding how the resonators are coupled, here's an interesting thought experiment: The examples of resonance I've seen in discussions and definitions of 'classic' resonance all seem to rely on a pressure wave of some sort being transmitted through some sort of coupling medium (air, in the case of resonating musical instruments; the movement plate in the case of resonating pendulum clocks.) So how about a situation where the two balances are connected directly to each other by a rigid rod, like. . . um, the wheels of a steam locomotive? This seems to clearly NOT be resonance; but in the case of the Haldimann watch, where it's the springs that are coupled. . .
Jack
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Can we have a serious discussion about resonance?
By: ThomasM : March 3rd, 2005-03:03
I think that nearly everyone with any background or even sense about physics and technology has a gut or intuitive sense of resonance. Certainly, even the layman has an intuitive feel for the subject, in the sense of something "resonating" - echos; a stri...
A little bit. . .
By: Jack Forster : March 3rd, 2005-09:09
. . .from me; I just read an interesting article archived to a physics newsgroup on the famous Tacoma Narrows bridge collapes, which is often presented in physics textbooks (having not seen the inside of a physics textbook in years, I must take this on fa...
I am sure that acoustic resonance still exists
By: tony p : March 3rd, 2005-01:13
within the Journe watch, despite what you say about drag effects between the two balances. It has been described elsewhere on ThePuristS (from memory, by Felipe) how a Journe watch's two movements will start to beat in synchrony a few minutes after windin...
Tacoma Bridge paper
By: Greg D : March 3rd, 2005-02:14
Jack, I think this is the paper you're talking about. Well worth a read - it basically highlights that there is much more to this than meets the eye - and the simplistic explanations aren't correct. http://www-mtl.mit.edu/research/mems-salon/sriram_Billah...
Are you sure that the balances in the Journe Resonance
By: IanS : March 3rd, 2005-10:22
rotate in the same direction Jack ? I have always understood that they rotated in opposite directions which would make air flow a possibility: though Suitbert mentions elsewhere that Journe has found the same effect in a vacumn chamber, which if correct, ...
Yes indeed. . .
By: Jack Forster : March 4th, 2005-04:04
. . .straight from Our Man Inside; in fact he mentions it in his review of the Journe Resonance specifically (and chided me gently for not being observant enough to have noticed it in the write-up) . I wondered the same thing John- given the need to place...
The true resonance? It must be Bulova Accutron with tuning fork...
By: Wichai : March 4th, 2005-05:05
Dear all, Just an addendum to this wonderful discussion, the probably most understandable case of resonance utilized in watch's movement could be of a Bulova Accutron. The oscillator makes the tuning forks vibrate with their natural frequency all the time...
A brace of extracurricular . . .
By: Dr No : March 3rd, 2005-01:13
. . . examples before moving on to watches. First up is the legendary Lockheed P-38 Lightning which was the fighter plane flown by the two highest-scoring American aces of WWII - the twin-engine design employed contra-rotating propellers which were credit...
Yes, but in the P-38 the propellers were contra-rotating. . .
By: Jack Forster : March 3rd, 2005-01:13
. . .which would have produced vibrations that tended to cancel each other; this is the opposite of resonance, isn't it? And in the Journe watch, as I understand it the balances are actually rotating in the same direction. . . Jack
Resonance in-phase vs out-of-phase . . .
By: Dr No : March 3rd, 2005-02:14
. . . hmm, this is getting complicated. In both of my extra-horological examples, the employment of out-of-phase resonance cancellation succeeded in improving the physical characteristics of the device in question. (Paranthetically, the P-38's purchased f...
A frew thoughts on this...
By: Greg D : March 3rd, 2005-03:15
The physics to two simple coupled oscillators isn't hard. If we're talking two coupled pendulums that will have two modes - one where they move together, and another where they move in opposite directions. These two modes will occur at different frequenci...
Hi Greg, great stuff- a question. . .
By: Jack Forster : March 3rd, 2005-03:15
. . .from a physicist's perspective, are coupled oscillators necessarily resonating? The definitions I've read all define resonance in terms of an oscillator being driven at one of its natural frequencies by some external source, and also specify (often) ...
Actually AFAIK the 'vaccum chamber test' has . . .
By: Jack Forster : March 4th, 2005-04:04
. . .not been done on the Journe watch. With respect to classic linear resonance where a 'passive' oscillator is driven by some external force at one of its natural frequencies, I don't think (pardon the nitpicking but this thread is all about picking nit...
every object or system has a natural frequency
By: ei8htohms : March 4th, 2005-03:15
Hi Jack, A passive oscillator does have a natural frequency and it is precisely this fact that allows resonance to occur. In addition to a natural frequency there are also harmonics above and/or below the natural frequency that can be exploited by/for res...
More info for consideration....
By: Curtis for David Lou : March 4th, 2005-01:13
Hi all, A few bits of info to add to the murky waters... The first bit is a LINK to an article I posted a couple of years ago written by Anthony Randall regarding Journe's Resonance. For a frame of reference regarding Anthony Randall - he majored in physi...
Hi Curtis, extremely interesting. . .
By: Jack Forster : March 4th, 2005-02:14
. . .it's probably worth carefully noting that resonance effects can take place through almost unbelievably subtle mechanical linkages. I've been reading 'Tuxedo Park' which is a biography of Alfred Lee Loomis, who financed (among other things) the Americ...
Thanks, Curtis, for these clarifications.
By: tony p : March 4th, 2005-03:15
I have to say Jack, though your horological expertise is not in question, you still seem to be missing my point about resonance. Firstly: when I referred to the frequency of the unpowered oscillator, I was of course referring to its natural resonant frequ...
Dynamo
By: Alex : March 10th, 2005-08:08
About Resonance, and also the "Project 150"
By: Justin Koullapis : March 10th, 2005-06:18
Gentlemen, I have read your posts on this subject with great interest?I have recently been giving resonance a lot of thought, and specifically how it relates to current and past horological creations. It would seem to me that any system of coupled oscilla...