PSN-L Email List Message

Subject: Re: material choices and/or configuration changes
From: Charles Patton charles.r.patton@........
Date: Tue, 16 Aug 2011 11:01:50 -0700

I was confused, too, and would like to understand the spring being 
Charles R. Patton

On 8/16/2011 10:12 AM, Pete Rowe wrote:
> Hi Randall
> In your discussion of the cosine shaped strips, my mental picture got 
> really fuzzy at the end. If I have 4 strips and I weld pairs together 
> I now have  2 units. I have trouble visualizing the 2 units arranged 
> so they have 4 fold symmetry. I missed something..
> Pete
> ------------------------------------------------------------------------
> *From:* Randall Peters 
> *To:* "'psnlist@..............." 
> *Sent:* Tuesday, August 16, 2011 8:35 AM
> *Subject:* material choices and/or configuration changes
> I read with much interest several of your recent comments concerning 
> materials other than the conventional (standard alloy) metal for use 
> in the spring of a vertical.  The comment about nano tubes caused me 
> to think about how I will never forget the lecture given at TTU years 
> ago by the discoverer of the ‘bucky ball’ (Richard Smalley, Rice 
> University Chemist).  Several of us made bets on how long it would 
> take for him to receive the Nobel Prize for this work.   He 
> ‘punctuated’ the serendipitous nature of his discovery by mentioning 
> “how he expected there would have been a ‘telephone ringing from 
> heaven’ had he not finally realized what ‘lay before him in plain sight’.
>      How I wish that I had some samples on hand to do experiments with 
> various exotic materials involving nanotubes, since my guess is that 
> they just “might be the ticket’ to solving a lot of our problems.   In 
> the meantime, I would like to propose that somebody take the lead to 
> look at possible (significantly different) other ways to maybe improve 
> what we’ve presently got to live with.  Would it be smart, for 
> example, to try and use torsional restoration as opposed to the 
> conventional coiled spring.  Yes, Lucien LacCoste changed the history 
> of seismology (as a tennis player, while solving a problem given to 
> him by his physics professor Romberg, while at UT Austin).  He ‘pulled 
> a coil inside out’ to generate a zero-length configuration that is 
> much less susceptible to creep than previous springs.  I have often 
> wondered if any of the gravimeters he built may have also used fuzed 
> silica (quartz), since it is a much more stable material than most 
> other types (unfortunately brittle and nonconductive).
> Then Erhard came along and invented (patented) the astatic spring to 
> give similar performance.  So there may be several ways to ‘skin a 
> meso-anelastic cat’.
>         One of my ideas that was shown as a prototype at the broadband 
> conference I would like for some of you to think about.  You can find 
> a picture of my “compound vertical seismometer” on the IRIS link by 
> simply typing the keywords into Google.   And if you want to better 
> understand the physics of how it works (benefit of period lengthening 
> being possible by using the ‘beauty’ of the eccentric in latest 
> generation bows), you might want to read the other paper that follows, 
> titled “Archer’s compound bow, smart use of nonlinearity”.
>        When I showed this prototype to some of those in attendance at 
> the broadband conference—several of them were positively impressed.  
> They seemed to think of it more as a toy, however, than being 
> practical; but I believe Erhard was in earnest when he mentioned that 
> I should try to get the amateur seismology community interested in 
> doing some experiments with it.
>      Be apprised that it is susceptible to creep, as shown in my 
> paper, titled “creep enhanced sensitivity of seismometers”, online at
>      The approach using torsional restoration could be closer , in 
> fact, to that of operating with a coil than you might think.  Few 
> people in my experience realize that the spring constant of a coil 
> depends on the shear modulus.   In other words, it is the twisting of 
> the wire of the coil that is key  One of the truly impressive physics 
> demonstrations, that shows that the coil actually wants (unless 
> constrained otherwise) to wind and unwind under load change—is the 
> Wilberforce pendulum which exhibits mesmerizing mode coupling behavior.
>      And for those of you who want to retain the remarkable properties 
> of force balance, there is no reason why you can’t use it with this 
> compound vertical instrument.
> Also, mention was made of the possible use of single crystal silicon.  
> I have used reject (previous generation 3-in) wafers to great 
> advantage in some of my experimental efforts.  It is very easy to 
> diamond scribe and cleave them into rectangular shapes.  They are more 
> elastic than one might tend to believe, and it may be possible to make 
> some useful springs out of them.  They should be much better than any 
> metals that I know about, because a given atom is far more prone to 
> stay where it is supposed to.
>       Finally, I would like to mention some work, involving springs, 
> by the gentleman who changed the world of earth field measurements.  
>  Jim E. Faller pioneered the free-fall method of measuring g, by 
> counting fringes as a cube-corner reflector falls in a vacuum (within 
> a vacuum) to eliminate air drag.  Using a laser interferometric setup 
> to generate the fringes, he improved the accuracy of the g-measurement 
> by several orders of magnitude.
>      When Jim gave a seminar years ago at TTU, he also mentioned to me 
> some ideas about springs that he had.  Don’t know whether he ever 
> refined and published his thoughts along the following lines.
>     Take four strips of elastic rectangular pieces, several times 
> longer than wide.  Form a single-cycle cosine wave permanent 
> (unstrained) shape in each of the strips.  Take two of the thus formed 
> strips and ‘weld’ their ends together to form a shape similar to the 
> leaf spring of an old truck.  Do the same with the other pair, and 
> then assemble the four into a single structure having 4-fold 
> rotational symmetry.  Thus it has a stand-alone (stable arrangement) 
> capability to support a load that would be placed on its top.   Has 
> anybody tried something like this?  It should be possible to gang 
> several of them together to increase the operational length and 
> decrease the net spring constant (like springs in series).
>       Randall


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