Re: [Phys-L] Q for band width is not valid. Was: Re: finding Q from band width?

[Bernard Cleyet <bernard@cleyet.org>]

On 2013, Oct 21, , at 16:05, brian whatcott <betwys1@sbcglobal.net> wrote:

> On 10/21/2013 3:49 PM, Bernard Cleyet wrote [in small part]:
> > some better clocks use silica pendula in addition to reduced thermal sensitivity.
> /snip/
> > bc maths declined, so won't even try a trial solution.
>
> I recall that a fused silica rod may be purchased at inconsiderable cost from a US source.
> These shiny glass surfaces have a quasi-hygroscopic property which has apparently defeated some precise measurements of  small weights

and the optical quality (IR) of silica is largely dependent on the water content.  

http://en.wikipedia.org/wiki/Suprasil

> : still, the wooden pendulum has a thermal coefficient which may be quite low, but is also rather hygroscopic.   

An HSN article discussed this including pressure treatment.   I think breath driven wooden instruments are immersed in a bath of wax, evacuated and then when let down to air are thereby protected.  I found the amount of wax is awesome when I forgot my best recorder on the back ledge of my VW bug.  I had to ream out the cavity!  



>   I recall some suggestions that miniature ball races cleaned of all lubricant can serve as relatively low-loss pivots, eliminating the flexure's variation in effective pendular length with amplitude and mass.  

The current RMSs sold by Vernier are also lubricant free.  

bc's   disst. research used Suprasil prisms.



> Brian Whatcott     Altus OK
> _______________________________________________
> Forum for Physics Educators
> Phys-l@phys-l.org
> http://www.phys-l.org/mailman/listinfo/phys-l