Re: [Phys-L] Bourdon tube foundations

[brian whatcott <betwys1@sbcglobal.net>]

On 10/26/2012 10:56 AM, Roberto Carabajal wrote:
> Hello:
>   
> Please, I would appreciate a link to a detailed description of the Bourdon
> tube gauge pressure operation, because in general what I have founded show
> the final formula but not the foundations including Hooke`s and Young`s
> laws.
> Thanks for your time.
> My best regards.
> Rob
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Perhaps, depending on the age of the target audience, an explanation 
could be offered which provides more  toehold for the intellect?
 I visualize a concertina walled tube, restrained along one lengthwise 
surface strip  with a tape.    If this device is inflated, it will curl 
towards the tape. There is no great difficulty here.

If we make such a tube in a curve, we may fix a flexible tape to either 
the exterior ridges at the perimeter, or at the most minor perimeter. It 
will be evident that a structure of this kind can be made to uncurl, or 
to curl, when inflated.

It's true that this leaves the educator with a remaining bridge to 
cross: how to explain the necessity of an elliptical cross section, if 
we would avoid a pleated arrangement?

Perhaps one could argue from the geometry: for  circular arcs bound 
together by structure an action which necessitates their distance 
increasing  but their length remaining the same is resolved by an 
increased radius for both?

Brian W