[TR] Speedo indicator calibration

[Anthony Rhodes]

Well, you are right, the spring constant isn't perfectly linear but the coiled hair spring is probably fairly linear and linear enough. 

Also, it is feasible to print the dial face with a non-linear spacing.  But when I measured the spacing of the 10mph ticks, it was equal throughout.    

-Tony

Sent from my 1837 Babbage Analytical Engine

> On Feb 19, 2017, at 2:00 PM, triumphs-request at autox.team.net wrote:
> 
> essage: 5
> Date: Sun, 19 Feb 2017 16:25:00 +0000
> From: "Reihing, Randall S." <Randall.Reihing at utoledo.edu>
> To: Geo Hahn <ahwahneetr at gmail.com>, Anthony Rhodes
>    <spamiam at comcast.net>
> Cc: Triumphs <triumphs at autox.team.net>
> Subject: Re:e [TR] Speedo indicator calibration
> Message-ID:
>    <5DF59F06A5E05E47A21C0E72057265D901706B7BE2 at msgdb11.utad.utoledo.edu>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> I think Tony has hit on the core of the problem. I believe 100% mechanical, non-electric or non-electronic, analog meters were primarily designed to exhibit their greatest accuracy in the middle third of their full range to account for a lack of consistency in spring rates. To accomodate that, meter scales could be originally calibrated to account for spring rate deviations throughout their range of movement, but vehicle speedometers always seem to have consistent spacing. So, if the scale has consistent spacing then I don't see how it would be possible for the meter to exhibit accurate indications throughout it's full range, unless the meter movement has three or more internal mechanisms to account for variable spring rates in p-lace of just one set of springs used for full scale deflection.
> 
> Pretty interesting stuff, really.
> 
> Randall S.