Re: [ATM] Bearing smoothness limit

["Don Clement" <don_clement@charter.net>]

Hi Richard,



There are limitations to the using flexural bearings, full rotation for
example. But by clever design one may take advantage of  the flexural pivot
superior smoothness. For example using a hex pod with flexural end pivots
for limited movement and ball bearings or fluid bearings for larger
movement. My focuser is another example of the use of flexural bearings for
linear movement. If the single leadscrew that I presently use were replaced
with a solenoid (voice coil), piezo or other type actuator there would be
absolutely no rolling or sliding parts. As it is I use a pair of precision
instrument bearings for knob rotation and the self-lubricating Turcite for
the leadscrew nuts. Note that the contact of the instrument bearings is
internal and oil lubricated, protected from grit and dirt contamination.
Unlike the typical crayford type which uses open roller or sliding bearings
exposed to grit and dirt contamination. Imagine taking an open race grade 9
precision ball bearing race out side to run in the elements. BTW Turcite is
the modern equivalent to lignum vitae of which John Harrison used so
effectivly in making long lasting wooden clocks.
http://en.wikipedia.org/wiki/John_Harrison  Some of Harrison's original
wooden clocks are still running. I saw a tuat band clock the other day in
which the pendulum was suspended by a steel band. You wind these clocks once
every 600 days and the Atmos clock also uses a taut band pendulum, never
needs winding see: http://www.compadapt.com/atmos.html



Don Clement

Running Springs, California




> Hi Don,
>
> Monday, August 21, 2006, 9:42:16 PM, you wrote:
>
> DC> There is a limit to how
> DC> smooth  mechanical movement that depends on sliding or rolling
surfaces can
> DC> be. Flexural bearings don't seem to have the same limits on how smooth
> DC> mechanical movement can be.
>
> But how, pray, does one replace a rolling bearing with a
> fluxural element and achieve full rotation?
>
> -- 
>
> Best regards,
>   Richard in the UK
>
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