In a message dated 07/11/05, wandc@....... writes:

> 

Hi Wayne,

> > Regarding this, I had heard that in addition to choosing materials with 
> > low sliding friction, a second bearing material was often used for ease of 
> > subsequent maintenance. Don't know if this wear/replacement business 
> >

       Sliding friction in a bearing and rolling friction are two very 
different situations.
Sliding, or rolling on a compliant / rubbery type surface both inevitably 
involve energy loss. We try hard to avoid this. 

       For a seismometer suspension, you need an extremely low energy loss 
hinge action. Even foils flexing in a cross hinge involve some loss. The rolling 
wire / foil type does appear capable of giving lower losses. For a rolling 
contact type (ball on a flat or crossed cylinder) we need two surfaces which are 
hard, strong, don't tend to weld or corrode and remain near perfectly elastic 
at the contact point, which is quite highly stressed. 

       Regards,

       Chris Chapman 
In a message=20=
dated 07/11/05, wandc@....... writes:



Subject: Re: low friction h=
inge discusson



Hi Wayne,



> Regarding this, I had=20=
heard that in addition to choosing materials with=20

> low sliding friction, a second bearing material was often used for=20=
ease of=20

> subsequent maintenance. Don't know if this wear/replacement busines=
s=20

> has any bearing (pun intended) on seismo hinges, however. 



       Sliding friction in a bearing and r=
olling friction are two very different situations.

Sliding, or rolling on a compliant / rubbery type surface both inevitabl=
y involve energy loss. We try hard to avoid this.=20



       For a seismometer suspension, you n=
eed an extremely low energy loss hinge action. Even foils flexing in a cross=
 hinge involve some loss. The rolling wire / foil type does appear capable o=
f giving lower losses. For a rolling contact type (ball on a flat or crossed=
 cylinder) we need two surfaces which are hard, strong, don't tend to weld o=
r corrode and remain near perfectly elastic at the contact point, which is q=
uite highly stressed.=20



       Regards,



       Chris Chapman