Hi Chris and all,

Out of curiosity, today I did try a S-G pivot configuration where;  two
glued carbide flats were attached to the boom and they were
oscillating on two frame fixed/glued ruby balls, to see if the setup would
freely oscillate longer.  The undampened oscillation time
result was exactly the same (~within 1 minute) as when the the ruby balls
were attached to the boom and pivoting on two carbide flats.

Of course the above isn't near equitable to a quite different Lehman setup.
It does make me wonder why a Lehman boom end flat that
is pivoting on a mast fixed ball is significantly better?   I think I can
conprehend using a larger diameter ball as you have, and get
measureably less friction.  I hope I'am not putting you on the spot...(no
pun intended)...you're usually right about everything.

Take care, Meredith



On Tue, Jul 15, 2008 at 9:23 AM,  wrote:

>
> I plan to use an 1/8"sapphire ball against two of the rods
> for an improved Lehman pivot.
>
>
>
>        I suggest that you either use crossed carbide rods with the vertical
> rod on the support post, or that you put the ball on the vertical support
> post. A ball rolling on a plane is considerably inferior to a plane rolling
> on a ball. A two rods rolling on a ball are likely to have a higher
> frictional loss than crossed rods.
>
>        Regards,
>
>        Chris Chapman
Hi Chris and all,
 
Out of curiosity, today I did try a S-G pivot configuration where;  two glued carbide flats were attached to the boom and they were
oscillating on two frame fixed/glued ruby balls, to see if the setup would freely oscillate longer.  The undampened oscillation time
result was exactly the same (~within 1 minute) as when the the ruby balls were attached to the boom and pivoting on two carbide flats.
 
Of course the above isn't near equitable to a quite different Lehman setup.  It does make me wonder why a Lehman boom end flat that
is pivoting on a mast fixed ball is significantly better?   I think I can conprehend using a larger diameter ball as you have, and get 
measureably less friction.  I hope I'am not putting you on the spot...(no pun intended)...you're usually right about everything.  
 
Take care, Meredith


 
On Tue, Jul 15, 2008 at 9:23 AM, <ChrisAtUpw@.......> wrote:




I plan to use an 1/8"sapphire ball against two of the rods
for an improved Lehman pivot.


       I suggest that you either use crossed carbide rods with the vertical rod on the support post, or that you put the ball on the vertical support post. A ball rolling on a plane is considerably inferior to a plane rolling on a ball. A two rods rolling on a ball are likely to have a higher frictional loss than crossed rods.


       Regards,

       Chris Chapman