The bottom pivot on a Lehman seismometer may have to take quite an 
appreciable load. It is known that a ball bearing which gives rolling contact 
is quite satisfactory, but it does need a hard smooth surface to press 
against. It occurs to me that it should be perfectly satisfactory to use two 
bearing rollers mounted at right angles. They have highly polished hard 
surfaces. One might be stuck vertically onto the central support. A 
horizontal hole could be bored at the end of the swinging arm, the outside 
1/3 of the hole cut / filed away and the other bearing glued into the 2/3 
hole, leaving the curved surface projecting.  

       I would be interested to hear of anyone who has tried this.

       Regards,

       Chris Chapman
       The bottom pivot on a Lehman seismometer may hav
e to take quite an 

appreciable load. It is known that a ball bearing which gives rolling contact 

is quite satisfactory, but it does need a hard smooth surface to press 

against. It occurs to me that it should be perfectly satisfactory to use two 

bearing rollers mounted at right angles. They have highly polished hard 

surfaces. One might be stuck vertically onto the central support. A 

horizontal hole could be bored at the end of the swinging arm, the outside 

1/3 of the hole cut / filed away and the other bearing glued into the 2/3 

hole, leaving the curved surface projecting.  



       I would be interested to hear of anyone who has tried this.



       Regards,



       Chris Chapman